@wip

Signed-off-by: Michael Carroll <mjcarroll@intrinsic.ai>

CODEOWNERS

@@ -0,0 +1,2 @@
+# This file was generated by https://github.com/audrow/update-ros2-repos
+* @ivanpauno @hidmic @wjwwood

README.md

@@ -8,7 +8,8 @@ rclcpp provides the standard C++ API for interacting with ROS 2.
 
 `#include "rclcpp/rclcpp.hpp"` allows use of the most common elements of the ROS 2 system.
 
-Visit the [rclcpp API documentation](http://docs.ros2.org/latest/api/rclcpp/) for a complete list of its main components.
+The link to the latest API documentation can be found on the rclcpp package info page, at the [ROS Index](https://index.ros.org/p/rclcpp/).
+
 
 ### Examples
 

rclcpp/CHANGELOG.rst

@@ -2,6 +2,87 @@
 Changelog for package rclcpp
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+20.0.0 (2023-04-13)
+-------------------
+* applied tracepoints for ring_buffer (`#2091 <https://github.com/ros2/rclcpp/issues/2091>`_)
+* Dynamic Subscription (REP-2011 Subset): Stubs for rclcpp (`#2165 <https://github.com/ros2/rclcpp/issues/2165>`_)
+* Add type_hash to cpp TopicEndpointInfo (`#2137 <https://github.com/ros2/rclcpp/issues/2137>`_)
+* Trigger the intraprocess guard condition with data (`#2164 <https://github.com/ros2/rclcpp/issues/2164>`_)
+* Minor grammar fix (`#2149 <https://github.com/ros2/rclcpp/issues/2149>`_)
+* Fix unnecessary allocations in executor.cpp (`#2135 <https://github.com/ros2/rclcpp/issues/2135>`_)
+* add Logger::get_effective_level(). (`#2141 <https://github.com/ros2/rclcpp/issues/2141>`_)
+* Remove deprecated header (`#2139 <https://github.com/ros2/rclcpp/issues/2139>`_)
+* Implement matched event (`#2105 <https://github.com/ros2/rclcpp/issues/2105>`_)
+* use allocator via init_options argument. (`#2129 <https://github.com/ros2/rclcpp/issues/2129>`_)
+* Fixes to silence some clang warnings. (`#2127 <https://github.com/ros2/rclcpp/issues/2127>`_)
+* Documentation improvements on the executor (`#2125 <https://github.com/ros2/rclcpp/issues/2125>`_)
+* Avoid losing waitable handles while using MultiThreadedExecutor (`#2109 <https://github.com/ros2/rclcpp/issues/2109>`_)
+* Hook up the incompatible type event inside of rclcpp (`#2069 <https://github.com/ros2/rclcpp/issues/2069>`_)
+* Update all rclcpp packages to C++17. (`#2121 <https://github.com/ros2/rclcpp/issues/2121>`_)
+* Fix clang warning: bugprone-use-after-move (`#2116 <https://github.com/ros2/rclcpp/issues/2116>`_)
+* Contributors: Barry Xu, Chris Lalancette, Christopher Wecht, Emerson Knapp, Michael Carroll, Tomoya Fujita, Yadu, mauropasse, methylDragon, ymski
+
+19.3.0 (2023-03-01)
+-------------------
+* Fix memory leak in tracetools::get_symbol() (`#2104 <https://github.com/ros2/rclcpp/issues/2104>`_)
+* Service introspection (`#1985 <https://github.com/ros2/rclcpp/issues/1985>`_)
+* Allow publishing borrowed messages with intra-process enabled (`#2108 <https://github.com/ros2/rclcpp/issues/2108>`_)
+* to fix flaky test about TestTimeSource.callbacks (`#2111 <https://github.com/ros2/rclcpp/issues/2111>`_)
+* Contributors: Brian, Chen Lihui, Christophe Bedard, Miguel Company
+
+19.2.0 (2023-02-24)
+-------------------
+* to create a sublogger while getting child of Logger (`#1717 <https://github.com/ros2/rclcpp/issues/1717>`_)
+* Fix documentation of Context class (`#2107 <https://github.com/ros2/rclcpp/issues/2107>`_)
+* fixes for rmw callbacks in qos_event class (`#2102 <https://github.com/ros2/rclcpp/issues/2102>`_)
+* Contributors: Alberto Soragna, Chen Lihui, Silvio Traversaro
+
+19.1.0 (2023-02-14)
+-------------------
+* Add support for timers on reset callback (`#1979 <https://github.com/ros2/rclcpp/issues/1979>`_)
+* Topic node guard condition in executor (`#2074 <https://github.com/ros2/rclcpp/issues/2074>`_)
+* Fix bug on the disorder of calling shutdown callback (`#2097 <https://github.com/ros2/rclcpp/issues/2097>`_)
+* Contributors: Barry Xu, Chen Lihui, mauropasse
+
+19.0.0 (2023-01-30)
+-------------------
+* Add default constructor to NodeInterfaces (`#2094 <https://github.com/ros2/rclcpp/issues/2094>`_)
+* Fix clock state cached time to be a copy, not a reference. (`#2092 <https://github.com/ros2/rclcpp/issues/2092>`_)
+* Fix -Wmaybe-uninitialized warning (`#2081 <https://github.com/ros2/rclcpp/issues/2081>`_)
+* Fix the keep_last warning when using system defaults. (`#2082 <https://github.com/ros2/rclcpp/issues/2082>`_)
+* Add in a fix for older compilers. (`#2075 <https://github.com/ros2/rclcpp/issues/2075>`_)
+* Contributors: Alexander Hans, Chris Lalancette, Shane Loretz
+
+18.0.0 (2022-12-29)
+-------------------
+* Implement Unified Node Interface (NodeInterfaces class) (`#2041 <https://github.com/ros2/rclcpp/issues/2041>`_)
+* Do not throw exception if trying to dequeue an empty intra-process buffer (`#2061 <https://github.com/ros2/rclcpp/issues/2061>`_)
+* Move event callback binding to PublisherBase and SubscriptionBase (`#2066 <https://github.com/ros2/rclcpp/issues/2066>`_)
+* Implement validity checks for rclcpp::Clock (`#2040 <https://github.com/ros2/rclcpp/issues/2040>`_)
+* Explicitly set callback type (`#2059 <https://github.com/ros2/rclcpp/issues/2059>`_)
+* Fix logging macros to build with msvc and cpp20 (`#2063 <https://github.com/ros2/rclcpp/issues/2063>`_)
+* Add clock type to node_options (`#1982 <https://github.com/ros2/rclcpp/issues/1982>`_)
+* Fix nullptr dereference in prune_requests_older_than (`#2008 <https://github.com/ros2/rclcpp/issues/2008>`_)
+* Remove templating on to_rcl_subscription_options (`#2056 <https://github.com/ros2/rclcpp/issues/2056>`_)
+* Fix SharedFuture from async_send_request never becoming valid (`#2044 <https://github.com/ros2/rclcpp/issues/2044>`_)
+* Add in a warning for a KeepLast depth of 0. (`#2048 <https://github.com/ros2/rclcpp/issues/2048>`_)
+* Mark rclcpp::Clock::now() as const (`#2050 <https://github.com/ros2/rclcpp/issues/2050>`_)
+* Fix a case that did not throw ParameterUninitializedException (`#2036 <https://github.com/ros2/rclcpp/issues/2036>`_)
+* Update maintainers (`#2043 <https://github.com/ros2/rclcpp/issues/2043>`_)
+* Contributors: Alberto Soragna, Audrow Nash, Chen Lihui, Chris Lalancette, Jeffery Hsu, Lei Liu, Mateusz Szczygielski, Shane Loretz, andrei, mauropasse, methylDragon
+
+17.1.0 (2022-11-02)
+-------------------
+* MultiThreadExecutor number of threads is at least 2+ in default. (`#2032 <https://github.com/ros2/rclcpp/issues/2032>`_)
+* Fix bug that a callback not reached (`#1640 <https://github.com/ros2/rclcpp/issues/1640>`_)
+* Set the minimum number of threads of the Multithreaded executor to 2 (`#2030 <https://github.com/ros2/rclcpp/issues/2030>`_)
+* check thread whether joinable before join (`#2019 <https://github.com/ros2/rclcpp/issues/2019>`_)
+* Set cpplint test timeout to 3 minutes (`#2022 <https://github.com/ros2/rclcpp/issues/2022>`_)
+* Make sure to include-what-you-use in the node_interfaces. (`#2018 <https://github.com/ros2/rclcpp/issues/2018>`_)
+* Do not clear entities callbacks on destruction (`#2002 <https://github.com/ros2/rclcpp/issues/2002>`_)
+* fix mismatched issue if using zero_allocate (`#1995 <https://github.com/ros2/rclcpp/issues/1995>`_)
+* Contributors: Alexis Paques, Chen Lihui, Chris Lalancette, Cristóbal Arroyo, Tomoya Fujita, mauropasse, uupks
+
 17.0.0 (2022-09-13)
 -------------------
 * Make ParameterService and Sync/AsyncParameterClient accept rclcpp::QoS (`#1978 <https://github.com/ros2/rclcpp/issues/1978>`_)

rclcpp/CMakeLists.txt

@@ -25,6 +25,7 @@ find_package(tracetools REQUIRED)
 # Default to C++17
 if(NOT CMAKE_CXX_STANDARD)
   set(CMAKE_CXX_STANDARD 17)
+  set(CMAKE_CXX_STANDARD_REQUIRED ON)
 endif()
 if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
   # About -Wno-sign-conversion: With Clang, -Wconversion implies -Wsign-conversion. There are a number of
@@ -48,16 +49,25 @@ set(${PROJECT_NAME}_SRCS
   src/rclcpp/detail/rmw_implementation_specific_subscription_payload.cpp
   src/rclcpp/detail/utilities.cpp
   src/rclcpp/duration.cpp
+  src/rclcpp/dynamic_typesupport/dynamic_message.cpp
+  src/rclcpp/dynamic_typesupport/dynamic_message_type.cpp
+  src/rclcpp/dynamic_typesupport/dynamic_message_type_builder.cpp
+  src/rclcpp/dynamic_typesupport/dynamic_message_type_support.cpp
+  src/rclcpp/dynamic_typesupport/dynamic_serialization_support.cpp
   src/rclcpp/event.cpp
   src/rclcpp/exceptions/exceptions.cpp
   src/rclcpp/executable_list.cpp
   src/rclcpp/executor.cpp
   src/rclcpp/executors.cpp
+  src/rclcpp/executors/executor_entities_collection.cpp
+  src/rclcpp/executors/executor_entities_collector.cpp
+  src/rclcpp/executors/executor_notify_waitable.cpp
   src/rclcpp/executors/multi_threaded_executor.cpp
   src/rclcpp/executors/single_threaded_executor.cpp
-  src/rclcpp/executors/static_executor_entities_collector.cpp
   src/rclcpp/executors/static_single_threaded_executor.cpp
   src/rclcpp/expand_topic_or_service_name.cpp
+  src/rclcpp/experimental/executors/events_executor/events_executor.cpp
+  src/rclcpp/experimental/timers_manager.cpp
   src/rclcpp/future_return_code.cpp
   src/rclcpp/generic_publisher.cpp
   src/rclcpp/generic_subscription.cpp
@@ -92,7 +102,7 @@ set(${PROJECT_NAME}_SRCS
   src/rclcpp/parameter_value.cpp
   src/rclcpp/publisher_base.cpp
   src/rclcpp/qos.cpp
-  src/rclcpp/qos_event.cpp
+  src/rclcpp/event_handler.cpp
   src/rclcpp/qos_overriding_options.cpp
   src/rclcpp/serialization.cpp
   src/rclcpp/serialized_message.cpp
@@ -259,4 +269,8 @@ if(TEST cppcheck)
   set_tests_properties(cppcheck PROPERTIES TIMEOUT 500)
 endif()
 
+if(TEST cpplint)
+  set_tests_properties(cpplint PROPERTIES TIMEOUT 180)
+endif()
+
 ament_generate_version_header(${PROJECT_NAME})

rclcpp/include/rclcpp/allocator/allocator_common.hpp

@@ -15,6 +15,7 @@
 #ifndef RCLCPP__ALLOCATOR__ALLOCATOR_COMMON_HPP_
 #define RCLCPP__ALLOCATOR__ALLOCATOR_COMMON_HPP_
 
+#include <cstring>
 #include <memory>
 
 #include "rcl/allocator.h"
@@ -39,6 +40,22 @@ void * retyped_allocate(size_t size, void * untyped_allocator)
   return std::allocator_traits<Alloc>::allocate(*typed_allocator, size);
 }
 
+template<typename Alloc>
+void * retyped_zero_allocate(size_t number_of_elem, size_t size_of_elem, void * untyped_allocator)
+{
+  auto typed_allocator = static_cast<Alloc *>(untyped_allocator);
+  if (!typed_allocator) {
+    throw std::runtime_error("Received incorrect allocator type");
+  }
+  size_t size = number_of_elem * size_of_elem;
+  void * allocated_memory =
+    std::allocator_traits<Alloc>::allocate(*typed_allocator, size);
+  if (allocated_memory) {
+    std::memset(allocated_memory, 0, size);
+  }
+  return allocated_memory;
+}
+
 template<typename T, typename Alloc>
 void retyped_deallocate(void * untyped_pointer, void * untyped_allocator)
 {
@@ -73,6 +90,7 @@ rcl_allocator_t get_rcl_allocator(Alloc & allocator)
   rcl_allocator_t rcl_allocator = rcl_get_default_allocator();
 #ifndef _WIN32
   rcl_allocator.allocate = &retyped_allocate<Alloc>;
+  rcl_allocator.zero_allocate = &retyped_zero_allocate<Alloc>;
   rcl_allocator.deallocate = &retyped_deallocate<T, Alloc>;
   rcl_allocator.reallocate = &retyped_reallocate<T, Alloc>;
   rcl_allocator.state = &allocator;

rclcpp/include/rclcpp/any_service_callback.hpp

@@ -191,10 +191,14 @@ public:
 #ifndef TRACETOOLS_DISABLED
     std::visit(
       [this](auto && arg) {
-        TRACEPOINT(
-          rclcpp_callback_register,
-          static_cast<const void *>(this),
-          tracetools::get_symbol(arg));
+        if (TRACEPOINT_ENABLED(rclcpp_callback_register)) {
+          char * symbol = tracetools::get_symbol(arg);
+          DO_TRACEPOINT(
+            rclcpp_callback_register,
+            static_cast<const void *>(this),
+            symbol);
+          std::free(symbol);
+        }
       }, callback_);
 #endif  // TRACETOOLS_DISABLED
   }

rclcpp/include/rclcpp/any_subscription_callback.hpp

@@ -965,10 +965,14 @@ public:
 #ifndef TRACETOOLS_DISABLED
     std::visit(
       [this](auto && callback) {
-        TRACEPOINT(
-          rclcpp_callback_register,
-          static_cast<const void *>(this),
-          tracetools::get_symbol(callback));
+        if (TRACEPOINT_ENABLED(rclcpp_callback_register)) {
+          char * symbol = tracetools::get_symbol(callback);
+          DO_TRACEPOINT(
+            rclcpp_callback_register,
+            static_cast<const void *>(this),
+            symbol);
+          std::free(symbol);
+        }
       }, callback_variant_);
 #endif  // TRACETOOLS_DISABLED
   }

rclcpp/include/rclcpp/callback_group.hpp

@@ -16,11 +16,14 @@
 #define RCLCPP__CALLBACK_GROUP_HPP_
 
 #include <atomic>
+#include <functional>
+#include <memory>
 #include <mutex>
-#include <string>
 #include <vector>
 
 #include "rclcpp/client.hpp"
+#include "rclcpp/context.hpp"
+#include "rclcpp/guard_condition.hpp"
 #include "rclcpp/publisher_base.hpp"
 #include "rclcpp/service.hpp"
 #include "rclcpp/subscription_base.hpp"
@@ -90,11 +93,58 @@ public:
    *   determines whether a callback group is automatically added to an executor
    *   with the node with which it is associated.
    */
+  [[deprecated("Use CallbackGroup constructor with context function argument")]]
   RCLCPP_PUBLIC
   explicit CallbackGroup(
     CallbackGroupType group_type,
     bool automatically_add_to_executor_with_node = true);
 
+  /// Constructor for CallbackGroup.
+  /**
+   * Callback Groups have a type, either 'Mutually Exclusive' or 'Reentrant'
+   * and when creating one the type must be specified.
+   *
+   * Callbacks in Reentrant Callback Groups must be able to:
+   *   - run at the same time as themselves (reentrant)
+   *   - run at the same time as other callbacks in their group
+   *   - run at the same time as other callbacks in other groups
+   *
+   * Callbacks in Mutually Exclusive Callback Groups:
+   *   - will not be run multiple times simultaneously (non-reentrant)
+   *   - will not be run at the same time as other callbacks in their group
+   *   - but must run at the same time as callbacks in other groups
+   *
+   * Additionally, callback groups have a property which determines whether or
+   * not they are added to an executor with their associated node automatically.
+   * When creating a callback group the automatically_add_to_executor_with_node
+   * argument determines this behavior, and if true it will cause the newly
+   * created callback group to be added to an executor with the node when the
+   * Executor::add_node method is used.
+   * If false, this callback group will not be added automatically and would
+   * have to be added to an executor manually using the
+   * Executor::add_callback_group method.
+   *
+   * Whether the node was added to the executor before creating the callback
+   * group, or after, is irrelevant; the callback group will be automatically
+   * added to the executor in either case.
+   *
+   * \param[in] group_type The type of the callback group.
+   * \param[in] get_node_context Lambda to retrieve the node context when
+   *   checking that the creating node is valid and using the guard condition.
+   * \param[in] automatically_add_to_executor_with_node A boolean that
+   *   determines whether a callback group is automatically added to an executor
+   *   with the node with which it is associated.
+   */
+  RCLCPP_PUBLIC
+  explicit CallbackGroup(
+    CallbackGroupType group_type,
+    std::function<rclcpp::Context::SharedPtr(void)> get_node_context,
+    bool automatically_add_to_executor_with_node = true);
+
+  /// Default destructor.
+  RCLCPP_PUBLIC
+  ~CallbackGroup();
+
   template<typename Function>
   rclcpp::SubscriptionBase::SharedPtr
   find_subscription_ptrs_if(Function func) const
@@ -130,14 +180,42 @@ public:
     return _find_ptrs_if_impl<rclcpp::Waitable, Function>(func, waitable_ptrs_);
   }
 
+  /// Get the total number of entities in this callback group.
+  /**
+   * \return the number of entities in the callback group.
+   */
+  RCLCPP_PUBLIC
+  size_t size() const;
+
+  /// Return a reference to the 'can be taken' atomic boolean.
+  /**
+   * The resulting bool will be true in the case that no executor is currently
+   * using an executable entity from this group.
+   * The resulting bool will be false in the case that an executor is currently
+   * using an executable entity from this group, and the group policy doesn't
+   * allow a second take (eg mutual exclusion)
+   * \return a reference to the flag
+   */
   RCLCPP_PUBLIC
   std::atomic_bool &
   can_be_taken_from();
 
+  /// Get the group type.
+  /**
+   * \return the group type
+   */
   RCLCPP_PUBLIC
   const CallbackGroupType &
   type() const;
 
+  /// Collect all of the entity pointers contained in this callback group.
+  /**
+   * \param[in] sub_func Function to execute for each subscription
+   * \param[in] service_func Function to execute for each service
+   * \param[in] client_func Function to execute for each client
+   * \param[in] timer_func Function to execute for each timer
+   * \param[in] waitable_fuinc Function to execute for each waitable
+   */
   RCLCPP_PUBLIC
   void collect_all_ptrs(
     std::function<void(const rclcpp::SubscriptionBase::SharedPtr &)> sub_func,
@@ -171,6 +249,29 @@ public:
   bool
   automatically_add_to_executor_with_node() const;
 
+  /// Retrieve the guard condition used to signal changes to this callback group.
+  /**
+   * \param[in] context_ptr context to use when creating the guard condition
+   * \return guard condition if it is valid, otherwise nullptr.
+   */
+  [[deprecated("Use get_notify_guard_condition() without arguments")]]
+  RCLCPP_PUBLIC
+  rclcpp::GuardCondition::SharedPtr
+  get_notify_guard_condition(const rclcpp::Context::SharedPtr context_ptr);
+
+  /// Retrieve the guard condition used to signal changes to this callback group.
+  /**
+   * \return guard condition if it is valid, otherwise nullptr.
+   */
+  RCLCPP_PUBLIC
+  rclcpp::GuardCondition::SharedPtr
+  get_notify_guard_condition();
+
+  /// Trigger the notify guard condition.
+  RCLCPP_PUBLIC
+  void
+  trigger_notify_guard_condition();
+
 protected:
   RCLCPP_DISABLE_COPY(CallbackGroup)
 
@@ -213,6 +314,11 @@ protected:
   std::vector<rclcpp::Waitable::WeakPtr> waitable_ptrs_;
   std::atomic_bool can_be_taken_from_;
   const bool automatically_add_to_executor_with_node_;
+  // defer the creation of the guard condition
+  std::shared_ptr<rclcpp::GuardCondition> notify_guard_condition_ = nullptr;
+  std::recursive_mutex notify_guard_condition_mutex_;
+
+  std::function<rclcpp::Context::SharedPtr(void)> get_context_;
 
 private:
   template<typename TypeT, typename Function>

rclcpp/include/rclcpp/client.hpp

@@ -16,14 +16,15 @@
 #define RCLCPP__CLIENT_HPP_
 
 #include <atomic>
+#include <functional>
 #include <future>
-#include <unordered_map>
 #include <memory>
 #include <mutex>
 #include <optional>  // NOLINT, cpplint doesn't think this is a cpp std header
 #include <sstream>
 #include <string>
 #include <tuple>
+#include <unordered_map>
 #include <utility>
 #include <variant>  // NOLINT
 #include <vector>
@@ -31,8 +32,10 @@
 #include "rcl/client.h"
 #include "rcl/error_handling.h"
 #include "rcl/event_callback.h"
+#include "rcl/service_introspection.h"
 #include "rcl/wait.h"
 
+#include "rclcpp/clock.hpp"
 #include "rclcpp/detail/cpp_callback_trampoline.hpp"
 #include "rclcpp/exceptions.hpp"
 #include "rclcpp/expand_topic_or_service_name.hpp"
@@ -130,7 +133,7 @@ public:
     rclcpp::node_interfaces::NodeGraphInterface::SharedPtr node_graph);
 
   RCLCPP_PUBLIC
-  virtual ~ClientBase();
+  virtual ~ClientBase() = default;
 
   /// Take the next response for this client as a type erased pointer.
   /**
@@ -312,7 +315,7 @@ public:
     // This two-step setting, prevents a gap where the old std::function has
     // been replaced but the middleware hasn't been told about the new one yet.
     set_on_new_response_callback(
-      rclcpp::detail::cpp_callback_trampoline<const void *, size_t>,
+      rclcpp::detail::cpp_callback_trampoline<decltype(new_callback), const void *, size_t>,
       static_cast<const void *>(&new_callback));
 
     // Store the std::function to keep it in scope, also overwrites the existing one.
@@ -320,7 +323,8 @@ public:
 
     // Set it again, now using the permanent storage.
     set_on_new_response_callback(
-      rclcpp::detail::cpp_callback_trampoline<const void *, size_t>,
+      rclcpp::detail::cpp_callback_trampoline<
+        decltype(on_new_response_callback_), const void *, size_t>,
       static_cast<const void *>(&on_new_response_callback_));
   }
 
@@ -466,15 +470,13 @@ public:
     rclcpp::node_interfaces::NodeGraphInterface::SharedPtr node_graph,
     const std::string & service_name,
     rcl_client_options_t & client_options)
-  : ClientBase(node_base, node_graph)
+  : ClientBase(node_base, node_graph),
+    srv_type_support_handle_(rosidl_typesupport_cpp::get_service_type_support_handle<ServiceT>())
   {
-    using rosidl_typesupport_cpp::get_service_type_support_handle;
-    auto service_type_support_handle =
-      get_service_type_support_handle<ServiceT>();
     rcl_ret_t ret = rcl_client_init(
       this->get_client_handle().get(),
       this->get_rcl_node_handle(),
-      service_type_support_handle,
+      srv_type_support_handle_,
       service_name.c_str(),
       &client_options);
     if (ret != RCL_RET_OK) {
@@ -769,7 +771,9 @@ public:
     auto old_size = pending_requests_.size();
     for (auto it = pending_requests_.begin(), last = pending_requests_.end(); it != last; ) {
       if (it->second.first < time_point) {
-        pruned_requests->push_back(it->first);
+        if (pruned_requests) {
+          pruned_requests->push_back(it->first);
+        }
         it = pending_requests_.erase(it);
       } else {
         ++it;
@@ -778,6 +782,33 @@ public:
     return old_size - pending_requests_.size();
   }
 
+  /// Configure client introspection.
+  /**
+   * \param[in] clock clock to use to generate introspection timestamps
+   * \param[in] qos_service_event_pub QoS settings to use when creating the introspection publisher
+   * \param[in] introspection_state the state to set introspection to
+   */
+  void
+  configure_introspection(
+    Clock::SharedPtr clock, const QoS & qos_service_event_pub,
+    rcl_service_introspection_state_t introspection_state)
+  {
+    rcl_publisher_options_t pub_opts = rcl_publisher_get_default_options();
+    pub_opts.qos = qos_service_event_pub.get_rmw_qos_profile();
+
+    rcl_ret_t ret = rcl_client_configure_service_introspection(
+      client_handle_.get(),
+      node_handle_.get(),
+      clock->get_clock_handle(),
+      srv_type_support_handle_,
+      pub_opts,
+      introspection_state);
+
+    if (RCL_RET_OK != ret) {
+      rclcpp::exceptions::throw_from_rcl_error(ret, "failed to configure client introspection");
+    }
+  }
+
 protected:
   using CallbackTypeValueVariant = std::tuple<CallbackType, SharedFuture, Promise>;
   using CallbackWithRequestTypeValueVariant = std::tuple<
@@ -792,16 +823,14 @@ protected:
   async_send_request_impl(const Request & request, CallbackInfoVariant value)
   {
     int64_t sequence_number;
+    std::lock_guard<std::mutex> lock(pending_requests_mutex_);
     rcl_ret_t ret = rcl_send_request(get_client_handle().get(), &request, &sequence_number);
     if (RCL_RET_OK != ret) {
       rclcpp::exceptions::throw_from_rcl_error(ret, "failed to send request");
     }
-    {
-      std::lock_guard<std::mutex> lock(pending_requests_mutex_);
-      pending_requests_.try_emplace(
-        sequence_number,
-        std::make_pair(std::chrono::system_clock::now(), std::move(value)));
-    }
+    pending_requests_.try_emplace(
+      sequence_number,
+      std::make_pair(std::chrono::system_clock::now(), std::move(value)));
     return sequence_number;
   }
 
@@ -830,6 +859,9 @@ protected:
       CallbackInfoVariant>>
   pending_requests_;
   std::mutex pending_requests_mutex_;
+
+private:
+  const rosidl_service_type_support_t * srv_type_support_handle_;
 };
 
 }  // namespace rclcpp

rclcpp/include/rclcpp/clock.hpp

@@ -77,7 +77,7 @@ public:
    */
   RCLCPP_PUBLIC
   Time
-  now();
+  now() const;
 
   /**
    * Sleep until a specified Time, according to clock type.
@@ -137,6 +137,51 @@ public:
     Duration rel_time,
     Context::SharedPtr context = contexts::get_global_default_context());
 
+  /**
+   * Check if the clock is started.
+   *
+   * A started clock is a clock that reflects non-zero time.
+   * Typically a clock will be unstarted if it is using RCL_ROS_TIME with ROS time and
+   * nothing has been published on the clock topic yet.
+   *
+   * \return true if clock is started
+   * \throws std::runtime_error if the clock is not rcl_clock_valid
+   */
+  RCLCPP_PUBLIC
+  bool
+  started();
+
+  /**
+   * Wait until clock to start.
+   *
+   * \rclcpp::Clock::started
+   * \param context the context to wait in
+   * \return true if clock was already started or became started
+   * \throws std::runtime_error if the context is invalid or clock is not rcl_clock_valid
+   */
+  RCLCPP_PUBLIC
+  bool
+  wait_until_started(Context::SharedPtr context = contexts::get_global_default_context());
+
+  /**
+   * Wait for clock to start, with timeout.
+   *
+   * The timeout is waited in steady time.
+   *
+   * \rclcpp::Clock::started
+   * \param timeout the maximum time to wait for.
+   * \param context the context to wait in.
+   * \param wait_tick_ns the time to wait between each iteration of the wait loop (in nanoseconds).
+   * \return true if clock was or became valid
+   * \throws std::runtime_error if the context is invalid or clock is not rcl_clock_valid
+   */
+  RCLCPP_PUBLIC
+  bool
+  wait_until_started(
+    const rclcpp::Duration & timeout,
+    Context::SharedPtr context = contexts::get_global_default_context(),
+    const rclcpp::Duration & wait_tick_ns = rclcpp::Duration(0, static_cast<uint32_t>(1e7)));
+
   /**
    * Returns the clock of the type `RCL_ROS_TIME` is active.
    *

rclcpp/include/rclcpp/context.hpp

@@ -65,8 +65,11 @@ using PreShutdownCallbackHandle = ShutdownCallbackHandle;
 /// Context which encapsulates shared state between nodes and other similar entities.
 /**
  * A context also represents the lifecycle between init and shutdown of rclcpp.
- * It is often used in conjunction with rclcpp::init, or rclcpp::init_local,
- * and rclcpp::shutdown.
+ * Nodes may be attached to a particular context by passing to the rclcpp::Node
+ * constructor a rclcpp::NodeOptions instance in which the Context is set via
+ * rclcpp::NodeOptions::context.
+ * Nodes will be automatically removed from the context when destructed.
+ * Contexts may be shutdown by calling rclcpp::shutdown.
  */
 class Context : public std::enable_shared_from_this<Context>
 {
@@ -376,10 +379,10 @@ private:
   // attempt to acquire another sub context.
   std::recursive_mutex sub_contexts_mutex_;
 
-  std::unordered_set<std::shared_ptr<OnShutdownCallback>> on_shutdown_callbacks_;
+  std::vector<std::shared_ptr<OnShutdownCallback>> on_shutdown_callbacks_;
   mutable std::mutex on_shutdown_callbacks_mutex_;
 
-  std::unordered_set<std::shared_ptr<PreShutdownCallback>> pre_shutdown_callbacks_;
+  std::vector<std::shared_ptr<PreShutdownCallback>> pre_shutdown_callbacks_;
   mutable std::mutex pre_shutdown_callbacks_mutex_;
 
   /// Condition variable for timed sleep (see sleep_for).
@@ -398,20 +401,22 @@ private:
 
   using ShutdownCallback = ShutdownCallbackHandle::ShutdownCallbackType;
 
+  template<ShutdownType shutdown_type>
   RCLCPP_LOCAL
   ShutdownCallbackHandle
   add_shutdown_callback(
-    ShutdownType shutdown_type,
     ShutdownCallback callback);
 
+  template<ShutdownType shutdown_type>
   RCLCPP_LOCAL
   bool
   remove_shutdown_callback(
-    ShutdownType shutdown_type,
     const ShutdownCallbackHandle & callback_handle);
 
+  template<ShutdownType shutdown_type>
+  RCLCPP_LOCAL
   std::vector<rclcpp::Context::ShutdownCallback>
-  get_shutdown_callback(ShutdownType shutdown_type) const;
+  get_shutdown_callback() const;
 };
 
 /// Return a copy of the list of context shared pointers.

rclcpp/include/rclcpp/detail/cpp_callback_trampoline.hpp

@@ -41,6 +41,7 @@ namespace detail
  * so no exceptions should be thrown at this point, and doing so results in
  * undefined behavior.
  *
+ * \tparam UserDataRealT Declared type of the passed function
  * \tparam UserDataT Deduced type based on what is passed for user data,
  *   usually this type is either `void *` or `const void *`.
  * \tparam Args the arguments being passed to the callback
@@ -50,6 +51,7 @@ namespace detail
  * \returns whatever the callback returns, if anything
  */
 template<
+  typename UserDataRealT,
   typename UserDataT,
   typename ... Args,
   typename ReturnT = void
@@ -57,7 +59,7 @@ template<
 ReturnT
 cpp_callback_trampoline(UserDataT user_data, Args ... args) noexcept
 {
-  auto & actual_callback = *reinterpret_cast<const std::function<ReturnT(Args...)> *>(user_data);
+  auto & actual_callback = *static_cast<const UserDataRealT *>(user_data);
   return actual_callback(args ...);
 }
 

rclcpp/include/rclcpp/detail/template_contains.hpp

@@ -0,0 +1,47 @@
+// Copyright 2022 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__DETAIL__TEMPLATE_CONTAINS_HPP_
+#define RCLCPP__DETAIL__TEMPLATE_CONTAINS_HPP_
+
+#include <type_traits>
+
+namespace rclcpp
+{
+namespace detail
+{
+
+/// Template meta-function that checks if a given T is contained in the list Us.
+template<typename T, typename ... Us>
+struct template_contains;
+
+template<typename ... Args>
+inline constexpr bool template_contains_v = template_contains<Args ...>::value;
+
+template<typename T, typename NextT, typename ... Us>
+struct template_contains<T, NextT, Us ...>
+{
+  enum { value = (std::is_same_v<T, NextT>|| template_contains_v<T, Us ...>)};
+};
+
+template<typename T>
+struct template_contains<T>
+{
+  enum { value = false };
+};
+
+}  // namespace detail
+}  // namespace rclcpp
+
+#endif  // RCLCPP__DETAIL__TEMPLATE_CONTAINS_HPP_

rclcpp/include/rclcpp/detail/template_unique.hpp

@@ -0,0 +1,49 @@
+// Copyright 2022 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__DETAIL__TEMPLATE_UNIQUE_HPP_
+#define RCLCPP__DETAIL__TEMPLATE_UNIQUE_HPP_
+
+#include <type_traits>
+
+#include "rclcpp/detail/template_contains.hpp"
+
+namespace rclcpp
+{
+namespace detail
+{
+
+/// Template meta-function that checks if a given list Ts contains unique types.
+template<typename ... Ts>
+struct template_unique;
+
+template<typename ... Args>
+inline constexpr bool template_unique_v = template_unique<Args ...>::value;
+
+template<typename NextT, typename ... Ts>
+struct template_unique<NextT, Ts ...>
+{
+  enum { value = !template_contains_v<NextT, Ts ...>&& template_unique_v<Ts ...>};
+};
+
+template<typename T>
+struct template_unique<T>
+{
+  enum { value = true };
+};
+
+}  // namespace detail
+}  // namespace rclcpp
+
+#endif  // RCLCPP__DETAIL__TEMPLATE_UNIQUE_HPP_

rclcpp/include/rclcpp/dynamic_typesupport/dynamic_message.hpp

@@ -0,0 +1,70 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_HPP_
+#define RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_HPP_
+
+#include <rcl/allocator.h>
+#include <rcl/types.h>
+#include <rosidl_dynamic_typesupport/types.h>
+
+#include <memory>
+#include <string>
+
+#include "rclcpp/dynamic_typesupport/dynamic_message_type.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
+#include "rclcpp/macros.hpp"
+#include "rclcpp/visibility_control.hpp"
+
+namespace rclcpp
+{
+namespace dynamic_typesupport
+{
+
+/// Utility wrapper class for rosidl_dynamic_typesupport_dynamic_data_t
+/// STUBBED OUT
+class DynamicMessage : public std::enable_shared_from_this<DynamicMessage>
+{
+public:
+  RCLCPP_SMART_PTR_ALIASES_ONLY(DynamicMessage)
+
+  RCLCPP_PUBLIC
+  virtual ~DynamicMessage();
+
+protected:
+  // NOTE(methylDragon):
+  // This is just here to extend the lifetime of the serialization support
+  // It isn't actually used by the builder since the builder should compose its own support
+  //
+  // ... Though ideally it should be the exact same support as the one stored in the
+  // DynamicSerializationSupport
+  DynamicSerializationSupport::SharedPtr serialization_support_;
+
+  rosidl_dynamic_typesupport_dynamic_data_t rosidl_dynamic_data_;
+  bool is_loaned_;
+
+  // Used for returning the loaned value, and lifetime management
+  DynamicMessage::SharedPtr parent_data_;
+
+private:
+  RCLCPP_DISABLE_COPY(DynamicMessage)
+
+  RCLCPP_PUBLIC
+  DynamicMessage();
+};
+
+}  // namespace dynamic_typesupport
+}  // namespace rclcpp
+
+#endif  // RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_HPP_

rclcpp/include/rclcpp/dynamic_typesupport/dynamic_message_type.hpp

@@ -0,0 +1,64 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_TYPE_HPP_
+#define RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_TYPE_HPP_
+
+#include <rcl/allocator.h>
+#include <rosidl_dynamic_typesupport/types.h>
+
+#include <memory>
+#include <string>
+
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
+#include "rclcpp/macros.hpp"
+#include "rclcpp/visibility_control.hpp"
+
+namespace rclcpp
+{
+namespace dynamic_typesupport
+{
+
+/// Utility wrapper class for `rosidl_dynamic_typesupport_dynamic_type_t`
+/// STUBBED OUT
+class DynamicMessageType : public std::enable_shared_from_this<DynamicMessageType>
+{
+public:
+  RCLCPP_SMART_PTR_ALIASES_ONLY(DynamicMessageType)
+
+  RCLCPP_PUBLIC
+  virtual ~DynamicMessageType();
+
+protected:
+  // NOTE(methylDragon):
+  // This is just here to extend the lifetime of the serialization support
+  // It isn't actually used by the builder since the builder should compose its own support
+  //
+  // ... Though ideally it should be the exact same support as the one stored in the
+  // `DynamicSerializationSupport`
+  DynamicSerializationSupport::SharedPtr serialization_support_;
+
+  rosidl_dynamic_typesupport_dynamic_type_t rosidl_dynamic_type_;
+
+private:
+  RCLCPP_DISABLE_COPY(DynamicMessageType)
+
+  RCLCPP_PUBLIC
+  DynamicMessageType();
+};
+
+}  // namespace dynamic_typesupport
+}  // namespace rclcpp
+
+#endif  // RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_TYPE_HPP_

rclcpp/include/rclcpp/dynamic_typesupport/dynamic_message_type_builder.hpp

@@ -0,0 +1,65 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_TYPE_BUILDER_HPP_
+#define RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_TYPE_BUILDER_HPP_
+
+#include <rcl/allocator.h>
+#include <rosidl_dynamic_typesupport/types.h>
+
+#include <memory>
+#include <string>
+
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
+#include "rclcpp/macros.hpp"
+#include "rclcpp/visibility_control.hpp"
+
+namespace rclcpp
+{
+namespace dynamic_typesupport
+{
+
+/// Utility wrapper class for `rosidl_dynamic_typesupport_dynamic_type_builder_t *`
+/// STUBBED OUT
+class DynamicMessageTypeBuilder : public std::enable_shared_from_this<DynamicMessageTypeBuilder>
+{
+public:
+  RCLCPP_SMART_PTR_ALIASES_ONLY(DynamicMessageTypeBuilder)
+
+  RCLCPP_PUBLIC
+  virtual ~DynamicMessageTypeBuilder();
+
+protected:
+  // NOTE(methylDragon):
+  // This is just here to extend the lifetime of the serialization support
+  // It isn't actually used by the builder since the builder should compose its own support
+  //
+  // ... Though ideally it should be the exact same support as the one stored in the
+  // `DynamicSerializationSupport`
+  DynamicSerializationSupport::SharedPtr serialization_support_;
+
+  rosidl_dynamic_typesupport_dynamic_type_builder_t rosidl_dynamic_type_builder_;
+
+private:
+  RCLCPP_DISABLE_COPY(DynamicMessageTypeBuilder)
+
+  RCLCPP_PUBLIC
+  DynamicMessageTypeBuilder();
+};
+
+}  // namespace dynamic_typesupport
+}  // namespace rclcpp
+
+
+#endif  // RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_TYPE_BUILDER_HPP_

rclcpp/include/rclcpp/dynamic_typesupport/dynamic_message_type_support.hpp

@@ -0,0 +1,67 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_TYPE_SUPPORT_HPP_
+#define RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_TYPE_SUPPORT_HPP_
+
+#include <rcl/allocator.h>
+
+#include <rosidl_dynamic_typesupport/dynamic_message_type_support_struct.h>
+#include <rosidl_dynamic_typesupport/types.h>
+#include <rosidl_runtime_c/message_type_support_struct.h>
+#include <rosidl_runtime_c/type_description/type_description__struct.h>
+
+#include <memory>
+#include <string>
+
+#include "rclcpp/dynamic_typesupport/dynamic_message.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
+
+#include "rclcpp/macros.hpp"
+#include "rclcpp/visibility_control.hpp"
+
+namespace rclcpp
+{
+namespace dynamic_typesupport
+{
+
+/// Utility wrapper class for `rosidl_message_type_support_t` containing managed
+/// STUBBED OUT
+class DynamicMessageTypeSupport : public std::enable_shared_from_this<DynamicMessageTypeSupport>
+{
+public:
+  RCLCPP_SMART_PTR_ALIASES_ONLY(DynamicMessageTypeSupport)
+
+  RCLCPP_PUBLIC
+  virtual ~DynamicMessageTypeSupport();
+
+protected:
+  DynamicSerializationSupport::SharedPtr serialization_support_;
+  DynamicMessageType::SharedPtr dynamic_message_type_;
+  DynamicMessage::SharedPtr dynamic_message_;
+
+  rosidl_message_type_support_t rosidl_message_type_support_;
+
+private:
+  RCLCPP_DISABLE_COPY(DynamicMessageTypeSupport)
+
+  RCLCPP_PUBLIC
+  DynamicMessageTypeSupport();
+};
+
+}  // namespace dynamic_typesupport
+}  // namespace rclcpp
+
+#endif  // RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_MESSAGE_TYPE_SUPPORT_HPP_

rclcpp/include/rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp

@@ -0,0 +1,60 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_SERIALIZATION_SUPPORT_HPP_
+#define RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_SERIALIZATION_SUPPORT_HPP_
+
+#include <rcl/allocator.h>
+#include <rosidl_dynamic_typesupport/api/serialization_support.h>
+#include <rosidl_dynamic_typesupport/types.h>
+
+#include <memory>
+#include <string>
+
+#include "rclcpp/macros.hpp"
+#include "rclcpp/visibility_control.hpp"
+
+namespace rclcpp
+{
+namespace dynamic_typesupport
+{
+
+/// Utility wrapper class for rosidl_dynamic_typesupport_serialization_support_t
+class DynamicSerializationSupport : public std::enable_shared_from_this<DynamicSerializationSupport>
+{
+public:
+  RCLCPP_SMART_PTR_ALIASES_ONLY(DynamicSerializationSupport)
+
+  RCLCPP_PUBLIC
+  explicit DynamicSerializationSupport(rcl_allocator_t allocator = rcl_get_default_allocator());
+
+  RCLCPP_PUBLIC
+  DynamicSerializationSupport(
+    const std::string & serialization_library_name,
+    rcl_allocator_t allocator = rcl_get_default_allocator());
+
+  RCLCPP_PUBLIC
+  virtual ~DynamicSerializationSupport();
+
+protected:
+  rosidl_dynamic_typesupport_serialization_support_t rosidl_serialization_support_;
+
+private:
+  RCLCPP_DISABLE_COPY(DynamicSerializationSupport)
+};
+
+}  // namespace dynamic_typesupport
+}  // namespace rclcpp
+
+#endif  // RCLCPP__DYNAMIC_TYPESUPPORT__DYNAMIC_SERIALIZATION_SUPPORT_HPP_

rclcpp/include/rclcpp/event_handler.hpp

@@ -0,0 +1,311 @@
+// Copyright 2019 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__EVENT_HANDLER_HPP_
+#define RCLCPP__EVENT_HANDLER_HPP_
+
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <stdexcept>
+#include <string>
+
+#include "rcl/error_handling.h"
+#include "rcl/event_callback.h"
+#include "rmw/impl/cpp/demangle.hpp"
+#include "rmw/incompatible_qos_events_statuses.h"
+#include "rmw/events_statuses/incompatible_type.h"
+
+#include "rcutils/logging_macros.h"
+
+#include "rclcpp/detail/cpp_callback_trampoline.hpp"
+#include "rclcpp/exceptions.hpp"
+#include "rclcpp/function_traits.hpp"
+#include "rclcpp/logging.hpp"
+#include "rclcpp/waitable.hpp"
+
+namespace rclcpp
+{
+
+using QOSDeadlineRequestedInfo = rmw_requested_deadline_missed_status_t;
+using QOSDeadlineOfferedInfo = rmw_offered_deadline_missed_status_t;
+using QOSLivelinessChangedInfo = rmw_liveliness_changed_status_t;
+using QOSLivelinessLostInfo = rmw_liveliness_lost_status_t;
+using QOSMessageLostInfo = rmw_message_lost_status_t;
+using QOSOfferedIncompatibleQoSInfo = rmw_offered_qos_incompatible_event_status_t;
+using QOSRequestedIncompatibleQoSInfo = rmw_requested_qos_incompatible_event_status_t;
+
+using IncompatibleTypeInfo = rmw_incompatible_type_status_t;
+using MatchedInfo = rmw_matched_status_t;
+
+using QOSDeadlineRequestedCallbackType = std::function<void (QOSDeadlineRequestedInfo &)>;
+using QOSDeadlineOfferedCallbackType = std::function<void (QOSDeadlineOfferedInfo &)>;
+using QOSLivelinessChangedCallbackType = std::function<void (QOSLivelinessChangedInfo &)>;
+using QOSLivelinessLostCallbackType = std::function<void (QOSLivelinessLostInfo &)>;
+using QOSMessageLostCallbackType = std::function<void (QOSMessageLostInfo &)>;
+using QOSOfferedIncompatibleQoSCallbackType = std::function<void (QOSOfferedIncompatibleQoSInfo &)>;
+using QOSRequestedIncompatibleQoSCallbackType =
+  std::function<void (QOSRequestedIncompatibleQoSInfo &)>;
+
+using IncompatibleTypeCallbackType = std::function<void (IncompatibleTypeInfo &)>;
+using PublisherMatchedCallbackType = std::function<void (MatchedInfo &)>;
+using SubscriptionMatchedCallbackType = std::function<void (MatchedInfo &)>;
+
+/// Contains callbacks for various types of events a Publisher can receive from the middleware.
+struct PublisherEventCallbacks
+{
+  QOSDeadlineOfferedCallbackType deadline_callback;
+  QOSLivelinessLostCallbackType liveliness_callback;
+  QOSOfferedIncompatibleQoSCallbackType incompatible_qos_callback;
+  IncompatibleTypeCallbackType incompatible_type_callback;
+  PublisherMatchedCallbackType matched_callback;
+};
+
+/// Contains callbacks for non-message events that a Subscription can receive from the middleware.
+struct SubscriptionEventCallbacks
+{
+  QOSDeadlineRequestedCallbackType deadline_callback;
+  QOSLivelinessChangedCallbackType liveliness_callback;
+  QOSRequestedIncompatibleQoSCallbackType incompatible_qos_callback;
+  QOSMessageLostCallbackType message_lost_callback;
+  IncompatibleTypeCallbackType incompatible_type_callback;
+  SubscriptionMatchedCallbackType matched_callback;
+};
+
+class UnsupportedEventTypeException : public exceptions::RCLErrorBase, public std::runtime_error
+{
+public:
+  RCLCPP_PUBLIC
+  UnsupportedEventTypeException(
+    rcl_ret_t ret,
+    const rcl_error_state_t * error_state,
+    const std::string & prefix);
+
+  RCLCPP_PUBLIC
+  UnsupportedEventTypeException(
+    const exceptions::RCLErrorBase & base_exc,
+    const std::string & prefix);
+};
+
+class EventHandlerBase : public Waitable
+{
+public:
+  enum class EntityType : std::size_t
+  {
+    Event,
+  };
+
+  RCLCPP_PUBLIC
+  virtual ~EventHandlerBase();
+
+  /// Get the number of ready events
+  RCLCPP_PUBLIC
+  size_t
+  get_number_of_ready_events() override;
+
+  /// Add the Waitable to a wait set.
+  RCLCPP_PUBLIC
+  void
+  add_to_wait_set(rcl_wait_set_t * wait_set) override;
+
+  /// Check if the Waitable is ready.
+  RCLCPP_PUBLIC
+  bool
+  is_ready(rcl_wait_set_t * wait_set) override;
+
+  /// Set a callback to be called when each new event instance occurs.
+  /**
+   * The callback receives a size_t which is the number of events that occurred
+   * since the last time this callback was called.
+   * Normally this is 1, but can be > 1 if events occurred before any
+   * callback was set.
+   *
+   * The callback also receives an int identifier argument.
+   * This is needed because a Waitable may be composed of several distinct entities,
+   * such as subscriptions, services, etc.
+   * The application should provide a generic callback function that will be then
+   * forwarded by the waitable to all of its entities.
+   * Before forwarding, a different value for the identifier argument will be
+   * bond to the function.
+   * This implies that the provided callback can use the identifier to behave
+   * differently depending on which entity triggered the waitable to become ready.
+   *
+   * Since this callback is called from the middleware, you should aim to make
+   * it fast and not blocking.
+   * If you need to do a lot of work or wait for some other event, you should
+   * spin it off to another thread, otherwise you risk blocking the middleware.
+   *
+   * Calling it again will clear any previously set callback.
+   *
+   * An exception will be thrown if the callback is not callable.
+   *
+   * This function is thread-safe.
+   *
+   * If you want more information available in the callback, like the qos event
+   * or other information, you may use a lambda with captures or std::bind.
+   *
+   * \sa rmw_event_set_callback
+   * \sa rcl_event_set_callback
+   *
+   * \param[in] callback functor to be called when a new event occurs
+   */
+  void
+  set_on_ready_callback(std::function<void(size_t, int)> callback) override
+  {
+    if (!callback) {
+      throw std::invalid_argument(
+              "The callback passed to set_on_ready_callback "
+              "is not callable.");
+    }
+
+    // Note: we bind the int identifier argument to this waitable's entity types
+    auto new_callback =
+      [callback, this](size_t number_of_events) {
+        try {
+          callback(number_of_events, static_cast<int>(EntityType::Event));
+        } catch (const std::exception & exception) {
+          RCLCPP_ERROR_STREAM(
+            // TODO(wjwwood): get this class access to the node logger it is associated with
+            rclcpp::get_logger("rclcpp"),
+            "rclcpp::EventHandlerBase@" << this <<
+              " caught " << rmw::impl::cpp::demangle(exception) <<
+              " exception in user-provided callback for the 'on ready' callback: " <<
+              exception.what());
+        } catch (...) {
+          RCLCPP_ERROR_STREAM(
+            rclcpp::get_logger("rclcpp"),
+            "rclcpp::EventHandlerBase@" << this <<
+              " caught unhandled exception in user-provided callback " <<
+              "for the 'on ready' callback");
+        }
+      };
+
+    std::lock_guard<std::recursive_mutex> lock(callback_mutex_);
+
+    // Set it temporarily to the new callback, while we replace the old one.
+    // This two-step setting, prevents a gap where the old std::function has
+    // been replaced but the middleware hasn't been told about the new one yet.
+    set_on_new_event_callback(
+      rclcpp::detail::cpp_callback_trampoline<decltype(new_callback), const void *, size_t>,
+      static_cast<const void *>(&new_callback));
+
+    // Store the std::function to keep it in scope, also overwrites the existing one.
+    on_new_event_callback_ = new_callback;
+
+    // Set it again, now using the permanent storage.
+    set_on_new_event_callback(
+      rclcpp::detail::cpp_callback_trampoline<
+        decltype(on_new_event_callback_), const void *, size_t>,
+      static_cast<const void *>(&on_new_event_callback_));
+  }
+
+  /// Unset the callback registered for new events, if any.
+  void
+  clear_on_ready_callback() override
+  {
+    std::lock_guard<std::recursive_mutex> lock(callback_mutex_);
+    if (on_new_event_callback_) {
+      set_on_new_event_callback(nullptr, nullptr);
+      on_new_event_callback_ = nullptr;
+    }
+  }
+
+protected:
+  RCLCPP_PUBLIC
+  void
+  set_on_new_event_callback(rcl_event_callback_t callback, const void * user_data);
+
+  std::recursive_mutex callback_mutex_;
+  std::function<void(size_t)> on_new_event_callback_{nullptr};
+
+  rcl_event_t event_handle_;
+  size_t wait_set_event_index_;
+};
+
+using QOSEventHandlerBase [[deprecated("Use rclcpp::EventHandlerBase")]] = EventHandlerBase;
+
+template<typename EventCallbackT, typename ParentHandleT>
+class EventHandler : public EventHandlerBase
+{
+public:
+  template<typename InitFuncT, typename EventTypeEnum>
+  EventHandler(
+    const EventCallbackT & callback,
+    InitFuncT init_func,
+    ParentHandleT parent_handle,
+    EventTypeEnum event_type)
+  : parent_handle_(parent_handle), event_callback_(callback)
+  {
+    event_handle_ = rcl_get_zero_initialized_event();
+    rcl_ret_t ret = init_func(&event_handle_, parent_handle.get(), event_type);
+    if (ret != RCL_RET_OK) {
+      if (ret == RCL_RET_UNSUPPORTED) {
+        UnsupportedEventTypeException exc(ret, rcl_get_error_state(), "Failed to initialize event");
+        rcl_reset_error();
+        throw exc;
+      } else {
+        rclcpp::exceptions::throw_from_rcl_error(ret, "Failed to initialize event");
+      }
+    }
+  }
+
+  /// Take data so that the callback cannot be scheduled again
+  std::shared_ptr<void>
+  take_data() override
+  {
+    EventCallbackInfoT callback_info;
+    rcl_ret_t ret = rcl_take_event(&event_handle_, &callback_info);
+    if (ret != RCL_RET_OK) {
+      RCUTILS_LOG_ERROR_NAMED(
+        "rclcpp",
+        "Couldn't take event info: %s", rcl_get_error_string().str);
+      return nullptr;
+    }
+    return std::static_pointer_cast<void>(std::make_shared<EventCallbackInfoT>(callback_info));
+  }
+
+  std::shared_ptr<void>
+  take_data_by_entity_id(size_t id) override
+  {
+    (void)id;
+    return take_data();
+  }
+
+  /// Execute any entities of the Waitable that are ready.
+  void
+  execute(std::shared_ptr<void> & data) override
+  {
+    if (!data) {
+      throw std::runtime_error("'data' is empty");
+    }
+    auto callback_ptr = std::static_pointer_cast<EventCallbackInfoT>(data);
+    event_callback_(*callback_ptr);
+    callback_ptr.reset();
+  }
+
+private:
+  using EventCallbackInfoT = typename std::remove_reference<typename
+      rclcpp::function_traits::function_traits<EventCallbackT>::template argument_type<0>>::type;
+
+  ParentHandleT parent_handle_;
+  EventCallbackT event_callback_;
+};
+
+template<typename EventCallbackT, typename ParentHandleT>
+using QOSEventHandler [[deprecated("Use rclcpp::EventHandler")]] = EventHandler<EventCallbackT,
+    ParentHandleT>;
+
+}  // namespace rclcpp
+
+#endif  // RCLCPP__EVENT_HANDLER_HPP_

rclcpp/include/rclcpp/executor.hpp

@@ -19,6 +19,7 @@
 #include <cassert>
 #include <chrono>
 #include <cstdlib>
+#include <deque>
 #include <iostream>
 #include <list>
 #include <map>
@@ -29,28 +30,27 @@
 
 #include "rcl/guard_condition.h"
 #include "rcl/wait.h"
+#include "rclcpp/executors/executor_notify_waitable.hpp"
 #include "rcpputils/scope_exit.hpp"
 
 #include "rclcpp/context.hpp"
 #include "rclcpp/contexts/default_context.hpp"
 #include "rclcpp/guard_condition.hpp"
 #include "rclcpp/executor_options.hpp"
+#include "rclcpp/executors/executor_entities_collection.hpp"
+#include "rclcpp/executors/executor_entities_collector.hpp"
 #include "rclcpp/future_return_code.hpp"
-#include "rclcpp/memory_strategies.hpp"
-#include "rclcpp/memory_strategy.hpp"
 #include "rclcpp/node_interfaces/node_base_interface.hpp"
 #include "rclcpp/utilities.hpp"
 #include "rclcpp/visibility_control.hpp"
+#include "rclcpp/wait_set.hpp"
 
 namespace rclcpp
 {
 
-typedef std::map<rclcpp::CallbackGroup::WeakPtr,
-    rclcpp::node_interfaces::NodeBaseInterface::WeakPtr,
-    std::owner_less<rclcpp::CallbackGroup::WeakPtr>> WeakCallbackGroupsToNodesMap;
-
 // Forward declaration is used in convenience method signature.
 class Node;
+class ExecutorImplementation;
 
 /// Coordinate the order and timing of available communication tasks.
 /**
@@ -315,6 +315,16 @@ public:
   virtual void
   spin_all(std::chrono::nanoseconds max_duration);
 
+
+  /// Collect work once and execute the next available work, optionally within a duration.
+  /**
+   * This function can be overridden.  The default implementation is suitable for
+   * a single-thread model of execution.
+   * Adding subscriptions, timers, services, etc. with blocking callbacks will cause this function
+   * to block (which may have unintended consequences).
+   * \param[in] timeout The maximum amount of time to spend waiting for work.
+   *   `-1` is potentially block forever waiting for work.
+   */
   RCLCPP_PUBLIC
   virtual void
   spin_once(std::chrono::nanoseconds timeout = std::chrono::nanoseconds(-1));
@@ -392,17 +402,6 @@ public:
   void
   cancel();
 
-  /// Support dynamic switching of the memory strategy.
-  /**
-   * Switching the memory strategy while the executor is spinning in another threading could have
-   * unintended consequences.
-   * \param[in] memory_strategy Shared pointer to the memory strategy to set.
-   * \throws std::runtime_error if memory_strategy is null
-   */
-  RCLCPP_PUBLIC
-  void
-  set_memory_strategy(memory_strategy::MemoryStrategy::SharedPtr memory_strategy);
-
   /// Returns true if the executor is currently spinning.
   /**
    * This function can be called asynchronously from any thread.
@@ -413,12 +412,29 @@ public:
   is_spinning();
 
 protected:
+  /// Add a node to executor, execute the next available unit of work, and remove the node.
+  /**
+   * Implementation of spin_node_once using std::chrono::nanoseconds
+   * \param[in] node Shared pointer to the node to add.
+   * \param[in] timeout How long to wait for work to become available. Negative values cause
+   *   spin_node_once to block indefinitely (the default behavior). A timeout of 0 causes this
+   *   function to be non-blocking.
+   */
   RCLCPP_PUBLIC
   void
   spin_node_once_nanoseconds(
     rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node,
     std::chrono::nanoseconds timeout);
 
+  /// Collect work and execute available work, optionally within a duration.
+  /**
+   * Implementation of spin_some and spin_all.
+   * The exhaustive flag controls if the function will re-collect available work within the duration.
+   *
+   * \param[in] max_duration The maximum amount of time to spend executing work, or 0 for no limit.
+   * \param[in] exhaustive when set to true, continue to collect work and execute (spin_all)
+   *                       when set to false, return when all collected work is executed (spin_some)
+   */
   RCLCPP_PUBLIC
   void
   spin_some_impl(std::chrono::nanoseconds max_duration, bool exhaustive);
@@ -433,124 +449,97 @@ protected:
   void
   execute_any_executable(AnyExecutable & any_exec);
 
+  /// Run subscription executable.
+  /**
+   * Do necessary setup and tear-down as well as executing the subscription.
+   * \param[in] subscription Subscription to execute
+   */
   RCLCPP_PUBLIC
   static void
   execute_subscription(
     rclcpp::SubscriptionBase::SharedPtr subscription);
 
+  /// Run timer executable.
+  /**
+   * Do necessary setup and tear-down as well as executing the timer callback.
+   * \param[in] timer Timer to execute
+   */
   RCLCPP_PUBLIC
   static void
   execute_timer(rclcpp::TimerBase::SharedPtr timer);
 
+  /// Run service server executable.
+  /**
+   * Do necessary setup and tear-down as well as executing the service server callback.
+   * \param[in] service Service to execute
+   */
   RCLCPP_PUBLIC
   static void
   execute_service(rclcpp::ServiceBase::SharedPtr service);
 
+  /// Run service client executable.
+  /**
+   * Do necessary setup and tear-down as well as executing the service client callback.
+   * \param[in] service Service to execute
+   */
   RCLCPP_PUBLIC
   static void
   execute_client(rclcpp::ClientBase::SharedPtr client);
 
+  /// Gather all of the waitable entities from associated nodes and callback groups.
+  RCLCPP_PUBLIC
+  void
+  collect_entities();
+
+  /// Block until more work becomes avilable or timeout is reached.
   /**
+   * Builds a set of waitable entities, which are passed to the middleware.
+   * After building wait set, waits on middleware to notify.
+   * \param[in] timeout duration to wait for new work to become available.
    * \throws std::runtime_error if the wait set can be cleared
    */
   RCLCPP_PUBLIC
   void
   wait_for_work(std::chrono::nanoseconds timeout = std::chrono::nanoseconds(-1));
 
-  RCLCPP_PUBLIC
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr
-  get_node_by_group(
-    const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes,
-    rclcpp::CallbackGroup::SharedPtr group);
-
-  /// Return true if the node has been added to this executor.
+  /// Check for executable in ready state and populate union structure.
   /**
-   * \param[in] node_ptr a shared pointer that points to a node base interface
-   * \param[in] weak_groups_to_nodes map to nodes to lookup
-   * \return true if the node is associated with the executor, otherwise false
+   * \param[out] any_executable populated union structure of ready executable
+   * \return true if an executable was ready and any_executable was populated,
+   *   otherwise false
    */
   RCLCPP_PUBLIC
   bool
-  has_node(
-    const rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-    const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes) const;
-
-  RCLCPP_PUBLIC
-  rclcpp::CallbackGroup::SharedPtr
-  get_group_by_timer(rclcpp::TimerBase::SharedPtr timer);
-
-  /// Add a callback group to an executor
-  /**
-   * \see rclcpp::Executor::add_callback_group
-   */
-  RCLCPP_PUBLIC
-  virtual void
-  add_callback_group_to_map(
-    rclcpp::CallbackGroup::SharedPtr group_ptr,
-    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-    WeakCallbackGroupsToNodesMap & weak_groups_to_nodes,
-    bool notify = true) RCPPUTILS_TSA_REQUIRES(mutex_);
-
-  /// Remove a callback group from the executor.
-  /**
-   * \see rclcpp::Executor::remove_callback_group
-   */
-  RCLCPP_PUBLIC
-  virtual void
-  remove_callback_group_from_map(
-    rclcpp::CallbackGroup::SharedPtr group_ptr,
-    WeakCallbackGroupsToNodesMap & weak_groups_to_nodes,
-    bool notify = true) RCPPUTILS_TSA_REQUIRES(mutex_);
-
-  RCLCPP_PUBLIC
-  bool
   get_next_ready_executable(AnyExecutable & any_executable);
 
-  RCLCPP_PUBLIC
-  bool
-  get_next_ready_executable_from_map(
-    AnyExecutable & any_executable,
-    const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
-
+  /// Wait for executable in ready state and populate union structure.
+  /**
+   * If an executable is ready, it will return immediately, otherwise
+   * block based on the timeout for work to become ready.
+   *
+   * \param[out] any_executable populated union structure of ready executable
+   * \param[in] timeout duration of time to wait for work, a negative value
+   *   (the defualt behavior), will make this function block indefinitely
+   * \return true if an executable was ready and any_executable was populated,
+   *   otherwise false
+   */
   RCLCPP_PUBLIC
   bool
   get_next_executable(
     AnyExecutable & any_executable,
     std::chrono::nanoseconds timeout = std::chrono::nanoseconds(-1));
 
-  /// Add all callback groups that can be automatically added from associated nodes.
-  /**
-   * The executor, before collecting entities, verifies if any callback group from
-   * nodes associated with the executor, which is not already associated to an executor,
-   * can be automatically added to this executor.
-   * This takes care of any callback group that has been added to a node but not explicitly added
-   * to the executor.
-   * It is important to note that in order for the callback groups to be automatically added to an
-   * executor through this function, the node of the callback groups needs to have been added
-   * through the `add_node` method.
-   */
-  RCLCPP_PUBLIC
-  virtual void
-  add_callback_groups_from_nodes_associated_to_executor() RCPPUTILS_TSA_REQUIRES(mutex_);
-
   /// Spinning state, used to prevent multi threaded calls to spin and to cancel blocking spins.
   std::atomic_bool spinning;
 
   /// Guard condition for signaling the rmw layer to wake up for special events.
-  rclcpp::GuardCondition interrupt_guard_condition_;
+  std::shared_ptr<rclcpp::GuardCondition> interrupt_guard_condition_;
 
+  /// Guard condition for signaling the rmw layer to wake up for system shutdown.
   std::shared_ptr<rclcpp::GuardCondition> shutdown_guard_condition_;
 
-  /// Wait set for managing entities that the rmw layer waits on.
-  rcl_wait_set_t wait_set_ = rcl_get_zero_initialized_wait_set();
-
-  // Mutex to protect the subsequent memory_strategy_.
   mutable std::mutex mutex_;
 
-  /// The memory strategy: an interface for handling user-defined memory allocation strategies.
-  memory_strategy::MemoryStrategy::SharedPtr
-  memory_strategy_ RCPPUTILS_TSA_PT_GUARDED_BY(mutex_);
-
   /// The context associated with this executor.
   std::shared_ptr<rclcpp::Context> context_;
 
@@ -560,33 +549,39 @@ protected:
   virtual void
   spin_once_impl(std::chrono::nanoseconds timeout);
 
-  typedef std::map<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr,
-      const rclcpp::GuardCondition *,
-      std::owner_less<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr>>
-    WeakNodesToGuardConditionsMap;
+  /// Waitable containing guard conditions controlling the executor flow.
+  /**
+   * This waitable contains the interrupt and shutdown guard condition, as well
+   * as the guard condition associated with each node and callback group.
+   * By default, if any change is detected in the monitored entities, the notify
+   * waitable will awake the executor and rebuild  the collections.
+   */
+  std::shared_ptr<rclcpp::executors::ExecutorNotifyWaitable> notify_waitable_;
 
-  /// maps nodes to guard conditions
-  WeakNodesToGuardConditionsMap
-  weak_nodes_to_guard_conditions_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+  std::atomic_bool entities_need_rebuild_;
 
-  /// maps callback groups associated to nodes
-  WeakCallbackGroupsToNodesMap
-  weak_groups_associated_with_executor_to_nodes_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+  /// Collector used to associate executable entities from nodes and guard conditions
+  rclcpp::executors::ExecutorEntitiesCollector collector_;
 
-  /// maps callback groups to nodes associated with executor
-  WeakCallbackGroupsToNodesMap
-  weak_groups_to_nodes_associated_with_executor_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+  /// Waitset to be waited on.
+  rclcpp::WaitSet wait_set_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
 
-  /// maps all callback groups to nodes
-  WeakCallbackGroupsToNodesMap
-  weak_groups_to_nodes_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+  /// Hold the current state of the collection being waited on by the waitset
+  rclcpp::executors::ExecutorEntitiesCollection current_collection_ RCPPUTILS_TSA_GUARDED_BY(
+    mutex_);
 
-  /// nodes that are associated with the executor
-  std::list<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr>
-  weak_nodes_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+  /// Hold the current state of the notify waitable being waited on by the waitset
+  std::shared_ptr<rclcpp::executors::ExecutorNotifyWaitable> current_notify_waitable_
+  RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// Hold the list of executables currently available to be executed.
+  std::deque<rclcpp::AnyExecutable> ready_executables_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
 
   /// shutdown callback handle registered to Context
   rclcpp::OnShutdownCallbackHandle shutdown_callback_handle_;
+
+  /// Pointer to implementation
+  std::unique_ptr<ExecutorImplementation> impl_;
 };
 
 }  // namespace rclcpp

rclcpp/include/rclcpp/executors.hpp

@@ -21,6 +21,7 @@
 #include "rclcpp/executors/multi_threaded_executor.hpp"
 #include "rclcpp/executors/single_threaded_executor.hpp"
 #include "rclcpp/executors/static_single_threaded_executor.hpp"
+#include "rclcpp/experimental/executors/events_executor/events_executor.hpp"
 #include "rclcpp/node.hpp"
 #include "rclcpp/utilities.hpp"
 #include "rclcpp/visibility_control.hpp"

rclcpp/include/rclcpp/executors/executor_entities_collection.hpp

@@ -0,0 +1,213 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__EXECUTORS__EXECUTOR_ENTITIES_COLLECTION_HPP_
+#define RCLCPP__EXECUTORS__EXECUTOR_ENTITIES_COLLECTION_HPP_
+
+#include <deque>
+#include <functional>
+#include <unordered_map>
+#include <vector>
+
+#include <rclcpp/any_executable.hpp>
+#include <rclcpp/node_interfaces/node_base.hpp>
+#include <rclcpp/callback_group.hpp>
+#include <rclcpp/executors/executor_notify_waitable.hpp>
+#include <rclcpp/visibility_control.hpp>
+#include <rclcpp/wait_result.hpp>
+#include <rclcpp/wait_set.hpp>
+
+namespace rclcpp
+{
+namespace executors
+{
+
+/// Structure to represent a single entity's entry in a collection
+template<typename EntityValueType>
+struct CollectionEntry
+{
+  /// Weak pointer to entity type
+  using EntityWeakPtr = typename EntityValueType::WeakPtr;
+  /// Shared pointer to entity type
+  using EntitySharedPtr = typename EntityValueType::SharedPtr;
+
+  /// The entity
+  EntityWeakPtr entity;
+
+  /// If relevant, the entity's corresponding callback_group
+  rclcpp::CallbackGroup::WeakPtr callback_group;
+};
+
+/// Update a collection based on another collection
+/*
+ * Iterates update_from and update_to to see which entities have been added/removed between
+ * the two collections.
+ *
+ * For each new entry (in update_from, but not in update_to),
+ *   add the entity and fire the on_added callback
+ * For each removed entry (in update_to, but not in update_from),
+ *   remove the entity and fire the on_removed callback.
+ *
+ *  \param[in] update_from The collection representing the next iteration's state
+ *  \param[inout] update_to The collection representing the current iteration's state
+ *  \param[in] on_added Callback fired when a new entity is detected
+ *  \param[in] on_removed Callback fired when an entity is removed
+ */
+template<typename CollectionType>
+void update_entities(
+  const CollectionType & update_from,
+  CollectionType & update_to,
+  std::function<void(const typename CollectionType::EntitySharedPtr &)> on_added,
+  std::function<void(const typename CollectionType::EntitySharedPtr &)> on_removed
+)
+{
+  for (auto it = update_to.begin(); it != update_to.end(); ) {
+    if (update_from.count(it->first) == 0) {
+      auto entity = it->second.entity.lock();
+      if (entity) {
+        on_removed(entity);
+      }
+      it = update_to.erase(it);
+    } else {
+      ++it;
+    }
+  }
+  for (auto it = update_from.begin(); it != update_from.end(); ++it) {
+    if (update_to.count(it->first) == 0) {
+      auto entity = it->second.entity.lock();
+      if (entity) {
+        on_added(entity);
+      }
+      update_to.insert(*it);
+    }
+  }
+}
+
+/// A collection of entities, indexed by their corresponding handles
+template<typename EntityKeyType, typename EntityValueType>
+class EntityCollection
+  : public std::unordered_map<const EntityKeyType *, CollectionEntry<EntityValueType>>
+{
+public:
+  /// Key type of the map
+  using Key = const EntityKeyType *;
+
+  /// Weak pointer to entity type
+  using EntityWeakPtr = typename EntityValueType::WeakPtr;
+
+  /// Shared pointer to entity type
+  using EntitySharedPtr = typename EntityValueType::SharedPtr;
+
+  /// Update this collection based on the contents of another collection
+  /**
+   * Update the internal state of this collection, firing callbacks when entities have been
+   * added or removed.
+   *
+   * \param[in] other Collection to compare to
+   * \param[in] on_added Callback for when entities have been added
+   * \param[in] on_removed Callback for when entities have been removed
+   */
+  void update(
+    const EntityCollection<EntityKeyType, EntityValueType> & other,
+    std::function<void(const EntitySharedPtr &)> on_added,
+    std::function<void(const EntitySharedPtr &)> on_removed)
+  {
+    update_entities(other, *this, on_added, on_removed);
+  }
+};
+
+/// Represent the total set of entities for a single executor
+/**
+ * This allows the entities to be stored from ExecutorEntitiesCollector.
+ * The structure also makes in convenient to re-evaluate when entities have been added or removed.
+ */
+struct ExecutorEntitiesCollection
+{
+  /// Collection type for timer entities
+  using TimerCollection = EntityCollection<rcl_timer_t, rclcpp::TimerBase>;
+
+  /// Collection type for subscription entities
+  using SubscriptionCollection = EntityCollection<rcl_subscription_t, rclcpp::SubscriptionBase>;
+
+  /// Collection type for client entities
+  using ClientCollection = EntityCollection<rcl_client_t, rclcpp::ClientBase>;
+
+  /// Collection type for service entities
+  using ServiceCollection = EntityCollection<rcl_service_t, rclcpp::ServiceBase>;
+
+  /// Collection type for waitable entities
+  using WaitableCollection = EntityCollection<rclcpp::Waitable, rclcpp::Waitable>;
+
+  /// Collection type for guard condition entities
+  using GuardConditionCollection = EntityCollection<rcl_guard_condition_t, rclcpp::GuardCondition>;
+
+  /// Collection of timers currently in use by the executor.
+  TimerCollection timers;
+
+  /// Collection of subscriptions currently in use by the executor.
+  SubscriptionCollection subscriptions;
+
+  /// Collection of clients currently in use by the executor.
+  ClientCollection clients;
+
+  /// Collection of services currently in use by the executor.
+  ServiceCollection services;
+
+  /// Collection of guard conditions currently in use by the executor.
+  GuardConditionCollection guard_conditions;
+
+  /// Collection of waitables currently in use by the executor.
+  WaitableCollection waitables;
+
+  /// Check if the entities collection is empty
+  /**
+   * \return true if all member collections are empty, false otherwise
+  */
+  bool empty() const;
+
+  /// Clear the entities collection
+  void clear();
+};
+
+/// Build an entities collection from callback groups
+/**
+ * Iterates a list of callback groups and adds entities from each valid group
+ *
+ * \param[in] callback_groups List of callback groups to check for entities
+ * \param[inout] colletion Entities collection to populate with found entities
+ */
+void
+build_entities_collection(
+  const std::vector<rclcpp::CallbackGroup::WeakPtr> & callback_groups,
+  ExecutorEntitiesCollection & collection);
+
+/// Build a queue of executables ready to be executed
+/**
+ * Iterates a list of entities and adds them to a queue if they are ready.
+ *
+ * \param[in] collection Collection of entities corresponding to the current wait set.
+ * \param[in] wait_result Result of rclcpp::WaitSet::wait corresponding to the collection.
+ * \param[inout] queue of executables to append new ready executables to
+ * \return number of new ready executables
+ */
+size_t
+ready_executables(
+  const ExecutorEntitiesCollection & collection,
+  rclcpp::WaitResult<rclcpp::WaitSet> & wait_result,
+  std::deque<rclcpp::AnyExecutable> & executables
+);
+}  // namespace executors
+}  // namespace rclcpp
+
+#endif  // RCLCPP__EXECUTORS__EXECUTOR_ENTITIES_COLLECTION_HPP_

rclcpp/include/rclcpp/executors/executor_entities_collector.hpp

@@ -0,0 +1,270 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__EXECUTORS__EXECUTOR_ENTITIES_COLLECTOR_HPP_
+#define RCLCPP__EXECUTORS__EXECUTOR_ENTITIES_COLLECTOR_HPP_
+
+#include <map>
+#include <memory>
+#include <mutex>
+#include <set>
+#include <vector>
+
+#include "rcpputils/thread_safety_annotations.hpp"
+
+#include <rclcpp/any_executable.hpp>
+#include <rclcpp/node_interfaces/node_base.hpp>
+#include <rclcpp/callback_group.hpp>
+#include <rclcpp/executors/executor_notify_waitable.hpp>
+#include <rclcpp/visibility_control.hpp>
+#include <rclcpp/wait_set.hpp>
+#include <rclcpp/wait_result.hpp>
+
+namespace rclcpp
+{
+namespace executors
+{
+
+/// Class to monitor a set of nodes and callback groups for changes in entity membership
+/**
+ * This is to be used with an executor to track the membership of various nodes, groups,
+ * and entities (timers, subscriptions, clients, services, etc) and report status to the
+ * executor.
+ *
+ * In general, users will add either nodes or callback groups to an executor.
+ * Each node may have callback groups that are automatically associated with executors,
+ * or callback groups that must be manually associated with an executor.
+ *
+ * This object tracks both types of callback groups as well as nodes that have been
+ * previously added to the executor.
+ * When a new callback group is added/removed or new entities are added/removed, the
+ * corresponding node or callback group will signal this to the executor so that the
+ * entity collection may be rebuilt according to that executor's implementation.
+ *
+ */
+class ExecutorEntitiesCollector
+{
+public:
+  /// Constructor
+  /**
+   * \param[in] notify_waitable Waitable that is used to signal to the executor
+   *   when nodes or callback groups have been added or removed.
+   */
+  RCLCPP_PUBLIC
+  explicit ExecutorEntitiesCollector(
+    std::shared_ptr<ExecutorNotifyWaitable> notify_waitable);
+
+  /// Destructor
+  RCLCPP_PUBLIC
+  ~ExecutorEntitiesCollector();
+
+  /// Indicate if the entities collector has pending additions or removals.
+  /**
+   * \return true if there are pending additions or removals
+   */
+  bool has_pending() const;
+
+  /// Add a node to the entity collector
+  /**
+   * \param[in] node_ptr a shared pointer that points to a node base interface
+   * \throw std::runtime_error if the node is associated with an executor
+   */
+  RCLCPP_PUBLIC
+  void
+  add_node(rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr);
+
+  /// Remove a node from the entity collector
+  /**
+   * \param[in] node_ptr a shared pointer that points to a node base interface
+   * \throw std::runtime_error if the node is associated with an executor
+   * \throw std::runtime_error if the node is associated with this executor
+   */
+  RCLCPP_PUBLIC
+  void
+  remove_node(rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr);
+
+  /// Add a callback group to the entity collector
+  /**
+   * \param[in] group_ptr a shared pointer that points to a callback group
+   * \throw std::runtime_error if the callback_group is associated with an executor
+   */
+  RCLCPP_PUBLIC
+  void
+  add_callback_group(rclcpp::CallbackGroup::SharedPtr group_ptr);
+
+  /// Remove a callback group from the entity collector
+  /**
+   * \param[in] group_ptr a shared pointer that points to a callback group
+   * \throw std::runtime_error if the callback_group is not associated with an executor
+   * \throw std::runtime_error if the callback_group is not associated with this executor
+   */
+  RCLCPP_PUBLIC
+  void
+  remove_callback_group(rclcpp::CallbackGroup::SharedPtr group_ptr);
+
+  /// Get all callback groups known to this entity collector
+  /**
+   * This will include manually added and automatically added (node associated) groups
+   * \return vector of all callback groups
+   */
+  RCLCPP_PUBLIC
+  std::vector<rclcpp::CallbackGroup::WeakPtr>
+  get_all_callback_groups() const;
+
+  /// Get manually-added callback groups known to this entity collector
+  /**
+   * This will include callback groups that have been added via add_callback_group
+   * \return vector of manually-added callback groups
+   */
+  RCLCPP_PUBLIC
+  std::vector<rclcpp::CallbackGroup::WeakPtr>
+  get_manually_added_callback_groups() const;
+
+  /// Get automatically-added callback groups known to this entity collector
+  /**
+   * This will include callback groups that are associated with nodes added via add_node
+   * \return vector of automatically-added callback groups
+   */
+  RCLCPP_PUBLIC
+  std::vector<rclcpp::CallbackGroup::WeakPtr>
+  get_automatically_added_callback_groups() const;
+
+  /// Update the underlying collections
+  /**
+   * This will prune nodes and callback groups that are no longer valid as well
+   * as add new callback groups from any associated nodes.
+   */
+  RCLCPP_PUBLIC
+  void
+  update_collections();
+
+protected:
+  using NodeCollection = std::set<
+    rclcpp::node_interfaces::NodeBaseInterface::WeakPtr,
+    std::owner_less<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr>>;
+
+  using CallbackGroupCollection = std::set<
+    rclcpp::CallbackGroup::WeakPtr,
+    std::owner_less<rclcpp::CallbackGroup::WeakPtr>>;
+
+  using WeakNodesToGuardConditionsMap = std::map<
+    rclcpp::node_interfaces::NodeBaseInterface::WeakPtr,
+    rclcpp::GuardCondition::WeakPtr,
+    std::owner_less<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr>>;
+
+  using WeakGroupsToGuardConditionsMap = std::map<
+    rclcpp::CallbackGroup::WeakPtr,
+    rclcpp::GuardCondition::WeakPtr,
+    std::owner_less<rclcpp::CallbackGroup::WeakPtr>>;
+
+  /// Implementation of removing a node from the collector.
+  /**
+   * This will disassociate the node from the collector and remove any
+   * automatically-added callback groups
+   *
+   * This takes and returns an iterator so it may be used as:
+   *
+   * it = remove_weak_node(it);
+   *
+   * \param[in] weak_node iterator to the weak node to be removed
+   * \return Valid updated iterator in the same collection
+   */
+  RCLCPP_PUBLIC
+  NodeCollection::iterator
+  remove_weak_node(NodeCollection::iterator weak_node) RCPPUTILS_TSA_REQUIRES(mutex_);
+
+  /// Implementation of removing a callback group from the collector.
+  /**
+   * This will disassociate the callback group from the collector
+   *
+   * This takes and returns an iterator so it may be used as:
+   *
+   * it = remove_weak_callback_group(it);
+   *
+   * \param[in] weak_group_it iterator to the weak group to be removed
+   * \param[in] collection the collection to remove the group from
+   *   (manually or automatically added)
+   * \return Valid updated iterator in the same collection
+   */
+  RCLCPP_PUBLIC
+  CallbackGroupCollection::iterator
+  remove_weak_callback_group(
+    CallbackGroupCollection::iterator weak_group_it,
+    CallbackGroupCollection & collection) RCPPUTILS_TSA_REQUIRES(mutex_);
+
+  /// Implementation of adding a callback group
+  /**
+   * \param[in] group_ptr the group to add
+   * \param[in] collection the collection to add the group to
+   */
+  RCLCPP_PUBLIC
+  void
+  add_callback_group_to_collection(
+    rclcpp::CallbackGroup::SharedPtr group_ptr,
+    CallbackGroupCollection & collection)  RCPPUTILS_TSA_REQUIRES(mutex_);
+
+  /// Iterate over queued added/remove nodes and callback_groups
+  RCLCPP_PUBLIC
+  void
+  process_queues() RCPPUTILS_TSA_REQUIRES(mutex_);
+
+  /// Check a collection of nodes and add any new callback_groups that
+  /// are set to be automatically associated via the node.
+  RCLCPP_PUBLIC
+  void
+  add_automatically_associated_callback_groups(
+    const NodeCollection & nodes_to_check) RCPPUTILS_TSA_REQUIRES(mutex_);
+
+  /// Check all nodes and group for expired weak pointers and remove them.
+  RCLCPP_PUBLIC
+  void
+  prune_invalid_nodes_and_groups() RCPPUTILS_TSA_REQUIRES(mutex_);
+
+  /// mutex to protect collections and pending queues
+  mutable std::mutex mutex_;
+
+  /// Callback groups that were added via `add_callback_group`
+  CallbackGroupCollection manually_added_groups_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// Callback groups that were added by their association with added nodes
+  CallbackGroupCollection automatically_added_groups_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// nodes that are associated with the executor
+  NodeCollection weak_nodes_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// Track guard conditions associated with added nodes
+  WeakNodesToGuardConditionsMap weak_nodes_to_guard_conditions_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// Track guard conditions associated with added callback groups
+  WeakGroupsToGuardConditionsMap weak_groups_to_guard_conditions_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// nodes that have been added since the last update.
+  NodeCollection pending_added_nodes_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// nodes that have been removed since the last update.
+  NodeCollection pending_removed_nodes_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// callback groups that have been added since the last update.
+  CallbackGroupCollection pending_manually_added_groups_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// callback groups that have been removed since the last update.
+  CallbackGroupCollection pending_manually_removed_groups_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+
+  /// Waitable to add guard conditions to
+  std::shared_ptr<ExecutorNotifyWaitable> notify_waitable_;
+};
+}  // namespace executors
+}  // namespace rclcpp
+//
+#endif  // RCLCPP__EXECUTORS__EXECUTOR_ENTITIES_COLLECTOR_HPP_

rclcpp/include/rclcpp/executors/executor_notify_waitable.hpp

@@ -0,0 +1,158 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__EXECUTORS__EXECUTOR_NOTIFY_WAITABLE_HPP_
+#define RCLCPP__EXECUTORS__EXECUTOR_NOTIFY_WAITABLE_HPP_
+
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <set>
+
+#include "rclcpp/guard_condition.hpp"
+#include "rclcpp/waitable.hpp"
+
+namespace rclcpp
+{
+namespace executors
+{
+
+/// Maintain a collection of guard conditions from associated nodes and callback groups
+/// to signal to the executor when associated entities have changed.
+class ExecutorNotifyWaitable : public rclcpp::Waitable
+{
+public:
+  RCLCPP_SMART_PTR_DEFINITIONS(ExecutorNotifyWaitable)
+
+  // Constructor
+  /**
+   * \param[in] on_execute_callback Callback to execute when one of the conditions
+   *   of this waitable has signaled the wait_set.
+   */
+  RCLCPP_PUBLIC
+  explicit ExecutorNotifyWaitable(std::function<void(void)> on_execute_callback = {});
+
+  // Destructor
+  RCLCPP_PUBLIC
+  ~ExecutorNotifyWaitable() override = default;
+
+  RCLCPP_PUBLIC
+  ExecutorNotifyWaitable(const ExecutorNotifyWaitable & other);
+
+
+  RCLCPP_PUBLIC
+  ExecutorNotifyWaitable & operator=(const ExecutorNotifyWaitable & other);
+
+  /// Add conditions to the wait set
+  /**
+   * \param[inout] wait_set structure that conditions will be added to
+   */
+  RCLCPP_PUBLIC
+  void
+  add_to_wait_set(rcl_wait_set_t * wait_set) override;
+
+  /// Check conditions against the wait set
+  /**
+   * \param[inout] wait_set structure that internal elements will be checked against.
+   * \return true if this waitable is ready to be executed, false otherwise.
+   */
+  RCLCPP_PUBLIC
+  bool
+  is_ready(rcl_wait_set_t * wait_set) override;
+
+  /// Perform work associated with the waitable.
+  /**
+   * This will call the callback provided in the constructor.
+   * \param[in] data Data to be use for the execute, if available, else nullptr.
+   */
+  RCLCPP_PUBLIC
+  void
+  execute(std::shared_ptr<void> & data) override;
+
+  /// Retrieve data to be used in the next execute call.
+  /**
+   * \return If available, data to be used, otherwise nullptr
+   */
+  RCLCPP_PUBLIC
+  std::shared_ptr<void>
+  take_data() override;
+
+  /// Take the data from an entity ID so that it can be consumed with `execute`.
+  /**
+   * \param[in] id ID of the entity to take data from.
+   * \return If available, data to be used, otherwise nullptr
+   * \sa rclcpp::Waitable::take_data_by_entity_id
+   */
+  RCLCPP_PUBLIC
+  std::shared_ptr<void>
+  take_data_by_entity_id(size_t id) override;
+
+  /// Set a callback to be called whenever the waitable becomes ready.
+  /**
+   * \param[in] callback callback to set
+   * \sa rclcpp::Waitable::set_on_ready_callback
+   */
+  RCLCPP_PUBLIC
+  void
+  set_on_ready_callback(std::function<void(size_t, int)> callback) override;
+
+  /// Add a guard condition to be waited on.
+  /**
+   * \param[in] guard_condition The guard condition to add.
+   */
+  RCLCPP_PUBLIC
+  void
+  add_guard_condition(rclcpp::GuardCondition::WeakPtr guard_condition);
+
+  /// Unset any callback registered via set_on_ready_callback.
+  /**
+   * \sa rclcpp::Waitable::clear_on_ready_callback
+   */
+  RCLCPP_PUBLIC
+  void
+  clear_on_ready_callback() override;
+
+  /// Remove a guard condition from being waited on.
+  /**
+   * \param[in] weak_guard_condition The guard condition to remove.
+   */
+  RCLCPP_PUBLIC
+  void
+  remove_guard_condition(rclcpp::GuardCondition::WeakPtr weak_guard_condition);
+
+  /// Get the number of ready guard_conditions
+  /**
+   * \return The number of guard_conditions associated with the Waitable.
+   */
+  RCLCPP_PUBLIC
+  size_t
+  get_number_of_ready_guard_conditions() override;
+
+private:
+  /// Callback to run when waitable executes
+  std::function<void(void)> execute_callback_;
+
+  std::mutex guard_condition_mutex_;
+
+  std::function<void(size_t)> on_ready_callback_;
+
+  /// The collection of guard conditions to be waited on.
+  std::set<rclcpp::GuardCondition::WeakPtr,
+    std::owner_less<rclcpp::GuardCondition::WeakPtr>> notify_guard_conditions_;
+};
+
+}  // namespace executors
+}  // namespace rclcpp
+
+#endif  // RCLCPP__EXECUTORS__EXECUTOR_NOTIFY_WAITABLE_HPP_

rclcpp/include/rclcpp/executors/multi_threaded_executor.hpp

@@ -47,7 +47,7 @@ public:
    *
    * \param options common options for all executors
    * \param number_of_threads number of threads to have in the thread pool,
-   *   the default 0 will use the number of cpu cores found instead
+   *   the default 0 will use the number of cpu cores found (minimum of 2)
    * \param yield_before_execute if true std::this_thread::yield() is called
    * \param timeout maximum time to wait
    */

rclcpp/include/rclcpp/executors/static_executor_entities_collector.hpp

@@ -1,357 +0,0 @@
-// Copyright 2020 Open Source Robotics Foundation, Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#ifndef RCLCPP__EXECUTORS__STATIC_EXECUTOR_ENTITIES_COLLECTOR_HPP_
-#define RCLCPP__EXECUTORS__STATIC_EXECUTOR_ENTITIES_COLLECTOR_HPP_
-
-#include <chrono>
-#include <list>
-#include <map>
-#include <memory>
-#include <vector>
-
-#include "rcl/guard_condition.h"
-#include "rcl/wait.h"
-
-#include "rclcpp/experimental/executable_list.hpp"
-#include "rclcpp/macros.hpp"
-#include "rclcpp/memory_strategy.hpp"
-#include "rclcpp/visibility_control.hpp"
-#include "rclcpp/waitable.hpp"
-
-namespace rclcpp
-{
-namespace executors
-{
-typedef std::map<rclcpp::CallbackGroup::WeakPtr,
-    rclcpp::node_interfaces::NodeBaseInterface::WeakPtr,
-    std::owner_less<rclcpp::CallbackGroup::WeakPtr>> WeakCallbackGroupsToNodesMap;
-
-class StaticExecutorEntitiesCollector final
-  : public rclcpp::Waitable,
-  public std::enable_shared_from_this<StaticExecutorEntitiesCollector>
-{
-public:
-  RCLCPP_SMART_PTR_DEFINITIONS(StaticExecutorEntitiesCollector)
-
-  // Constructor
-  RCLCPP_PUBLIC
-  StaticExecutorEntitiesCollector() = default;
-
-  // Destructor
-  RCLCPP_PUBLIC
-  ~StaticExecutorEntitiesCollector();
-
-  /// Initialize StaticExecutorEntitiesCollector
-  /**
-   * \param p_wait_set A reference to the wait set to be used in the executor
-   * \param memory_strategy Shared pointer to the memory strategy to set.
-   * \throws std::runtime_error if memory strategy is null
-   */
-  RCLCPP_PUBLIC
-  void
-  init(
-    rcl_wait_set_t * p_wait_set,
-    rclcpp::memory_strategy::MemoryStrategy::SharedPtr memory_strategy);
-
-  /// Finalize StaticExecutorEntitiesCollector to clear resources
-  RCLCPP_PUBLIC
-  bool
-  is_init() {return initialized_;}
-
-  RCLCPP_PUBLIC
-  void
-  fini();
-
-  /// Execute the waitable.
-  RCLCPP_PUBLIC
-  void
-  execute(std::shared_ptr<void> & data) override;
-
-  /// Take the data so that it can be consumed with `execute`.
-  /**
-   * For `StaticExecutorEntitiesCollector`, this always return `nullptr`.
-   * \sa rclcpp::Waitable::take_data()
-   */
-  RCLCPP_PUBLIC
-  std::shared_ptr<void>
-  take_data() override;
-
-  /// Function to add_handles_to_wait_set and wait for work and
-  /**
-   * block until the wait set is ready or until the timeout has been exceeded.
-   * \throws std::runtime_error if wait set couldn't be cleared or filled.
-   * \throws any rcl errors from rcl_wait, \see rclcpp::exceptions::throw_from_rcl_error()
-   */
-  RCLCPP_PUBLIC
-  void
-  refresh_wait_set(std::chrono::nanoseconds timeout = std::chrono::nanoseconds(-1));
-
-  /**
-   * \throws std::runtime_error if it couldn't add guard condition to wait set
-   */
-  RCLCPP_PUBLIC
-  void
-  add_to_wait_set(rcl_wait_set_t * wait_set) override;
-
-  RCLCPP_PUBLIC
-  size_t
-  get_number_of_ready_guard_conditions() override;
-
-  /// Add a callback group to an executor.
-  /**
-   * \see rclcpp::Executor::add_callback_group
-   */
-  RCLCPP_PUBLIC
-  bool
-  add_callback_group(
-    rclcpp::CallbackGroup::SharedPtr group_ptr,
-    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr);
-
-  /// Add a callback group to an executor.
-  /**
-   * \see rclcpp::Executor::add_callback_group
-   * \return boolean whether the node from the callback group is new
-   */
-  RCLCPP_PUBLIC
-  bool
-  add_callback_group(
-    rclcpp::CallbackGroup::SharedPtr group_ptr,
-    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-    WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
-
-  /// Remove a callback group from the executor.
-  /**
-   * \see rclcpp::Executor::remove_callback_group
-   */
-  RCLCPP_PUBLIC
-  bool
-  remove_callback_group(
-    rclcpp::CallbackGroup::SharedPtr group_ptr);
-
-  /// Remove a callback group from the executor.
-  /**
-   * \see rclcpp::Executor::remove_callback_group_from_map
-   */
-  RCLCPP_PUBLIC
-  bool
-  remove_callback_group_from_map(
-    rclcpp::CallbackGroup::SharedPtr group_ptr,
-    WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
-
-  /**
-   * \see rclcpp::Executor::add_node()
-   * \throw std::runtime_error if node was already added
-   */
-  RCLCPP_PUBLIC
-  bool
-  add_node(
-    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr);
-
-  /**
-   * \see rclcpp::Executor::remove_node()
-   * \throw std::runtime_error if no guard condition is associated with node.
-   */
-  RCLCPP_PUBLIC
-  bool
-  remove_node(
-    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr);
-
-  RCLCPP_PUBLIC
-  std::vector<rclcpp::CallbackGroup::WeakPtr>
-  get_all_callback_groups();
-
-  /// Get callback groups that belong to executor.
-  /**
-   * \see rclcpp::Executor::get_manually_added_callback_groups()
-   */
-  RCLCPP_PUBLIC
-  std::vector<rclcpp::CallbackGroup::WeakPtr>
-  get_manually_added_callback_groups();
-
-  /// Get callback groups that belong to executor.
-  /**
-   * \see rclcpp::Executor::get_automatically_added_callback_groups_from_nodes()
-   */
-  RCLCPP_PUBLIC
-  std::vector<rclcpp::CallbackGroup::WeakPtr>
-  get_automatically_added_callback_groups_from_nodes();
-
-  /// Complete all available queued work without blocking.
-  /**
-   * This function checks if after the guard condition was triggered
-   * (or a spurious wakeup happened) we are really ready to execute
-   * i.e. re-collect entities
-   */
-  RCLCPP_PUBLIC
-  bool
-  is_ready(rcl_wait_set_t * wait_set) override;
-
-  /// Return number of timers
-  /**
-   * \return number of timers
-   */
-  RCLCPP_PUBLIC
-  size_t
-  get_number_of_timers() {return exec_list_.number_of_timers;}
-
-  /// Return number of subscriptions
-  /**
-   * \return number of subscriptions
-   */
-  RCLCPP_PUBLIC
-  size_t
-  get_number_of_subscriptions() {return exec_list_.number_of_subscriptions;}
-
-  /// Return number of services
-  /**
-   * \return number of services
-   */
-  RCLCPP_PUBLIC
-  size_t
-  get_number_of_services() {return exec_list_.number_of_services;}
-
-  /// Return number of clients
-  /**
-   * \return number of clients
-   */
-  RCLCPP_PUBLIC
-  size_t
-  get_number_of_clients() {return exec_list_.number_of_clients;}
-
-  /// Return number of waitables
-  /**
-   * \return number of waitables
-   */
-  RCLCPP_PUBLIC
-  size_t
-  get_number_of_waitables() {return exec_list_.number_of_waitables;}
-
-  /** Return a SubscritionBase Sharedptr by index.
-   * \param[in] i The index of the SubscritionBase
-   * \return a SubscritionBase shared pointer
-   * \throws std::out_of_range if the argument is higher than the size of the structrue.
-   */
-  RCLCPP_PUBLIC
-  rclcpp::SubscriptionBase::SharedPtr
-  get_subscription(size_t i) {return exec_list_.subscription[i];}
-
-  /** Return a TimerBase Sharedptr by index.
-   * \param[in] i The index of the TimerBase
-   * \return a TimerBase shared pointer
-   * \throws std::out_of_range if the argument is higher than the size.
-   */
-  RCLCPP_PUBLIC
-  rclcpp::TimerBase::SharedPtr
-  get_timer(size_t i) {return exec_list_.timer[i];}
-
-  /** Return a ServiceBase Sharedptr by index.
-   * \param[in] i The index of the ServiceBase
-   * \return a ServiceBase shared pointer
-   * \throws std::out_of_range if the argument is higher than the size.
-   */
-  RCLCPP_PUBLIC
-  rclcpp::ServiceBase::SharedPtr
-  get_service(size_t i) {return exec_list_.service[i];}
-
-  /** Return a ClientBase Sharedptr by index
-   * \param[in] i The index of the ClientBase
-   * \return a ClientBase shared pointer
-   * \throws std::out_of_range if the argument is higher than the size.
-   */
-  RCLCPP_PUBLIC
-  rclcpp::ClientBase::SharedPtr
-  get_client(size_t i) {return exec_list_.client[i];}
-
-  /** Return a Waitable Sharedptr by index
-   * \param[in] i The index of the Waitable
-   * \return a Waitable shared pointer
-   * \throws std::out_of_range if the argument is higher than the size.
-   */
-  RCLCPP_PUBLIC
-  rclcpp::Waitable::SharedPtr
-  get_waitable(size_t i) {return exec_list_.waitable[i];}
-
-private:
-  /// Function to reallocate space for entities in the wait set.
-  /**
-   * \throws std::runtime_error if wait set couldn't be cleared or resized.
-   */
-  void
-  prepare_wait_set();
-
-  void
-  fill_executable_list();
-
-  void
-  fill_memory_strategy();
-
-  /// Return true if the node belongs to the collector
-  /**
-   * \param[in] node_ptr a node base interface shared pointer
-   * \param[in] weak_groups_to_nodes map to nodes to lookup
-   * \return boolean whether a node belongs the collector
-   */
-  bool
-  has_node(
-    const rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-    const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes) const;
-
-  /// Add all callback groups that can be automatically added by any executor
-  /// and is not already associated with an executor from nodes
-  /// that are associated with executor
-  /**
-   * \see rclcpp::Executor::add_callback_groups_from_nodes_associated_to_executor()
-   */
-  void
-  add_callback_groups_from_nodes_associated_to_executor();
-
-  void
-  fill_executable_list_from_map(const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
-
-  /// Memory strategy: an interface for handling user-defined memory allocation strategies.
-  rclcpp::memory_strategy::MemoryStrategy::SharedPtr memory_strategy_;
-
-  // maps callback groups to nodes.
-  WeakCallbackGroupsToNodesMap weak_groups_associated_with_executor_to_nodes_;
-  // maps callback groups to nodes.
-  WeakCallbackGroupsToNodesMap weak_groups_to_nodes_associated_with_executor_;
-
-  typedef std::map<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr,
-      const rclcpp::GuardCondition *,
-      std::owner_less<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr>>
-    WeakNodesToGuardConditionsMap;
-  WeakNodesToGuardConditionsMap weak_nodes_to_guard_conditions_;
-
-  /// List of weak nodes registered in the static executor
-  std::list<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr> weak_nodes_;
-
-  // Mutex to protect vector of new nodes.
-  std::mutex new_nodes_mutex_;
-  std::vector<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr> new_nodes_;
-
-  /// Wait set for managing entities that the rmw layer waits on.
-  rcl_wait_set_t * p_wait_set_ = nullptr;
-
-  /// Executable list: timers, subscribers, clients, services and waitables
-  rclcpp::experimental::ExecutableList exec_list_;
-
-  /// Bool to check if the entities collector has been initialized
-  bool initialized_ = false;
-};
-
-}  // namespace executors
-}  // namespace rclcpp
-
-#endif  // RCLCPP__EXECUTORS__STATIC_EXECUTOR_ENTITIES_COLLECTOR_HPP_

rclcpp/include/rclcpp/executors/static_single_threaded_executor.hpp

@@ -15,24 +15,13 @@
 #ifndef RCLCPP__EXECUTORS__STATIC_SINGLE_THREADED_EXECUTOR_HPP_
 #define RCLCPP__EXECUTORS__STATIC_SINGLE_THREADED_EXECUTOR_HPP_
 
+#include <atomic>
 #include <chrono>
-#include <cassert>
-#include <cstdlib>
 #include <memory>
-#include <vector>
-#include <string>
-
-#include "rmw/rmw.h"
 
 #include "rclcpp/executor.hpp"
-#include "rclcpp/executors/static_executor_entities_collector.hpp"
-#include "rclcpp/experimental/executable_list.hpp"
-#include "rclcpp/macros.hpp"
-#include "rclcpp/memory_strategies.hpp"
-#include "rclcpp/node.hpp"
-#include "rclcpp/rate.hpp"
-#include "rclcpp/utilities.hpp"
-#include "rclcpp/visibility_control.hpp"
+#include "rclcpp/executors/executor_entities_collection.hpp"
+#include "rclcpp/executors/single_threaded_executor.hpp"
 
 namespace rclcpp
 {
@@ -65,7 +54,7 @@ public:
   explicit StaticSingleThreadedExecutor(
     const rclcpp::ExecutorOptions & options = rclcpp::ExecutorOptions());
 
-  /// Default destrcutor.
+  /// Default destructor.
   RCLCPP_PUBLIC
   virtual ~StaticSingleThreadedExecutor();
 
@@ -116,92 +105,20 @@ public:
   void
   spin_all(std::chrono::nanoseconds max_duration) override;
 
-  /// Add a callback group to an executor.
-  /**
-   * \sa rclcpp::Executor::add_callback_group
-   */
-  RCLCPP_PUBLIC
-  void
-  add_callback_group(
-    rclcpp::CallbackGroup::SharedPtr group_ptr,
-    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-    bool notify = true) override;
-
-  /// Remove callback group from the executor
-  /**
-   * \sa rclcpp::Executor::remove_callback_group
-   */
-  RCLCPP_PUBLIC
-  void
-  remove_callback_group(
-    rclcpp::CallbackGroup::SharedPtr group_ptr,
-    bool notify = true) override;
-
-  /// Add a node to the executor.
-  /**
-   * \sa rclcpp::Executor::add_node
-   */
-  RCLCPP_PUBLIC
-  void
-  add_node(
-    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-    bool notify = true) override;
-
-  /// Convenience function which takes Node and forwards NodeBaseInterface.
-  /**
-   * \sa rclcpp::StaticSingleThreadedExecutor::add_node
-   */
-  RCLCPP_PUBLIC
-  void
-  add_node(std::shared_ptr<rclcpp::Node> node_ptr, bool notify = true) override;
-
-  /// Remove a node from the executor.
-  /**
-   * \sa rclcpp::Executor::remove_node
-   */
-  RCLCPP_PUBLIC
-  void
-  remove_node(
-    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-    bool notify = true) override;
-
-  /// Convenience function which takes Node and forwards NodeBaseInterface.
-  /**
-   * \sa rclcpp::Executor::remove_node
-   */
-  RCLCPP_PUBLIC
-  void
-  remove_node(std::shared_ptr<rclcpp::Node> node_ptr, bool notify = true) override;
-
-  RCLCPP_PUBLIC
-  std::vector<rclcpp::CallbackGroup::WeakPtr>
-  get_all_callback_groups() override;
-
-  /// Get callback groups that belong to executor.
-  /**
-   * \sa rclcpp::Executor::get_manually_added_callback_groups()
-   */
-  RCLCPP_PUBLIC
-  std::vector<rclcpp::CallbackGroup::WeakPtr>
-  get_manually_added_callback_groups() override;
-
-  /// Get callback groups that belong to executor.
-  /**
-   * \sa rclcpp::Executor::get_automatically_added_callback_groups_from_nodes()
-   */
-  RCLCPP_PUBLIC
-  std::vector<rclcpp::CallbackGroup::WeakPtr>
-  get_automatically_added_callback_groups_from_nodes() override;
-
 protected:
   /**
    * @brief Executes ready executables from wait set.
+   * @param collection entities to evaluate for ready executables.
+   * @param wait_result result to check for ready executables.
    * @param spin_once if true executes only the first ready executable.
    * @return true if any executable was ready.
    */
   RCLCPP_PUBLIC
   bool
-  execute_ready_executables(bool spin_once = false);
+  execute_ready_executables(
+    const rclcpp::executors::ExecutorEntitiesCollection & collection,
+    rclcpp::WaitResult<rclcpp::WaitSet> & wait_result,
+    bool spin_once);
 
   RCLCPP_PUBLIC
   void
@@ -213,8 +130,6 @@ protected:
 
 private:
   RCLCPP_DISABLE_COPY(StaticSingleThreadedExecutor)
-
-  StaticExecutorEntitiesCollector::SharedPtr entities_collector_;
 };
 
 }  // namespace executors

rclcpp/include/rclcpp/experimental/buffers/intra_process_buffer.hpp

@@ -24,6 +24,7 @@
 #include "rclcpp/allocator/allocator_deleter.hpp"
 #include "rclcpp/experimental/buffers/buffer_implementation_base.hpp"
 #include "rclcpp/macros.hpp"
+#include "tracetools/tracetools.h"
 
 namespace rclcpp
 {
@@ -94,6 +95,10 @@ public:
 
     buffer_ = std::move(buffer_impl);
 
+    TRACEPOINT(
+      rclcpp_buffer_to_ipb,
+      static_cast<const void *>(buffer_.get()),
+      static_cast<const void *>(this));
     if (!allocator) {
       message_allocator_ = std::make_shared<MessageAlloc>();
     } else {

rclcpp/include/rclcpp/experimental/buffers/ring_buffer_implementation.hpp

@@ -25,6 +25,7 @@
 #include "rclcpp/logging.hpp"
 #include "rclcpp/macros.hpp"
 #include "rclcpp/visibility_control.hpp"
+#include "tracetools/tracetools.h"
 
 namespace rclcpp
 {
@@ -51,6 +52,7 @@ public:
     if (capacity == 0) {
       throw std::invalid_argument("capacity must be a positive, non-zero value");
     }
+    TRACEPOINT(rclcpp_construct_ring_buffer, static_cast<const void *>(this), capacity_);
   }
 
   virtual ~RingBufferImplementation() {}
@@ -67,6 +69,12 @@ public:
 
     write_index_ = next_(write_index_);
     ring_buffer_[write_index_] = std::move(request);
+    TRACEPOINT(
+      rclcpp_ring_buffer_enqueue,
+      static_cast<const void *>(this),
+      write_index_,
+      size_ + 1,
+      is_full_());
 
     if (is_full_()) {
       read_index_ = next_(read_index_);
@@ -86,11 +94,15 @@ public:
     std::lock_guard<std::mutex> lock(mutex_);
 
     if (!has_data_()) {
-      RCLCPP_ERROR(rclcpp::get_logger("rclcpp"), "Calling dequeue on empty intra-process buffer");
-      throw std::runtime_error("Calling dequeue on empty intra-process buffer");
+      return BufferT();
     }
 
     auto request = std::move(ring_buffer_[read_index_]);
+    TRACEPOINT(
+      rclcpp_ring_buffer_dequeue,
+      static_cast<const void *>(this),
+      read_index_,
+      size_ - 1);
     read_index_ = next_(read_index_);
 
     size_--;
@@ -136,7 +148,10 @@ public:
     return is_full_();
   }
 
-  void clear() {}
+  void clear()
+  {
+    TRACEPOINT(rclcpp_ring_buffer_clear, static_cast<const void *>(this));
+  }
 
 private:
   /// Get the next index value for the ring buffer

rclcpp/include/rclcpp/experimental/executors/events_executor/events_executor.hpp

@@ -0,0 +1,286 @@
+// Copyright 2023 iRobot Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__EVENTS_EXECUTOR_HPP_
+#define RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__EVENTS_EXECUTOR_HPP_
+
+#include <atomic>
+#include <chrono>
+#include <memory>
+#include <vector>
+
+#include "rclcpp/executor.hpp"
+#include "rclcpp/executors/executor_entities_collection.hpp"
+#include "rclcpp/executors/executor_entities_collector.hpp"
+#include "rclcpp/experimental/executors/events_executor/events_executor_event_types.hpp"
+#include "rclcpp/experimental/executors/events_executor/events_queue.hpp"
+#include "rclcpp/experimental/executors/events_executor/simple_events_queue.hpp"
+#include "rclcpp/experimental/timers_manager.hpp"
+#include "rclcpp/node.hpp"
+
+namespace rclcpp
+{
+namespace experimental
+{
+namespace executors
+{
+
+/// Events executor implementation
+/**
+ * This executor uses an events queue and a timers manager to execute entities from its
+ * associated nodes and callback groups.
+ * ROS 2 entities allow to set callback functions that are invoked when the entity is triggered
+ * or has work to do. The events-executor sets these callbacks such that they push an
+ * event into its queue.
+ *
+ * This executor tries to reduce as much as possible the amount of maintenance operations.
+ * This allows to use customized `EventsQueue` classes to achieve different goals such
+ * as very low CPU usage, bounded memory requirement, determinism, etc.
+ *
+ * The executor uses a weak ownership model and it locks entities only while executing
+ * their related events.
+ *
+ * To run this executor:
+ * rclcpp::experimental::executors::EventsExecutor executor;
+ * executor.add_node(node);
+ * executor.spin();
+ * executor.remove_node(node);
+ */
+class EventsExecutor : public rclcpp::Executor
+{
+  friend class EventsExecutorEntitiesCollector;
+
+public:
+  RCLCPP_SMART_PTR_DEFINITIONS(EventsExecutor)
+
+  /// Default constructor. See the default constructor for Executor.
+  /**
+   * \param[in] events_queue The queue used to store events.
+   * \param[in] execute_timers_separate_thread If true, timers are executed in a separate
+   * thread. If false, timers are executed in the same thread as all other entities.
+   * \param[in] options Options used to configure the executor.
+   */
+  RCLCPP_PUBLIC
+  explicit EventsExecutor(
+    rclcpp::experimental::executors::EventsQueue::UniquePtr events_queue = std::make_unique<
+      rclcpp::experimental::executors::SimpleEventsQueue>(),
+    bool execute_timers_separate_thread = false,
+    const rclcpp::ExecutorOptions & options = rclcpp::ExecutorOptions());
+
+  /// Default destructor.
+  RCLCPP_PUBLIC
+  virtual ~EventsExecutor();
+
+  /// Events executor implementation of spin.
+  /**
+   * This function will block until work comes in, execute it, and keep blocking.
+   * It will only be interrupted by a CTRL-C (managed by the global signal handler).
+   * \throws std::runtime_error when spin() called while already spinning
+   */
+  RCLCPP_PUBLIC
+  void
+  spin() override;
+
+  /// Events executor implementation of spin some
+  /**
+   * This non-blocking function will execute the timers and events
+   * that were ready when this API was called, until timeout or no
+   * more work available. New ready-timers/events arrived while
+   * executing work, won't be taken into account here.
+   *
+   * Example:
+   *   while(condition) {
+   *     spin_some();
+   *     sleep(); // User should have some sync work or
+   *              // sleep to avoid a 100% CPU usage
+   *   }
+   */
+  RCLCPP_PUBLIC
+  void
+  spin_some(std::chrono::nanoseconds max_duration = std::chrono::nanoseconds(0)) override;
+
+  /// Events executor implementation of spin all
+  /**
+   * This non-blocking function will execute timers and events
+   * until timeout or no more work available. If new ready-timers/events
+   * arrive while executing work available, they will be executed
+   * as long as the timeout hasn't expired.
+   *
+   * Example:
+   *   while(condition) {
+   *     spin_all();
+   *     sleep(); // User should have some sync work or
+   *              // sleep to avoid a 100% CPU usage
+   *   }
+   */
+  RCLCPP_PUBLIC
+  void
+  spin_all(std::chrono::nanoseconds max_duration) override;
+
+  /// Add a node to the executor.
+  /**
+   * \sa rclcpp::Executor::add_node
+   */
+  RCLCPP_PUBLIC
+  void
+  add_node(
+    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
+    bool notify = true) override;
+
+  /// Convenience function which takes Node and forwards NodeBaseInterface.
+  /**
+   * \sa rclcpp::EventsExecutor::add_node
+   */
+  RCLCPP_PUBLIC
+  void
+  add_node(std::shared_ptr<rclcpp::Node> node_ptr, bool notify = true) override;
+
+  /// Remove a node from the executor.
+  /**
+   * \sa rclcpp::Executor::remove_node
+   */
+  RCLCPP_PUBLIC
+  void
+  remove_node(
+    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
+    bool notify = true) override;
+
+  /// Convenience function which takes Node and forwards NodeBaseInterface.
+  /**
+   * \sa rclcpp::Executor::remove_node
+   */
+  RCLCPP_PUBLIC
+  void
+  remove_node(std::shared_ptr<rclcpp::Node> node_ptr, bool notify = true) override;
+
+  /// Add a callback group to an executor.
+  /**
+   * \sa rclcpp::Executor::add_callback_group
+   */
+  RCLCPP_PUBLIC
+  void
+  add_callback_group(
+    rclcpp::CallbackGroup::SharedPtr group_ptr,
+    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
+    bool notify = true) override;
+
+  /// Remove callback group from the executor
+  /**
+   * \sa rclcpp::Executor::remove_callback_group
+   */
+  RCLCPP_PUBLIC
+  void
+  remove_callback_group(
+    rclcpp::CallbackGroup::SharedPtr group_ptr,
+    bool notify = true) override;
+
+  /// Get callback groups that belong to executor.
+  /**
+   * \sa rclcpp::Executor::get_all_callback_groups()
+   */
+  RCLCPP_PUBLIC
+  std::vector<rclcpp::CallbackGroup::WeakPtr>
+  get_all_callback_groups() override;
+
+  /// Get callback groups that belong to executor.
+  /**
+   * \sa rclcpp::Executor::get_manually_added_callback_groups()
+   */
+  RCLCPP_PUBLIC
+  std::vector<rclcpp::CallbackGroup::WeakPtr>
+  get_manually_added_callback_groups() override;
+
+  /// Get callback groups that belong to executor.
+  /**
+   * \sa rclcpp::Executor::get_automatically_added_callback_groups_from_nodes()
+   */
+  RCLCPP_PUBLIC
+  std::vector<rclcpp::CallbackGroup::WeakPtr>
+  get_automatically_added_callback_groups_from_nodes() override;
+
+protected:
+  /// Internal implementation of spin_once
+  RCLCPP_PUBLIC
+  void
+  spin_once_impl(std::chrono::nanoseconds timeout) override;
+
+  /// Internal implementation of spin_some
+  RCLCPP_PUBLIC
+  void
+  spin_some_impl(std::chrono::nanoseconds max_duration, bool exhaustive);
+
+private:
+  RCLCPP_DISABLE_COPY(EventsExecutor)
+
+  /// Execute a provided executor event if its associated entities are available
+  void
+  execute_event(const ExecutorEvent & event);
+
+  /// Collect entities from callback groups and refresh the current collection with them
+  void
+  refresh_current_collection_from_callback_groups();
+
+  /// Refresh the current collection using the provided new_collection
+  void
+  refresh_current_collection(const rclcpp::executors::ExecutorEntitiesCollection & new_collection);
+
+  /// Create a listener callback function for the provided entity
+  std::function<void(size_t)>
+  create_entity_callback(void * entity_key, ExecutorEventType type);
+
+  /// Create a listener callback function for the provided waitable entity
+  std::function<void(size_t, int)>
+  create_waitable_callback(const rclcpp::Waitable * waitable_id);
+
+  /// Searches for the provided entity_id in the collection and returns the entity if valid
+  template<typename CollectionType>
+  typename CollectionType::EntitySharedPtr
+  retrieve_entity(typename CollectionType::Key entity_id, CollectionType & collection)
+  {
+    // Check if the entity_id is in the collection
+    auto it = collection.find(entity_id);
+    if (it == collection.end()) {
+      return nullptr;
+    }
+
+    // Check if the entity associated with the entity_id is valid
+    // and remove it from the collection if it isn't
+    auto entity = it->second.entity.lock();
+    if (!entity) {
+      collection.erase(it);
+    }
+
+    // Return the retrieved entity (this can be a nullptr if the entity was not valid)
+    return entity;
+  }
+
+  /// Queue where entities can push events
+  rclcpp::experimental::executors::EventsQueue::UniquePtr events_queue_;
+
+  std::shared_ptr<rclcpp::executors::ExecutorEntitiesCollector> entities_collector_;
+  std::shared_ptr<rclcpp::executors::ExecutorEntitiesCollection> current_entities_collection_;
+  std::shared_ptr<rclcpp::executors::ExecutorNotifyWaitable> notify_waitable_;
+
+  /// Flag used to reduce the number of unnecessary waitable events
+  std::atomic<bool> notify_waitable_event_pushed_ {false};
+
+  /// Timers manager used to track and/or execute associated timers
+  std::shared_ptr<rclcpp::experimental::TimersManager> timers_manager_;
+};
+
+}  // namespace executors
+}  // namespace experimental
+}  // namespace rclcpp
+
+#endif  // RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__EVENTS_EXECUTOR_HPP_

rclcpp/include/rclcpp/experimental/executors/events_executor/events_executor_event_types.hpp

@@ -0,0 +1,46 @@
+// Copyright 2023 iRobot Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__EVENTS_EXECUTOR_EVENT_TYPES_HPP_
+#define RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__EVENTS_EXECUTOR_EVENT_TYPES_HPP_
+
+namespace rclcpp
+{
+namespace experimental
+{
+namespace executors
+{
+
+enum ExecutorEventType
+{
+  CLIENT_EVENT,
+  SUBSCRIPTION_EVENT,
+  SERVICE_EVENT,
+  TIMER_EVENT,
+  WAITABLE_EVENT
+};
+
+struct ExecutorEvent
+{
+  const void * entity_key;
+  int waitable_data;
+  ExecutorEventType type;
+  size_t num_events;
+};
+
+}  // namespace executors
+}  // namespace experimental
+}  // namespace rclcpp
+
+#endif  // RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__EVENTS_EXECUTOR_EVENT_TYPES_HPP_

rclcpp/include/rclcpp/experimental/executors/events_executor/events_queue.hpp

@@ -0,0 +1,100 @@
+// Copyright 2023 iRobot Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__EVENTS_QUEUE_HPP_
+#define RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__EVENTS_QUEUE_HPP_
+
+#include <queue>
+
+#include "rclcpp/macros.hpp"
+#include "rclcpp/visibility_control.hpp"
+
+#include "rclcpp/experimental/executors/events_executor/events_executor_event_types.hpp"
+
+namespace rclcpp
+{
+namespace experimental
+{
+namespace executors
+{
+
+/**
+ * @brief This abstract class can be used to implement different types of queues
+ * where `ExecutorEvent` can be stored.
+ * The derived classes should choose which underlying container to use and
+ * the strategy for pushing and popping events.
+ * For example a queue implementation may be bounded or unbounded and have
+ * different pruning strategies.
+ * Implementations may or may not check the validity of events and decide how to handle
+ * the situation where an event is not valid anymore (e.g. a subscription history cache overruns)
+ */
+class EventsQueue
+{
+public:
+  RCLCPP_SMART_PTR_ALIASES_ONLY(EventsQueue)
+
+  RCLCPP_PUBLIC
+  EventsQueue() = default;
+
+  /**
+   * @brief Destruct the object.
+   */
+  RCLCPP_PUBLIC
+  virtual ~EventsQueue() = default;
+
+  /**
+   * @brief push event into the queue
+   * @param event The event to push into the queue
+   */
+  RCLCPP_PUBLIC
+  virtual
+  void
+  enqueue(const rclcpp::experimental::executors::ExecutorEvent & event) = 0;
+
+  /**
+   * @brief Extracts an event from the queue, eventually waiting until timeout
+   * if none is available.
+   * @return true if event has been found, false if timeout
+   */
+  RCLCPP_PUBLIC
+  virtual
+  bool
+  dequeue(
+    rclcpp::experimental::executors::ExecutorEvent & event,
+    std::chrono::nanoseconds timeout = std::chrono::nanoseconds::max()) = 0;
+
+  /**
+   * @brief Test whether queue is empty
+   * @return true if the queue's size is 0, false otherwise.
+   */
+  RCLCPP_PUBLIC
+  virtual
+  bool
+  empty() const = 0;
+
+  /**
+   * @brief Returns the number of elements in the queue.
+   * @return the number of elements in the queue.
+   */
+  RCLCPP_PUBLIC
+  virtual
+  size_t
+  size() const = 0;
+};
+
+}  // namespace executors
+}  // namespace experimental
+}  // namespace rclcpp
+
+#endif  // RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__EVENTS_QUEUE_HPP_

rclcpp/include/rclcpp/experimental/executors/events_executor/simple_events_queue.hpp

@@ -0,0 +1,134 @@
+// Copyright 2023 iRobot Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__SIMPLE_EVENTS_QUEUE_HPP_
+#define RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__SIMPLE_EVENTS_QUEUE_HPP_
+
+#include <condition_variable>
+#include <mutex>
+#include <queue>
+#include <utility>
+
+#include "rclcpp/experimental/executors/events_executor/events_queue.hpp"
+
+namespace rclcpp
+{
+namespace experimental
+{
+namespace executors
+{
+
+/**
+ * @brief This class implements an EventsQueue as a simple wrapper around a std::queue.
+ * It does not perform any checks about the size of queue, which can grow
+ * unbounded without being pruned.
+ * The simplicity of this implementation makes it suitable for optimizing CPU usage.
+ */
+class SimpleEventsQueue : public EventsQueue
+{
+public:
+  RCLCPP_PUBLIC
+  ~SimpleEventsQueue() override = default;
+
+  /**
+   * @brief enqueue event into the queue
+   * Thread safe
+   * @param event The event to enqueue into the queue
+   */
+  RCLCPP_PUBLIC
+  void
+  enqueue(const rclcpp::experimental::executors::ExecutorEvent & event) override
+  {
+    rclcpp::experimental::executors::ExecutorEvent single_event = event;
+    single_event.num_events = 1;
+    {
+      std::unique_lock<std::mutex> lock(mutex_);
+      for (size_t ev = 0; ev < event.num_events; ev++) {
+        event_queue_.push(single_event);
+      }
+    }
+    events_queue_cv_.notify_one();
+  }
+
+  /**
+   * @brief waits for an event until timeout, gets a single event
+   * Thread safe
+   * @return true if event, false if timeout
+   */
+  RCLCPP_PUBLIC
+  bool
+  dequeue(
+    rclcpp::experimental::executors::ExecutorEvent & event,
+    std::chrono::nanoseconds timeout = std::chrono::nanoseconds::max()) override
+  {
+    std::unique_lock<std::mutex> lock(mutex_);
+
+    // Initialize to true because it's only needed if we have a valid timeout
+    bool has_data = true;
+    if (timeout != std::chrono::nanoseconds::max()) {
+      has_data =
+        events_queue_cv_.wait_for(lock, timeout, [this]() {return !event_queue_.empty();});
+    } else {
+      events_queue_cv_.wait(lock, [this]() {return !event_queue_.empty();});
+    }
+
+    if (has_data) {
+      event = event_queue_.front();
+      event_queue_.pop();
+      return true;
+    }
+
+    return false;
+  }
+
+  /**
+   * @brief Test whether queue is empty
+   * Thread safe
+   * @return true if the queue's size is 0, false otherwise.
+   */
+  RCLCPP_PUBLIC
+  bool
+  empty() const override
+  {
+    std::unique_lock<std::mutex> lock(mutex_);
+    return event_queue_.empty();
+  }
+
+  /**
+   * @brief Returns the number of elements in the queue.
+   * Thread safe
+   * @return the number of elements in the queue.
+   */
+  RCLCPP_PUBLIC
+  size_t
+  size() const override
+  {
+    std::unique_lock<std::mutex> lock(mutex_);
+    return event_queue_.size();
+  }
+
+private:
+  // The underlying queue implementation
+  std::queue<rclcpp::experimental::executors::ExecutorEvent> event_queue_;
+  // Mutex to protect read/write access to the queue
+  mutable std::mutex mutex_;
+  // Variable used to notify when an event is added to the queue
+  std::condition_variable events_queue_cv_;
+};
+
+}  // namespace executors
+}  // namespace experimental
+}  // namespace rclcpp
+
+#endif  // RCLCPP__EXPERIMENTAL__EXECUTORS__EVENTS_EXECUTOR__SIMPLE_EVENTS_QUEUE_HPP_

rclcpp/include/rclcpp/experimental/intra_process_manager.hpp

@@ -454,6 +454,8 @@ private:
         if (std::next(it) == subscription_ids.end()) {
           // If this is the last subscription, give up ownership
           subscription->provide_intra_process_data(std::move(message));
+          // Last message delivered, break from for loop
+          break;
         } else {
           // Copy the message since we have additional subscriptions to serve
           Deleter deleter = message.get_deleter();
@@ -493,6 +495,8 @@ private:
           if (std::next(it) == subscription_ids.end()) {
             // If this is the last subscription, give up ownership
             ros_message_subscription->provide_intra_process_message(std::move(message));
+            // Last message delivered, break from for loop
+            break;
           } else {
             // Copy the message since we have additional subscriptions to serve
             Deleter deleter = message.get_deleter();

rclcpp/include/rclcpp/experimental/subscription_intra_process.hpp

@@ -109,9 +109,22 @@ public:
 
     if (any_callback_.use_take_shared_method()) {
       shared_msg = this->buffer_->consume_shared();
+      if (!shared_msg) {
+        return nullptr;
+      }
     } else {
       unique_msg = this->buffer_->consume_unique();
+      if (!unique_msg) {
+        return nullptr;
+      }
     }
+
+    if (this->buffer_->has_data()) {
+      // If there is data still to be processed, indicate to the
+      // executor or waitset by triggering the guard condition.
+      this->trigger_guard_condition();
+    }
+
     return std::static_pointer_cast<void>(
       std::make_shared<std::pair<ConstMessageSharedPtr, MessageUniquePtr>>(
         std::pair<ConstMessageSharedPtr, MessageUniquePtr>(
@@ -138,7 +151,7 @@ protected:
   execute_impl(std::shared_ptr<void> & data)
   {
     if (!data) {
-      throw std::runtime_error("'data' is empty");
+      return;
     }
 
     rmw_message_info_t msg_info;

rclcpp/include/rclcpp/experimental/subscription_intra_process_base.hpp

@@ -52,7 +52,7 @@ public:
   {}
 
   RCLCPP_PUBLIC
-  virtual ~SubscriptionIntraProcessBase();
+  virtual ~SubscriptionIntraProcessBase() = default;
 
   RCLCPP_PUBLIC
   size_t

rclcpp/include/rclcpp/experimental/subscription_intra_process_buffer.hpp

@@ -31,6 +31,8 @@
 #include "rclcpp/qos.hpp"
 #include "rclcpp/type_support_decl.hpp"
 
+#include "tracetools/tracetools.h"
+
 namespace rclcpp
 {
 namespace experimental
@@ -91,6 +93,10 @@ public:
       buffer_type,
       qos_profile,
       std::make_shared<Alloc>(subscribed_type_allocator_));
+    TRACEPOINT(
+      rclcpp_ipb_to_subscription,
+      static_cast<const void *>(buffer_.get()),
+      static_cast<const void *>(this));
   }
 
   bool

rclcpp/include/rclcpp/experimental/timers_manager.hpp

@@ -0,0 +1,553 @@
+// Copyright 2023 iRobot Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__EXPERIMENTAL__TIMERS_MANAGER_HPP_
+#define RCLCPP__EXPERIMENTAL__TIMERS_MANAGER_HPP_
+
+#include <algorithm>
+#include <atomic>
+#include <chrono>
+#include <condition_variable>
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <thread>
+#include <utility>
+#include <vector>
+
+#include "rclcpp/context.hpp"
+#include "rclcpp/timer.hpp"
+
+namespace rclcpp
+{
+namespace experimental
+{
+
+/**
+ * @brief This class provides a way for storing and executing timer objects.
+ * It provides APIs to suit the needs of different applications and execution models.
+ * All public APIs provided by this class are thread-safe.
+ *
+ * Timers management
+ * This class provides APIs to add/remove timers to/from an internal storage.
+ * It keeps a list of weak pointers from added timers, and locks them only when
+ * they need to be executed or modified.
+ * Timers are kept ordered in a binary-heap priority queue.
+ * Calls to add/remove APIs will temporarily block the execution of the timers and
+ * will require to reorder the internal priority queue.
+ * Because of this, they have a not-negligible impact on the performance.
+ *
+ * Timers execution
+ * The most efficient use of this class consists in letting a TimersManager object
+ * to spawn a thread where timers are monitored and optionally executed.
+ * This can be controlled via the `start` and `stop` methods.
+ * Ready timers can either be executed or an on_ready_callback can be used to notify
+ * other entities that they are ready and need to be executed.
+ * Other APIs allow to directly execute a given timer.
+ *
+ * This class assumes that the `execute_callback()` API of the stored timers is never
+ * called by other entities, but it can only be called from here.
+ * If this assumption is not respected, the heap property may be invalidated,
+ * so timers may be executed out of order, without this object noticing it.
+ *
+ */
+class TimersManager
+{
+public:
+  RCLCPP_SMART_PTR_DEFINITIONS_NOT_COPYABLE(TimersManager)
+
+  /**
+   * @brief Construct a new TimersManager object
+   *
+   * @param context custom context to be used.
+   * Shared ownership of the context is held until destruction.
+   * @param on_ready_callback The timers on ready callback. The presence of this function
+   * indicates what to do when the TimersManager is running and a timer becomes ready.
+   * The TimersManager is considered "running" when the `start` method has been called.
+   * If it's callable, it will be invoked instead of the timer callback.
+   * If it's not callable, then the TimersManager will
+   * directly execute timers when they are ready.
+   * All the methods that execute a given timer (e.g. `execute_head_timer`
+   * or `execute_ready_timer`) without the TimersManager being `running`, i.e.
+   * without actually explicitly waiting for the timer to become ready, will ignore this
+   * callback.
+   */
+  RCLCPP_PUBLIC
+  TimersManager(
+    std::shared_ptr<rclcpp::Context> context,
+    std::function<void(const rclcpp::TimerBase *)> on_ready_callback = nullptr);
+
+  /**
+   * @brief Destruct the TimersManager object making sure to stop thread and release memory.
+   */
+  RCLCPP_PUBLIC
+  ~TimersManager();
+
+  /**
+   * @brief Adds a new timer to the storage, maintaining weak ownership of it.
+   * Function is thread safe and it can be called regardless of the state of the timers thread.
+   *
+   * @param timer the timer to add.
+   * @throws std::invalid_argument if timer is a nullptr.
+   */
+  RCLCPP_PUBLIC
+  void add_timer(rclcpp::TimerBase::SharedPtr timer);
+
+  /**
+   * @brief Remove a single timer from the object storage.
+   * Will do nothing if the timer was not being stored here.
+   * Function is thread safe and it can be called regardless of the state of the timers thread.
+   *
+   * @param timer the timer to remove.
+   */
+  RCLCPP_PUBLIC
+  void remove_timer(rclcpp::TimerBase::SharedPtr timer);
+
+  /**
+   * @brief Remove all the timers stored in the object.
+   * Function is thread safe and it can be called regardless of the state of the timers thread.
+   */
+  RCLCPP_PUBLIC
+  void clear();
+
+  /**
+   * @brief Starts a thread that takes care of executing the timers stored in this object.
+   * Function will throw an error if the timers thread was already running.
+   */
+  RCLCPP_PUBLIC
+  void start();
+
+  /**
+   * @brief Stops the timers thread.
+   * Will do nothing if the timer thread was not running.
+   */
+  RCLCPP_PUBLIC
+  void stop();
+
+  /**
+   * @brief Get the number of timers that are currently ready.
+   * This function is thread safe.
+   *
+   * @return size_t number of ready timers.
+   * @throws std::runtime_error if the timers thread was already running.
+   */
+  RCLCPP_PUBLIC
+  size_t get_number_ready_timers();
+
+  /**
+   * @brief Executes head timer if ready.
+   * This function is thread safe.
+   * This function will try to execute the timer callback regardless of whether
+   * the TimersManager on_ready_callback was passed during construction.
+   *
+   * @return true if head timer was ready.
+   * @throws std::runtime_error if the timers thread was already running.
+   */
+  RCLCPP_PUBLIC
+  bool execute_head_timer();
+
+  /**
+   * @brief Executes timer identified by its ID.
+   * This function is thread safe.
+   * This function will try to execute the timer callback regardless of whether
+   * the TimersManager on_ready_callback was passed during construction.
+   *
+   * @param timer_id the timer ID of the timer to execute
+   */
+  RCLCPP_PUBLIC
+  void execute_ready_timer(const rclcpp::TimerBase * timer_id);
+
+  /**
+   * @brief Get the amount of time before the next timer triggers.
+   * This function is thread safe.
+   *
+   * @return std::chrono::nanoseconds to wait,
+   * the returned value could be negative if the timer is already expired
+   * or std::chrono::nanoseconds::max() if there are no timers stored in the object.
+   * @throws std::runtime_error if the timers thread was already running.
+   */
+  RCLCPP_PUBLIC
+  std::chrono::nanoseconds get_head_timeout();
+
+private:
+  RCLCPP_DISABLE_COPY(TimersManager)
+
+  using TimerPtr = rclcpp::TimerBase::SharedPtr;
+  using WeakTimerPtr = rclcpp::TimerBase::WeakPtr;
+
+  // Forward declaration
+  class TimersHeap;
+
+  /**
+   * @brief This class allows to store weak pointers to timers in a heap-like data structure.
+   * The root of the heap is the timer that triggers first.
+   * Since this class uses weak ownership, it is not guaranteed that it represents a valid heap
+   * at any point in time as timers could go out of scope, thus invalidating it.
+   * The "validate_and_lock" API allows to restore the heap property and also returns a locked version
+   * of the timers heap.
+   * This class is not thread safe and requires external mutexes to protect its usage.
+   */
+  class WeakTimersHeap
+  {
+public:
+    /**
+     * @brief Add a new timer to the heap. After the addition, the heap property is enforced.
+     *
+     * @param timer new timer to add.
+     * @return true if timer has been added, false if it was already there.
+     */
+    bool add_timer(TimerPtr timer)
+    {
+      TimersHeap locked_heap = this->validate_and_lock();
+      bool added = locked_heap.add_timer(std::move(timer));
+
+      if (added) {
+        // Re-create the weak heap with the new timer added
+        this->store(locked_heap);
+      }
+
+      return added;
+    }
+
+    /**
+     * @brief Remove a timer from the heap. After the removal, the heap property is enforced.
+     *
+     * @param timer timer to remove.
+     * @return true if timer has been removed, false if it was not there.
+     */
+    bool remove_timer(TimerPtr timer)
+    {
+      TimersHeap locked_heap = this->validate_and_lock();
+      bool removed = locked_heap.remove_timer(std::move(timer));
+
+      if (removed) {
+        // Re-create the weak heap with the timer removed
+        this->store(locked_heap);
+      }
+
+      return removed;
+    }
+
+    /**
+     * @brief Retrieve the timer identified by the key
+     * @param timer_id The ID of the timer to retrieve.
+     * @return TimerPtr if there's a timer associated with the ID, nullptr otherwise
+     */
+    TimerPtr get_timer(const rclcpp::TimerBase * timer_id)
+    {
+      for (auto & weak_timer : weak_heap_) {
+        auto timer = weak_timer.lock();
+        if (timer.get() == timer_id) {
+          return timer;
+        }
+      }
+      return nullptr;
+    }
+
+    /**
+     * @brief Returns a const reference to the front element.
+     */
+    const WeakTimerPtr & front() const
+    {
+      return weak_heap_.front();
+    }
+
+    /**
+     * @brief Returns whether the heap is empty or not.
+     */
+    bool empty() const
+    {
+      return weak_heap_.empty();
+    }
+
+    /**
+     * @brief This function restores the current object as a valid heap
+     * and it returns a locked version of it.
+     * Timers that went out of scope are removed from the container.
+     * It is the only public API to access and manipulate the stored timers.
+     *
+     * @return TimersHeap owned timers corresponding to the current object
+     */
+    TimersHeap validate_and_lock()
+    {
+      TimersHeap locked_heap;
+      bool any_timer_destroyed = false;
+
+      for (auto weak_timer : weak_heap_) {
+        auto timer = weak_timer.lock();
+        if (timer) {
+          // This timer is valid, so add it to the locked heap
+          // Note: we access friend private `owned_heap_` member field.
+          locked_heap.owned_heap_.push_back(std::move(timer));
+        } else {
+          // This timer went out of scope, so we don't add it to locked heap
+          // and we mark the corresponding flag.
+          // It's not needed to erase it from weak heap, as we are going to re-heapify.
+          // Note: we can't exit from the loop here, as we need to find all valid timers.
+          any_timer_destroyed = true;
+        }
+      }
+
+      // If a timer has gone out of scope, then the remaining elements do not represent
+      // a valid heap anymore. We need to re-heapify the timers heap.
+      if (any_timer_destroyed) {
+        locked_heap.heapify();
+        // Re-create the weak heap now that elements have been heapified again
+        this->store(locked_heap);
+      }
+
+      return locked_heap;
+    }
+
+    /**
+     * @brief This function allows to recreate the heap of weak pointers
+     * from an heap of owned pointers.
+     * It is required to be called after a locked TimersHeap generated from this object
+     * has been modified in any way (e.g. timers triggered, added, removed).
+     *
+     * @param heap timers heap to store as weak pointers
+     */
+    void store(const TimersHeap & heap)
+    {
+      weak_heap_.clear();
+      // Note: we access friend private `owned_heap_` member field.
+      for (auto t : heap.owned_heap_) {
+        weak_heap_.push_back(t);
+      }
+    }
+
+    /**
+     * @brief Remove all timers from the heap.
+     */
+    void clear()
+    {
+      weak_heap_.clear();
+    }
+
+private:
+    std::vector<WeakTimerPtr> weak_heap_;
+  };
+
+  /**
+   * @brief This class is the equivalent of WeakTimersHeap but with ownership of the timers.
+   * It can be generated by locking the weak version.
+   * It provides operations to manipulate the heap.
+   * This class is not thread safe and requires external mutexes to protect its usage.
+   */
+  class TimersHeap
+  {
+public:
+    /**
+     * @brief Try to add a new timer to the heap.
+     * After the addition, the heap property is preserved.
+     * @param timer new timer to add.
+     * @return true if timer has been added, false if it was already there.
+     */
+    bool add_timer(TimerPtr timer)
+    {
+      // Nothing to do if the timer is already stored here
+      auto it = std::find(owned_heap_.begin(), owned_heap_.end(), timer);
+      if (it != owned_heap_.end()) {
+        return false;
+      }
+
+      owned_heap_.push_back(std::move(timer));
+      std::push_heap(owned_heap_.begin(), owned_heap_.end(), timer_greater);
+
+      return true;
+    }
+
+    /**
+     * @brief Try to remove a timer from the heap.
+     * After the removal, the heap property is preserved.
+     * @param timer timer to remove.
+     * @return true if timer has been removed, false if it was not there.
+     */
+    bool remove_timer(TimerPtr timer)
+    {
+      // Nothing to do if the timer is not stored here
+      auto it = std::find(owned_heap_.begin(), owned_heap_.end(), timer);
+      if (it == owned_heap_.end()) {
+        return false;
+      }
+
+      owned_heap_.erase(it);
+      this->heapify();
+
+      return true;
+    }
+
+    /**
+     * @brief Returns a reference to the front element.
+     * @return reference to front element.
+     */
+    TimerPtr & front()
+    {
+      return owned_heap_.front();
+    }
+
+    /**
+     * @brief Returns a const reference to the front element.
+     * @return const reference to front element.
+     */
+    const TimerPtr & front() const
+    {
+      return owned_heap_.front();
+    }
+
+    /**
+     * @brief Returns whether the heap is empty or not.
+     * @return true if the heap is empty.
+     */
+    bool empty() const
+    {
+      return owned_heap_.empty();
+    }
+
+    /**
+     * @brief Returns the size of the heap.
+     * @return the number of valid timers in the heap.
+     */
+    size_t size() const
+    {
+      return owned_heap_.size();
+    }
+
+    /**
+     * @brief Get the number of timers that are currently ready.
+     * @return size_t number of ready timers.
+     */
+    size_t get_number_ready_timers() const
+    {
+      size_t ready_timers = 0;
+
+      for (TimerPtr t : owned_heap_) {
+        if (t->is_ready()) {
+          ready_timers++;
+        }
+      }
+
+      return ready_timers;
+    }
+
+    /**
+    * @brief Restore a valid heap after the root value has been replaced (e.g. timer triggered).
+    */
+    void heapify_root()
+    {
+      // The following code is a more efficient version than doing
+      // pop_heap, pop_back, push_back, push_heap
+      // as it removes the need for the last push_heap
+
+      // Push the modified element (i.e. the current root) at the bottom of the heap
+      owned_heap_.push_back(owned_heap_[0]);
+      // Exchange first and last-1 elements and reheapify
+      std::pop_heap(owned_heap_.begin(), owned_heap_.end(), timer_greater);
+      // Remove last element
+      owned_heap_.pop_back();
+    }
+
+    /**
+     * @brief Completely restores the structure to a valid heap
+     */
+    void heapify()
+    {
+      std::make_heap(owned_heap_.begin(), owned_heap_.end(), timer_greater);
+    }
+
+    /**
+     * @brief Helper function to clear the "on_reset_callback" on all associated timers.
+     */
+    void clear_timers_on_reset_callbacks()
+    {
+      for (TimerPtr & t : owned_heap_) {
+        t->clear_on_reset_callback();
+      }
+    }
+
+    /**
+     * @brief Friend declaration to allow the `validate_and_lock()` function to access the
+     * underlying heap container
+     */
+    friend TimersHeap WeakTimersHeap::validate_and_lock();
+
+    /**
+     * @brief Friend declaration to allow the `store()` function to access the
+     * underlying heap container
+     */
+    friend void WeakTimersHeap::store(const TimersHeap & heap);
+
+private:
+    /**
+     * @brief Comparison function between timers.
+     * @return true if `a` triggers after `b`.
+     */
+    static bool timer_greater(TimerPtr a, TimerPtr b)
+    {
+      // TODO(alsora): this can cause an error if timers are using different clocks
+      return a->time_until_trigger() > b->time_until_trigger();
+    }
+
+    std::vector<TimerPtr> owned_heap_;
+  };
+
+  /**
+   * @brief Implements a loop that keeps executing ready timers.
+   * This function is executed in the timers thread.
+   */
+  void run_timers();
+
+  /**
+   * @brief Get the amount of time before the next timer triggers.
+   * This function is not thread safe, acquire a mutex before calling it.
+   *
+   * @return std::chrono::nanoseconds to wait,
+   * the returned value could be negative if the timer is already expired
+   * or std::chrono::nanoseconds::max() if the heap is empty.
+   * This function is not thread safe, acquire the timers_mutex_ before calling it.
+   */
+  std::chrono::nanoseconds get_head_timeout_unsafe();
+
+  /**
+   * @brief Executes all the timers currently ready when the function is invoked
+   * while keeping the heap correctly sorted.
+   * This function is not thread safe, acquire the timers_mutex_ before calling it.
+   */
+  void execute_ready_timers_unsafe();
+
+  // Callback to be called when timer is ready
+  std::function<void(const rclcpp::TimerBase *)> on_ready_callback_ = nullptr;
+
+  // Thread used to run the timers execution task
+  std::thread timers_thread_;
+  // Protects access to timers
+  std::mutex timers_mutex_;
+  // Protects access to stop()
+  std::mutex stop_mutex_;
+  // Notifies the timers thread whenever timers are added/removed
+  std::condition_variable timers_cv_;
+  // Flag used as predicate by timers_cv_ that denotes one or more timers being added/removed
+  bool timers_updated_ {false};
+  // Indicates whether the timers thread is currently running or not
+  std::atomic<bool> running_ {false};
+  // Parent context used to understand if ROS is still active
+  std::shared_ptr<rclcpp::Context> context_;
+  // Timers heap storage with weak ownership
+  WeakTimersHeap weak_timers_heap_;
+};
+
+}  // namespace experimental
+}  // namespace rclcpp
+
+#endif  // RCLCPP__EXPERIMENTAL__TIMERS_MANAGER_HPP_

rclcpp/include/rclcpp/generic_publisher.hpp

@@ -78,38 +78,12 @@ public:
       node_base,
       topic_name,
       *rclcpp::get_typesupport_handle(topic_type, "rosidl_typesupport_cpp", *ts_lib),
-      options.template to_rcl_publisher_options<rclcpp::SerializedMessage>(qos)),
+      options.template to_rcl_publisher_options<rclcpp::SerializedMessage>(qos),
+      // NOTE(methylDragon): Passing these args separately is necessary for event binding
+      options.event_callbacks,
+      options.use_default_callbacks),
     ts_lib_(ts_lib)
-  {
-    // This is unfortunately duplicated with the code in publisher.hpp.
-    // TODO(nnmm): Deduplicate by moving this into PublisherBase.
-    if (options.event_callbacks.deadline_callback) {
-      this->add_event_handler(
-        options.event_callbacks.deadline_callback,
-        RCL_PUBLISHER_OFFERED_DEADLINE_MISSED);
-    }
-    if (options.event_callbacks.liveliness_callback) {
-      this->add_event_handler(
-        options.event_callbacks.liveliness_callback,
-        RCL_PUBLISHER_LIVELINESS_LOST);
-    }
-    if (options.event_callbacks.incompatible_qos_callback) {
-      this->add_event_handler(
-        options.event_callbacks.incompatible_qos_callback,
-        RCL_PUBLISHER_OFFERED_INCOMPATIBLE_QOS);
-    } else if (options.use_default_callbacks) {
-      // Register default callback when not specified
-      try {
-        this->add_event_handler(
-          [this](QOSOfferedIncompatibleQoSInfo & info) {
-            this->default_incompatible_qos_callback(info);
-          },
-          RCL_PUBLISHER_OFFERED_INCOMPATIBLE_QOS);
-      } catch (UnsupportedEventTypeException & /*exc*/) {
-        // pass
-      }
-    }
-  }
+  {}
 
   RCLCPP_PUBLIC
   virtual ~GenericPublisher() = default;

rclcpp/include/rclcpp/generic_subscription.hpp

@@ -81,45 +81,13 @@ public:
       node_base,
       *rclcpp::get_typesupport_handle(topic_type, "rosidl_typesupport_cpp", *ts_lib),
       topic_name,
-      options.template to_rcl_subscription_options<rclcpp::SerializedMessage>(qos),
-      true),
+      options.to_rcl_subscription_options(qos),
+      options.event_callbacks,
+      options.use_default_callbacks,
+      DeliveredMessageKind::SERIALIZED_MESSAGE),
     callback_(callback),
     ts_lib_(ts_lib)
-  {
-    // This is unfortunately duplicated with the code in subscription.hpp.
-    // TODO(nnmm): Deduplicate by moving this into SubscriptionBase.
-    if (options.event_callbacks.deadline_callback) {
-      this->add_event_handler(
-        options.event_callbacks.deadline_callback,
-        RCL_SUBSCRIPTION_REQUESTED_DEADLINE_MISSED);
-    }
-    if (options.event_callbacks.liveliness_callback) {
-      this->add_event_handler(
-        options.event_callbacks.liveliness_callback,
-        RCL_SUBSCRIPTION_LIVELINESS_CHANGED);
-    }
-    if (options.event_callbacks.incompatible_qos_callback) {
-      this->add_event_handler(
-        options.event_callbacks.incompatible_qos_callback,
-        RCL_SUBSCRIPTION_REQUESTED_INCOMPATIBLE_QOS);
-    } else if (options.use_default_callbacks) {
-      // Register default callback when not specified
-      try {
-        this->add_event_handler(
-          [this](QOSRequestedIncompatibleQoSInfo & info) {
-            this->default_incompatible_qos_callback(info);
-          },
-          RCL_SUBSCRIPTION_REQUESTED_INCOMPATIBLE_QOS);
-      } catch (UnsupportedEventTypeException & /*exc*/) {
-        // pass
-      }
-    }
-    if (options.event_callbacks.message_lost_callback) {
-      this->add_event_handler(
-        options.event_callbacks.message_lost_callback,
-        RCL_SUBSCRIPTION_MESSAGE_LOST);
-    }
-  }
+  {}
 
   RCLCPP_PUBLIC
   virtual ~GenericSubscription() = default;
@@ -155,6 +123,31 @@ public:
   RCLCPP_PUBLIC
   void return_serialized_message(std::shared_ptr<rclcpp::SerializedMessage> & message) override;
 
+
+  // DYNAMIC TYPE ==================================================================================
+  RCLCPP_PUBLIC
+  rclcpp::dynamic_typesupport::DynamicMessageType::SharedPtr get_shared_dynamic_message_type()
+  override;
+
+  RCLCPP_PUBLIC
+  rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr get_shared_dynamic_message() override;
+
+  RCLCPP_PUBLIC
+  rclcpp::dynamic_typesupport::DynamicSerializationSupport::SharedPtr
+  get_shared_dynamic_serialization_support() override;
+
+  RCLCPP_PUBLIC
+  rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr create_dynamic_message() override;
+
+  RCLCPP_PUBLIC
+  void return_dynamic_message(
+    rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr & message) override;
+
+  RCLCPP_PUBLIC
+  void handle_dynamic_message(
+    const rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr & message,
+    const rclcpp::MessageInfo & message_info) override;
+
 private:
   RCLCPP_DISABLE_COPY(GenericSubscription)
 

rclcpp/include/rclcpp/logger.hpp

@@ -17,6 +17,7 @@
 
 #include <memory>
 #include <string>
+#include <utility>
 
 #include "rclcpp/visibility_control.hpp"
 
@@ -122,6 +123,7 @@ private:
   : name_(new std::string(name)) {}
 
   std::shared_ptr<const std::string> name_;
+  std::shared_ptr<std::pair<std::string, std::string>> logger_sublogger_pairname_ = nullptr;
 
 public:
   RCLCPP_PUBLIC
@@ -157,13 +159,7 @@ public:
    */
   RCLCPP_PUBLIC
   Logger
-  get_child(const std::string & suffix)
-  {
-    if (!name_) {
-      return Logger();
-    }
-    return Logger(*name_ + "." + suffix);
-  }
+  get_child(const std::string & suffix);
 
   /// Set level for current logger.
   /**
@@ -174,6 +170,24 @@ public:
   RCLCPP_PUBLIC
   void
   set_level(Level level);
+
+  /// Get effective level for current logger.
+  /**
+   * The effective level is determined as the severity level of
+   * the logger if it is set, otherwise it is the first specified severity
+   * level of the logger's ancestors, starting with its closest ancestor.
+   * The ancestor hierarchy is signified by logger names being separated by dots:
+   * a logger named `x` is an ancestor of `x.y`, and both `x` and `x.y` are
+   * ancestors of `x.y.z`, etc.
+   * If the level has not been set for the logger nor any of its
+   * ancestors, the default level is used.
+   *
+   * \throws rclcpp::exceptions::RCLError if any error happens.
+   * \return Level for the current logger.
+   */
+  RCLCPP_PUBLIC
+  Level
+  get_effective_level() const;
 };
 
 }  // namespace rclcpp

rclcpp/include/rclcpp/node.hpp

@@ -740,17 +740,21 @@ public:
   /**
    * If the parameter has not been declared, then this method may throw the
    * rclcpp::exceptions::ParameterNotDeclaredException exception.
+   * If the parameter has not been initialized, then this method may throw the
+   * rclcpp::exceptions::ParameterUninitializedException exception.
    *
    * If undeclared parameters are allowed, see the node option
    * rclcpp::NodeOptions::allow_undeclared_parameters, then this method will
-   * not throw an exception, and instead return a default initialized
-   * rclcpp::Parameter, which has a type of
+   * not throw the rclcpp::exceptions::ParameterNotDeclaredException exception,
+   * and instead return a default initialized rclcpp::Parameter, which has a type of
    * rclcpp::ParameterType::PARAMETER_NOT_SET.
    *
    * \param[in] name The name of the parameter to get.
    * \return The requested parameter inside of a rclcpp parameter object.
    * \throws rclcpp::exceptions::ParameterNotDeclaredException if the parameter
    *   has not been declared and undeclared parameters are not allowed.
+   * \throws rclcpp::exceptions::ParameterUninitializedException if the parameter
+   *   has not been initialized.
    */
   RCLCPP_PUBLIC
   rclcpp::Parameter
@@ -834,12 +838,12 @@ public:
 
   /// Return the parameters by the given parameter names.
   /**
-   * Like get_parameters(), this method may throw the
+   * Like get_parameter(const std::string &), this method may throw the
    * rclcpp::exceptions::ParameterNotDeclaredException exception if the
    * requested parameter has not been declared and undeclared parameters are
-   * not allowed.
+   * not allowed, and may throw the rclcpp::exceptions::ParameterUninitializedException exception.
    *
-   * Also like get_parameters(), if undeclared parameters are allowed and the
+   * Also like get_parameter(const std::string &), if undeclared parameters are allowed and the
    * parameter has not been declared, then the corresponding rclcpp::Parameter
    * will be default initialized and therefore have the type
    * rclcpp::ParameterType::PARAMETER_NOT_SET.
@@ -849,6 +853,8 @@ public:
    * \throws rclcpp::exceptions::ParameterNotDeclaredException if any of the
    *   parameters have not been declared and undeclared parameters are not
    *   allowed.
+   * \throws rclcpp::exceptions::ParameterUninitializedException if any of the
+   *   parameters have not been initialized.
    */
   RCLCPP_PUBLIC
   std::vector<rclcpp::Parameter>

rclcpp/include/rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp

@@ -0,0 +1,208 @@
+// Copyright 2022 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__NODE_INTERFACES__DETAIL__NODE_INTERFACES_HELPERS_HPP_
+#define RCLCPP__NODE_INTERFACES__DETAIL__NODE_INTERFACES_HELPERS_HPP_
+
+#include <memory>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "rclcpp/visibility_control.hpp"
+
+namespace rclcpp
+{
+namespace node_interfaces
+{
+namespace detail
+{
+
+// Support and Helper template classes for the NodeInterfaces class.
+
+template<typename NodeT, typename ... Ts>
+std::tuple<std::shared_ptr<Ts>...>
+init_tuple(NodeT & n);
+
+/// Stores the interfaces in a tuple, provides constructors, and getters.
+template<typename ... InterfaceTs>
+struct NodeInterfacesStorage
+{
+  template<typename NodeT>
+  NodeInterfacesStorage(NodeT & node)  // NOLINT(runtime/explicit)
+  : interfaces_(init_tuple<decltype(node), InterfaceTs ...>(node))
+  {}
+
+  NodeInterfacesStorage()
+  : interfaces_()
+  {}
+
+  explicit NodeInterfacesStorage(std::shared_ptr<InterfaceTs>... args)
+  : interfaces_(args ...)
+  {}
+
+  /// Individual Node Interface non-const getter.
+  template<typename NodeInterfaceT>
+  std::shared_ptr<NodeInterfaceT>
+  get()
+  {
+    static_assert(
+      (std::is_same_v<NodeInterfaceT, InterfaceTs>|| ...),
+      "NodeInterfaces class does not contain given NodeInterfaceT");
+    return std::get<std::shared_ptr<NodeInterfaceT>>(interfaces_);
+  }
+
+  /// Individual Node Interface const getter.
+  template<typename NodeInterfaceT>
+  std::shared_ptr<const NodeInterfaceT>
+  get() const
+  {
+    static_assert(
+      (std::is_same_v<NodeInterfaceT, InterfaceTs>|| ...),
+      "NodeInterfaces class does not contain given NodeInterfaceT");
+    return std::get<std::shared_ptr<NodeInterfaceT>>(interfaces_);
+  }
+
+protected:
+  std::tuple<std::shared_ptr<InterfaceTs>...> interfaces_;
+};
+
+/// Prototype of NodeInterfacesSupports.
+/**
+ * Should read NodeInterfacesSupports<..., T, ...> as "NodeInterfaces supports T", and
+ * if NodeInterfacesSupport is specialized for T, the is_supported should be
+ * set to std::true_type, but by default it is std::false_type, which will
+ * lead to a compiler error when trying to use T with NodeInterfaces.
+ */
+template<typename StorageClassT, typename ... Ts>
+struct NodeInterfacesSupports;
+
+/// Prototype of NodeInterfacesSupportCheck template meta-function.
+/**
+ * This meta-function checks that all the types given are supported,
+ * throwing a more human-readable error if an unsupported type is used.
+ */
+template<typename StorageClassT, typename ... InterfaceTs>
+struct NodeInterfacesSupportCheck;
+
+/// Iterating specialization that ensures classes are supported and inherited.
+template<typename StorageClassT, typename NextInterfaceT, typename ... RemainingInterfaceTs>
+struct NodeInterfacesSupportCheck<StorageClassT, NextInterfaceT, RemainingInterfaceTs ...>
+  : public NodeInterfacesSupportCheck<StorageClassT, RemainingInterfaceTs ...>
+{
+  static_assert(
+    NodeInterfacesSupports<StorageClassT, NextInterfaceT>::is_supported::value,
+    "given NodeInterfaceT is not supported by rclcpp::node_interfaces::NodeInterfaces");
+};
+
+/// Terminating case when there are no more "RemainingInterfaceTs".
+template<typename StorageClassT>
+struct NodeInterfacesSupportCheck<StorageClassT>
+{};
+
+/// Default specialization, needs to be specialized for each supported interface.
+template<typename StorageClassT, typename ... RemainingInterfaceTs>
+struct NodeInterfacesSupports
+{
+  // Specializations need to set this to std::true_type in addition to other interfaces.
+  using is_supported = std::false_type;
+};
+
+/// Terminating specialization of NodeInterfacesSupports.
+template<typename StorageClassT>
+struct NodeInterfacesSupports<StorageClassT>
+  : public StorageClassT
+{
+  /// Perfect forwarding constructor to get arguments down to StorageClassT.
+  template<typename ... ArgsT>
+  explicit NodeInterfacesSupports(ArgsT && ... args)
+  : StorageClassT(std::forward<ArgsT>(args) ...)
+  {}
+};
+
+// Helper functions to initialize the tuple in NodeInterfaces.
+
+template<typename StorageClassT, typename ElementT, typename TupleT, typename NodeT>
+void
+init_element(TupleT & t, NodeT & n)
+{
+  std::get<std::shared_ptr<ElementT>>(t) =
+    NodeInterfacesSupports<StorageClassT, ElementT>::get_from_node_like(n);
+}
+
+template<typename NodeT, typename ... Ts>
+std::tuple<std::shared_ptr<Ts>...>
+init_tuple(NodeT & n)
+{
+  using StorageClassT = NodeInterfacesStorage<Ts ...>;
+  std::tuple<std::shared_ptr<Ts>...> t;
+  (init_element<StorageClassT, Ts>(t, n), ...);
+  return t;
+}
+
+/// Macro for creating specializations with less boilerplate.
+/**
+ * You can use this macro to add support for your interface class if:
+ *
+ * - The standard getter is get_node_{NodeInterfaceName}_interface(), and
+ * - the getter returns a non-const shared_ptr<{NodeInterfaceType}>
+ *
+ * Examples of using this can be seen in the standard node interface headers
+ * in rclcpp, e.g. rclcpp/node_interfaces/node_base_interface.hpp has:
+ *
+ *   RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeBaseInterface, base)
+ *
+ * If your interface has a non-standard getter, or you want to instrument it or
+ * something like that, then you'll need to create your own specialization of
+ * the NodeInterfacesSupports struct without this macro.
+ */
+#define RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(NodeInterfaceType, NodeInterfaceName) \
+  namespace rclcpp::node_interfaces::detail { \
+  template<typename StorageClassT, typename ... RemainingInterfaceTs> \
+  struct NodeInterfacesSupports< \
+    StorageClassT, \
+    NodeInterfaceType, \
+    RemainingInterfaceTs ...> \
+    : public NodeInterfacesSupports<StorageClassT, RemainingInterfaceTs ...> \
+  { \
+    using is_supported = std::true_type; \
+ \
+    template<typename NodeT> \
+    static \
+    std::shared_ptr<NodeInterfaceType> \
+    get_from_node_like(NodeT & node_like) \
+    { \
+      return node_like.get_node_ ## NodeInterfaceName ## _interface(); \
+    } \
+ \
+    /* Perfect forwarding constructor to get arguments down to StorageClassT (eventually). */ \
+    template<typename ... ArgsT> \
+    explicit NodeInterfacesSupports(ArgsT && ... args) \
+      : NodeInterfacesSupports<StorageClassT, RemainingInterfaceTs ...>( \
+        std::forward<ArgsT>(args) ...) \
+    {} \
+ \
+    std::shared_ptr<NodeInterfaceType> \
+    get_node_ ## NodeInterfaceName ## _interface() \
+    { \
+      return StorageClassT::template get<NodeInterfaceType>(); \
+    } \
+  }; \
+  }  // namespace rclcpp::node_interfaces::detail
+
+}  // namespace detail
+}  // namespace node_interfaces
+}  // namespace rclcpp
+
+#endif  // RCLCPP__NODE_INTERFACES__DETAIL__NODE_INTERFACES_HELPERS_HPP_

rclcpp/include/rclcpp/node_interfaces/node_base.hpp

@@ -15,7 +15,7 @@
 #ifndef RCLCPP__NODE_INTERFACES__NODE_BASE_HPP_
 #define RCLCPP__NODE_INTERFACES__NODE_BASE_HPP_
 
-#include <functional>
+#include <atomic>
 #include <memory>
 #include <mutex>
 #include <string>
@@ -121,10 +121,19 @@ public:
   std::atomic_bool &
   get_associated_with_executor_atomic() override;
 
+  [[deprecated("Use get_shared_notify_guard_condition or trigger_notify_guard_condition instead")]]
   RCLCPP_PUBLIC
   rclcpp::GuardCondition &
   get_notify_guard_condition() override;
 
+  RCLCPP_PUBLIC
+  rclcpp::GuardCondition::SharedPtr
+  get_shared_notify_guard_condition() override;
+
+  RCLCPP_PUBLIC
+  void
+  trigger_notify_guard_condition() override;
+
   RCLCPP_PUBLIC
   bool
   get_use_intra_process_default() const override;
@@ -153,7 +162,7 @@ private:
 
   /// Guard condition for notifying the Executor of changes to this node.
   mutable std::recursive_mutex notify_guard_condition_mutex_;
-  rclcpp::GuardCondition notify_guard_condition_;
+  std::shared_ptr<rclcpp::GuardCondition> notify_guard_condition_;
   bool notify_guard_condition_is_valid_;
 };
 

rclcpp/include/rclcpp/node_interfaces/node_base_interface.hpp

@@ -15,10 +15,10 @@
 #ifndef RCLCPP__NODE_INTERFACES__NODE_BASE_INTERFACE_HPP_
 #define RCLCPP__NODE_INTERFACES__NODE_BASE_INTERFACE_HPP_
 
+#include <atomic>
+#include <functional>
 #include <memory>
-#include <mutex>
 #include <string>
-#include <vector>
 
 #include "rcl/node.h"
 
@@ -26,6 +26,7 @@
 #include "rclcpp/context.hpp"
 #include "rclcpp/guard_condition.hpp"
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/visibility_control.hpp"
 
 namespace rclcpp
@@ -147,13 +148,33 @@ public:
   /**
    * For example, this should be notified when a publisher is added or removed.
    *
-   * \return the GuardCondition if it is valid, else thow runtime error
+   * \return the GuardCondition if it is valid, else throw runtime error
    */
   RCLCPP_PUBLIC
   virtual
   rclcpp::GuardCondition &
   get_notify_guard_condition() = 0;
 
+  /// Return a guard condition that should be notified when the internal node state changes.
+  /**
+   * For example, this should be notified when a publisher is added or removed.
+   *
+   * \return the GuardCondition if it is valid, else nullptr
+   */
+  RCLCPP_PUBLIC
+  virtual
+  rclcpp::GuardCondition::SharedPtr
+  get_shared_notify_guard_condition() = 0;
+
+  /// Trigger the guard condition that notifies of internal node state changes.
+  /**
+   * For example, this should be notified when a publisher is added or removed.
+   */
+  RCLCPP_PUBLIC
+  virtual
+  void
+  trigger_notify_guard_condition() = 0;
+
   /// Return the default preference for using intra process communication.
   RCLCPP_PUBLIC
   virtual
@@ -177,4 +198,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeBaseInterface, base)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_BASE_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/node_clock.hpp

@@ -15,6 +15,7 @@
 #ifndef RCLCPP__NODE_INTERFACES__NODE_CLOCK_HPP_
 #define RCLCPP__NODE_INTERFACES__NODE_CLOCK_HPP_
 
+#include "rcl/time.h"
 #include "rclcpp/clock.hpp"
 #include "rclcpp/macros.hpp"
 #include "rclcpp/node_interfaces/node_base_interface.hpp"
@@ -42,7 +43,8 @@ public:
     rclcpp::node_interfaces::NodeTopicsInterface::SharedPtr node_topics,
     rclcpp::node_interfaces::NodeGraphInterface::SharedPtr node_graph,
     rclcpp::node_interfaces::NodeServicesInterface::SharedPtr node_services,
-    rclcpp::node_interfaces::NodeLoggingInterface::SharedPtr node_logging);
+    rclcpp::node_interfaces::NodeLoggingInterface::SharedPtr node_logging,
+    rcl_clock_type_t clock_type);
 
   RCLCPP_PUBLIC
   virtual
@@ -67,7 +69,7 @@ private:
   rclcpp::node_interfaces::NodeServicesInterface::SharedPtr node_services_;
   rclcpp::node_interfaces::NodeLoggingInterface::SharedPtr node_logging_;
 
-  rclcpp::Clock::SharedPtr ros_clock_;
+  rclcpp::Clock::SharedPtr clock_;
 };
 
 }  // namespace node_interfaces

rclcpp/include/rclcpp/node_interfaces/node_clock_interface.hpp

@@ -17,6 +17,7 @@
 
 #include "rclcpp/clock.hpp"
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/visibility_control.hpp"
 
 namespace rclcpp
@@ -50,4 +51,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeClockInterface, clock)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_CLOCK_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/node_graph.hpp

@@ -15,7 +15,9 @@
 #ifndef RCLCPP__NODE_INTERFACES__NODE_GRAPH_HPP_
 #define RCLCPP__NODE_INTERFACES__NODE_GRAPH_HPP_
 
+#include <atomic>
 #include <chrono>
+#include <condition_variable>
 #include <map>
 #include <memory>
 #include <mutex>

rclcpp/include/rclcpp/node_interfaces/node_graph_interface.hpp

@@ -29,6 +29,7 @@
 
 #include "rclcpp/event.hpp"
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/qos.hpp"
 #include "rclcpp/visibility_control.hpp"
 
@@ -56,7 +57,8 @@ public:
     node_namespace_(info.node_namespace),
     topic_type_(info.topic_type),
     endpoint_type_(static_cast<rclcpp::EndpointType>(info.endpoint_type)),
-    qos_profile_({info.qos_profile.history, info.qos_profile.depth}, info.qos_profile)
+    qos_profile_({info.qos_profile.history, info.qos_profile.depth}, info.qos_profile),
+    topic_type_hash_(info.topic_type_hash)
   {
     std::copy(info.endpoint_gid, info.endpoint_gid + RMW_GID_STORAGE_SIZE, endpoint_gid_.begin());
   }
@@ -121,6 +123,16 @@ public:
   const rclcpp::QoS &
   qos_profile() const;
 
+  /// Get a mutable reference to the type hash of the topic endpoint.
+  RCLCPP_PUBLIC
+  rosidl_type_hash_t &
+  topic_type_hash();
+
+  /// Get a const reference to the type hash of the topic endpoint.
+  RCLCPP_PUBLIC
+  const rosidl_type_hash_t &
+  topic_type_hash() const;
+
 private:
   std::string node_name_;
   std::string node_namespace_;
@@ -128,6 +140,7 @@ private:
   rclcpp::EndpointType endpoint_type_;
   std::array<uint8_t, RMW_GID_STORAGE_SIZE> endpoint_gid_;
   rclcpp::QoS qos_profile_;
+  rosidl_type_hash_t topic_type_hash_;
 };
 
 namespace node_interfaces
@@ -382,4 +395,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeGraphInterface, graph)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_GRAPH_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/node_interfaces.hpp

@@ -0,0 +1,164 @@
+// Copyright 2022 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__NODE_INTERFACES__NODE_INTERFACES_HPP_
+#define RCLCPP__NODE_INTERFACES__NODE_INTERFACES_HPP_
+
+#include <memory>
+
+#include "rclcpp/detail/template_unique.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
+
+#define ALL_RCLCPP_NODE_INTERFACES \
+  rclcpp::node_interfaces::NodeBaseInterface, \
+  rclcpp::node_interfaces::NodeClockInterface, \
+  rclcpp::node_interfaces::NodeGraphInterface, \
+  rclcpp::node_interfaces::NodeLoggingInterface, \
+  rclcpp::node_interfaces::NodeParametersInterface, \
+  rclcpp::node_interfaces::NodeServicesInterface, \
+  rclcpp::node_interfaces::NodeTimeSourceInterface, \
+  rclcpp::node_interfaces::NodeTimersInterface, \
+  rclcpp::node_interfaces::NodeTopicsInterface, \
+  rclcpp::node_interfaces::NodeWaitablesInterface
+
+
+namespace rclcpp
+{
+namespace node_interfaces
+{
+
+
+/// A helper class for aggregating node interfaces.
+template<typename ... InterfaceTs>
+class NodeInterfaces
+  : public detail::NodeInterfacesSupportCheck<
+    detail::NodeInterfacesStorage<InterfaceTs ...>,
+    InterfaceTs ...
+  >,
+  public detail::NodeInterfacesSupports<
+    detail::NodeInterfacesStorage<InterfaceTs ...>,
+    InterfaceTs ...
+  >
+{
+  static_assert(
+    0 != sizeof ...(InterfaceTs),
+    "must provide at least one interface as a template argument");
+  static_assert(
+    rclcpp::detail::template_unique_v<InterfaceTs ...>,
+    "must provide unique template parameters");
+
+  using NodeInterfacesSupportsT = detail::NodeInterfacesSupports<
+    detail::NodeInterfacesStorage<InterfaceTs ...>,
+    InterfaceTs ...
+  >;
+
+public:
+  /// Create a new NodeInterfaces object using the given node-like object's interfaces.
+  /**
+   * Specify which interfaces you need by passing them as template parameters.
+   *
+   * This allows you to aggregate interfaces from different sources together to pass as a single
+   * aggregate object to any functions that take node interfaces or node-likes, without needing to
+   * templatize that function.
+   *
+   * You may also use this constructor to create a NodeInterfaces that contains a subset of
+   * another NodeInterfaces' interfaces.
+   *
+   * Finally, this class supports implicit conversion from node-like objects, allowing you to
+   * directly pass a node-like to a function that takes a NodeInterfaces object.
+   *
+   * Usage examples:
+   *   ```cpp
+   *   // Suppose we have some function:
+   *   void fn(NodeInterfaces<NodeBaseInterface, NodeClockInterface> interfaces);
+   *
+   *   // Then we can, explicitly:
+   *   rclcpp::Node node("some_node");
+   *   auto ni = NodeInterfaces<NodeBaseInterface, NodeClockInterface>(node);
+   *   fn(ni);
+   *
+   *   // But also:
+   *   fn(node);
+   *
+   *   // Subsetting a NodeInterfaces object also works!
+   *   auto ni_base = NodeInterfaces<NodeBaseInterface>(ni);
+   *
+   *   // Or aggregate them (you could aggregate interfaces from disparate node-likes)
+   *   auto ni_aggregated = NodeInterfaces<NodeBaseInterface, NodeClockInterface>(
+   *     node->get_node_base_interface(),
+   *     node->get_node_clock_interface()
+   *   )
+   *
+   *   // And then to access the interfaces:
+   *   // Get with get<>
+   *   auto base = ni.get<NodeBaseInterface>();
+   *
+   *   // Or the appropriate getter
+   *   auto clock = ni.get_clock_interface();
+   *   ```
+   *
+   * You may use any of the standard node interfaces that come with rclcpp:
+   *   - rclcpp::node_interfaces::NodeBaseInterface
+   *   - rclcpp::node_interfaces::NodeClockInterface
+   *   - rclcpp::node_interfaces::NodeGraphInterface
+   *   - rclcpp::node_interfaces::NodeLoggingInterface
+   *   - rclcpp::node_interfaces::NodeParametersInterface
+   *   - rclcpp::node_interfaces::NodeServicesInterface
+   *   - rclcpp::node_interfaces::NodeTimeSourceInterface
+   *   - rclcpp::node_interfaces::NodeTimersInterface
+   *   - rclcpp::node_interfaces::NodeTopicsInterface
+   *   - rclcpp::node_interfaces::NodeWaitablesInterface
+   *
+   * Or you use custom interfaces as long as you make a template specialization
+   * of the rclcpp::node_interfaces::detail::NodeInterfacesSupport struct using
+   * the RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT macro.
+   *
+   * Usage example:
+   *   ```RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeBaseInterface, base)```
+   *
+   * If you choose not to use the helper macro, then you can specialize the
+   * template yourself, but you must:
+   *
+   *   - Provide a template specialization of the get_from_node_like method that gets the interface
+   *     from any node-like that stores the interface, using the node-like's getter
+   *   - Designate the is_supported type as std::true_type using a using directive
+   *   - Provide any number of getter methods to be used to obtain the interface with the
+   *     NodeInterface object, noting that the getters of the storage class will apply to all
+   *     supported interfaces.
+   *     - The getter method names should not clash in name with any other interface getter
+   *       specializations if those other interfaces are meant to be aggregated in the same
+   *       NodeInterfaces object.
+   *
+   * \param[in] node Node-like object from which to get the node interfaces
+   */
+  template<typename NodeT>
+  NodeInterfaces(NodeT & node)  // NOLINT(runtime/explicit)
+  : NodeInterfacesSupportsT(node)
+  {}
+
+  // Create a NodeInterfaces object with no bound interfaces
+  NodeInterfaces()
+  : NodeInterfacesSupportsT()
+  {}
+
+  explicit NodeInterfaces(std::shared_ptr<InterfaceTs>... args)
+  : NodeInterfacesSupportsT(args ...)
+  {}
+};
+
+
+}  // namespace node_interfaces
+}  // namespace rclcpp
+
+#endif  // RCLCPP__NODE_INTERFACES__NODE_INTERFACES_HPP_

rclcpp/include/rclcpp/node_interfaces/node_logging_interface.hpp

@@ -19,6 +19,7 @@
 
 #include "rclcpp/logger.hpp"
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/visibility_control.hpp"
 
 namespace rclcpp
@@ -58,4 +59,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeLoggingInterface, logging)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_LOGGING_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/node_parameters.hpp

@@ -15,9 +15,10 @@
 #ifndef RCLCPP__NODE_INTERFACES__NODE_PARAMETERS_HPP_
 #define RCLCPP__NODE_INTERFACES__NODE_PARAMETERS_HPP_
 
+#include <list>
 #include <map>
 #include <memory>
-#include <list>
+#include <mutex>
 #include <string>
 #include <vector>
 

rclcpp/include/rclcpp/node_interfaces/node_parameters_interface.hpp

@@ -15,8 +15,8 @@
 #ifndef RCLCPP__NODE_INTERFACES__NODE_PARAMETERS_INTERFACE_HPP_
 #define RCLCPP__NODE_INTERFACES__NODE_PARAMETERS_INTERFACE_HPP_
 
+#include <functional>
 #include <map>
-#include <memory>
 #include <string>
 #include <vector>
 
@@ -25,6 +25,7 @@
 #include "rcl_interfaces/msg/set_parameters_result.hpp"
 
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/parameter.hpp"
 #include "rclcpp/visibility_control.hpp"
 
@@ -276,4 +277,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeParametersInterface, parameters)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_PARAMETERS_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/node_services_interface.hpp

@@ -20,6 +20,7 @@
 #include "rclcpp/callback_group.hpp"
 #include "rclcpp/client.hpp"
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/service.hpp"
 #include "rclcpp/visibility_control.hpp"
 
@@ -62,4 +63,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeServicesInterface, services)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_SERVICES_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/node_time_source_interface.hpp

@@ -16,6 +16,7 @@
 #define RCLCPP__NODE_INTERFACES__NODE_TIME_SOURCE_INTERFACE_HPP_
 
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/visibility_control.hpp"
 
 namespace rclcpp
@@ -37,4 +38,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeTimeSourceInterface, time_source)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_TIME_SOURCE_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/node_timers_interface.hpp

@@ -17,6 +17,7 @@
 
 #include "rclcpp/callback_group.hpp"
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/timer.hpp"
 #include "rclcpp/visibility_control.hpp"
 
@@ -47,4 +48,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeTimersInterface, timers)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_TIMERS_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/node_topics_interface.hpp

@@ -15,8 +15,6 @@
 #ifndef RCLCPP__NODE_INTERFACES__NODE_TOPICS_INTERFACE_HPP_
 #define RCLCPP__NODE_INTERFACES__NODE_TOPICS_INTERFACE_HPP_
 
-#include <functional>
-#include <memory>
 #include <string>
 
 #include "rcl/publisher.h"
@@ -24,6 +22,7 @@
 
 #include "rclcpp/callback_group.hpp"
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/node_interfaces/node_base_interface.hpp"
 #include "rclcpp/node_interfaces/node_timers_interface.hpp"
 #include "rclcpp/publisher.hpp"
@@ -97,4 +96,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeTopicsInterface, topics)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_TOPICS_INTERFACE_HPP_

rclcpp/include/rclcpp/node_interfaces/node_waitables_interface.hpp

@@ -17,6 +17,7 @@
 
 #include "rclcpp/callback_group.hpp"
 #include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
 #include "rclcpp/visibility_control.hpp"
 #include "rclcpp/waitable.hpp"
 
@@ -54,4 +55,6 @@ public:
 }  // namespace node_interfaces
 }  // namespace rclcpp
 
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(rclcpp::node_interfaces::NodeWaitablesInterface, waitables)
+
 #endif  // RCLCPP__NODE_INTERFACES__NODE_WAITABLES_INTERFACE_HPP_

rclcpp/include/rclcpp/node_options.hpp

@@ -19,6 +19,7 @@
 #include <string>
 #include <vector>
 
+#include "rcl/time.h"
 #include "rcl/node_options.h"
 #include "rclcpp/context.hpp"
 #include "rclcpp/contexts/default_context.hpp"
@@ -46,6 +47,7 @@ public:
    *   - enable_topic_statistics = false
    *   - start_parameter_services = true
    *   - start_parameter_event_publisher = true
+   *   - clock_type = RCL_ROS_TIME
    *   - clock_qos = rclcpp::ClockQoS()
    *   - use_clock_thread = true
    *   - rosout_qos = rclcpp::RosoutQoS()
@@ -246,6 +248,19 @@ public:
   NodeOptions &
   start_parameter_event_publisher(bool start_parameter_event_publisher);
 
+  /// Return a reference to the clock type.
+  RCLCPP_PUBLIC
+  const rcl_clock_type_t &
+  clock_type() const;
+
+  /// Set the clock type.
+  /**
+   * The clock type to be used by the node.
+   */
+  RCLCPP_PUBLIC
+  NodeOptions &
+  clock_type(const rcl_clock_type_t & clock_type);
+
   /// Return a reference to the clock QoS.
   RCLCPP_PUBLIC
   const rclcpp::QoS &
@@ -400,6 +415,8 @@ private:
 
   bool start_parameter_event_publisher_ {true};
 
+  rcl_clock_type_t clock_type_ {RCL_ROS_TIME};
+
   rclcpp::QoS clock_qos_ = rclcpp::ClockQoS();
 
   bool use_clock_thread_ {true};

rclcpp/include/rclcpp/publisher.hpp

@@ -131,40 +131,16 @@ public:
       node_base,
       topic,
       rclcpp::get_message_type_support_handle<MessageT>(),
-      options.template to_rcl_publisher_options<MessageT>(qos)),
+      options.template to_rcl_publisher_options<MessageT>(qos),
+      // NOTE(methylDragon): Passing these args separately is necessary for event binding
+      options.event_callbacks,
+      options.use_default_callbacks),
     options_(options),
     published_type_allocator_(*options.get_allocator()),
     ros_message_type_allocator_(*options.get_allocator())
   {
     allocator::set_allocator_for_deleter(&published_type_deleter_, &published_type_allocator_);
     allocator::set_allocator_for_deleter(&ros_message_type_deleter_, &ros_message_type_allocator_);
-
-    if (options_.event_callbacks.deadline_callback) {
-      this->add_event_handler(
-        options_.event_callbacks.deadline_callback,
-        RCL_PUBLISHER_OFFERED_DEADLINE_MISSED);
-    }
-    if (options_.event_callbacks.liveliness_callback) {
-      this->add_event_handler(
-        options_.event_callbacks.liveliness_callback,
-        RCL_PUBLISHER_LIVELINESS_LOST);
-    }
-    if (options_.event_callbacks.incompatible_qos_callback) {
-      this->add_event_handler(
-        options_.event_callbacks.incompatible_qos_callback,
-        RCL_PUBLISHER_OFFERED_INCOMPATIBLE_QOS);
-    } else if (options_.use_default_callbacks) {
-      // Register default callback when not specified
-      try {
-        this->add_event_handler(
-          [this](QOSOfferedIncompatibleQoSInfo & info) {
-            this->default_incompatible_qos_callback(info);
-          },
-          RCL_PUBLISHER_OFFERED_INCOMPATIBLE_QOS);
-      } catch (UnsupportedEventTypeException & /*exc*/) {
-        // pass
-      }
-    }
     // Setup continues in the post construction method, post_init_setup().
   }
 
@@ -405,10 +381,6 @@ public:
     if (!loaned_msg.is_valid()) {
       throw std::runtime_error("loaned message is not valid");
     }
-    if (intra_process_is_enabled_) {
-      // TODO(Karsten1987): support loaned message passed by intraprocess
-      throw std::runtime_error("storing loaned messages in intra process is not supported yet");
-    }
 
     // verify that publisher supports loaned messages
     // TODO(Karsten1987): This case separation has to be done in rclcpp
@@ -422,7 +394,7 @@ public:
     } else {
       // we don't release the ownership, let the middleware copy the ros message
       // and thus the destructor of rclcpp::LoanedMessage cleans up the memory.
-      this->do_inter_process_publish(loaned_msg.get());
+      this->publish(loaned_msg.get());
     }
   }
 
@@ -512,6 +484,10 @@ protected:
     if (!msg) {
       throw std::runtime_error("cannot publish msg which is a null pointer");
     }
+    TRACEPOINT(
+      rclcpp_intra_publish,
+      static_cast<const void *>(publisher_handle_.get()),
+      msg.get());
 
     ipm->template do_intra_process_publish<PublishedType, ROSMessageType, AllocatorT>(
       intra_process_publisher_id_,
@@ -530,6 +506,10 @@ protected:
     if (!msg) {
       throw std::runtime_error("cannot publish msg which is a null pointer");
     }
+    TRACEPOINT(
+      rclcpp_intra_publish,
+      static_cast<const void *>(publisher_handle_.get()),
+      msg.get());
 
     ipm->template do_intra_process_publish<ROSMessageType, ROSMessageType, AllocatorT>(
       intra_process_publisher_id_,
@@ -549,6 +529,10 @@ protected:
     if (!msg) {
       throw std::runtime_error("cannot publish msg which is a null pointer");
     }
+    TRACEPOINT(
+      rclcpp_intra_publish,
+      static_cast<const void *>(publisher_handle_.get()),
+      msg.get());
 
     return ipm->template do_intra_process_publish_and_return_shared<ROSMessageType, ROSMessageType,
              AllocatorT>(

rclcpp/include/rclcpp/publisher_base.hpp

@@ -33,7 +33,7 @@
 #include "rclcpp/macros.hpp"
 #include "rclcpp/network_flow_endpoint.hpp"
 #include "rclcpp/qos.hpp"
-#include "rclcpp/qos_event.hpp"
+#include "rclcpp/event_handler.hpp"
 #include "rclcpp/type_support_decl.hpp"
 #include "rclcpp/visibility_control.hpp"
 #include "rcpputils/time.hpp"
@@ -78,11 +78,18 @@ public:
     rclcpp::node_interfaces::NodeBaseInterface * node_base,
     const std::string & topic,
     const rosidl_message_type_support_t & type_support,
-    const rcl_publisher_options_t & publisher_options);
+    const rcl_publisher_options_t & publisher_options,
+    const PublisherEventCallbacks & event_callbacks,
+    bool use_default_callbacks);
 
   RCLCPP_PUBLIC
   virtual ~PublisherBase();
 
+  /// Add event handlers for passed in event_callbacks.
+  RCLCPP_PUBLIC
+  void
+  bind_event_callbacks(const PublisherEventCallbacks & event_callbacks, bool use_default_callbacks);
+
   /// Get the topic that this publisher publishes on.
   /** \return The topic name. */
   RCLCPP_PUBLIC
@@ -117,7 +124,7 @@ public:
   /** \return The map of QoS event handlers. */
   RCLCPP_PUBLIC
   const
-  std::unordered_map<rcl_publisher_event_type_t, std::shared_ptr<rclcpp::QOSEventHandlerBase>> &
+  std::unordered_map<rcl_publisher_event_type_t, std::shared_ptr<rclcpp::EventHandlerBase>> &
   get_event_handlers() const;
 
   /// Get subscription count
@@ -269,7 +276,7 @@ public:
    * If you want more information available in the callback, like the qos event
    * or other information, you may use a lambda with captures or std::bind.
    *
-   * \sa rclcpp::QOSEventHandlerBase::set_on_ready_callback
+   * \sa rclcpp::EventHandlerBase::set_on_ready_callback
    *
    * \param[in] callback functor to be called when a new event occurs
    * \param[in] event_type identifier for the qos event we want to attach the callback to
@@ -320,7 +327,7 @@ protected:
     const EventCallbackT & callback,
     const rcl_publisher_event_type_t event_type)
   {
-    auto handler = std::make_shared<QOSEventHandler<EventCallbackT,
+    auto handler = std::make_shared<EventHandler<EventCallbackT,
         std::shared_ptr<rcl_publisher_t>>>(
       callback,
       rcl_publisher_event_init,
@@ -332,12 +339,15 @@ protected:
   RCLCPP_PUBLIC
   void default_incompatible_qos_callback(QOSOfferedIncompatibleQoSInfo & info) const;
 
+  RCLCPP_PUBLIC
+  void default_incompatible_type_callback(IncompatibleTypeInfo & info) const;
+
   std::shared_ptr<rcl_node_t> rcl_node_handle_;
 
   std::shared_ptr<rcl_publisher_t> publisher_handle_;
 
   std::unordered_map<rcl_publisher_event_type_t,
-    std::shared_ptr<rclcpp::QOSEventHandlerBase>> event_handlers_;
+    std::shared_ptr<rclcpp::EventHandlerBase>> event_handlers_;
 
   using IntraProcessManagerWeakPtr =
     std::weak_ptr<rclcpp::experimental::IntraProcessManager>;
@@ -348,6 +358,8 @@ protected:
   rmw_gid_t rmw_gid_;
 
   const rosidl_message_type_support_t type_support_;
+
+  const PublisherEventCallbacks event_callbacks_;
 };
 
 }  // namespace rclcpp

rclcpp/include/rclcpp/publisher_options.hpp

@@ -26,7 +26,7 @@
 #include "rclcpp/detail/rmw_implementation_specific_publisher_payload.hpp"
 #include "rclcpp/intra_process_setting.hpp"
 #include "rclcpp/qos.hpp"
-#include "rclcpp/qos_event.hpp"
+#include "rclcpp/event_handler.hpp"
 #include "rclcpp/qos_overriding_options.hpp"
 
 namespace rclcpp

rclcpp/include/rclcpp/qos.hpp

@@ -80,7 +80,9 @@ struct RCLCPP_PUBLIC QoSInitialization
   size_t depth;
 
   /// Constructor which takes both a history policy and a depth (even if it would be unused).
-  QoSInitialization(rmw_qos_history_policy_t history_policy_arg, size_t depth_arg);
+  QoSInitialization(
+    rmw_qos_history_policy_t history_policy_arg, size_t depth_arg,
+    bool print_depth_warning = true);
 
   /// Create a QoSInitialization from an existing rmw_qos_profile_t, using its history and depth.
   static
@@ -97,7 +99,7 @@ struct RCLCPP_PUBLIC KeepAll : public rclcpp::QoSInitialization
 /// Use to initialize the QoS with the keep_last history setting and the given depth.
 struct RCLCPP_PUBLIC KeepLast : public rclcpp::QoSInitialization
 {
-  explicit KeepLast(size_t depth);
+  explicit KeepLast(size_t depth, bool print_depth_warning = true);
 };
 
 /// Encapsulation of Quality of Service settings.

rclcpp/include/rclcpp/qos_event.hpp

@@ -15,277 +15,8 @@
 #ifndef RCLCPP__QOS_EVENT_HPP_
 #define RCLCPP__QOS_EVENT_HPP_
 
-#include <functional>
-#include <memory>
-#include <mutex>
-#include <stdexcept>
-#include <string>
+#warning This header is obsolete, please include rclcpp/event_handler.hpp instead
 
-#include "rcl/error_handling.h"
-#include "rcl/event_callback.h"
-#include "rmw/impl/cpp/demangle.hpp"
-#include "rmw/incompatible_qos_events_statuses.h"
-
-#include "rcutils/logging_macros.h"
-
-#include "rclcpp/detail/cpp_callback_trampoline.hpp"
-#include "rclcpp/exceptions.hpp"
-#include "rclcpp/function_traits.hpp"
-#include "rclcpp/logging.hpp"
-#include "rclcpp/waitable.hpp"
-
-namespace rclcpp
-{
-
-using QOSDeadlineRequestedInfo = rmw_requested_deadline_missed_status_t;
-using QOSDeadlineOfferedInfo = rmw_offered_deadline_missed_status_t;
-using QOSLivelinessChangedInfo = rmw_liveliness_changed_status_t;
-using QOSLivelinessLostInfo = rmw_liveliness_lost_status_t;
-using QOSMessageLostInfo = rmw_message_lost_status_t;
-using QOSOfferedIncompatibleQoSInfo = rmw_offered_qos_incompatible_event_status_t;
-using QOSRequestedIncompatibleQoSInfo = rmw_requested_qos_incompatible_event_status_t;
-
-using QOSDeadlineRequestedCallbackType = std::function<void (QOSDeadlineRequestedInfo &)>;
-using QOSDeadlineOfferedCallbackType = std::function<void (QOSDeadlineOfferedInfo &)>;
-using QOSLivelinessChangedCallbackType = std::function<void (QOSLivelinessChangedInfo &)>;
-using QOSLivelinessLostCallbackType = std::function<void (QOSLivelinessLostInfo &)>;
-using QOSMessageLostCallbackType = std::function<void (QOSMessageLostInfo &)>;
-using QOSOfferedIncompatibleQoSCallbackType = std::function<void (QOSOfferedIncompatibleQoSInfo &)>;
-using QOSRequestedIncompatibleQoSCallbackType =
-  std::function<void (QOSRequestedIncompatibleQoSInfo &)>;
-
-/// Contains callbacks for various types of events a Publisher can receive from the middleware.
-struct PublisherEventCallbacks
-{
-  QOSDeadlineOfferedCallbackType deadline_callback;
-  QOSLivelinessLostCallbackType liveliness_callback;
-  QOSOfferedIncompatibleQoSCallbackType incompatible_qos_callback;
-};
-
-/// Contains callbacks for non-message events that a Subscription can receive from the middleware.
-struct SubscriptionEventCallbacks
-{
-  QOSDeadlineRequestedCallbackType deadline_callback;
-  QOSLivelinessChangedCallbackType liveliness_callback;
-  QOSRequestedIncompatibleQoSCallbackType incompatible_qos_callback;
-  QOSMessageLostCallbackType message_lost_callback;
-};
-
-class UnsupportedEventTypeException : public exceptions::RCLErrorBase, public std::runtime_error
-{
-public:
-  RCLCPP_PUBLIC
-  UnsupportedEventTypeException(
-    rcl_ret_t ret,
-    const rcl_error_state_t * error_state,
-    const std::string & prefix);
-
-  RCLCPP_PUBLIC
-  UnsupportedEventTypeException(
-    const exceptions::RCLErrorBase & base_exc,
-    const std::string & prefix);
-};
-
-class QOSEventHandlerBase : public Waitable
-{
-public:
-  enum class EntityType : std::size_t
-  {
-    Event,
-  };
-
-  RCLCPP_PUBLIC
-  virtual ~QOSEventHandlerBase();
-
-  /// Get the number of ready events
-  RCLCPP_PUBLIC
-  size_t
-  get_number_of_ready_events() override;
-
-  /// Add the Waitable to a wait set.
-  RCLCPP_PUBLIC
-  void
-  add_to_wait_set(rcl_wait_set_t * wait_set) override;
-
-  /// Check if the Waitable is ready.
-  RCLCPP_PUBLIC
-  bool
-  is_ready(rcl_wait_set_t * wait_set) override;
-
-  /// Set a callback to be called when each new event instance occurs.
-  /**
-   * The callback receives a size_t which is the number of events that occurred
-   * since the last time this callback was called.
-   * Normally this is 1, but can be > 1 if events occurred before any
-   * callback was set.
-   *
-   * The callback also receives an int identifier argument.
-   * This is needed because a Waitable may be composed of several distinct entities,
-   * such as subscriptions, services, etc.
-   * The application should provide a generic callback function that will be then
-   * forwarded by the waitable to all of its entities.
-   * Before forwarding, a different value for the identifier argument will be
-   * bond to the function.
-   * This implies that the provided callback can use the identifier to behave
-   * differently depending on which entity triggered the waitable to become ready.
-   *
-   * Since this callback is called from the middleware, you should aim to make
-   * it fast and not blocking.
-   * If you need to do a lot of work or wait for some other event, you should
-   * spin it off to another thread, otherwise you risk blocking the middleware.
-   *
-   * Calling it again will clear any previously set callback.
-   *
-   * An exception will be thrown if the callback is not callable.
-   *
-   * This function is thread-safe.
-   *
-   * If you want more information available in the callback, like the qos event
-   * or other information, you may use a lambda with captures or std::bind.
-   *
-   * \sa rmw_event_set_callback
-   * \sa rcl_event_set_callback
-   *
-   * \param[in] callback functor to be called when a new event occurs
-   */
-  void
-  set_on_ready_callback(std::function<void(size_t, int)> callback) override
-  {
-    if (!callback) {
-      throw std::invalid_argument(
-              "The callback passed to set_on_ready_callback "
-              "is not callable.");
-    }
-
-    // Note: we bind the int identifier argument to this waitable's entity types
-    auto new_callback =
-      [callback, this](size_t number_of_events) {
-        try {
-          callback(number_of_events, static_cast<int>(EntityType::Event));
-        } catch (const std::exception & exception) {
-          RCLCPP_ERROR_STREAM(
-            // TODO(wjwwood): get this class access to the node logger it is associated with
-            rclcpp::get_logger("rclcpp"),
-            "rclcpp::QOSEventHandlerBase@" << this <<
-              " caught " << rmw::impl::cpp::demangle(exception) <<
-              " exception in user-provided callback for the 'on ready' callback: " <<
-              exception.what());
-        } catch (...) {
-          RCLCPP_ERROR_STREAM(
-            rclcpp::get_logger("rclcpp"),
-            "rclcpp::QOSEventHandlerBase@" << this <<
-              " caught unhandled exception in user-provided callback " <<
-              "for the 'on ready' callback");
-        }
-      };
-
-    std::lock_guard<std::recursive_mutex> lock(callback_mutex_);
-
-    // Set it temporarily to the new callback, while we replace the old one.
-    // This two-step setting, prevents a gap where the old std::function has
-    // been replaced but the middleware hasn't been told about the new one yet.
-    set_on_new_event_callback(
-      rclcpp::detail::cpp_callback_trampoline<const void *, size_t>,
-      static_cast<const void *>(&new_callback));
-
-    // Store the std::function to keep it in scope, also overwrites the existing one.
-    on_new_event_callback_ = new_callback;
-
-    // Set it again, now using the permanent storage.
-    set_on_new_event_callback(
-      rclcpp::detail::cpp_callback_trampoline<const void *, size_t>,
-      static_cast<const void *>(&on_new_event_callback_));
-  }
-
-  /// Unset the callback registered for new events, if any.
-  void
-  clear_on_ready_callback() override
-  {
-    std::lock_guard<std::recursive_mutex> lock(callback_mutex_);
-    if (on_new_event_callback_) {
-      set_on_new_event_callback(nullptr, nullptr);
-      on_new_event_callback_ = nullptr;
-    }
-  }
-
-protected:
-  RCLCPP_PUBLIC
-  void
-  set_on_new_event_callback(rcl_event_callback_t callback, const void * user_data);
-
-  rcl_event_t event_handle_;
-  size_t wait_set_event_index_;
-  std::recursive_mutex callback_mutex_;
-  std::function<void(size_t)> on_new_event_callback_{nullptr};
-};
-
-template<typename EventCallbackT, typename ParentHandleT>
-class QOSEventHandler : public QOSEventHandlerBase
-{
-public:
-  template<typename InitFuncT, typename EventTypeEnum>
-  QOSEventHandler(
-    const EventCallbackT & callback,
-    InitFuncT init_func,
-    ParentHandleT parent_handle,
-    EventTypeEnum event_type)
-  : parent_handle_(parent_handle), event_callback_(callback)
-  {
-    event_handle_ = rcl_get_zero_initialized_event();
-    rcl_ret_t ret = init_func(&event_handle_, parent_handle.get(), event_type);
-    if (ret != RCL_RET_OK) {
-      if (ret == RCL_RET_UNSUPPORTED) {
-        UnsupportedEventTypeException exc(ret, rcl_get_error_state(), "Failed to initialize event");
-        rcl_reset_error();
-        throw exc;
-      } else {
-        rclcpp::exceptions::throw_from_rcl_error(ret, "Failed to initialize event");
-      }
-    }
-  }
-
-  /// Take data so that the callback cannot be scheduled again
-  std::shared_ptr<void>
-  take_data() override
-  {
-    EventCallbackInfoT callback_info;
-    rcl_ret_t ret = rcl_take_event(&event_handle_, &callback_info);
-    if (ret != RCL_RET_OK) {
-      RCUTILS_LOG_ERROR_NAMED(
-        "rclcpp",
-        "Couldn't take event info: %s", rcl_get_error_string().str);
-      return nullptr;
-    }
-    return std::static_pointer_cast<void>(std::make_shared<EventCallbackInfoT>(callback_info));
-  }
-
-  std::shared_ptr<void>
-  take_data_by_entity_id(size_t id) override
-  {
-    (void)id;
-    return take_data();
-  }
-
-  /// Execute any entities of the Waitable that are ready.
-  void
-  execute(std::shared_ptr<void> & data) override
-  {
-    if (!data) {
-      throw std::runtime_error("'data' is empty");
-    }
-    auto callback_ptr = std::static_pointer_cast<EventCallbackInfoT>(data);
-    event_callback_(*callback_ptr);
-    callback_ptr.reset();
-  }
-
-private:
-  using EventCallbackInfoT = typename std::remove_reference<typename
-      rclcpp::function_traits::function_traits<EventCallbackT>::template argument_type<0>>::type;
-
-  ParentHandleT parent_handle_;
-  EventCallbackT event_callback_;
-};
-
-}  // namespace rclcpp
+#include "rclcpp/event_handler.hpp"
 
 #endif  // RCLCPP__QOS_EVENT_HPP_

rclcpp/include/rclcpp/rclcpp.hpp

@@ -117,6 +117,18 @@
  * - Allocator related items:
  *   - rclcpp/allocator/allocator_common.hpp
  *   - rclcpp/allocator/allocator_deleter.hpp
+ * - Dynamic typesupport wrappers
+ *   - rclcpp::dynamic_typesupport::DynamicMessage
+ *   - rclcpp::dynamic_typesupport::DynamicMessageType
+ *   - rclcpp::dynamic_typesupport::DynamicMessageTypeBuilder
+ *   - rclcpp::dynamic_typesupport::DynamicSerializationSupport
+ *   - rclcpp/dynamic_typesupport/dynamic_message.hpp
+ *   - rclcpp/dynamic_typesupport/dynamic_message_type.hpp
+ *   - rclcpp/dynamic_typesupport/dynamic_message_type_builder.hpp
+ *   - rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp
+ * - Dynamic typesupport
+ *   - rclcpp::dynamic_typesupport::DynamicMessageTypeSupport
+ *   - rclcpp/dynamic_typesupport/dynamic_message_type_support.hpp
  * - Generic publisher
  *   - rclcpp::Node::create_generic_publisher()
  *   - rclcpp::GenericPublisher

rclcpp/include/rclcpp/scope_exit.hpp

@@ -1,56 +0,0 @@
-// Copyright 2015 Open Source Robotics Foundation, Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// Based on: http://the-witness.net/news/2012/11/scopeexit-in-c11/
-// But I changed the lambda to include by reference rather than value, see:
-// http://the-witness.net/news/2012/11/scopeexit-in-c11/comment-page-1/#comment-86873
-
-#ifndef RCLCPP__SCOPE_EXIT_HPP_
-#define RCLCPP__SCOPE_EXIT_HPP_
-
-// TODO(christophebedard) remove this header completely in I-turtle
-
-#warning rclcpp/scope_exit.hpp has been deprecated, please use rcpputils/scope_exit.hpp instead
-
-#include <functional>
-
-#include "rclcpp/macros.hpp"
-
-namespace rclcpp
-{
-
-template<typename Callable>
-struct ScopeExit
-{
-  explicit ScopeExit(Callable callable)
-  : callable_(callable) {}
-  ~ScopeExit() {callable_();}
-
-private:
-  Callable callable_;
-};
-
-template<typename Callable>
-ScopeExit<Callable>
-make_scope_exit(Callable callable)
-{
-  return ScopeExit<Callable>(callable);
-}
-
-}  // namespace rclcpp
-
-#define RCLCPP_SCOPE_EXIT(code) \
-  auto RCLCPP_STRING_JOIN(scope_exit_, __LINE__) = rclcpp::make_scope_exit([&]() {code;})
-
-#endif  // RCLCPP__SCOPE_EXIT_HPP_

rclcpp/include/rclcpp/service.hpp

@@ -26,6 +26,7 @@
 #include "rcl/error_handling.h"
 #include "rcl/event_callback.h"
 #include "rcl/service.h"
+#include "rcl/service_introspection.h"
 
 #include "rmw/error_handling.h"
 #include "rmw/impl/cpp/demangle.hpp"
@@ -34,6 +35,7 @@
 #include "tracetools/tracetools.h"
 
 #include "rclcpp/any_service_callback.hpp"
+#include "rclcpp/clock.hpp"
 #include "rclcpp/detail/cpp_callback_trampoline.hpp"
 #include "rclcpp/exceptions.hpp"
 #include "rclcpp/expand_topic_or_service_name.hpp"
@@ -55,7 +57,7 @@ public:
   explicit ServiceBase(std::shared_ptr<rcl_node_t> node_handle);
 
   RCLCPP_PUBLIC
-  virtual ~ServiceBase();
+  virtual ~ServiceBase() = default;
 
   /// Return the name of the service.
   /** \return The name of the service. */
@@ -222,7 +224,7 @@ public:
     // This two-step setting, prevents a gap where the old std::function has
     // been replaced but the middleware hasn't been told about the new one yet.
     set_on_new_request_callback(
-      rclcpp::detail::cpp_callback_trampoline<const void *, size_t>,
+      rclcpp::detail::cpp_callback_trampoline<decltype(new_callback), const void *, size_t>,
       static_cast<const void *>(&new_callback));
 
     // Store the std::function to keep it in scope, also overwrites the existing one.
@@ -230,7 +232,8 @@ public:
 
     // Set it again, now using the permanent storage.
     set_on_new_request_callback(
-      rclcpp::detail::cpp_callback_trampoline<const void *, size_t>,
+      rclcpp::detail::cpp_callback_trampoline<
+        decltype(on_new_request_callback_), const void *, size_t>,
       static_cast<const void *>(&on_new_request_callback_));
   }
 
@@ -307,11 +310,9 @@ public:
     const std::string & service_name,
     AnyServiceCallback<ServiceT> any_callback,
     rcl_service_options_t & service_options)
-  : ServiceBase(node_handle), any_callback_(any_callback)
+  : ServiceBase(node_handle), any_callback_(any_callback),
+    srv_type_support_handle_(rosidl_typesupport_cpp::get_service_type_support_handle<ServiceT>())
   {
-    using rosidl_typesupport_cpp::get_service_type_support_handle;
-    auto service_type_support_handle = get_service_type_support_handle<ServiceT>();
-
     // rcl does the static memory allocation here
     service_handle_ = std::shared_ptr<rcl_service_t>(
       new rcl_service_t, [handle = node_handle_, service_name](rcl_service_t * service)
@@ -330,7 +331,7 @@ public:
     rcl_ret_t ret = rcl_service_init(
       service_handle_.get(),
       node_handle.get(),
-      service_type_support_handle,
+      srv_type_support_handle_,
       service_name.c_str(),
       &service_options);
     if (ret != RCL_RET_OK) {
@@ -370,8 +371,8 @@ public:
     std::shared_ptr<rcl_node_t> node_handle,
     std::shared_ptr<rcl_service_t> service_handle,
     AnyServiceCallback<ServiceT> any_callback)
-  : ServiceBase(node_handle),
-    any_callback_(any_callback)
+  : ServiceBase(node_handle), any_callback_(any_callback),
+    srv_type_support_handle_(rosidl_typesupport_cpp::get_service_type_support_handle<ServiceT>())
   {
     // check if service handle was initialized
     if (!rcl_service_is_valid(service_handle.get())) {
@@ -405,8 +406,8 @@ public:
     std::shared_ptr<rcl_node_t> node_handle,
     rcl_service_t * service_handle,
     AnyServiceCallback<ServiceT> any_callback)
-  : ServiceBase(node_handle),
-    any_callback_(any_callback)
+  : ServiceBase(node_handle), any_callback_(any_callback),
+    srv_type_support_handle_(rosidl_typesupport_cpp::get_service_type_support_handle<ServiceT>())
   {
     // check if service handle was initialized
     if (!rcl_service_is_valid(service_handle)) {
@@ -486,10 +487,39 @@ public:
     }
   }
 
+  /// Configure client introspection.
+  /**
+   * \param[in] clock clock to use to generate introspection timestamps
+   * \param[in] qos_service_event_pub QoS settings to use when creating the introspection publisher
+   * \param[in] introspection_state the state to set introspection to
+   */
+  void
+  configure_introspection(
+    Clock::SharedPtr clock, const QoS & qos_service_event_pub,
+    rcl_service_introspection_state_t introspection_state)
+  {
+    rcl_publisher_options_t pub_opts = rcl_publisher_get_default_options();
+    pub_opts.qos = qos_service_event_pub.get_rmw_qos_profile();
+
+    rcl_ret_t ret = rcl_service_configure_service_introspection(
+      service_handle_.get(),
+      node_handle_.get(),
+      clock->get_clock_handle(),
+      srv_type_support_handle_,
+      pub_opts,
+      introspection_state);
+
+    if (RCL_RET_OK != ret) {
+      rclcpp::exceptions::throw_from_rcl_error(ret, "failed to configure service introspection");
+    }
+  }
+
 private:
   RCLCPP_DISABLE_COPY(Service)
 
   AnyServiceCallback<ServiceT> any_callback_;
+
+  const rosidl_service_type_support_t * srv_type_support_handle_;
 };
 
 }  // namespace rclcpp

rclcpp/include/rclcpp/strategies/allocator_memory_strategy.hpp

@@ -17,6 +17,7 @@
 
 #include <memory>
 #include <vector>
+#include <utility>
 
 #include "rcl/allocator.h"
 
@@ -120,8 +121,8 @@ public:
       }
     }
     for (size_t i = 0; i < waitable_handles_.size(); ++i) {
-      if (!waitable_handles_[i]->is_ready(wait_set)) {
-        waitable_handles_[i].reset();
+      if (waitable_handles_[i]->is_ready(wait_set)) {
+        waitable_triggered_handles_.emplace_back(std::move(waitable_handles_[i]));
       }
     }
 
@@ -145,10 +146,7 @@ public:
       timer_handles_.end()
     );
 
-    waitable_handles_.erase(
-      std::remove(waitable_handles_.begin(), waitable_handles_.end(), nullptr),
-      waitable_handles_.end()
-    );
+    waitable_handles_.clear();
   }
 
   bool collect_entities(const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes) override
@@ -392,8 +390,9 @@ public:
     rclcpp::AnyExecutable & any_exec,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes) override
   {
-    auto it = waitable_handles_.begin();
-    while (it != waitable_handles_.end()) {
+    auto & waitable_handles = waitable_triggered_handles_;
+    auto it = waitable_handles.begin();
+    while (it != waitable_handles.end()) {
       std::shared_ptr<Waitable> & waitable = *it;
       if (waitable) {
         // Find the group for this handle and see if it can be serviced
@@ -401,7 +400,7 @@ public:
         if (!group) {
           // Group was not found, meaning the waitable is not valid...
           // Remove it from the ready list and continue looking
-          it = waitable_handles_.erase(it);
+          it = waitable_handles.erase(it);
           continue;
         }
         if (!group->can_be_taken_from().load()) {
@@ -414,11 +413,11 @@ public:
         any_exec.waitable = waitable;
         any_exec.callback_group = group;
         any_exec.node_base = get_node_by_group(group, weak_groups_to_nodes);
-        waitable_handles_.erase(it);
+        waitable_handles.erase(it);
         return;
       }
       // Else, the waitable is no longer valid, remove it and continue
-      it = waitable_handles_.erase(it);
+      it = waitable_handles.erase(it);
     }
   }
 
@@ -499,6 +498,8 @@ private:
   VectorRebind<std::shared_ptr<const rcl_timer_t>> timer_handles_;
   VectorRebind<std::shared_ptr<Waitable>> waitable_handles_;
 
+  VectorRebind<std::shared_ptr<Waitable>> waitable_triggered_handles_;
+
   std::shared_ptr<VoidAlloc> allocator_;
 };
 

rclcpp/include/rclcpp/subscription.hpp

@@ -140,44 +140,15 @@ public:
       node_base,
       type_support_handle,
       topic_name,
-      options.template to_rcl_subscription_options<ROSMessageType>(qos),
-      callback.is_serialized_message_callback()),
+      options.to_rcl_subscription_options(qos),
+      // NOTE(methylDragon): Passing these args separately is necessary for event binding
+      options.event_callbacks,
+      options.use_default_callbacks,
+      callback.is_serialized_message_callback() ? DeliveredMessageKind::SERIALIZED_MESSAGE : DeliveredMessageKind::ROS_MESSAGE),  // NOLINT
     any_callback_(callback),
     options_(options),
     message_memory_strategy_(message_memory_strategy)
   {
-    if (options_.event_callbacks.deadline_callback) {
-      this->add_event_handler(
-        options_.event_callbacks.deadline_callback,
-        RCL_SUBSCRIPTION_REQUESTED_DEADLINE_MISSED);
-    }
-    if (options_.event_callbacks.liveliness_callback) {
-      this->add_event_handler(
-        options_.event_callbacks.liveliness_callback,
-        RCL_SUBSCRIPTION_LIVELINESS_CHANGED);
-    }
-    if (options_.event_callbacks.incompatible_qos_callback) {
-      this->add_event_handler(
-        options_.event_callbacks.incompatible_qos_callback,
-        RCL_SUBSCRIPTION_REQUESTED_INCOMPATIBLE_QOS);
-    } else if (options_.use_default_callbacks) {
-      // Register default callback when not specified
-      try {
-        this->add_event_handler(
-          [this](QOSRequestedIncompatibleQoSInfo & info) {
-            this->default_incompatible_qos_callback(info);
-          },
-          RCL_SUBSCRIPTION_REQUESTED_INCOMPATIBLE_QOS);
-      } catch (UnsupportedEventTypeException & /*exc*/) {
-        // pass
-      }
-    }
-    if (options_.event_callbacks.message_lost_callback) {
-      this->add_event_handler(
-        options_.event_callbacks.message_lost_callback,
-        RCL_SUBSCRIPTION_MESSAGE_LOST);
-    }
-
     // Setup intra process publishing if requested.
     if (rclcpp::detail::resolve_use_intra_process(options_, *node_base)) {
       using rclcpp::detail::resolve_intra_process_buffer_type;
@@ -417,6 +388,57 @@ public:
     return any_callback_.use_take_shared_method();
   }
 
+  // DYNAMIC TYPE ==================================================================================
+  // TODO(methylDragon): Reorder later
+  // TODO(methylDragon): Implement later...
+  rclcpp::dynamic_typesupport::DynamicMessageType::SharedPtr
+  get_shared_dynamic_message_type() override
+  {
+    throw rclcpp::exceptions::UnimplementedError(
+            "get_shared_dynamic_message_type is not implemented for Subscription");
+  }
+
+  rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr
+  get_shared_dynamic_message() override
+  {
+    throw rclcpp::exceptions::UnimplementedError(
+            "get_shared_dynamic_message is not implemented for Subscription");
+  }
+
+  rclcpp::dynamic_typesupport::DynamicSerializationSupport::SharedPtr
+  get_shared_dynamic_serialization_support() override
+  {
+    throw rclcpp::exceptions::UnimplementedError(
+            "get_shared_dynamic_serialization_support is not implemented for Subscription");
+  }
+
+  rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr
+  create_dynamic_message() override
+  {
+    throw rclcpp::exceptions::UnimplementedError(
+            "create_dynamic_message is not implemented for Subscription");
+  }
+
+  void
+  return_dynamic_message(
+    rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr & message) override
+  {
+    (void) message;
+    throw rclcpp::exceptions::UnimplementedError(
+            "return_dynamic_message is not implemented for Subscription");
+  }
+
+  void
+  handle_dynamic_message(
+    const rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr & message,
+    const rclcpp::MessageInfo & message_info) override
+  {
+    (void) message;
+    (void) message_info;
+    throw rclcpp::exceptions::UnimplementedError(
+            "handle_dynamic_message is not implemented for Subscription");
+  }
+
 private:
   RCLCPP_DISABLE_COPY(Subscription)
 

rclcpp/include/rclcpp/subscription_base.hpp

@@ -31,13 +31,16 @@
 
 #include "rclcpp/any_subscription_callback.hpp"
 #include "rclcpp/detail/cpp_callback_trampoline.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
 #include "rclcpp/experimental/intra_process_manager.hpp"
 #include "rclcpp/experimental/subscription_intra_process_base.hpp"
 #include "rclcpp/macros.hpp"
 #include "rclcpp/message_info.hpp"
 #include "rclcpp/network_flow_endpoint.hpp"
 #include "rclcpp/qos.hpp"
-#include "rclcpp/qos_event.hpp"
+#include "rclcpp/event_handler.hpp"
 #include "rclcpp/serialized_message.hpp"
 #include "rclcpp/subscription_content_filter_options.hpp"
 #include "rclcpp/type_support_decl.hpp"
@@ -60,6 +63,27 @@ namespace experimental
 class IntraProcessManager;
 }  // namespace experimental
 
+/// The kind of message that the subscription delivers in its callback, used by the executor
+/**
+ * This enum needs to exist because the callback handle is not accessible to the executor's scope.
+ *
+ * "Kind" is used since what is being delivered is a category of messages, for example, there are
+ * different ROS message types that can be delivered, but they're all ROS messages.
+ *
+ * As a concrete example, all of the following callbacks will be considered ROS_MESSAGE for
+ * DeliveredMessageKind:
+ *   - void callback(const std_msgs::msg::String &)
+ *   - void callback(const std::string &)  // type adaption
+ *   - void callback(std::unique_ptr<std_msgs::msg::String>)
+ */
+enum class DeliveredMessageKind : uint8_t
+{
+  INVALID = 0,
+  ROS_MESSAGE = 1,  // The subscription delivers a ROS message to its callback
+  SERIALIZED_MESSAGE = 2,  // The subscription delivers a serialized message to its callback
+  DYNAMIC_MESSAGE = 3,  // The subscription delivers a dynamic message to its callback
+};
+
 /// Virtual base class for subscriptions. This pattern allows us to iterate over different template
 /// specializations of Subscription, among other things.
 class SubscriptionBase : public std::enable_shared_from_this<SubscriptionBase>
@@ -76,7 +100,8 @@ public:
    * \param[in] type_support_handle rosidl type support struct, for the Message type of the topic.
    * \param[in] topic_name Name of the topic to subscribe to.
    * \param[in] subscription_options Options for the subscription.
-   * \param[in] is_serialized is true if the message will be delivered still serialized
+   * \param[in] delivered_message_kind Enum flag to change how the message will be received and
+   *            delivered
    */
   RCLCPP_PUBLIC
   SubscriptionBase(
@@ -84,12 +109,20 @@ public:
     const rosidl_message_type_support_t & type_support_handle,
     const std::string & topic_name,
     const rcl_subscription_options_t & subscription_options,
-    bool is_serialized = false);
+    const SubscriptionEventCallbacks & event_callbacks,
+    bool use_default_callbacks,
+    DeliveredMessageKind delivered_message_kind = DeliveredMessageKind::ROS_MESSAGE);
 
   /// Destructor.
   RCLCPP_PUBLIC
   virtual ~SubscriptionBase();
 
+  /// Add event handlers for passed in event_callbacks.
+  RCLCPP_PUBLIC
+  void
+  bind_event_callbacks(
+    const SubscriptionEventCallbacks & event_callbacks, bool use_default_callbacks);
+
   /// Get the topic that this subscription is subscribed on.
   RCLCPP_PUBLIC
   const char *
@@ -107,7 +140,7 @@ public:
   /** \return The map of QoS event handlers. */
   RCLCPP_PUBLIC
   const
-  std::unordered_map<rcl_subscription_event_type_t, std::shared_ptr<rclcpp::QOSEventHandlerBase>> &
+  std::unordered_map<rcl_subscription_event_type_t, std::shared_ptr<rclcpp::EventHandlerBase>> &
   get_event_handlers() const;
 
   /// Get the actual QoS settings, after the defaults have been determined.
@@ -227,6 +260,14 @@ public:
   bool
   is_serialized() const;
 
+  /// Return the type of the subscription.
+  /**
+   * \return `DeliveredMessageKind`, which adjusts how messages are received and delivered.
+   */
+  RCLCPP_PUBLIC
+  DeliveredMessageKind
+  get_subscription_type() const;
+
   /// Get matching publisher count.
   /** \return The number of publishers on this topic. */
   RCLCPP_PUBLIC
@@ -348,7 +389,7 @@ public:
     // This two-step setting, prevents a gap where the old std::function has
     // been replaced but the middleware hasn't been told about the new one yet.
     set_on_new_message_callback(
-      rclcpp::detail::cpp_callback_trampoline<const void *, size_t>,
+      rclcpp::detail::cpp_callback_trampoline<decltype(new_callback), const void *, size_t>,
       static_cast<const void *>(&new_callback));
 
     // Store the std::function to keep it in scope, also overwrites the existing one.
@@ -356,7 +397,8 @@ public:
 
     // Set it again, now using the permanent storage.
     set_on_new_message_callback(
-      rclcpp::detail::cpp_callback_trampoline<const void *, size_t>,
+      rclcpp::detail::cpp_callback_trampoline<
+        decltype(on_new_message_callback_), const void *, size_t>,
       static_cast<const void *>(&on_new_message_callback_));
   }
 
@@ -448,7 +490,7 @@ public:
    * If you want more information available in the callback, like the qos event
    * or other information, you may use a lambda with captures or std::bind.
    *
-   * \sa rclcpp::QOSEventHandlerBase::set_on_ready_callback
+   * \sa rclcpp::EventHandlerBase::set_on_ready_callback
    *
    * \param[in] callback functor to be called when a new event occurs
    * \param[in] event_type identifier for the qos event we want to attach the callback to
@@ -526,6 +568,49 @@ public:
   rclcpp::ContentFilterOptions
   get_content_filter() const;
 
+  // DYNAMIC TYPE ==================================================================================
+  // TODO(methylDragon): Reorder later
+  RCLCPP_PUBLIC
+  virtual
+  rclcpp::dynamic_typesupport::DynamicMessageType::SharedPtr
+  get_shared_dynamic_message_type() = 0;
+
+  RCLCPP_PUBLIC
+  virtual
+  rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr
+  get_shared_dynamic_message() = 0;
+
+  RCLCPP_PUBLIC
+  virtual
+  rclcpp::dynamic_typesupport::DynamicSerializationSupport::SharedPtr
+  get_shared_dynamic_serialization_support() = 0;
+
+  /// Borrow a new serialized message (this clones!)
+  /** \return Shared pointer to a rclcpp::dynamic_typesupport::DynamicMessage. */
+  RCLCPP_PUBLIC
+  virtual
+  rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr
+  create_dynamic_message() = 0;
+
+  RCLCPP_PUBLIC
+  virtual
+  void
+  return_dynamic_message(rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr & message) = 0;
+
+  RCLCPP_PUBLIC
+  virtual
+  void
+  handle_dynamic_message(
+    const rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr & message,
+    const rclcpp::MessageInfo & message_info) = 0;
+
+  RCLCPP_PUBLIC
+  bool
+  take_dynamic_message(
+    rclcpp::dynamic_typesupport::DynamicMessage & message_out,
+    rclcpp::MessageInfo & message_info_out);
+  // ===============================================================================================
+
 protected:
   template<typename EventCallbackT>
   void
@@ -533,7 +618,7 @@ protected:
     const EventCallbackT & callback,
     const rcl_subscription_event_type_t event_type)
   {
-    auto handler = std::make_shared<QOSEventHandler<EventCallbackT,
+    auto handler = std::make_shared<EventHandler<EventCallbackT,
         std::shared_ptr<rcl_subscription_t>>>(
       callback,
       rcl_subscription_event_init,
@@ -546,6 +631,9 @@ protected:
   RCLCPP_PUBLIC
   void default_incompatible_qos_callback(QOSRequestedIncompatibleQoSInfo & info) const;
 
+  RCLCPP_PUBLIC
+  void default_incompatible_type_callback(IncompatibleTypeInfo & info) const;
+
   RCLCPP_PUBLIC
   bool
   matches_any_intra_process_publishers(const rmw_gid_t * sender_gid) const;
@@ -562,22 +650,24 @@ protected:
   rclcpp::Logger node_logger_;
 
   std::unordered_map<rcl_subscription_event_type_t,
-    std::shared_ptr<rclcpp::QOSEventHandlerBase>> event_handlers_;
+    std::shared_ptr<rclcpp::EventHandlerBase>> event_handlers_;
 
   bool use_intra_process_;
   IntraProcessManagerWeakPtr weak_ipm_;
   uint64_t intra_process_subscription_id_;
   std::shared_ptr<rclcpp::experimental::SubscriptionIntraProcessBase> subscription_intra_process_;
 
+  const SubscriptionEventCallbacks event_callbacks_;
+
 private:
   RCLCPP_DISABLE_COPY(SubscriptionBase)
 
   rosidl_message_type_support_t type_support_;
-  bool is_serialized_;
+  DeliveredMessageKind delivered_message_type_;
 
   std::atomic<bool> subscription_in_use_by_wait_set_{false};
   std::atomic<bool> intra_process_subscription_waitable_in_use_by_wait_set_{false};
-  std::unordered_map<rclcpp::QOSEventHandlerBase *,
+  std::unordered_map<rclcpp::EventHandlerBase *,
     std::atomic<bool>> qos_events_in_use_by_wait_set_;
 
   std::recursive_mutex callback_mutex_;

rclcpp/include/rclcpp/subscription_options.hpp

@@ -26,7 +26,7 @@
 #include "rclcpp/intra_process_buffer_type.hpp"
 #include "rclcpp/intra_process_setting.hpp"
 #include "rclcpp/qos.hpp"
-#include "rclcpp/qos_event.hpp"
+#include "rclcpp/event_handler.hpp"
 #include "rclcpp/qos_overriding_options.hpp"
 #include "rclcpp/subscription_content_filter_options.hpp"
 #include "rclcpp/topic_statistics_state.hpp"
@@ -110,7 +110,6 @@ struct SubscriptionOptionsWithAllocator : public SubscriptionOptionsBase
    * \param qos QoS profile for subcription.
    * \return rcl_subscription_options_t structure based on the rclcpp::QoS
    */
-  template<typename MessageT>
   rcl_subscription_options_t
   to_rcl_subscription_options(const rclcpp::QoS & qos) const
   {

rclcpp/include/rclcpp/timer.hpp

@@ -149,11 +149,48 @@ public:
   bool
   exchange_in_use_by_wait_set_state(bool in_use_state);
 
+  /// Set a callback to be called when the timer is reset
+  /**
+   * You should aim to make this callback fast and not blocking.
+   * If you need to do a lot of work or wait for some other event, you should
+   * spin it off to another thread.
+   *
+   * Calling it again will override any previously set callback.
+   * An exception will be thrown if the callback is not callable.
+   *
+   * This function is thread-safe.
+   *
+   * If you want more information available in the callback,
+   * you may use a lambda with captures or std::bind.
+   *
+   * \param[in] callback functor to be called whenever timer is reset
+   */
+  RCLCPP_PUBLIC
+  void
+  set_on_reset_callback(std::function<void(size_t)> callback);
+
+  /// Unset the callback registered for reset timer
+  RCLCPP_PUBLIC
+  void
+  clear_on_reset_callback();
+
 protected:
+  std::recursive_mutex callback_mutex_;
+  // Declare callback before timer_handle_, so on destruction
+  // the callback is destroyed last. Otherwise, the rcl timer
+  // callback would point briefly to a destroyed function.
+  // Clearing the callback on timer destructor also makes sure
+  // the rcl callback is cleared before on_reset_callback_.
+  std::function<void(size_t)> on_reset_callback_{nullptr};
+
   Clock::SharedPtr clock_;
   std::shared_ptr<rcl_timer_t> timer_handle_;
 
   std::atomic<bool> in_use_by_wait_set_{false};
+
+  RCLCPP_PUBLIC
+  void
+  set_on_reset_callback(rcl_event_callback_t callback, const void * user_data);
 };
 
 
@@ -190,10 +227,16 @@ public:
       rclcpp_timer_callback_added,
       static_cast<const void *>(get_timer_handle().get()),
       reinterpret_cast<const void *>(&callback_));
-    TRACEPOINT(
-      rclcpp_callback_register,
-      reinterpret_cast<const void *>(&callback_),
-      tracetools::get_symbol(callback_));
+#ifndef TRACETOOLS_DISABLED
+    if (TRACEPOINT_ENABLED(rclcpp_callback_register)) {
+      char * symbol = tracetools::get_symbol(callback_);
+      DO_TRACEPOINT(
+        rclcpp_callback_register,
+        reinterpret_cast<const void *>(&callback_),
+        symbol);
+      std::free(symbol);
+    }
+#endif
   }
 
   /// Default destructor.

rclcpp/include/rclcpp/wait_set_policies/detail/storage_policy_common.hpp

@@ -104,7 +104,7 @@ protected:
       // TODO(wjwwood): support custom allocator, maybe restrict to polymorphic allocator
       rcl_get_default_allocator());
     if (RCL_RET_OK != ret) {
-      rclcpp::exceptions::throw_from_rcl_error(ret);
+      rclcpp::exceptions::throw_from_rcl_error(ret, "Failed to create wait set");
     }
 
     // (Re)build the wait set for the first time.
@@ -192,8 +192,7 @@ protected:
       size_t services_from_waitables = 0;
       size_t events_from_waitables = 0;
       for (const auto & waitable_entry : waitables) {
-        auto waitable_ptr_pair = get_raw_pointer_from_smart_pointer(waitable_entry.waitable);
-        if (nullptr == waitable_ptr_pair.second) {
+        if (!waitable_entry.waitable) {
           // In this case it was probably stored as a weak_ptr, but is now locking to nullptr.
           if (HasStrongOwnership) {
             // This will not happen in fixed sized storage, as it holds
@@ -204,13 +203,13 @@ protected:
           needs_pruning_ = true;
           continue;
         }
-        rclcpp::Waitable & waitable = *waitable_ptr_pair.second;
-        subscriptions_from_waitables += waitable.get_number_of_ready_subscriptions();
-        guard_conditions_from_waitables += waitable.get_number_of_ready_guard_conditions();
-        timers_from_waitables += waitable.get_number_of_ready_timers();
-        clients_from_waitables += waitable.get_number_of_ready_clients();
-        services_from_waitables += waitable.get_number_of_ready_services();
-        events_from_waitables += waitable.get_number_of_ready_events();
+        const auto & waitable = waitable_entry.waitable;
+        subscriptions_from_waitables += waitable->get_number_of_ready_subscriptions();
+        guard_conditions_from_waitables += waitable->get_number_of_ready_guard_conditions();
+        timers_from_waitables += waitable->get_number_of_ready_timers();
+        clients_from_waitables += waitable->get_number_of_ready_clients();
+        services_from_waitables += waitable->get_number_of_ready_services();
+        events_from_waitables += waitable->get_number_of_ready_events();
       }
       rcl_ret_t ret = rcl_wait_set_resize(
         &rcl_wait_set_,
@@ -222,7 +221,7 @@ protected:
         events_from_waitables
       );
       if (RCL_RET_OK != ret) {
-        rclcpp::exceptions::throw_from_rcl_error(ret);
+        rclcpp::exceptions::throw_from_rcl_error(ret, "Couldn't resize the wait set");
       }
       was_resized = true;
       // Assumption: the calling code ensures this function is not called
@@ -238,15 +237,13 @@ protected:
     if (!was_resized) {
       rcl_ret_t ret = rcl_wait_set_clear(&rcl_wait_set_);
       if (RCL_RET_OK != ret) {
-        rclcpp::exceptions::throw_from_rcl_error(ret);
+        rclcpp::exceptions::throw_from_rcl_error(ret, "Couldn't clear the wait set");
       }
     }
 
     // Add subscriptions.
     for (const auto & subscription_entry : subscriptions) {
-      auto subscription_ptr_pair =
-        get_raw_pointer_from_smart_pointer(subscription_entry.subscription);
-      if (nullptr == subscription_ptr_pair.second) {
+      if (!subscription_entry.subscription) {
         // In this case it was probably stored as a weak_ptr, but is now locking to nullptr.
         if (HasStrongOwnership) {
           // This will not happen in fixed sized storage, as it holds
@@ -257,12 +254,13 @@ protected:
         needs_pruning_ = true;
         continue;
       }
+
       rcl_ret_t ret = rcl_wait_set_add_subscription(
         &rcl_wait_set_,
-        subscription_ptr_pair.second->get_subscription_handle().get(),
+        subscription_entry.subscription->get_subscription_handle().get(),
         nullptr);
       if (RCL_RET_OK != ret) {
-        rclcpp::exceptions::throw_from_rcl_error(ret);
+        rclcpp::exceptions::throw_from_rcl_error(ret, "Couldn't fill wait set");
       }
     }
 
@@ -271,8 +269,7 @@ protected:
       [this](const auto & inner_guard_conditions)
       {
         for (const auto & guard_condition : inner_guard_conditions) {
-          auto guard_condition_ptr_pair = get_raw_pointer_from_smart_pointer(guard_condition);
-          if (nullptr == guard_condition_ptr_pair.second) {
+          if (!guard_condition) {
             // In this case it was probably stored as a weak_ptr, but is now locking to nullptr.
             if (HasStrongOwnership) {
               // This will not happen in fixed sized storage, as it holds
@@ -285,10 +282,10 @@ protected:
           }
           rcl_ret_t ret = rcl_wait_set_add_guard_condition(
             &rcl_wait_set_,
-            &guard_condition_ptr_pair.second->get_rcl_guard_condition(),
+            &guard_condition->get_rcl_guard_condition(),
             nullptr);
           if (RCL_RET_OK != ret) {
-            rclcpp::exceptions::throw_from_rcl_error(ret);
+            rclcpp::exceptions::throw_from_rcl_error(ret, "Couldn't fill wait set");
           }
         }
       };
@@ -301,8 +298,7 @@ protected:
 
     // Add timers.
     for (const auto & timer : timers) {
-      auto timer_ptr_pair = get_raw_pointer_from_smart_pointer(timer);
-      if (nullptr == timer_ptr_pair.second) {
+      if (!timer) {
         // In this case it was probably stored as a weak_ptr, but is now locking to nullptr.
         if (HasStrongOwnership) {
           // This will not happen in fixed sized storage, as it holds
@@ -315,17 +311,16 @@ protected:
       }
       rcl_ret_t ret = rcl_wait_set_add_timer(
         &rcl_wait_set_,
-        timer_ptr_pair.second->get_timer_handle().get(),
+        timer->get_timer_handle().get(),
         nullptr);
       if (RCL_RET_OK != ret) {
-        rclcpp::exceptions::throw_from_rcl_error(ret);
+        rclcpp::exceptions::throw_from_rcl_error(ret, "Couldn't fill wait set");
       }
     }
 
     // Add clients.
     for (const auto & client : clients) {
-      auto client_ptr_pair = get_raw_pointer_from_smart_pointer(client);
-      if (nullptr == client_ptr_pair.second) {
+      if (!client) {
         // In this case it was probably stored as a weak_ptr, but is now locking to nullptr.
         if (HasStrongOwnership) {
           // This will not happen in fixed sized storage, as it holds
@@ -338,17 +333,17 @@ protected:
       }
       rcl_ret_t ret = rcl_wait_set_add_client(
         &rcl_wait_set_,
-        client_ptr_pair.second->get_client_handle().get(),
+        client->get_client_handle().get(),
         nullptr);
       if (RCL_RET_OK != ret) {
         rclcpp::exceptions::throw_from_rcl_error(ret);
       }
     }
 
+
     // Add services.
     for (const auto & service : services) {
-      auto service_ptr_pair = get_raw_pointer_from_smart_pointer(service);
-      if (nullptr == service_ptr_pair.second) {
+      if (!service) {
         // In this case it was probably stored as a weak_ptr, but is now locking to nullptr.
         if (HasStrongOwnership) {
           // This will not happen in fixed sized storage, as it holds
@@ -361,17 +356,16 @@ protected:
       }
       rcl_ret_t ret = rcl_wait_set_add_service(
         &rcl_wait_set_,
-        service_ptr_pair.second->get_service_handle().get(),
+        service->get_service_handle().get(),
         nullptr);
       if (RCL_RET_OK != ret) {
-        rclcpp::exceptions::throw_from_rcl_error(ret);
+        rclcpp::exceptions::throw_from_rcl_error(ret, "Couldn't fill wait set");
       }
     }
 
     // Add waitables.
     for (auto & waitable_entry : waitables) {
-      auto waitable_ptr_pair = get_raw_pointer_from_smart_pointer(waitable_entry.waitable);
-      if (nullptr == waitable_ptr_pair.second) {
+      if (!waitable_entry.waitable) {
         // In this case it was probably stored as a weak_ptr, but is now locking to nullptr.
         if (HasStrongOwnership) {
           // This will not happen in fixed sized storage, as it holds
@@ -382,8 +376,7 @@ protected:
         needs_pruning_ = true;
         continue;
       }
-      rclcpp::Waitable & waitable = *waitable_ptr_pair.second;
-      waitable.add_to_wait_set(&rcl_wait_set_);
+      waitable_entry.waitable->add_to_wait_set(&rcl_wait_set_);
     }
   }
 

rclcpp/include/rclcpp/wait_set_policies/dynamic_storage.hpp

@@ -204,15 +204,19 @@ public:
   void
   storage_rebuild_rcl_wait_set(const ArrayOfExtraGuardConditions & extra_guard_conditions)
   {
+    this->storage_acquire_ownerships();
+
     this->storage_rebuild_rcl_wait_set_with_sets(
-      subscriptions_,
-      guard_conditions_,
+      shared_subscriptions_,
+      shared_guard_conditions_,
       extra_guard_conditions,
-      timers_,
-      clients_,
-      services_,
-      waitables_
+      shared_timers_,
+      shared_clients_,
+      shared_services_,
+      shared_waitables_
     );
+
+    this->storage_release_ownerships();
   }
 
   template<class EntityT, class SequenceOfEntitiesT>
@@ -407,6 +411,7 @@ public:
         }
       };
     // Lock all the weak pointers and hold them until released.
+    lock_all(subscriptions_, shared_subscriptions_);
     lock_all(guard_conditions_, shared_guard_conditions_);
     lock_all(timers_, shared_timers_);
     lock_all(clients_, shared_clients_);
@@ -438,6 +443,7 @@ public:
           shared_ptr.reset();
         }
       };
+    reset_all(shared_subscriptions_);
     reset_all(shared_guard_conditions_);
     reset_all(shared_timers_);
     reset_all(shared_clients_);

rclcpp/include/rclcpp/wait_set_policies/sequential_synchronization.hpp

@@ -290,7 +290,7 @@ protected:
         return create_wait_result(WaitResultKind::Empty);
       } else {
         // Some other error case, throw.
-        rclcpp::exceptions::throw_from_rcl_error(ret);
+        rclcpp::exceptions::throw_from_rcl_error(ret, "rcl_wait() failed");
       }
     } while (should_loop());
 

rclcpp/include/rclcpp/wait_set_template.hpp

@@ -516,7 +516,7 @@ public:
    * the waitable to be removed, but it will cause the associated entity pointer
    * to be nullptr when introspecting this waitable after waiting.
    *
-   * Note that rclcpp::QOSEventHandlerBase are just a special case of
+   * Note that rclcpp::EventHandlerBase is just a special case of
    * rclcpp::Waitable and can be added with this function.
    *
    * \param[in] waitable Waitable to be added.

rclcpp/package.xml

@@ -2,13 +2,17 @@
 <?xml-model href="http://download.ros.org/schema/package_format2.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
 <package format="2">
   <name>rclcpp</name>
-  <version>17.0.0</version>
+  <version>20.0.0</version>
   <description>The ROS client library in C++.</description>
+
   <maintainer email="ivanpauno@ekumenlabs.com">Ivan Paunovic</maintainer>
-  <maintainer email="jacob@openrobotics.org">Jacob Perron</maintainer>
+  <maintainer email="michel@ekumenlabs.com">Michel Hidalgo</maintainer>
   <maintainer email="william@openrobotics.org">William Woodall</maintainer>
+
   <license>Apache License 2.0</license>
+
   <author email="dthomas@openrobotics.org">Dirk Thomas</author>
+  <author email="jacob@openrobotics.org">Jacob Perron</author>
 
   <buildtool_depend>ament_cmake_ros</buildtool_depend>
   <buildtool_depend>ament_cmake_gen_version_h</buildtool_depend>
@@ -35,6 +39,7 @@
   <depend>rcpputils</depend>
   <depend>rcutils</depend>
   <depend>rmw</depend>
+  <depend>rosidl_dynamic_typesupport</depend>
   <depend>statistics_msgs</depend>
   <depend>tracetools</depend>
 

rclcpp/resource/logging.hpp.em

@@ -124,7 +124,7 @@ def get_rclcpp_suffix_from_features(features):
 ) \
   do { \
     static_assert( \
-      ::std::is_same<typename std::remove_cv<typename std::remove_reference<decltype(logger)>::type>::type, \
+      ::std::is_same<typename std::remove_cv_t<typename std::remove_reference_t<decltype(logger)>>, \
       typename ::rclcpp::Logger>::value, \
       "First argument to logging macros must be an rclcpp::Logger"); \
 @[ if 'throttle' in feature_combination]@ \

rclcpp/src/rclcpp/any_executable.cpp

@@ -16,13 +16,16 @@
 
 using rclcpp::AnyExecutable;
 
+RCLCPP_PUBLIC
 AnyExecutable::AnyExecutable()
 : subscription(nullptr),
   timer(nullptr),
   service(nullptr),
   client(nullptr),
+  waitable(nullptr),
   callback_group(nullptr),
-  node_base(nullptr)
+  node_base(nullptr),
+  data(nullptr)
 {}
 
 AnyExecutable::~AnyExecutable()

rclcpp/src/rclcpp/callback_group.cpp

@@ -12,21 +12,37 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "rclcpp/callback_group.hpp"
+#include <algorithm>
+#include <atomic>
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <stdexcept>
 
-#include <vector>
+#include "rclcpp/callback_group.hpp"
+#include "rclcpp/client.hpp"
+#include "rclcpp/service.hpp"
+#include "rclcpp/subscription_base.hpp"
+#include "rclcpp/timer.hpp"
+#include "rclcpp/waitable.hpp"
 
 using rclcpp::CallbackGroup;
 using rclcpp::CallbackGroupType;
 
 CallbackGroup::CallbackGroup(
   CallbackGroupType group_type,
+  std::function<rclcpp::Context::SharedPtr(void)> get_context,
   bool automatically_add_to_executor_with_node)
 : type_(group_type), associated_with_executor_(false),
   can_be_taken_from_(true),
-  automatically_add_to_executor_with_node_(automatically_add_to_executor_with_node)
+  automatically_add_to_executor_with_node_(automatically_add_to_executor_with_node),
+  get_context_(get_context)
 {}
 
+CallbackGroup::~CallbackGroup()
+{
+  trigger_notify_guard_condition();
+}
 
 std::atomic_bool &
 CallbackGroup::can_be_taken_from()
@@ -40,6 +56,17 @@ CallbackGroup::type() const
   return type_;
 }
 
+size_t
+CallbackGroup::size() const
+{
+  return
+    subscription_ptrs_.size() +
+    service_ptrs_.size() +
+    client_ptrs_.size() +
+    timer_ptrs_.size() +
+    waitable_ptrs_.size();
+}
+
 void CallbackGroup::collect_all_ptrs(
   std::function<void(const rclcpp::SubscriptionBase::SharedPtr &)> sub_func,
   std::function<void(const rclcpp::ServiceBase::SharedPtr &)> service_func,
@@ -97,6 +124,57 @@ CallbackGroup::automatically_add_to_executor_with_node() const
   return automatically_add_to_executor_with_node_;
 }
 
+// \TODO(mjcarroll) Deprecated, remove on tock
+rclcpp::GuardCondition::SharedPtr
+CallbackGroup::get_notify_guard_condition(const rclcpp::Context::SharedPtr context_ptr)
+{
+  std::lock_guard<std::recursive_mutex> lock(notify_guard_condition_mutex_);
+  if (notify_guard_condition_ && context_ptr != notify_guard_condition_->get_context()) {
+    if (associated_with_executor_) {
+      trigger_notify_guard_condition();
+    }
+    notify_guard_condition_ = nullptr;
+  }
+
+  if (!notify_guard_condition_) {
+    notify_guard_condition_ = std::make_shared<rclcpp::GuardCondition>(context_ptr);
+  }
+
+  return notify_guard_condition_;
+}
+
+rclcpp::GuardCondition::SharedPtr
+CallbackGroup::get_notify_guard_condition()
+{
+  std::lock_guard<std::recursive_mutex> lock(notify_guard_condition_mutex_);
+  if (!this->get_context_) {
+    throw std::runtime_error("Callback group was created without context and not passed context");
+  }
+  auto context_ptr = this->get_context_();
+  if (context_ptr && context_ptr->is_valid()) {
+    if (notify_guard_condition_ && context_ptr != notify_guard_condition_->get_context()) {
+      if (associated_with_executor_) {
+        trigger_notify_guard_condition();
+      }
+      notify_guard_condition_ = nullptr;
+    }
+    if (!notify_guard_condition_) {
+      notify_guard_condition_ = std::make_shared<rclcpp::GuardCondition>(context_ptr);
+    }
+    return notify_guard_condition_;
+  }
+  return nullptr;
+}
+
+void
+CallbackGroup::trigger_notify_guard_condition()
+{
+  std::lock_guard<std::recursive_mutex> lock(notify_guard_condition_mutex_);
+  if (notify_guard_condition_) {
+    notify_guard_condition_->trigger();
+  }
+}
+
 void
 CallbackGroup::add_subscription(
   const rclcpp::SubscriptionBase::SharedPtr subscription_ptr)

rclcpp/src/rclcpp/client.cpp

@@ -23,9 +23,11 @@
 #include "rcl/graph.h"
 #include "rcl/node.h"
 #include "rcl/wait.h"
+
 #include "rclcpp/exceptions.hpp"
 #include "rclcpp/node_interfaces/node_base_interface.hpp"
 #include "rclcpp/node_interfaces/node_graph_interface.hpp"
+#include "rclcpp/qos.hpp"
 #include "rclcpp/utilities.hpp"
 #include "rclcpp/logging.hpp"
 
@@ -65,13 +67,6 @@ ClientBase::ClientBase(
     });
 }
 
-ClientBase::~ClientBase()
-{
-  clear_on_new_response_callback();
-  // Make sure the client handle is destructed as early as possible and before the node handle
-  client_handle_.reset();
-}
-
 bool
 ClientBase::take_type_erased_response(void * response_out, rmw_request_id_t & request_header_out)
 {
@@ -248,7 +243,6 @@ ClientBase::set_on_new_response_callback(rcl_event_callback_t callback, const vo
     user_data);
 
   if (RCL_RET_OK != ret) {
-    using rclcpp::exceptions::throw_from_rcl_error;
     throw_from_rcl_error(ret, "failed to set the on new response callback for client");
   }
 }

rclcpp/src/rclcpp/clock.cpp

@@ -67,7 +67,7 @@ Clock::Clock(rcl_clock_type_t clock_type)
 Clock::~Clock() {}
 
 Time
-Clock::now()
+Clock::now() const
 {
   Time now(0, 0, impl_->rcl_clock_.type);
 
@@ -182,6 +182,71 @@ Clock::sleep_for(Duration rel_time, Context::SharedPtr context)
   return sleep_until(now() + rel_time, context);
 }
 
+bool
+Clock::started()
+{
+  if (!rcl_clock_valid(get_clock_handle())) {
+    throw std::runtime_error("clock is not rcl_clock_valid");
+  }
+  return rcl_clock_time_started(get_clock_handle());
+}
+
+bool
+Clock::wait_until_started(Context::SharedPtr context)
+{
+  if (!context || !context->is_valid()) {
+    throw std::runtime_error("context cannot be slept with because it's invalid");
+  }
+  if (!rcl_clock_valid(get_clock_handle())) {
+    throw std::runtime_error("clock cannot be waited on as it is not rcl_clock_valid");
+  }
+
+  if (started()) {
+    return true;
+  } else {
+    // Wait until the first non-zero time
+    return sleep_until(rclcpp::Time(0, 1, get_clock_type()), context);
+  }
+}
+
+bool
+Clock::wait_until_started(
+  const Duration & timeout,
+  Context::SharedPtr context,
+  const Duration & wait_tick_ns)
+{
+  if (!context || !context->is_valid()) {
+    throw std::runtime_error("context cannot be slept with because it's invalid");
+  }
+  if (!rcl_clock_valid(get_clock_handle())) {
+    throw std::runtime_error("clock cannot be waited on as it is not rcl_clock_valid");
+  }
+
+  Clock timeout_clock = Clock(RCL_STEADY_TIME);
+  Time start = timeout_clock.now();
+
+  // Check if the clock has started every wait_tick_ns nanoseconds
+  // Context check checks for rclcpp::shutdown()
+  while (!started() && context->is_valid()) {
+    if (timeout < wait_tick_ns) {
+      timeout_clock.sleep_for(timeout);
+    } else {
+      Duration time_left = start + timeout - timeout_clock.now();
+      if (time_left > wait_tick_ns) {
+        timeout_clock.sleep_for(Duration(wait_tick_ns));
+      } else {
+        timeout_clock.sleep_for(time_left);
+      }
+    }
+
+    if (timeout_clock.now() - start > timeout) {
+      return started();
+    }
+  }
+  return started();
+}
+
+
 bool
 Clock::ros_time_is_active()
 {

rclcpp/src/rclcpp/context.cpp

@@ -219,7 +219,7 @@ Context::init(
     if (0u == count) {
       ret = rcl_logging_configure_with_output_handler(
         &rcl_context_->global_arguments,
-        rcl_init_options_get_allocator(init_options_.get_rcl_init_options()),
+        rcl_init_options_get_allocator(init_options.get_rcl_init_options()),
         rclcpp_logging_output_handler);
       if (RCL_RET_OK != ret) {
         rcl_context_.reset();
@@ -365,49 +365,45 @@ Context::on_shutdown(OnShutdownCallback callback)
 rclcpp::OnShutdownCallbackHandle
 Context::add_on_shutdown_callback(OnShutdownCallback callback)
 {
-  return add_shutdown_callback(ShutdownType::on_shutdown, callback);
+  return add_shutdown_callback<ShutdownType::on_shutdown>(callback);
 }
 
 bool
 Context::remove_on_shutdown_callback(const OnShutdownCallbackHandle & callback_handle)
 {
-  return remove_shutdown_callback(ShutdownType::on_shutdown, callback_handle);
+  return remove_shutdown_callback<ShutdownType::on_shutdown>(callback_handle);
 }
 
 rclcpp::PreShutdownCallbackHandle
 Context::add_pre_shutdown_callback(PreShutdownCallback callback)
 {
-  return add_shutdown_callback(ShutdownType::pre_shutdown, callback);
+  return add_shutdown_callback<ShutdownType::pre_shutdown>(callback);
 }
 
 bool
 Context::remove_pre_shutdown_callback(
   const PreShutdownCallbackHandle & callback_handle)
 {
-  return remove_shutdown_callback(ShutdownType::pre_shutdown, callback_handle);
+  return remove_shutdown_callback<ShutdownType::pre_shutdown>(callback_handle);
 }
 
+template<Context::ShutdownType shutdown_type>
 rclcpp::ShutdownCallbackHandle
 Context::add_shutdown_callback(
-  ShutdownType shutdown_type,
   ShutdownCallback callback)
 {
   auto callback_shared_ptr =
     std::make_shared<ShutdownCallbackHandle::ShutdownCallbackType>(callback);
 
-  switch (shutdown_type) {
-    case ShutdownType::pre_shutdown:
-      {
-        std::lock_guard<std::mutex> lock(pre_shutdown_callbacks_mutex_);
-        pre_shutdown_callbacks_.emplace(callback_shared_ptr);
-      }
-      break;
-    case ShutdownType::on_shutdown:
-      {
-        std::lock_guard<std::mutex> lock(on_shutdown_callbacks_mutex_);
-        on_shutdown_callbacks_.emplace(callback_shared_ptr);
-      }
-      break;
+  static_assert(
+    shutdown_type == ShutdownType::pre_shutdown || shutdown_type == ShutdownType::on_shutdown);
+
+  if constexpr (shutdown_type == ShutdownType::pre_shutdown) {
+    std::lock_guard<std::mutex> lock(pre_shutdown_callbacks_mutex_);
+    pre_shutdown_callbacks_.emplace_back(callback_shared_ptr);
+  } else {
+    std::lock_guard<std::mutex> lock(on_shutdown_callbacks_mutex_);
+    on_shutdown_callbacks_.emplace_back(callback_shared_ptr);
   }
 
   ShutdownCallbackHandle callback_handle;
@@ -415,73 +411,74 @@ Context::add_shutdown_callback(
   return callback_handle;
 }
 
+template<Context::ShutdownType shutdown_type>
 bool
 Context::remove_shutdown_callback(
-  ShutdownType shutdown_type,
   const ShutdownCallbackHandle & callback_handle)
 {
-  std::mutex * mutex_ptr = nullptr;
-  std::unordered_set<
-    std::shared_ptr<ShutdownCallbackHandle::ShutdownCallbackType>> * callback_list_ptr;
-
-  switch (shutdown_type) {
-    case ShutdownType::pre_shutdown:
-      mutex_ptr = &pre_shutdown_callbacks_mutex_;
-      callback_list_ptr = &pre_shutdown_callbacks_;
-      break;
-    case ShutdownType::on_shutdown:
-      mutex_ptr = &on_shutdown_callbacks_mutex_;
-      callback_list_ptr = &on_shutdown_callbacks_;
-      break;
-  }
-
-  std::lock_guard<std::mutex> lock(*mutex_ptr);
-  auto callback_shared_ptr = callback_handle.callback.lock();
+  const auto callback_shared_ptr = callback_handle.callback.lock();
   if (callback_shared_ptr == nullptr) {
     return false;
   }
-  return callback_list_ptr->erase(callback_shared_ptr) == 1;
+
+  const auto remove_callback = [&callback_shared_ptr](auto & mutex, auto & callback_vector) {
+      const std::lock_guard<std::mutex> lock(mutex);
+      auto iter = callback_vector.begin();
+      for (; iter != callback_vector.end(); iter++) {
+        if ((*iter).get() == callback_shared_ptr.get()) {
+          break;
+        }
+      }
+      if (iter == callback_vector.end()) {
+        return false;
+      }
+      callback_vector.erase(iter);
+      return true;
+    };
+
+  static_assert(
+    shutdown_type == ShutdownType::pre_shutdown || shutdown_type == ShutdownType::on_shutdown);
+
+  if constexpr (shutdown_type == ShutdownType::pre_shutdown) {
+    return remove_callback(pre_shutdown_callbacks_mutex_, pre_shutdown_callbacks_);
+  } else {
+    return remove_callback(on_shutdown_callbacks_mutex_, on_shutdown_callbacks_);
+  }
 }
 
 std::vector<rclcpp::Context::OnShutdownCallback>
 Context::get_on_shutdown_callbacks() const
 {
-  return get_shutdown_callback(ShutdownType::on_shutdown);
+  return get_shutdown_callback<ShutdownType::on_shutdown>();
 }
 
 std::vector<rclcpp::Context::PreShutdownCallback>
 Context::get_pre_shutdown_callbacks() const
 {
-  return get_shutdown_callback(ShutdownType::pre_shutdown);
+  return get_shutdown_callback<ShutdownType::pre_shutdown>();
 }
 
+template<Context::ShutdownType shutdown_type>
 std::vector<rclcpp::Context::ShutdownCallback>
-Context::get_shutdown_callback(ShutdownType shutdown_type) const
+Context::get_shutdown_callback() const
 {
-  std::mutex * mutex_ptr = nullptr;
-  const std::unordered_set<
-    std::shared_ptr<ShutdownCallbackHandle::ShutdownCallbackType>> * callback_list_ptr;
+  const auto get_callback_vector = [this](auto & mutex, auto & callback_set) {
+      const std::lock_guard<std::mutex> lock(mutex);
+      std::vector<rclcpp::Context::ShutdownCallback> callbacks;
+      for (auto & callback : callback_set) {
+        callbacks.push_back(*callback);
+      }
+      return callbacks;
+    };
 
-  switch (shutdown_type) {
-    case ShutdownType::pre_shutdown:
-      mutex_ptr = &pre_shutdown_callbacks_mutex_;
-      callback_list_ptr = &pre_shutdown_callbacks_;
-      break;
-    case ShutdownType::on_shutdown:
-      mutex_ptr = &on_shutdown_callbacks_mutex_;
-      callback_list_ptr = &on_shutdown_callbacks_;
-      break;
+  static_assert(
+    shutdown_type == ShutdownType::pre_shutdown || shutdown_type == ShutdownType::on_shutdown);
+
+  if constexpr (shutdown_type == ShutdownType::pre_shutdown) {
+    return get_callback_vector(pre_shutdown_callbacks_mutex_, pre_shutdown_callbacks_);
+  } else {
+    return get_callback_vector(on_shutdown_callbacks_mutex_, on_shutdown_callbacks_);
   }
-
-  std::vector<rclcpp::Context::ShutdownCallback> callbacks;
-  {
-    std::lock_guard<std::mutex> lock(*mutex_ptr);
-    for (auto & iter : *callback_list_ptr) {
-      callbacks.emplace_back(*iter);
-    }
-  }
-
-  return callbacks;
 }
 
 std::shared_ptr<rcl_context_t>

rclcpp/src/rclcpp/dynamic_typesupport/dynamic_message.cpp

@@ -0,0 +1,40 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <rosidl_dynamic_typesupport/api/dynamic_type.h>
+#include <rosidl_dynamic_typesupport/api/dynamic_data.h>
+#include <rosidl_dynamic_typesupport/api/serialization_support.h>
+#include <rosidl_dynamic_typesupport/types.h>
+
+#include <memory>
+#include <string>
+
+#include "rcl/allocator.h"
+#include "rcl/types.h"
+#include "rcutils/logging_macros.h"
+
+#include "rclcpp/dynamic_typesupport/dynamic_message.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type_builder.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
+#include "rclcpp/exceptions.hpp"
+
+
+using rclcpp::dynamic_typesupport::DynamicMessage;
+using rclcpp::dynamic_typesupport::DynamicMessageType;
+using rclcpp::dynamic_typesupport::DynamicMessageTypeBuilder;
+using rclcpp::dynamic_typesupport::DynamicSerializationSupport;
+
+DynamicMessage::~DynamicMessage()
+{}  // STUBBED

rclcpp/src/rclcpp/dynamic_typesupport/dynamic_message_type.cpp

@@ -0,0 +1,38 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <rosidl_dynamic_typesupport/api/dynamic_data.h>
+#include <rosidl_dynamic_typesupport/api/dynamic_type.h>
+#include <rosidl_dynamic_typesupport/api/serialization_support.h>
+#include <rosidl_dynamic_typesupport/types.h>
+
+#include <memory>
+#include <string>
+
+#include "rcutils/logging_macros.h"
+
+#include "rclcpp/dynamic_typesupport/dynamic_message.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type_builder.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
+#include "rclcpp/exceptions.hpp"
+
+
+using rclcpp::dynamic_typesupport::DynamicMessage;
+using rclcpp::dynamic_typesupport::DynamicMessageType;
+using rclcpp::dynamic_typesupport::DynamicMessageTypeBuilder;
+using rclcpp::dynamic_typesupport::DynamicSerializationSupport;
+
+DynamicMessageType::~DynamicMessageType()
+{}  // STUBBED

rclcpp/src/rclcpp/dynamic_typesupport/dynamic_message_type_builder.cpp

@@ -0,0 +1,37 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <rosidl_dynamic_typesupport/api/dynamic_data.h>
+#include <rosidl_dynamic_typesupport/api/dynamic_type.h>
+#include <rosidl_dynamic_typesupport/api/serialization_support.h>
+#include <rosidl_dynamic_typesupport/types.h>
+
+#include <memory>
+#include <string>
+
+#include "rcutils/logging_macros.h"
+
+#include "rclcpp/dynamic_typesupport/dynamic_message.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type_builder.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
+#include "rclcpp/exceptions.hpp"
+
+using rclcpp::dynamic_typesupport::DynamicMessage;
+using rclcpp::dynamic_typesupport::DynamicMessageType;
+using rclcpp::dynamic_typesupport::DynamicMessageTypeBuilder;
+using rclcpp::dynamic_typesupport::DynamicSerializationSupport;
+
+DynamicMessageTypeBuilder::~DynamicMessageTypeBuilder()
+{}  // STUBBED

rclcpp/src/rclcpp/dynamic_typesupport/dynamic_message_type_support.cpp

@@ -0,0 +1,49 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <rosidl_dynamic_typesupport/identifier.h>
+#include <rosidl_dynamic_typesupport/types.h>
+#include <rosidl_runtime_c/message_type_support_struct.h>
+#include <rosidl_runtime_c/type_description_utils.h>
+#include <rosidl_runtime_c/type_description/type_description__functions.h>
+#include <rosidl_runtime_c/type_description/type_description__struct.h>
+#include <rosidl_runtime_c/type_description/type_source__functions.h>
+#include <rosidl_runtime_c/type_description/type_source__struct.h>
+
+#include <memory>
+#include <string>
+
+#include "rcl/allocator.h"
+#include "rcl/dynamic_message_type_support.h"
+#include "rcl/type_hash.h"
+#include "rcl/types.h"
+#include "rcutils/logging_macros.h"
+#include "rcutils/types/rcutils_ret.h"
+#include "rmw/dynamic_message_type_support.h"
+
+#include "rclcpp/dynamic_typesupport/dynamic_message.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_message_type_support.hpp"
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
+#include "rclcpp/exceptions.hpp"
+#include "rclcpp/macros.hpp"
+#include "rclcpp/visibility_control.hpp"
+
+using rclcpp::dynamic_typesupport::DynamicMessage;
+using rclcpp::dynamic_typesupport::DynamicMessageType;
+using rclcpp::dynamic_typesupport::DynamicMessageTypeSupport;
+using rclcpp::dynamic_typesupport::DynamicSerializationSupport;
+
+DynamicMessageTypeSupport::~DynamicMessageTypeSupport()
+{}  // STUBBED

rclcpp/src/rclcpp/dynamic_typesupport/dynamic_serialization_support.cpp

@@ -0,0 +1,46 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <rcl/allocator.h>
+#include <rcutils/logging_macros.h>
+#include <rmw/dynamic_message_type_support.h>
+#include <rmw/ret_types.h>
+#include <rosidl_dynamic_typesupport/api/serialization_support.h>
+
+#include <memory>
+#include <string>
+
+#include "rclcpp/dynamic_typesupport/dynamic_serialization_support.hpp"
+#include "rclcpp/exceptions.hpp"
+
+using rclcpp::dynamic_typesupport::DynamicSerializationSupport;
+
+// CONSTRUCTION ====================================================================================
+DynamicSerializationSupport::DynamicSerializationSupport(rcl_allocator_t allocator)
+: DynamicSerializationSupport::DynamicSerializationSupport("", allocator)
+{
+  throw std::runtime_error("Unimplemented");
+}
+
+DynamicSerializationSupport::DynamicSerializationSupport(
+  const std::string & /*serialization_library_name*/,
+  rcl_allocator_t /*allocator*/)
+: rosidl_serialization_support_(
+    rosidl_dynamic_typesupport_get_zero_initialized_serialization_support())
+{
+  throw std::runtime_error("Unimplemented");
+}
+
+DynamicSerializationSupport::~DynamicSerializationSupport()
+{}  // STUBBED

rclcpp/src/rclcpp/event_handler.cpp

@@ -12,9 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <stdexcept>
 #include <string>
 
-#include "rclcpp/qos_event.hpp"
+#include "rcl/event.h"
+
+#include "rclcpp/event_handler.hpp"
+#include "rclcpp/exceptions/exceptions.hpp"
 
 namespace rclcpp
 {
@@ -33,11 +37,14 @@ UnsupportedEventTypeException::UnsupportedEventTypeException(
   std::runtime_error(prefix + (prefix.empty() ? "" : ": ") + base_exc.formatted_message)
 {}
 
-QOSEventHandlerBase::~QOSEventHandlerBase()
+EventHandlerBase::~EventHandlerBase()
 {
-  if (on_new_event_callback_) {
-    clear_on_ready_callback();
-  }
+  // Since the rmw event listener holds a reference to
+  // this callback, we need to clear it on destruction of this class.
+  // This clearing is not needed for other rclcpp entities like pub/subs, since
+  // they do own the underlying rmw entities, which are destroyed
+  // on their rclcpp destructors, thus no risk of dangling pointers.
+  clear_on_ready_callback();
 
   if (rcl_event_fini(&event_handle_) != RCL_RET_OK) {
     RCUTILS_LOG_ERROR_NAMED(
@@ -49,14 +56,14 @@ QOSEventHandlerBase::~QOSEventHandlerBase()
 
 /// Get the number of ready events.
 size_t
-QOSEventHandlerBase::get_number_of_ready_events()
+EventHandlerBase::get_number_of_ready_events()
 {
   return 1;
 }
 
 /// Add the Waitable to a wait set.
 void
-QOSEventHandlerBase::add_to_wait_set(rcl_wait_set_t * wait_set)
+EventHandlerBase::add_to_wait_set(rcl_wait_set_t * wait_set)
 {
   rcl_ret_t ret = rcl_wait_set_add_event(wait_set, &event_handle_, &wait_set_event_index_);
   if (RCL_RET_OK != ret) {
@@ -66,13 +73,13 @@ QOSEventHandlerBase::add_to_wait_set(rcl_wait_set_t * wait_set)
 
 /// Check if the Waitable is ready.
 bool
-QOSEventHandlerBase::is_ready(rcl_wait_set_t * wait_set)
+EventHandlerBase::is_ready(rcl_wait_set_t * wait_set)
 {
   return wait_set->events[wait_set_event_index_] == &event_handle_;
 }
 
 void
-QOSEventHandlerBase::set_on_new_event_callback(
+EventHandlerBase::set_on_new_event_callback(
   rcl_event_callback_t callback,
   const void * user_data)
 {
@@ -83,7 +90,7 @@ QOSEventHandlerBase::set_on_new_event_callback(
 
   if (RCL_RET_OK != ret) {
     using rclcpp::exceptions::throw_from_rcl_error;
-    throw_from_rcl_error(ret, "failed to set the on new message callback for QOS Event");
+    throw_from_rcl_error(ret, "failed to set the on new message callback for Event");
   }
 }
 

rclcpp/src/rclcpp/executors/executor_entities_collection.cpp

@@ -0,0 +1,228 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "rclcpp/executors/executor_entities_collection.hpp"
+
+namespace rclcpp
+{
+namespace executors
+{
+bool ExecutorEntitiesCollection::empty() const
+{
+  return
+    subscriptions.empty() &&
+    timers.empty() &&
+    guard_conditions.empty() &&
+    clients.empty() &&
+    services.empty() &&
+    waitables.empty();
+}
+
+void ExecutorEntitiesCollection::clear()
+{
+  subscriptions.clear();
+  timers.clear();
+  guard_conditions.clear();
+  clients.clear();
+  services.clear();
+  waitables.clear();
+}
+
+void
+build_entities_collection(
+  const std::vector<rclcpp::CallbackGroup::WeakPtr> & callback_groups,
+  ExecutorEntitiesCollection & collection)
+{
+  collection.clear();
+
+  for (auto weak_group_ptr : callback_groups) {
+    auto group_ptr = weak_group_ptr.lock();
+    if (!group_ptr) {
+      continue;
+    }
+
+    if (group_ptr->can_be_taken_from().load()) {
+      group_ptr->collect_all_ptrs(
+        [&collection, weak_group_ptr](const rclcpp::SubscriptionBase::SharedPtr & subscription) {
+          collection.subscriptions.insert(
+            {
+              subscription->get_subscription_handle().get(),
+              {subscription, weak_group_ptr}
+            });
+        },
+        [&collection, weak_group_ptr](const rclcpp::ServiceBase::SharedPtr & service) {
+          collection.services.insert(
+            {
+              service->get_service_handle().get(),
+              {service, weak_group_ptr}
+            });
+        },
+        [&collection, weak_group_ptr](const rclcpp::ClientBase::SharedPtr & client) {
+          collection.clients.insert(
+            {
+              client->get_client_handle().get(),
+              {client, weak_group_ptr}
+            });
+        },
+        [&collection, weak_group_ptr](const rclcpp::TimerBase::SharedPtr & timer) {
+          collection.timers.insert(
+            {
+              timer->get_timer_handle().get(),
+              {timer, weak_group_ptr}
+            });
+        },
+        [&collection, weak_group_ptr](const rclcpp::Waitable::SharedPtr & waitable) {
+          collection.waitables.insert(
+            {
+              waitable.get(),
+              {waitable, weak_group_ptr}
+            });
+        }
+      );
+    }
+  }
+}
+
+size_t
+ready_executables(
+  const ExecutorEntitiesCollection & collection,
+  rclcpp::WaitResult<rclcpp::WaitSet> & wait_result,
+  std::deque<rclcpp::AnyExecutable> & executables
+)
+{
+  size_t added = 0;
+  if (wait_result.kind() != rclcpp::WaitResultKind::Ready) {
+    return added;
+  }
+  auto rcl_wait_set = wait_result.get_wait_set().get_rcl_wait_set();
+
+  // Cache shared pointers to groups to avoid extra work re-locking them
+  std::map<rclcpp::CallbackGroup::WeakPtr,
+    rclcpp::CallbackGroup::SharedPtr,
+    std::owner_less<rclcpp::CallbackGroup::WeakPtr>> group_map;
+
+  auto group_cache = [&group_map](const rclcpp::CallbackGroup::WeakPtr & weak_cbg_ptr)
+    {
+      if (group_map.count(weak_cbg_ptr) == 0) {
+        group_map.insert({weak_cbg_ptr, weak_cbg_ptr.lock()});
+      }
+      return group_map.find(weak_cbg_ptr)->second;
+    };
+
+  for (size_t ii = 0; ii < rcl_wait_set.size_of_timers; ++ii) {
+    if (nullptr == rcl_wait_set.timers[ii]) {continue;}
+    auto entity_iter = collection.timers.find(rcl_wait_set.timers[ii]);
+    if (entity_iter != collection.timers.end()) {
+      auto entity = entity_iter->second.entity.lock();
+      if (!entity) {
+        continue;
+      }
+      auto group_info = group_cache(entity_iter->second.callback_group);
+      if (group_info && !group_info->can_be_taken_from().load()) {
+        continue;
+      }
+      if (!entity->call()) {
+        continue;
+      }
+      rclcpp::AnyExecutable exec;
+      exec.timer = entity;
+      exec.callback_group = group_info;
+      executables.push_back(exec);
+      added++;
+    }
+  }
+
+  for (size_t ii = 0; ii < rcl_wait_set.size_of_subscriptions; ++ii) {
+    if (nullptr == rcl_wait_set.subscriptions[ii]) {continue;}
+    auto entity_iter = collection.subscriptions.find(rcl_wait_set.subscriptions[ii]);
+    if (entity_iter != collection.subscriptions.end()) {
+      auto entity = entity_iter->second.entity.lock();
+      if (!entity) {
+        continue;
+      }
+      auto group_info = group_cache(entity_iter->second.callback_group);
+      if (group_info && !group_info->can_be_taken_from().load()) {
+        continue;
+      }
+      rclcpp::AnyExecutable exec;
+      exec.subscription = entity;
+      exec.callback_group = group_info;
+      executables.push_back(exec);
+      added++;
+    }
+  }
+
+  for (size_t ii = 0; ii < rcl_wait_set.size_of_services; ++ii) {
+    if (nullptr == rcl_wait_set.services[ii]) {continue;}
+    auto entity_iter = collection.services.find(rcl_wait_set.services[ii]);
+    if (entity_iter != collection.services.end()) {
+      auto entity = entity_iter->second.entity.lock();
+      if (!entity) {
+        continue;
+      }
+      auto group_info = group_cache(entity_iter->second.callback_group);
+      if (group_info && !group_info->can_be_taken_from().load()) {
+        continue;
+      }
+      rclcpp::AnyExecutable exec;
+      exec.service = entity;
+      exec.callback_group = group_info;
+      executables.push_back(exec);
+      added++;
+    }
+  }
+
+  for (size_t ii = 0; ii < rcl_wait_set.size_of_clients; ++ii) {
+    if (nullptr == rcl_wait_set.clients[ii]) {continue;}
+    auto entity_iter = collection.clients.find(rcl_wait_set.clients[ii]);
+    if (entity_iter != collection.clients.end()) {
+      auto entity = entity_iter->second.entity.lock();
+      if (!entity) {
+        continue;
+      }
+      auto group_info = group_cache(entity_iter->second.callback_group);
+      if (group_info && !group_info->can_be_taken_from().load()) {
+        continue;
+      }
+      rclcpp::AnyExecutable exec;
+      exec.client = entity;
+      exec.callback_group = group_info;
+      executables.push_back(exec);
+      added++;
+    }
+  }
+
+  for (auto & [handle, entry] : collection.waitables) {
+    auto waitable = entry.entity.lock();
+    if (!waitable) {
+      continue;
+    }
+    if (!waitable->is_ready(&rcl_wait_set)) {
+      continue;
+    }
+    auto group_info = group_cache(entry.callback_group);
+    if (group_info && !group_info->can_be_taken_from().load()) {
+      continue;
+    }
+    rclcpp::AnyExecutable exec;
+    exec.waitable = waitable;
+    exec.callback_group = group_info;
+    exec.data = waitable->take_data();
+    executables.push_back(exec);
+    added++;
+  }
+  return added;
+}
+}  // namespace executors
+}  // namespace rclcpp

rclcpp/src/rclcpp/executors/executor_entities_collector.cpp

@@ -0,0 +1,420 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <set>
+
+#include "rclcpp/executors/executor_entities_collector.hpp"
+#include "rclcpp/executors/executor_notify_waitable.hpp"
+#include "rclcpp/node_interfaces/node_base_interface.hpp"
+
+namespace rclcpp
+{
+namespace executors
+{
+
+ExecutorEntitiesCollector::ExecutorEntitiesCollector(
+  std::shared_ptr<ExecutorNotifyWaitable> notify_waitable)
+: notify_waitable_(notify_waitable)
+{
+}
+
+ExecutorEntitiesCollector::~ExecutorEntitiesCollector()
+{
+  for (auto weak_node_it = weak_nodes_.begin(); weak_node_it != weak_nodes_.end(); ) {
+    weak_node_it = remove_weak_node(weak_node_it);
+  }
+
+  for (auto weak_group_it = automatically_added_groups_.begin();
+    weak_group_it != automatically_added_groups_.end(); )
+  {
+    weak_group_it = remove_weak_callback_group(weak_group_it, automatically_added_groups_);
+  }
+
+  for (auto weak_group_it = manually_added_groups_.begin();
+    weak_group_it != manually_added_groups_.end(); )
+  {
+    weak_group_it = remove_weak_callback_group(weak_group_it, manually_added_groups_);
+  }
+
+  for (auto weak_node_ptr : pending_added_nodes_) {
+    auto node_ptr = weak_node_ptr.lock();
+    if (node_ptr) {
+      node_ptr->get_associated_with_executor_atomic().store(false);
+    }
+  }
+  pending_added_nodes_.clear();
+  pending_removed_nodes_.clear();
+
+  for (auto weak_group_ptr : pending_manually_added_groups_) {
+    auto group_ptr = weak_group_ptr.lock();
+    if (group_ptr) {
+      group_ptr->get_associated_with_executor_atomic().store(false);
+    }
+  }
+  pending_manually_added_groups_.clear();
+  pending_manually_removed_groups_.clear();
+}
+
+bool
+ExecutorEntitiesCollector::has_pending() const
+{
+  std::lock_guard<std::mutex> lock(mutex_);
+  return pending_manually_added_groups_.size() != 0 ||
+         pending_manually_removed_groups_.size() != 0 ||
+         pending_added_nodes_.size() != 0 ||
+         pending_removed_nodes_.size() != 0;
+}
+
+void
+ExecutorEntitiesCollector::add_node(rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr)
+{
+  // If the node already has an executor
+  std::atomic_bool & has_executor = node_ptr->get_associated_with_executor_atomic();
+  if (has_executor.exchange(true)) {
+    throw std::runtime_error(
+            std::string("Node '") + node_ptr->get_fully_qualified_name() +
+            "' has already been added to an executor.");
+  }
+
+  std::lock_guard<std::mutex> lock(mutex_);
+  bool associated = weak_nodes_.count(node_ptr) != 0;
+  bool add_queued = pending_added_nodes_.count(node_ptr) != 0;
+  bool remove_queued = pending_removed_nodes_.count(node_ptr) != 0;
+
+  if ((associated || add_queued) && !remove_queued) {
+    throw std::runtime_error(
+            std::string("Node '") + node_ptr->get_fully_qualified_name() +
+            "' has already been added to this executor.");
+  }
+
+  this->pending_added_nodes_.insert(node_ptr);
+}
+
+void
+ExecutorEntitiesCollector::remove_node(
+  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr)
+{
+  std::atomic_bool & has_executor = node_ptr->get_associated_with_executor_atomic();
+  if (!has_executor.exchange(false)) {
+    throw std::runtime_error(
+            std::string("Node '") + node_ptr->get_fully_qualified_name() +
+            "' needs to be associated with an executor.");
+  }
+
+  std::lock_guard<std::mutex> lock(mutex_);
+  bool associated = weak_nodes_.count(node_ptr) != 0;
+  bool add_queued = pending_added_nodes_.count(node_ptr) != 0;
+  bool remove_queued = pending_removed_nodes_.count(node_ptr) != 0;
+
+  if (!(associated || add_queued) || remove_queued) {
+    throw std::runtime_error(
+            std::string("Node '") + node_ptr->get_fully_qualified_name() +
+            "' needs to be associated with this executor.");
+  }
+
+  this->pending_removed_nodes_.insert(node_ptr);
+}
+
+void
+ExecutorEntitiesCollector::add_callback_group(rclcpp::CallbackGroup::SharedPtr group_ptr)
+{
+  std::atomic_bool & has_executor = group_ptr->get_associated_with_executor_atomic();
+  if (has_executor.exchange(true)) {
+    throw std::runtime_error("Callback group has already been added to an executor.");
+  }
+
+  std::lock_guard<std::mutex> lock(mutex_);
+  bool associated = manually_added_groups_.count(group_ptr) != 0;
+  bool add_queued = pending_manually_added_groups_.count(group_ptr) != 0;
+  bool remove_queued = pending_manually_removed_groups_.count(group_ptr) != 0;
+
+  if ((associated || add_queued) && !remove_queued) {
+    throw std::runtime_error("Callback group has already been added to this executor.");
+  }
+
+  this->pending_manually_added_groups_.insert(group_ptr);
+}
+
+void
+ExecutorEntitiesCollector::remove_callback_group(rclcpp::CallbackGroup::SharedPtr group_ptr)
+{
+  if (!group_ptr->get_associated_with_executor_atomic().load()) {
+    throw std::runtime_error("Callback group needs to be associated with an executor.");
+  }
+  /**
+   * TODO(mjcarroll): The callback groups, being created by a node, should never outlive
+   * the node. Since we haven't historically enforced this, turning this on may cause
+   * previously-functional code to fail.
+   * Consider re-enablng this check (along with corresponding CallbackGroup::has_valid_node),
+   * when we can guarantee node/group lifetimes.
+  if (!group_ptr->has_valid_node()) {
+    throw std::runtime_error("Node must not be deleted before its callback group(s).");
+  }
+  */
+  auto weak_group_ptr = rclcpp::CallbackGroup::WeakPtr(group_ptr);
+  std::lock_guard<std::mutex> lock(mutex_);
+  bool associated = manually_added_groups_.count(group_ptr) != 0;
+  bool add_queued = pending_manually_added_groups_.count(group_ptr) != 0;
+  bool remove_queued = pending_manually_removed_groups_.count(group_ptr) != 0;
+
+  if (!(associated || add_queued) || remove_queued) {
+    throw std::runtime_error("Callback group needs to be associated with this executor.");
+  }
+
+  this->pending_manually_removed_groups_.insert(group_ptr);
+}
+
+std::vector<rclcpp::CallbackGroup::WeakPtr>
+ExecutorEntitiesCollector::get_all_callback_groups() const
+{
+  std::vector<rclcpp::CallbackGroup::WeakPtr> groups;
+  std::lock_guard<std::mutex> lock(mutex_);
+  for (const auto & group_ptr : manually_added_groups_) {
+    groups.push_back(group_ptr);
+  }
+  for (auto const & group_ptr : automatically_added_groups_) {
+    groups.push_back(group_ptr);
+  }
+  return groups;
+}
+
+std::vector<rclcpp::CallbackGroup::WeakPtr>
+ExecutorEntitiesCollector::get_manually_added_callback_groups() const
+{
+  std::vector<rclcpp::CallbackGroup::WeakPtr> groups;
+  std::lock_guard<std::mutex> lock(mutex_);
+  for (const auto & group_ptr : manually_added_groups_) {
+    groups.push_back(group_ptr);
+  }
+  return groups;
+}
+
+std::vector<rclcpp::CallbackGroup::WeakPtr>
+ExecutorEntitiesCollector::get_automatically_added_callback_groups() const
+{
+  std::vector<rclcpp::CallbackGroup::WeakPtr> groups;
+  std::lock_guard<std::mutex> lock(mutex_);
+  for (auto const & group_ptr : automatically_added_groups_) {
+    groups.push_back(group_ptr);
+  }
+  return groups;
+}
+
+void
+ExecutorEntitiesCollector::update_collections()
+{
+  std::lock_guard<std::mutex> lock(mutex_);
+  this->process_queues();
+  this->add_automatically_associated_callback_groups(this->weak_nodes_);
+  this->prune_invalid_nodes_and_groups();
+}
+
+ExecutorEntitiesCollector::NodeCollection::iterator
+ExecutorEntitiesCollector::remove_weak_node(NodeCollection::iterator weak_node)
+{
+  // Disassociate the guard condition from the executor notify waitable
+  auto guard_condition_it = weak_nodes_to_guard_conditions_.find(*weak_node);
+  if (guard_condition_it != weak_nodes_to_guard_conditions_.end()) {
+    this->notify_waitable_->remove_guard_condition(guard_condition_it->second);
+    weak_nodes_to_guard_conditions_.erase(guard_condition_it);
+  }
+
+  // Mark the node as disassociated (if the node is still valid)
+  auto node_ptr = weak_node->lock();
+  if (node_ptr) {
+    std::atomic_bool & has_executor = node_ptr->get_associated_with_executor_atomic();
+    has_executor.store(false);
+  }
+
+  // Remove the node from tracked nodes
+  return weak_nodes_.erase(weak_node);
+}
+
+ExecutorEntitiesCollector::CallbackGroupCollection::iterator
+ExecutorEntitiesCollector::remove_weak_callback_group(
+  CallbackGroupCollection::iterator weak_group_it,
+  CallbackGroupCollection & collection
+)
+{
+  // Disassociate the guard condition from the executor notify waitable
+  auto guard_condition_it = weak_groups_to_guard_conditions_.find(*weak_group_it);
+  if (guard_condition_it != weak_groups_to_guard_conditions_.end()) {
+    this->notify_waitable_->remove_guard_condition(guard_condition_it->second);
+    weak_groups_to_guard_conditions_.erase(guard_condition_it);
+  }
+
+  // Mark the node as disassociated (if the group is still valid)
+  auto group_ptr = weak_group_it->lock();
+  if (group_ptr) {
+    /**
+     * TODO(mjcarroll): The callback groups, being created by a node, should never outlive
+     * the node. Since we haven't historically enforced this, turning this on may cause
+     * previously-functional code to fail.
+     * Consider re-enablng this check (along with corresponding CallbackGroup::has_valid_node),
+     * when we can guarantee node/group lifetimes.
+    if (!group_ptr->has_valid_node()) {
+      throw std::runtime_error("Node must not be deleted before its callback group(s).");
+    }
+    */
+    std::atomic_bool & has_executor = group_ptr->get_associated_with_executor_atomic();
+    has_executor.store(false);
+  }
+
+  // Remove the node from tracked nodes
+  return collection.erase(weak_group_it);
+}
+
+void
+ExecutorEntitiesCollector::add_callback_group_to_collection(
+  rclcpp::CallbackGroup::SharedPtr group_ptr,
+  CallbackGroupCollection & collection)
+{
+  auto iter = collection.insert(group_ptr);
+  if (iter.second == false) {
+    throw std::runtime_error("Callback group has already been added to this executor.");
+  }
+
+  // Store node guard condition in map and add it to the notify waitable
+  auto group_guard_condition = group_ptr->get_notify_guard_condition();
+  weak_groups_to_guard_conditions_.insert({group_ptr, group_guard_condition});
+  this->notify_waitable_->add_guard_condition(group_guard_condition);
+}
+
+void
+ExecutorEntitiesCollector::process_queues()
+{
+  for (auto weak_node_ptr : pending_added_nodes_) {
+    auto node_ptr = weak_node_ptr.lock();
+    if (!node_ptr) {
+      continue;
+    }
+    weak_nodes_.insert(weak_node_ptr);
+    this->add_automatically_associated_callback_groups({weak_node_ptr});
+
+    // Store node guard condition in map and add it to the notify waitable
+    auto node_guard_condition = node_ptr->get_shared_notify_guard_condition();
+    weak_nodes_to_guard_conditions_.insert({weak_node_ptr, node_guard_condition});
+    this->notify_waitable_->add_guard_condition(node_guard_condition);
+  }
+  pending_added_nodes_.clear();
+
+  for (auto weak_node_ptr : pending_removed_nodes_) {
+    auto node_it = weak_nodes_.find(weak_node_ptr);
+    if (node_it != weak_nodes_.end()) {
+      remove_weak_node(node_it);
+    } else {
+      // The node may have been destroyed and removed from the colletion before
+      // we processed the queues.  Don't throw if the pointer is already expired.
+      if (!weak_node_ptr.expired()) {
+        throw std::runtime_error("Node needs to be associated with this executor.");
+      }
+    }
+
+    auto node_ptr = weak_node_ptr.lock();
+    if (node_ptr) {
+      for (auto group_it = automatically_added_groups_.begin();
+        group_it != automatically_added_groups_.end(); )
+      {
+        auto group_ptr = group_it->lock();
+        if (node_ptr->callback_group_in_node(group_ptr)) {
+          group_it = remove_weak_callback_group(group_it, automatically_added_groups_);
+        } else {
+          ++group_it;
+        }
+      }
+    }
+  }
+  pending_removed_nodes_.clear();
+
+  for (auto weak_group_ptr : pending_manually_added_groups_) {
+    auto group_ptr = weak_group_ptr.lock();
+    if (group_ptr) {
+      this->add_callback_group_to_collection(group_ptr, manually_added_groups_);
+    }
+  }
+  pending_manually_added_groups_.clear();
+
+  for (auto weak_group_ptr : pending_manually_removed_groups_) {
+    auto group_ptr = weak_group_ptr.lock();
+    if (group_ptr) {
+      auto group_it = manually_added_groups_.find(group_ptr);
+      if (group_it != manually_added_groups_.end()) {
+        remove_weak_callback_group(group_it, manually_added_groups_);
+      } else {
+        throw std::runtime_error(
+                "Attempting to remove a callback group not added to this executor.");
+      }
+    }
+  }
+  pending_manually_removed_groups_.clear();
+}
+
+void
+ExecutorEntitiesCollector::add_automatically_associated_callback_groups(
+  const NodeCollection & nodes_to_check)
+{
+  for (auto & weak_node : nodes_to_check) {
+    auto node = weak_node.lock();
+    if (node) {
+      node->for_each_callback_group(
+        [this, node](rclcpp::CallbackGroup::SharedPtr group_ptr)
+        {
+          if (!group_ptr->get_associated_with_executor_atomic().load() &&
+          group_ptr->automatically_add_to_executor_with_node())
+          {
+            std::atomic_bool & has_executor = group_ptr->get_associated_with_executor_atomic();
+            if (has_executor.exchange(true)) {
+              throw std::runtime_error("Callback group has already been added to an executor.");
+            }
+            this->add_callback_group_to_collection(group_ptr, this->automatically_added_groups_);
+          }
+        });
+    }
+  }
+}
+
+void
+ExecutorEntitiesCollector::prune_invalid_nodes_and_groups()
+{
+  for (auto node_it = weak_nodes_.begin();
+    node_it != weak_nodes_.end(); )
+  {
+    if (node_it->expired()) {
+      node_it = remove_weak_node(node_it);
+    } else {
+      node_it++;
+    }
+  }
+  for (auto group_it = automatically_added_groups_.begin();
+    group_it != automatically_added_groups_.end(); )
+  {
+    if (group_it->expired()) {
+      group_it = remove_weak_callback_group(group_it, automatically_added_groups_);
+    } else {
+      group_it++;
+    }
+  }
+  for (auto group_it = manually_added_groups_.begin();
+    group_it != manually_added_groups_.end(); )
+  {
+    if (group_it->expired()) {
+      group_it = remove_weak_callback_group(group_it, manually_added_groups_);
+    } else {
+      group_it++;
+    }
+  }
+}
+
+}  // namespace executors
+}  // namespace rclcpp

rclcpp/src/rclcpp/executors/executor_notify_waitable.cpp

@@ -0,0 +1,181 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <iostream>
+
+#include "rclcpp/exceptions.hpp"
+#include "rclcpp/executors/executor_notify_waitable.hpp"
+
+namespace rclcpp
+{
+namespace executors
+{
+
+ExecutorNotifyWaitable::ExecutorNotifyWaitable(std::function<void(void)> on_execute_callback)
+: execute_callback_(on_execute_callback)
+{
+}
+
+ExecutorNotifyWaitable::ExecutorNotifyWaitable(const ExecutorNotifyWaitable & other)
+: ExecutorNotifyWaitable(other.execute_callback_)
+{
+  this->notify_guard_conditions_ = other.notify_guard_conditions_;
+}
+
+ExecutorNotifyWaitable & ExecutorNotifyWaitable::operator=(const ExecutorNotifyWaitable & other)
+{
+  if (this != &other) {
+    this->execute_callback_ = other.execute_callback_;
+    this->notify_guard_conditions_ = other.notify_guard_conditions_;
+  }
+  return *this;
+}
+
+void
+ExecutorNotifyWaitable::add_to_wait_set(rcl_wait_set_t * wait_set)
+{
+  std::lock_guard<std::mutex> lock(guard_condition_mutex_);
+  for (auto weak_guard_condition : this->notify_guard_conditions_) {
+    auto guard_condition = weak_guard_condition.lock();
+    if (!guard_condition) {continue;}
+
+    rcl_guard_condition_t * cond = &guard_condition->get_rcl_guard_condition();
+
+    rcl_ret_t ret = rcl_wait_set_add_guard_condition(
+      wait_set, cond, NULL);
+
+    if (RCL_RET_OK != ret) {
+      rclcpp::exceptions::throw_from_rcl_error(
+        ret, "failed to add guard condition to wait set");
+    }
+  }
+}
+
+bool
+ExecutorNotifyWaitable::is_ready(rcl_wait_set_t * wait_set)
+{
+  std::lock_guard<std::mutex> lock(guard_condition_mutex_);
+
+  bool any_ready = false;
+  for (size_t ii = 0; ii < wait_set->size_of_guard_conditions; ++ii) {
+    auto rcl_guard_condition = wait_set->guard_conditions[ii];
+
+    if (nullptr == rcl_guard_condition) {
+      continue;
+    }
+    for (auto weak_guard_condition : this->notify_guard_conditions_) {
+      auto guard_condition = weak_guard_condition.lock();
+      if (guard_condition && &guard_condition->get_rcl_guard_condition() == rcl_guard_condition) {
+        any_ready = true;
+      }
+    }
+  }
+  return any_ready;
+}
+
+void
+ExecutorNotifyWaitable::execute(std::shared_ptr<void> & data)
+{
+  (void) data;
+  this->execute_callback_();
+}
+
+std::shared_ptr<void>
+ExecutorNotifyWaitable::take_data()
+{
+  return nullptr;
+}
+
+std::shared_ptr<void>
+ExecutorNotifyWaitable::take_data_by_entity_id(size_t id)
+{
+  (void) id;
+  return nullptr;
+}
+
+void
+ExecutorNotifyWaitable::set_on_ready_callback(std::function<void(size_t, int)> callback)
+{
+  // The second argument of the callback could be used to identify which guard condition
+  // triggered the event.
+  // We could indicate which of the guard conditions was triggered, but the executor
+  // is already going to check that.
+  auto gc_callback = [callback](size_t count) {
+      callback(count, 0);
+    };
+
+  std::lock_guard<std::mutex> lock(guard_condition_mutex_);
+
+  on_ready_callback_ = gc_callback;
+  for (auto weak_gc : notify_guard_conditions_) {
+    auto gc = weak_gc.lock();
+    if (!gc) {
+      continue;
+    }
+    gc->set_on_trigger_callback(on_ready_callback_);
+  }
+}
+
+RCLCPP_PUBLIC
+void
+ExecutorNotifyWaitable::clear_on_ready_callback()
+{
+  std::lock_guard<std::mutex> lock(guard_condition_mutex_);
+
+  on_ready_callback_ = nullptr;
+  for (auto weak_gc : notify_guard_conditions_) {
+    auto gc = weak_gc.lock();
+    if (!gc) {
+      continue;
+    }
+    gc->set_on_trigger_callback(nullptr);
+  }
+}
+
+void
+ExecutorNotifyWaitable::add_guard_condition(rclcpp::GuardCondition::WeakPtr weak_guard_condition)
+{
+  std::lock_guard<std::mutex> lock(guard_condition_mutex_);
+  auto guard_condition = weak_guard_condition.lock();
+  if (guard_condition && notify_guard_conditions_.count(weak_guard_condition) == 0) {
+    notify_guard_conditions_.insert(weak_guard_condition);
+    if (on_ready_callback_) {
+      guard_condition->set_on_trigger_callback(on_ready_callback_);
+    }
+  }
+}
+
+void
+ExecutorNotifyWaitable::remove_guard_condition(rclcpp::GuardCondition::WeakPtr weak_guard_condition)
+{
+  std::lock_guard<std::mutex> lock(guard_condition_mutex_);
+  if (notify_guard_conditions_.count(weak_guard_condition) != 0) {
+    notify_guard_conditions_.erase(weak_guard_condition);
+    auto guard_condition = weak_guard_condition.lock();
+    // If this notify waitable doesn't have an on_ready_callback, then there's nothing to unset
+    if (guard_condition && on_ready_callback_) {
+      guard_condition->set_on_trigger_callback(nullptr);
+    }
+  }
+}
+
+size_t
+ExecutorNotifyWaitable::get_number_of_ready_guard_conditions()
+{
+  std::lock_guard<std::mutex> lock(guard_condition_mutex_);
+  return notify_guard_conditions_.size();
+}
+
+}  // namespace executors
+}  // namespace rclcpp

rclcpp/src/rclcpp/executors/multi_threaded_executor.cpp

@@ -21,6 +21,7 @@
 
 #include "rcpputils/scope_exit.hpp"
 
+#include "rclcpp/logging.hpp"
 #include "rclcpp/utilities.hpp"
 
 using rclcpp::executors::MultiThreadedExecutor;
@@ -34,9 +35,15 @@ MultiThreadedExecutor::MultiThreadedExecutor(
   yield_before_execute_(yield_before_execute),
   next_exec_timeout_(next_exec_timeout)
 {
-  number_of_threads_ = number_of_threads ? number_of_threads : std::thread::hardware_concurrency();
-  if (number_of_threads_ == 0) {
-    number_of_threads_ = 1;
+  number_of_threads_ = number_of_threads > 0 ?
+    number_of_threads :
+    std::max(std::thread::hardware_concurrency(), 2U);
+
+  if (number_of_threads_ == 1) {
+    RCLCPP_WARN(
+      rclcpp::get_logger("rclcpp"),
+      "MultiThreadedExecutor is used with a single thread.\n"
+      "Use the SingleThreadedExecutor instead.");
   }
 }
 
@@ -92,6 +99,19 @@ MultiThreadedExecutor::run(size_t this_thread_number)
 
     execute_any_executable(any_exec);
 
+    if (any_exec.callback_group &&
+      any_exec.callback_group->type() == CallbackGroupType::MutuallyExclusive &&
+      any_exec.callback_group->size() > 1)
+    {
+      try {
+        interrupt_guard_condition_->trigger();
+      } catch (const rclcpp::exceptions::RCLError & ex) {
+        throw std::runtime_error(
+                std::string(
+                  "Failed to trigger guard condition on callback group change: ") + ex.what());
+      }
+    }
+
     // Clear the callback_group to prevent the AnyExecutable destructor from
     // resetting the callback group `can_be_taken_from`
     any_exec.callback_group.reset();

rclcpp/src/rclcpp/executors/static_executor_entities_collector.cpp

@@ -1,524 +0,0 @@
-// Copyright 2020 Open Source Robotics Foundation, Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#include "rclcpp/executors/static_executor_entities_collector.hpp"
-
-#include <algorithm>
-#include <memory>
-#include <stdexcept>
-#include <string>
-#include <utility>
-#include <vector>
-
-#include "rclcpp/memory_strategy.hpp"
-#include "rclcpp/executors/static_single_threaded_executor.hpp"
-#include "rclcpp/detail/add_guard_condition_to_rcl_wait_set.hpp"
-
-using rclcpp::executors::StaticExecutorEntitiesCollector;
-
-StaticExecutorEntitiesCollector::~StaticExecutorEntitiesCollector()
-{
-  // Disassociate all callback groups and thus nodes.
-  for (const auto & pair : weak_groups_associated_with_executor_to_nodes_) {
-    auto group = pair.first.lock();
-    if (group) {
-      std::atomic_bool & has_executor = group->get_associated_with_executor_atomic();
-      has_executor.store(false);
-    }
-  }
-  for (const auto & pair : weak_groups_to_nodes_associated_with_executor_) {
-    auto group = pair.first.lock();
-    if (group) {
-      std::atomic_bool & has_executor = group->get_associated_with_executor_atomic();
-      has_executor.store(false);
-    }
-  }
-  // Disassociate all nodes
-  for (const auto & weak_node : weak_nodes_) {
-    auto node = weak_node.lock();
-    if (node) {
-      std::atomic_bool & has_executor = node->get_associated_with_executor_atomic();
-      has_executor.store(false);
-    }
-  }
-  weak_groups_associated_with_executor_to_nodes_.clear();
-  weak_groups_to_nodes_associated_with_executor_.clear();
-  exec_list_.clear();
-  weak_nodes_.clear();
-  weak_nodes_to_guard_conditions_.clear();
-}
-
-void
-StaticExecutorEntitiesCollector::init(
-  rcl_wait_set_t * p_wait_set,
-  rclcpp::memory_strategy::MemoryStrategy::SharedPtr memory_strategy)
-{
-  // Empty initialize executable list
-  exec_list_ = rclcpp::experimental::ExecutableList();
-  // Get executor's wait_set_ pointer
-  p_wait_set_ = p_wait_set;
-  // Get executor's memory strategy ptr
-  if (memory_strategy == nullptr) {
-    throw std::runtime_error("Received NULL memory strategy in executor waitable.");
-  }
-  memory_strategy_ = memory_strategy;
-
-  // Get memory strategy and executable list. Prepare wait_set_
-  std::shared_ptr<void> shared_ptr;
-  execute(shared_ptr);
-
-  // The entities collector is now initialized
-  initialized_ = true;
-}
-
-void
-StaticExecutorEntitiesCollector::fini()
-{
-  memory_strategy_->clear_handles();
-  exec_list_.clear();
-}
-
-std::shared_ptr<void>
-StaticExecutorEntitiesCollector::take_data()
-{
-  return nullptr;
-}
-
-void
-StaticExecutorEntitiesCollector::execute(std::shared_ptr<void> & data)
-{
-  (void) data;
-  // Fill memory strategy with entities coming from weak_nodes_
-  fill_memory_strategy();
-  // Fill exec_list_ with entities coming from weak_nodes_ (same as memory strategy)
-  fill_executable_list();
-  // Resize the wait_set_ based on memory_strategy handles (rcl_wait_set_resize)
-  prepare_wait_set();
-  // Add new nodes guard conditions to map
-  std::lock_guard<std::mutex> guard{new_nodes_mutex_};
-  for (const auto & weak_node : new_nodes_) {
-    if (auto node_ptr = weak_node.lock()) {
-      const auto & gc = node_ptr->get_notify_guard_condition();
-      weak_nodes_to_guard_conditions_[node_ptr] = &gc;
-    }
-  }
-  new_nodes_.clear();
-}
-
-void
-StaticExecutorEntitiesCollector::fill_memory_strategy()
-{
-  memory_strategy_->clear_handles();
-  bool has_invalid_weak_groups_or_nodes =
-    memory_strategy_->collect_entities(weak_groups_to_nodes_associated_with_executor_);
-  // Clean up any invalid nodes, if they were detected
-  if (has_invalid_weak_groups_or_nodes) {
-    std::vector<rclcpp::CallbackGroup::WeakPtr> invalid_group_ptrs;
-    for (const auto & pair : weak_groups_to_nodes_associated_with_executor_) {
-      auto & weak_group_ptr = pair.first;
-      auto & weak_node_ptr = pair.second;
-      if (weak_group_ptr.expired() || weak_node_ptr.expired()) {
-        invalid_group_ptrs.push_back(weak_group_ptr);
-      }
-    }
-    std::for_each(
-      invalid_group_ptrs.begin(), invalid_group_ptrs.end(),
-      [this](rclcpp::CallbackGroup::WeakPtr group_ptr) {
-        weak_groups_to_nodes_associated_with_executor_.erase(group_ptr);
-      });
-  }
-  has_invalid_weak_groups_or_nodes =
-    memory_strategy_->collect_entities(weak_groups_associated_with_executor_to_nodes_);
-  // Clean up any invalid nodes, if they were detected
-  if (has_invalid_weak_groups_or_nodes) {
-    std::vector<rclcpp::CallbackGroup::WeakPtr> invalid_group_ptrs;
-    for (const auto & pair : weak_groups_associated_with_executor_to_nodes_) {
-      auto & weak_group_ptr = pair.first;
-      const auto & weak_node_ptr = pair.second;
-      if (weak_group_ptr.expired() || weak_node_ptr.expired()) {
-        invalid_group_ptrs.push_back(weak_group_ptr);
-      }
-    }
-    std::for_each(
-      invalid_group_ptrs.begin(), invalid_group_ptrs.end(),
-      [this](rclcpp::CallbackGroup::WeakPtr group_ptr) {
-        weak_groups_associated_with_executor_to_nodes_.erase(group_ptr);
-      });
-  }
-
-  // Add the static executor waitable to the memory strategy
-  memory_strategy_->add_waitable_handle(this->shared_from_this());
-}
-
-void
-StaticExecutorEntitiesCollector::fill_executable_list()
-{
-  exec_list_.clear();
-  add_callback_groups_from_nodes_associated_to_executor();
-  fill_executable_list_from_map(weak_groups_associated_with_executor_to_nodes_);
-  fill_executable_list_from_map(weak_groups_to_nodes_associated_with_executor_);
-  // Add the executor's waitable to the executable list
-  exec_list_.add_waitable(shared_from_this());
-}
-void
-StaticExecutorEntitiesCollector::fill_executable_list_from_map(
-  const rclcpp::memory_strategy::MemoryStrategy::WeakCallbackGroupsToNodesMap &
-  weak_groups_to_nodes)
-{
-  for (const auto & pair : weak_groups_to_nodes) {
-    auto group = pair.first.lock();
-    auto node = pair.second.lock();
-    if (!node || !group || !group->can_be_taken_from().load()) {
-      continue;
-    }
-    group->find_timer_ptrs_if(
-      [this](const rclcpp::TimerBase::SharedPtr & timer) {
-        if (timer) {
-          exec_list_.add_timer(timer);
-        }
-        return false;
-      });
-    group->find_subscription_ptrs_if(
-      [this](const rclcpp::SubscriptionBase::SharedPtr & subscription) {
-        if (subscription) {
-          exec_list_.add_subscription(subscription);
-        }
-        return false;
-      });
-    group->find_service_ptrs_if(
-      [this](const rclcpp::ServiceBase::SharedPtr & service) {
-        if (service) {
-          exec_list_.add_service(service);
-        }
-        return false;
-      });
-    group->find_client_ptrs_if(
-      [this](const rclcpp::ClientBase::SharedPtr & client) {
-        if (client) {
-          exec_list_.add_client(client);
-        }
-        return false;
-      });
-    group->find_waitable_ptrs_if(
-      [this](const rclcpp::Waitable::SharedPtr & waitable) {
-        if (waitable) {
-          exec_list_.add_waitable(waitable);
-        }
-        return false;
-      });
-  }
-}
-
-void
-StaticExecutorEntitiesCollector::prepare_wait_set()
-{
-  // clear wait set
-  if (rcl_wait_set_clear(p_wait_set_) != RCL_RET_OK) {
-    throw std::runtime_error("Couldn't clear wait set");
-  }
-
-  // The size of waitables are accounted for in size of the other entities
-  rcl_ret_t ret = rcl_wait_set_resize(
-    p_wait_set_, memory_strategy_->number_of_ready_subscriptions(),
-    memory_strategy_->number_of_guard_conditions(), memory_strategy_->number_of_ready_timers(),
-    memory_strategy_->number_of_ready_clients(), memory_strategy_->number_of_ready_services(),
-    memory_strategy_->number_of_ready_events());
-
-  if (RCL_RET_OK != ret) {
-    throw std::runtime_error(
-            std::string("Couldn't resize the wait set: ") + rcl_get_error_string().str);
-  }
-}
-
-void
-StaticExecutorEntitiesCollector::refresh_wait_set(std::chrono::nanoseconds timeout)
-{
-  // clear wait set (memset to '0' all wait_set_ entities
-  // but keeps the wait_set_ number of entities)
-  if (rcl_wait_set_clear(p_wait_set_) != RCL_RET_OK) {
-    throw std::runtime_error("Couldn't clear wait set");
-  }
-
-  if (!memory_strategy_->add_handles_to_wait_set(p_wait_set_)) {
-    throw std::runtime_error("Couldn't fill wait set");
-  }
-
-  rcl_ret_t status =
-    rcl_wait(p_wait_set_, std::chrono::duration_cast<std::chrono::nanoseconds>(timeout).count());
-
-  if (status == RCL_RET_WAIT_SET_EMPTY) {
-    RCUTILS_LOG_WARN_NAMED(
-      "rclcpp",
-      "empty wait set received in rcl_wait(). This should never happen.");
-  } else if (status != RCL_RET_OK && status != RCL_RET_TIMEOUT) {
-    using rclcpp::exceptions::throw_from_rcl_error;
-    throw_from_rcl_error(status, "rcl_wait() failed");
-  }
-}
-
-void
-StaticExecutorEntitiesCollector::add_to_wait_set(rcl_wait_set_t * wait_set)
-{
-  // Add waitable guard conditions (one for each registered node) into the wait set.
-  for (const auto & pair : weak_nodes_to_guard_conditions_) {
-    auto & gc = pair.second;
-    detail::add_guard_condition_to_rcl_wait_set(*wait_set, *gc);
-  }
-}
-
-size_t StaticExecutorEntitiesCollector::get_number_of_ready_guard_conditions()
-{
-  std::lock_guard<std::mutex> guard{new_nodes_mutex_};
-  return weak_nodes_to_guard_conditions_.size() + new_nodes_.size();
-}
-
-bool
-StaticExecutorEntitiesCollector::add_node(
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr)
-{
-  bool is_new_node = false;
-  // If the node already has an executor
-  std::atomic_bool & has_executor = node_ptr->get_associated_with_executor_atomic();
-  if (has_executor.exchange(true)) {
-    throw std::runtime_error("Node has already been added to an executor.");
-  }
-  node_ptr->for_each_callback_group(
-    [this, node_ptr, &is_new_node](rclcpp::CallbackGroup::SharedPtr group_ptr)
-    {
-      if (
-        !group_ptr->get_associated_with_executor_atomic().load() &&
-        group_ptr->automatically_add_to_executor_with_node())
-      {
-        is_new_node = (add_callback_group(
-          group_ptr,
-          node_ptr,
-          weak_groups_to_nodes_associated_with_executor_) ||
-        is_new_node);
-      }
-    });
-  weak_nodes_.push_back(node_ptr);
-  return is_new_node;
-}
-
-bool
-StaticExecutorEntitiesCollector::add_callback_group(
-  rclcpp::CallbackGroup::SharedPtr group_ptr,
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-  rclcpp::memory_strategy::MemoryStrategy::WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
-{
-  // If the callback_group already has an executor
-  std::atomic_bool & has_executor = group_ptr->get_associated_with_executor_atomic();
-  if (has_executor.exchange(true)) {
-    throw std::runtime_error("Callback group has already been added to an executor.");
-  }
-  bool is_new_node = !has_node(node_ptr, weak_groups_associated_with_executor_to_nodes_) &&
-    !has_node(node_ptr, weak_groups_to_nodes_associated_with_executor_);
-  rclcpp::CallbackGroup::WeakPtr weak_group_ptr = group_ptr;
-  auto insert_info = weak_groups_to_nodes.insert(
-    std::make_pair(weak_group_ptr, node_ptr));
-  bool was_inserted = insert_info.second;
-  if (!was_inserted) {
-    throw std::runtime_error("Callback group was already added to executor.");
-  }
-  if (is_new_node) {
-    std::lock_guard<std::mutex> guard{new_nodes_mutex_};
-    new_nodes_.push_back(node_ptr);
-    return true;
-  }
-  return false;
-}
-
-bool
-StaticExecutorEntitiesCollector::add_callback_group(
-  rclcpp::CallbackGroup::SharedPtr group_ptr,
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr)
-{
-  return add_callback_group(group_ptr, node_ptr, weak_groups_associated_with_executor_to_nodes_);
-}
-
-bool
-StaticExecutorEntitiesCollector::remove_callback_group(
-  rclcpp::CallbackGroup::SharedPtr group_ptr)
-{
-  return this->remove_callback_group_from_map(
-    group_ptr,
-    weak_groups_associated_with_executor_to_nodes_);
-}
-
-bool
-StaticExecutorEntitiesCollector::remove_callback_group_from_map(
-  rclcpp::CallbackGroup::SharedPtr group_ptr,
-  rclcpp::memory_strategy::MemoryStrategy::WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
-{
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr;
-  rclcpp::CallbackGroup::WeakPtr weak_group_ptr = group_ptr;
-  auto iter = weak_groups_to_nodes.find(weak_group_ptr);
-  if (iter != weak_groups_to_nodes.end()) {
-    node_ptr = iter->second.lock();
-    if (node_ptr == nullptr) {
-      throw std::runtime_error("Node must not be deleted before its callback group(s).");
-    }
-    weak_groups_to_nodes.erase(iter);
-  } else {
-    throw std::runtime_error("Callback group needs to be associated with executor.");
-  }
-  // If the node was matched and removed, interrupt waiting.
-  if (!has_node(node_ptr, weak_groups_associated_with_executor_to_nodes_) &&
-    !has_node(node_ptr, weak_groups_to_nodes_associated_with_executor_))
-  {
-    rclcpp::node_interfaces::NodeBaseInterface::WeakPtr node_weak_ptr(node_ptr);
-    weak_nodes_to_guard_conditions_.erase(node_weak_ptr);
-    return true;
-  }
-  return false;
-}
-
-bool
-StaticExecutorEntitiesCollector::remove_node(
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr)
-{
-  if (!node_ptr->get_associated_with_executor_atomic().load()) {
-    return false;
-  }
-  bool node_found = false;
-  auto node_it = weak_nodes_.begin();
-  while (node_it != weak_nodes_.end()) {
-    bool matched = (node_it->lock() == node_ptr);
-    if (matched) {
-      weak_nodes_.erase(node_it);
-      node_found = true;
-      break;
-    }
-    ++node_it;
-  }
-  if (!node_found) {
-    return false;
-  }
-  std::vector<rclcpp::CallbackGroup::SharedPtr> found_group_ptrs;
-  std::for_each(
-    weak_groups_to_nodes_associated_with_executor_.begin(),
-    weak_groups_to_nodes_associated_with_executor_.end(),
-    [&found_group_ptrs, node_ptr](std::pair<rclcpp::CallbackGroup::WeakPtr,
-    rclcpp::node_interfaces::NodeBaseInterface::WeakPtr> key_value_pair) {
-      auto & weak_node_ptr = key_value_pair.second;
-      auto shared_node_ptr = weak_node_ptr.lock();
-      auto group_ptr = key_value_pair.first.lock();
-      if (shared_node_ptr == node_ptr) {
-        found_group_ptrs.push_back(group_ptr);
-      }
-    });
-  std::for_each(
-    found_group_ptrs.begin(), found_group_ptrs.end(), [this]
-      (rclcpp::CallbackGroup::SharedPtr group_ptr) {
-      this->remove_callback_group_from_map(
-        group_ptr,
-        weak_groups_to_nodes_associated_with_executor_);
-    });
-  std::atomic_bool & has_executor = node_ptr->get_associated_with_executor_atomic();
-  has_executor.store(false);
-  return true;
-}
-
-bool
-StaticExecutorEntitiesCollector::is_ready(rcl_wait_set_t * p_wait_set)
-{
-  // Check wait_set guard_conditions for added/removed entities to/from a node
-  for (size_t i = 0; i < p_wait_set->size_of_guard_conditions; ++i) {
-    if (p_wait_set->guard_conditions[i] != NULL) {
-      auto found_guard_condition = std::find_if(
-        weak_nodes_to_guard_conditions_.begin(), weak_nodes_to_guard_conditions_.end(),
-        [&](std::pair<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr,
-        const GuardCondition *> pair) -> bool {
-          const rcl_guard_condition_t & rcl_gc = pair.second->get_rcl_guard_condition();
-          return &rcl_gc == p_wait_set->guard_conditions[i];
-        });
-      if (found_guard_condition != weak_nodes_to_guard_conditions_.end()) {
-        return true;
-      }
-    }
-  }
-  // None of the guard conditions triggered belong to a registered node
-  return false;
-}
-
-// Returns true iff the weak_groups_to_nodes map has node_ptr as the value in any of its entry.
-bool
-StaticExecutorEntitiesCollector::has_node(
-  const rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-  const rclcpp::memory_strategy::MemoryStrategy::WeakCallbackGroupsToNodesMap &
-  weak_groups_to_nodes) const
-{
-  return std::find_if(
-    weak_groups_to_nodes.begin(),
-    weak_groups_to_nodes.end(),
-    [&](const WeakCallbackGroupsToNodesMap::value_type & other) -> bool {
-      auto other_ptr = other.second.lock();
-      return other_ptr == node_ptr;
-    }) != weak_groups_to_nodes.end();
-}
-
-void
-StaticExecutorEntitiesCollector::add_callback_groups_from_nodes_associated_to_executor()
-{
-  for (const auto & weak_node : weak_nodes_) {
-    auto node = weak_node.lock();
-    if (node) {
-      node->for_each_callback_group(
-        [this, node](rclcpp::CallbackGroup::SharedPtr shared_group_ptr)
-        {
-          if (shared_group_ptr->automatically_add_to_executor_with_node() &&
-          !shared_group_ptr->get_associated_with_executor_atomic().load())
-          {
-            add_callback_group(
-              shared_group_ptr,
-              node,
-              weak_groups_to_nodes_associated_with_executor_);
-          }
-        });
-    }
-  }
-}
-
-std::vector<rclcpp::CallbackGroup::WeakPtr>
-StaticExecutorEntitiesCollector::get_all_callback_groups()
-{
-  std::vector<rclcpp::CallbackGroup::WeakPtr> groups;
-  for (const auto & group_node_ptr : weak_groups_associated_with_executor_to_nodes_) {
-    groups.push_back(group_node_ptr.first);
-  }
-  for (const auto & group_node_ptr : weak_groups_to_nodes_associated_with_executor_) {
-    groups.push_back(group_node_ptr.first);
-  }
-  return groups;
-}
-
-std::vector<rclcpp::CallbackGroup::WeakPtr>
-StaticExecutorEntitiesCollector::get_manually_added_callback_groups()
-{
-  std::vector<rclcpp::CallbackGroup::WeakPtr> groups;
-  for (const auto & group_node_ptr : weak_groups_associated_with_executor_to_nodes_) {
-    groups.push_back(group_node_ptr.first);
-  }
-  return groups;
-}
-
-std::vector<rclcpp::CallbackGroup::WeakPtr>
-StaticExecutorEntitiesCollector::get_automatically_added_callback_groups_from_nodes()
-{
-  std::vector<rclcpp::CallbackGroup::WeakPtr> groups;
-  for (const auto & group_node_ptr : weak_groups_to_nodes_associated_with_executor_) {
-    groups.push_back(group_node_ptr.first);
-  }
-  return groups;
-}

rclcpp/src/rclcpp/executors/static_single_threaded_executor.cpp

@@ -12,31 +12,21 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "rclcpp/executors/static_single_threaded_executor.hpp"
-
-#include <chrono>
-#include <memory>
-#include <utility>
-#include <vector>
-
+#include "rclcpp/executors/executor_entities_collection.hpp"
+#include "rclcpp/executors/executor_notify_waitable.hpp"
 #include "rcpputils/scope_exit.hpp"
 
-using rclcpp::executors::StaticSingleThreadedExecutor;
-using rclcpp::experimental::ExecutableList;
+#include "rclcpp/executors/static_single_threaded_executor.hpp"
+#include "rclcpp/any_executable.hpp"
 
-StaticSingleThreadedExecutor::StaticSingleThreadedExecutor(
-  const rclcpp::ExecutorOptions & options)
+using rclcpp::executors::StaticSingleThreadedExecutor;
+
+StaticSingleThreadedExecutor::StaticSingleThreadedExecutor(const rclcpp::ExecutorOptions & options)
 : rclcpp::Executor(options)
 {
-  entities_collector_ = std::make_shared<StaticExecutorEntitiesCollector>();
 }
 
-StaticSingleThreadedExecutor::~StaticSingleThreadedExecutor()
-{
-  if (entities_collector_->is_init()) {
-    entities_collector_->fini();
-  }
-}
+StaticSingleThreadedExecutor::~StaticSingleThreadedExecutor() {}
 
 void
 StaticSingleThreadedExecutor::spin()
@@ -46,14 +36,25 @@ StaticSingleThreadedExecutor::spin()
   }
   RCPPUTILS_SCOPE_EXIT(this->spinning.store(false); );
 
-  // Set memory_strategy_ and exec_list_ based on weak_nodes_
-  // Prepare wait_set_ based on memory_strategy_
-  entities_collector_->init(&wait_set_, memory_strategy_);
-
+  // This is essentially the contents of the rclcpp::Executor::wait_for_work method,
+  // except we need to keep the wait result to reproduce the StaticSingleThreadedExecutor
+  // behavior.
   while (rclcpp::ok(this->context_) && spinning.load()) {
-    // Refresh wait set and wait for work
-    entities_collector_->refresh_wait_set();
-    execute_ready_executables();
+    std::deque<rclcpp::AnyExecutable> to_exec;
+
+    std::lock_guard<std::mutex> guard(mutex_);
+    if (current_collection_.empty() || this->entities_need_rebuild_.load()) {
+      this->collect_entities();
+    }
+
+    auto wait_result = wait_set_.wait(std::chrono::nanoseconds(-1));
+    if (wait_result.kind() == WaitResultKind::Empty) {
+      RCUTILS_LOG_WARN_NAMED(
+        "rclcpp",
+        "empty wait set received in wait(). This should never happen.");
+      continue;
+    }
+    execute_ready_executables(current_collection_, wait_result, false);
   }
 }
 
@@ -80,11 +81,6 @@ StaticSingleThreadedExecutor::spin_all(std::chrono::nanoseconds max_duration)
 void
 StaticSingleThreadedExecutor::spin_some_impl(std::chrono::nanoseconds max_duration, bool exhaustive)
 {
-  // Make sure the entities collector has been initialized
-  if (!entities_collector_->is_init()) {
-    entities_collector_->init(&wait_set_, memory_strategy_);
-  }
-
   auto start = std::chrono::steady_clock::now();
   auto max_duration_not_elapsed = [max_duration, start]() {
       if (std::chrono::nanoseconds(0) == max_duration) {
@@ -105,9 +101,21 @@ StaticSingleThreadedExecutor::spin_some_impl(std::chrono::nanoseconds max_durati
 
   while (rclcpp::ok(context_) && spinning.load() && max_duration_not_elapsed()) {
     // Get executables that are ready now
-    entities_collector_->refresh_wait_set(std::chrono::milliseconds::zero());
+    std::lock_guard<std::mutex> guard(mutex_);
+    if (current_collection_.empty() || this->entities_need_rebuild_.load()) {
+      this->collect_entities();
+    }
+
+    auto wait_result = wait_set_.wait(std::chrono::nanoseconds(0));
+    if (wait_result.kind() == WaitResultKind::Empty) {
+      RCUTILS_LOG_WARN_NAMED(
+        "rclcpp",
+        "empty wait set received in wait(). This should never happen.");
+      continue;
+    }
+
     // Execute ready executables
-    bool work_available = execute_ready_executables();
+    bool work_available = execute_ready_executables(current_collection_, wait_result, false);
     if (!work_available || !exhaustive) {
       break;
     }
@@ -117,164 +125,122 @@ StaticSingleThreadedExecutor::spin_some_impl(std::chrono::nanoseconds max_durati
 void
 StaticSingleThreadedExecutor::spin_once_impl(std::chrono::nanoseconds timeout)
 {
-  // Make sure the entities collector has been initialized
-  if (!entities_collector_->is_init()) {
-    entities_collector_->init(&wait_set_, memory_strategy_);
-  }
-
   if (rclcpp::ok(context_) && spinning.load()) {
-    // Wait until we have a ready entity or timeout expired
-    entities_collector_->refresh_wait_set(timeout);
+    std::lock_guard<std::mutex> guard(mutex_);
+    if (current_collection_.empty() || this->entities_need_rebuild_.load()) {
+      this->collect_entities();
+    }
+
+    auto wait_result = wait_set_.wait(std::chrono::nanoseconds(timeout));
+    if (wait_result.kind() == WaitResultKind::Empty) {
+      RCUTILS_LOG_WARN_NAMED(
+        "rclcpp",
+        "empty wait set received in wait(). This should never happen.");
+      return;
+    }
+
     // Execute ready executables
-    execute_ready_executables(true);
+    execute_ready_executables(current_collection_, wait_result, true);
   }
 }
 
-void
-StaticSingleThreadedExecutor::add_callback_group(
-  rclcpp::CallbackGroup::SharedPtr group_ptr,
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-  bool notify)
-{
-  bool is_new_node = entities_collector_->add_callback_group(group_ptr, node_ptr);
-  if (is_new_node && notify) {
-    // Interrupt waiting to handle new node
-    interrupt_guard_condition_.trigger();
-  }
-}
-
-void
-StaticSingleThreadedExecutor::add_node(
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr, bool notify)
-{
-  bool is_new_node = entities_collector_->add_node(node_ptr);
-  if (is_new_node && notify) {
-    // Interrupt waiting to handle new node
-    interrupt_guard_condition_.trigger();
-  }
-}
-
-void
-StaticSingleThreadedExecutor::add_node(std::shared_ptr<rclcpp::Node> node_ptr, bool notify)
-{
-  this->add_node(node_ptr->get_node_base_interface(), notify);
-}
-
-void
-StaticSingleThreadedExecutor::remove_callback_group(
-  rclcpp::CallbackGroup::SharedPtr group_ptr, bool notify)
-{
-  bool node_removed = entities_collector_->remove_callback_group(group_ptr);
-  // If the node was matched and removed, interrupt waiting
-  if (node_removed && notify) {
-    interrupt_guard_condition_.trigger();
-  }
-}
-
-void
-StaticSingleThreadedExecutor::remove_node(
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr, bool notify)
-{
-  bool node_removed = entities_collector_->remove_node(node_ptr);
-  if (!node_removed) {
-    throw std::runtime_error("Node needs to be associated with this executor.");
-  }
-  // If the node was matched and removed, interrupt waiting
-  if (notify) {
-    interrupt_guard_condition_.trigger();
-  }
-}
-
-std::vector<rclcpp::CallbackGroup::WeakPtr>
-StaticSingleThreadedExecutor::get_all_callback_groups()
-{
-  return entities_collector_->get_all_callback_groups();
-}
-
-std::vector<rclcpp::CallbackGroup::WeakPtr>
-StaticSingleThreadedExecutor::get_manually_added_callback_groups()
-{
-  return entities_collector_->get_manually_added_callback_groups();
-}
-
-std::vector<rclcpp::CallbackGroup::WeakPtr>
-StaticSingleThreadedExecutor::get_automatically_added_callback_groups_from_nodes()
-{
-  return entities_collector_->get_automatically_added_callback_groups_from_nodes();
-}
-
-void
-StaticSingleThreadedExecutor::remove_node(std::shared_ptr<rclcpp::Node> node_ptr, bool notify)
-{
-  this->remove_node(node_ptr->get_node_base_interface(), notify);
-}
-
-bool
-StaticSingleThreadedExecutor::execute_ready_executables(bool spin_once)
+// This preserves the "scheduling semantics" of the StaticSingleThreadedExecutor
+// from the original implementation.
+bool StaticSingleThreadedExecutor::execute_ready_executables(
+  const rclcpp::executors::ExecutorEntitiesCollection & collection,
+  rclcpp::WaitResult<rclcpp::WaitSet> & wait_result,
+  bool spin_once)
 {
   bool any_ready_executable = false;
 
-  // Execute all the ready subscriptions
-  for (size_t i = 0; i < wait_set_.size_of_subscriptions; ++i) {
-    if (i < entities_collector_->get_number_of_subscriptions()) {
-      if (wait_set_.subscriptions[i]) {
-        execute_subscription(entities_collector_->get_subscription(i));
-        if (spin_once) {
-          return true;
-        }
-        any_ready_executable = true;
-      }
-    }
+  if (wait_result.kind() != rclcpp::WaitResultKind::Ready) {
+    return any_ready_executable;
   }
-  // Execute all the ready timers
-  for (size_t i = 0; i < wait_set_.size_of_timers; ++i) {
-    if (i < entities_collector_->get_number_of_timers()) {
-      if (wait_set_.timers[i] && entities_collector_->get_timer(i)->is_ready()) {
-        auto timer = entities_collector_->get_timer(i);
-        timer->call();
-        execute_timer(std::move(timer));
-        if (spin_once) {
-          return true;
-        }
-        any_ready_executable = true;
+
+  auto rcl_wait_set = wait_result.get_wait_set().get_rcl_wait_set();
+
+  for (size_t ii = 0; ii < rcl_wait_set.size_of_timers; ++ii) {
+    if (nullptr == rcl_wait_set.timers[ii]) {continue;}
+    auto entity_iter = collection.timers.find(rcl_wait_set.timers[ii]);
+    if (entity_iter != collection.timers.end()) {
+      auto entity = entity_iter->second.entity.lock();
+      if (!entity) {
+        continue;
       }
-    }
-  }
-  // Execute all the ready services
-  for (size_t i = 0; i < wait_set_.size_of_services; ++i) {
-    if (i < entities_collector_->get_number_of_services()) {
-      if (wait_set_.services[i]) {
-        execute_service(entities_collector_->get_service(i));
-        if (spin_once) {
-          return true;
-        }
-        any_ready_executable = true;
+      if (!entity->call()) {
+        continue;
       }
-    }
-  }
-  // Execute all the ready clients
-  for (size_t i = 0; i < wait_set_.size_of_clients; ++i) {
-    if (i < entities_collector_->get_number_of_clients()) {
-      if (wait_set_.clients[i]) {
-        execute_client(entities_collector_->get_client(i));
-        if (spin_once) {
-          return true;
-        }
-        any_ready_executable = true;
-      }
-    }
-  }
-  // Execute all the ready waitables
-  for (size_t i = 0; i < entities_collector_->get_number_of_waitables(); ++i) {
-    auto waitable = entities_collector_->get_waitable(i);
-    if (waitable->is_ready(&wait_set_)) {
-      auto data = waitable->take_data();
-      waitable->execute(data);
+      execute_timer(entity);
       if (spin_once) {
         return true;
       }
       any_ready_executable = true;
     }
   }
+
+  for (size_t ii = 0; ii < rcl_wait_set.size_of_subscriptions; ++ii) {
+    if (nullptr == rcl_wait_set.subscriptions[ii]) {continue;}
+    auto entity_iter = collection.subscriptions.find(rcl_wait_set.subscriptions[ii]);
+    if (entity_iter != collection.subscriptions.end()) {
+      auto entity = entity_iter->second.entity.lock();
+      if (!entity) {
+        continue;
+      }
+      execute_subscription(entity);
+      if (spin_once) {
+        return true;
+      }
+      any_ready_executable = true;
+    }
+  }
+
+  for (size_t ii = 0; ii < rcl_wait_set.size_of_services; ++ii) {
+    if (nullptr == rcl_wait_set.services[ii]) {continue;}
+    auto entity_iter = collection.services.find(rcl_wait_set.services[ii]);
+    if (entity_iter != collection.services.end()) {
+      auto entity = entity_iter->second.entity.lock();
+      if (!entity) {
+        continue;
+      }
+      execute_service(entity);
+      if (spin_once) {
+        return true;
+      }
+      any_ready_executable = true;
+    }
+  }
+
+  for (size_t ii = 0; ii < rcl_wait_set.size_of_clients; ++ii) {
+    if (nullptr == rcl_wait_set.clients[ii]) {continue;}
+    auto entity_iter = collection.clients.find(rcl_wait_set.clients[ii]);
+    if (entity_iter != collection.clients.end()) {
+      auto entity = entity_iter->second.entity.lock();
+      if (!entity) {
+        continue;
+      }
+      execute_client(entity);
+      if (spin_once) {
+        return true;
+      }
+      any_ready_executable = true;
+    }
+  }
+
+  for (auto & [handle, entry] : collection.waitables) {
+    auto waitable = entry.entity.lock();
+    if (!waitable) {
+      continue;
+    }
+    if (!waitable->is_ready(&rcl_wait_set)) {
+      continue;
+    }
+
+    auto data = waitable->take_data();
+    waitable->execute(data);
+    if (spin_once) {
+      return true;
+    }
+    any_ready_executable = true;
+  }
   return any_ready_executable;
 }

rclcpp/src/rclcpp/experimental/executors/events_executor/events_executor.cpp

@@ -0,0 +1,488 @@
+// Copyright 2023 iRobot Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "rclcpp/experimental/executors/events_executor/events_executor.hpp"
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "rcpputils/scope_exit.hpp"
+
+using namespace std::chrono_literals;
+
+using rclcpp::experimental::executors::EventsExecutor;
+
+EventsExecutor::EventsExecutor(
+  rclcpp::experimental::executors::EventsQueue::UniquePtr events_queue,
+  bool execute_timers_separate_thread,
+  const rclcpp::ExecutorOptions & options)
+: rclcpp::Executor(options)
+{
+  // Get ownership of the queue used to store events.
+  if (!events_queue) {
+    throw std::invalid_argument("events_queue can't be a null pointer");
+  }
+  events_queue_ = std::move(events_queue);
+
+  // Create timers manager
+  // The timers manager can be used either to only track timers (in this case an expired
+  // timer will generate an executor event and then it will be executed by the executor thread)
+  // or it can also take care of executing expired timers in its dedicated thread.
+  std::function<void(const rclcpp::TimerBase *)> timer_on_ready_cb = nullptr;
+  if (!execute_timers_separate_thread) {
+    timer_on_ready_cb = [this](const rclcpp::TimerBase * timer_id) {
+        ExecutorEvent event = {timer_id, -1, ExecutorEventType::TIMER_EVENT, 1};
+        this->events_queue_->enqueue(event);
+      };
+  }
+  timers_manager_ =
+    std::make_shared<rclcpp::experimental::TimersManager>(context_, timer_on_ready_cb);
+
+  notify_waitable_ = std::make_shared<rclcpp::executors::ExecutorNotifyWaitable>(
+    [this]() {
+      // This callback is invoked when:
+      // - the interrupt or shutdown guard condition is triggered:
+      //    ---> we need to wake up the executor so that it can terminate
+      // - a node or callback group guard condition is triggered:
+      //    ---> the entities collection is changed, we need to update callbacks
+      notify_waitable_event_pushed_ = false;
+      this->refresh_current_collection_from_callback_groups();
+    });
+
+  notify_waitable_->add_guard_condition(interrupt_guard_condition_);
+  notify_waitable_->add_guard_condition(shutdown_guard_condition_);
+
+  notify_waitable_->set_on_ready_callback(
+    this->create_waitable_callback(notify_waitable_.get()));
+
+  auto notify_waitable_entity_id = notify_waitable_.get();
+  notify_waitable_->set_on_ready_callback(
+    [this, notify_waitable_entity_id](size_t num_events, int waitable_data) {
+      // The notify waitable has a special callback.
+      // We don't care about how many events as when we wake up the executor we are going to
+      // process everything regardless.
+      // For the same reason, if an event of this type has already been pushed but it has not been
+      // processed yet, we avoid pushing additional events.
+      (void)num_events;
+      if (notify_waitable_event_pushed_.exchange(true)) {
+        return;
+      }
+
+      ExecutorEvent event =
+      {notify_waitable_entity_id, waitable_data, ExecutorEventType::WAITABLE_EVENT, 1};
+      this->events_queue_->enqueue(event);
+    });
+
+  this->entities_collector_ =
+    std::make_shared<rclcpp::executors::ExecutorEntitiesCollector>(notify_waitable_);
+
+  this->current_entities_collection_ =
+    std::make_shared<rclcpp::executors::ExecutorEntitiesCollection>();
+}
+
+EventsExecutor::~EventsExecutor()
+{
+  spinning.store(false);
+  notify_waitable_->clear_on_ready_callback();
+  this->refresh_current_collection({});
+}
+
+void
+EventsExecutor::spin()
+{
+  if (spinning.exchange(true)) {
+    throw std::runtime_error("spin() called while already spinning");
+  }
+  RCPPUTILS_SCOPE_EXIT(this->spinning.store(false); );
+
+  timers_manager_->start();
+  RCPPUTILS_SCOPE_EXIT(timers_manager_->stop(); );
+
+  while (rclcpp::ok(context_) && spinning.load()) {
+    // Wait until we get an event
+    ExecutorEvent event;
+    bool has_event = events_queue_->dequeue(event);
+    if (has_event) {
+      this->execute_event(event);
+    }
+  }
+}
+
+void
+EventsExecutor::spin_some(std::chrono::nanoseconds max_duration)
+{
+  return this->spin_some_impl(max_duration, false);
+}
+
+void
+EventsExecutor::spin_all(std::chrono::nanoseconds max_duration)
+{
+  if (max_duration <= 0ns) {
+    throw std::invalid_argument("max_duration must be positive");
+  }
+  return this->spin_some_impl(max_duration, true);
+}
+
+void
+EventsExecutor::spin_some_impl(std::chrono::nanoseconds max_duration, bool exhaustive)
+{
+  if (spinning.exchange(true)) {
+    throw std::runtime_error("spin_some() called while already spinning");
+  }
+
+  RCPPUTILS_SCOPE_EXIT(this->spinning.store(false); );
+
+  auto start = std::chrono::steady_clock::now();
+
+  auto max_duration_not_elapsed = [max_duration, start]() {
+      if (std::chrono::nanoseconds(0) == max_duration) {
+        // told to spin forever if need be
+        return true;
+      } else if (std::chrono::steady_clock::now() - start < max_duration) {
+        // told to spin only for some maximum amount of time
+        return true;
+      }
+      // spun too long
+      return false;
+    };
+
+  // Get the number of events and timers ready at start
+  const size_t ready_events_at_start = events_queue_->size();
+  size_t executed_events = 0;
+  const size_t ready_timers_at_start = timers_manager_->get_number_ready_timers();
+  size_t executed_timers = 0;
+
+  while (rclcpp::ok(context_) && spinning.load() && max_duration_not_elapsed()) {
+    // Execute first ready event from queue if exists
+    if (exhaustive || (executed_events < ready_events_at_start)) {
+      bool has_event = !events_queue_->empty();
+
+      if (has_event) {
+        ExecutorEvent event;
+        bool ret = events_queue_->dequeue(event, std::chrono::nanoseconds(0));
+        if (ret) {
+          this->execute_event(event);
+          executed_events++;
+          continue;
+        }
+      }
+    }
+
+    // Execute first timer if it is ready
+    if (exhaustive || (executed_timers < ready_timers_at_start)) {
+      bool timer_executed = timers_manager_->execute_head_timer();
+      if (timer_executed) {
+        executed_timers++;
+        continue;
+      }
+    }
+
+    // If there's no more work available, exit
+    break;
+  }
+}
+
+void
+EventsExecutor::spin_once_impl(std::chrono::nanoseconds timeout)
+{
+  // In this context a negative input timeout means no timeout
+  if (timeout < 0ns) {
+    timeout = std::chrono::nanoseconds::max();
+  }
+
+  // Select the smallest between input timeout and timer timeout
+  bool is_timer_timeout = false;
+  auto next_timer_timeout = timers_manager_->get_head_timeout();
+  if (next_timer_timeout < timeout) {
+    timeout = next_timer_timeout;
+    is_timer_timeout = true;
+  }
+
+  ExecutorEvent event;
+  bool has_event = events_queue_->dequeue(event, timeout);
+
+  // If we wake up from the wait with an event, it means that it
+  // arrived before any of the timers expired.
+  if (has_event) {
+    this->execute_event(event);
+  } else if (is_timer_timeout) {
+    timers_manager_->execute_head_timer();
+  }
+}
+
+void
+EventsExecutor::add_node(
+  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr, bool notify)
+{
+  // This field is unused because we don't have to wake up the executor when a node is added.
+  (void) notify;
+
+  // Add node to entities collector
+  this->entities_collector_->add_node(node_ptr);
+
+  this->refresh_current_collection_from_callback_groups();
+}
+
+void
+EventsExecutor::add_node(std::shared_ptr<rclcpp::Node> node_ptr, bool notify)
+{
+  this->add_node(node_ptr->get_node_base_interface(), notify);
+}
+
+void
+EventsExecutor::remove_node(
+  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr, bool notify)
+{
+  // This field is unused because we don't have to wake up the executor when a node is removed.
+  (void)notify;
+
+  // Remove node from entities collector.
+  // This will result in un-setting all the event callbacks from its entities.
+  // After this function returns, this executor will not receive any more events associated
+  // to these entities.
+  this->entities_collector_->remove_node(node_ptr);
+
+  this->refresh_current_collection_from_callback_groups();
+}
+
+void
+EventsExecutor::remove_node(std::shared_ptr<rclcpp::Node> node_ptr, bool notify)
+{
+  this->remove_node(node_ptr->get_node_base_interface(), notify);
+}
+
+void
+EventsExecutor::execute_event(const ExecutorEvent & event)
+{
+  switch (event.type) {
+    case ExecutorEventType::CLIENT_EVENT:
+      {
+        auto client = this->retrieve_entity(
+          static_cast<const rcl_client_t *>(event.entity_key),
+          current_entities_collection_->clients);
+
+        if (client) {
+          for (size_t i = 0; i < event.num_events; i++) {
+            execute_client(client);
+          }
+        }
+
+        break;
+      }
+    case ExecutorEventType::SUBSCRIPTION_EVENT:
+      {
+        auto subscription = this->retrieve_entity(
+          static_cast<const rcl_subscription_t *>(event.entity_key),
+          current_entities_collection_->subscriptions);
+        if (subscription) {
+          for (size_t i = 0; i < event.num_events; i++) {
+            execute_subscription(subscription);
+          }
+        }
+        break;
+      }
+    case ExecutorEventType::SERVICE_EVENT:
+      {
+        auto service = this->retrieve_entity(
+          static_cast<const rcl_service_t *>(event.entity_key),
+          current_entities_collection_->services);
+
+        if (service) {
+          for (size_t i = 0; i < event.num_events; i++) {
+            execute_service(service);
+          }
+        }
+
+        break;
+      }
+    case ExecutorEventType::TIMER_EVENT:
+      {
+        timers_manager_->execute_ready_timer(
+          static_cast<const rclcpp::TimerBase *>(event.entity_key));
+        break;
+      }
+    case ExecutorEventType::WAITABLE_EVENT:
+      {
+        auto waitable = this->retrieve_entity(
+          static_cast<const rclcpp::Waitable *>(event.entity_key),
+          current_entities_collection_->waitables);
+        if (waitable) {
+          for (size_t i = 0; i < event.num_events; i++) {
+            auto data = waitable->take_data_by_entity_id(event.waitable_data);
+            waitable->execute(data);
+          }
+        }
+        break;
+      }
+  }
+}
+
+void
+EventsExecutor::add_callback_group(
+  rclcpp::CallbackGroup::SharedPtr group_ptr,
+  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
+  bool notify)
+{
+  // This field is unused because we don't have to wake up
+  // the executor when a callback group is added.
+  (void)notify;
+  (void)node_ptr;
+
+  this->entities_collector_->add_callback_group(group_ptr);
+
+  this->refresh_current_collection_from_callback_groups();
+}
+
+void
+EventsExecutor::remove_callback_group(
+  rclcpp::CallbackGroup::SharedPtr group_ptr, bool notify)
+{
+  // This field is unused because we don't have to wake up
+  // the executor when a callback group is removed.
+  (void)notify;
+
+  this->entities_collector_->remove_callback_group(group_ptr);
+
+  this->refresh_current_collection_from_callback_groups();
+}
+
+std::vector<rclcpp::CallbackGroup::WeakPtr>
+EventsExecutor::get_all_callback_groups()
+{
+  this->entities_collector_->update_collections();
+  return this->entities_collector_->get_all_callback_groups();
+}
+
+std::vector<rclcpp::CallbackGroup::WeakPtr>
+EventsExecutor::get_manually_added_callback_groups()
+{
+  this->entities_collector_->update_collections();
+  return this->entities_collector_->get_manually_added_callback_groups();
+}
+
+std::vector<rclcpp::CallbackGroup::WeakPtr>
+EventsExecutor::get_automatically_added_callback_groups_from_nodes()
+{
+  this->entities_collector_->update_collections();
+  return this->entities_collector_->get_automatically_added_callback_groups();
+}
+
+void
+EventsExecutor::refresh_current_collection_from_callback_groups()
+{
+  this->entities_collector_->update_collections();
+  auto callback_groups = this->entities_collector_->get_all_callback_groups();
+  rclcpp::executors::ExecutorEntitiesCollection new_collection;
+  rclcpp::executors::build_entities_collection(callback_groups, new_collection);
+
+  // TODO(alsora): this may be implemented in a better way.
+  // We need the notify waitable to be included in the executor "current_collection"
+  // because we need to be able to retrieve events for it.
+  // We could explicitly check for the notify waitable ID when we receive a waitable event
+  // but I think that it's better if the waitable was in the collection and it could be
+  // retrieved in the "standard" way.
+  // To do it, we need to add the notify waitable as an entry in both the new and
+  // current collections such that it's neither added or removed.
+  rclcpp::CallbackGroup::WeakPtr weak_group_ptr;
+  new_collection.waitables.insert(
+  {
+    this->notify_waitable_.get(),
+    {this->notify_waitable_, weak_group_ptr}
+  });
+
+  this->current_entities_collection_->waitables.insert(
+  {
+    this->notify_waitable_.get(),
+    {this->notify_waitable_, weak_group_ptr}
+  });
+
+  this->refresh_current_collection(new_collection);
+}
+
+void
+EventsExecutor::refresh_current_collection(
+  const rclcpp::executors::ExecutorEntitiesCollection & new_collection)
+{
+  current_entities_collection_->timers.update(
+    new_collection.timers,
+    [this](rclcpp::TimerBase::SharedPtr timer) {timers_manager_->add_timer(timer);},
+    [this](rclcpp::TimerBase::SharedPtr timer) {timers_manager_->remove_timer(timer);});
+
+  current_entities_collection_->subscriptions.update(
+    new_collection.subscriptions,
+    [this](auto subscription) {
+      subscription->set_on_new_message_callback(
+        this->create_entity_callback(
+          subscription->get_subscription_handle().get(), ExecutorEventType::SUBSCRIPTION_EVENT));
+    },
+    [](auto subscription) {subscription->clear_on_new_message_callback();});
+
+  current_entities_collection_->clients.update(
+    new_collection.clients,
+    [this](auto client) {
+      client->set_on_new_response_callback(
+        this->create_entity_callback(
+          client->get_client_handle().get(), ExecutorEventType::CLIENT_EVENT));
+    },
+    [](auto client) {client->clear_on_new_response_callback();});
+
+  current_entities_collection_->services.update(
+    new_collection.services,
+    [this](auto service) {
+      service->set_on_new_request_callback(
+        this->create_entity_callback(
+          service->get_service_handle().get(), ExecutorEventType::SERVICE_EVENT));
+    },
+    [](auto service) {service->clear_on_new_request_callback();});
+
+  // DO WE NEED THIS? WE ARE NOT DOING ANYTHING WITH GUARD CONDITIONS
+  /*
+  current_entities_collection_->guard_conditions.update(new_collection.guard_conditions,
+    [](auto guard_condition) {(void)guard_condition;},
+    [](auto guard_condition) {guard_condition->set_on_trigger_callback(nullptr);});
+  */
+
+  current_entities_collection_->waitables.update(
+    new_collection.waitables,
+    [this](auto waitable) {
+      waitable->set_on_ready_callback(
+        this->create_waitable_callback(waitable.get()));
+    },
+    [](auto waitable) {waitable->clear_on_ready_callback();});
+}
+
+std::function<void(size_t)>
+EventsExecutor::create_entity_callback(
+  void * entity_key, ExecutorEventType event_type)
+{
+  std::function<void(size_t)>
+  callback = [this, entity_key, event_type](size_t num_events) {
+      ExecutorEvent event = {entity_key, -1, event_type, num_events};
+      this->events_queue_->enqueue(event);
+    };
+  return callback;
+}
+
+std::function<void(size_t, int)>
+EventsExecutor::create_waitable_callback(const rclcpp::Waitable * entity_key)
+{
+  std::function<void(size_t, int)>
+  callback = [this, entity_key](size_t num_events, int waitable_data) {
+      ExecutorEvent event =
+      {entity_key, waitable_data, ExecutorEventType::WAITABLE_EVENT, num_events};
+      this->events_queue_->enqueue(event);
+    };
+  return callback;
+}

rclcpp/src/rclcpp/experimental/timers_manager.cpp

@@ -0,0 +1,299 @@
+// Copyright 2023 iRobot Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "rclcpp/experimental/timers_manager.hpp"
+
+#include <inttypes.h>
+
+#include <ctime>
+#include <iostream>
+#include <memory>
+#include <stdexcept>
+
+#include "rcpputils/scope_exit.hpp"
+
+using rclcpp::experimental::TimersManager;
+
+TimersManager::TimersManager(
+  std::shared_ptr<rclcpp::Context> context,
+  std::function<void(const rclcpp::TimerBase *)> on_ready_callback)
+{
+  context_ = context;
+  on_ready_callback_ = on_ready_callback;
+}
+
+TimersManager::~TimersManager()
+{
+  // Remove all timers
+  this->clear();
+
+  // Make sure timers thread is stopped before destroying this object
+  this->stop();
+}
+
+void TimersManager::add_timer(rclcpp::TimerBase::SharedPtr timer)
+{
+  if (!timer) {
+    throw std::invalid_argument("TimersManager::add_timer() trying to add nullptr timer");
+  }
+
+  bool added = false;
+  {
+    std::unique_lock<std::mutex> lock(timers_mutex_);
+    added = weak_timers_heap_.add_timer(timer);
+    timers_updated_ = timers_updated_ || added;
+  }
+
+  timer->set_on_reset_callback(
+    [this](size_t arg) {
+      {
+        (void)arg;
+        std::unique_lock<std::mutex> lock(timers_mutex_);
+        timers_updated_ = true;
+      }
+      timers_cv_.notify_one();
+    });
+
+  if (added) {
+    // Notify that a timer has been added
+    timers_cv_.notify_one();
+  }
+}
+
+void TimersManager::start()
+{
+  // Make sure that the thread is not already running
+  if (running_.exchange(true)) {
+    throw std::runtime_error("TimersManager::start() can't start timers thread as already running");
+  }
+
+  timers_thread_ = std::thread(&TimersManager::run_timers, this);
+}
+
+void TimersManager::stop()
+{
+  // Lock stop() function to prevent race condition in destructor
+  std::unique_lock<std::mutex> lock(stop_mutex_);
+  running_ = false;
+
+  // Notify the timers manager thread to wake up
+  {
+    std::unique_lock<std::mutex> lock(timers_mutex_);
+    timers_updated_ = true;
+  }
+  timers_cv_.notify_one();
+
+  // Join timers thread if it's running
+  if (timers_thread_.joinable()) {
+    timers_thread_.join();
+  }
+}
+
+std::chrono::nanoseconds TimersManager::get_head_timeout()
+{
+  // Do not allow to interfere with the thread running
+  if (running_) {
+    throw std::runtime_error(
+            "get_head_timeout() can't be used while timers thread is running");
+  }
+
+  std::unique_lock<std::mutex> lock(timers_mutex_);
+  return this->get_head_timeout_unsafe();
+}
+
+size_t TimersManager::get_number_ready_timers()
+{
+  // Do not allow to interfere with the thread running
+  if (running_) {
+    throw std::runtime_error(
+            "get_number_ready_timers() can't be used while timers thread is running");
+  }
+
+  std::unique_lock<std::mutex> lock(timers_mutex_);
+  TimersHeap locked_heap = weak_timers_heap_.validate_and_lock();
+  return locked_heap.get_number_ready_timers();
+}
+
+bool TimersManager::execute_head_timer()
+{
+  // Do not allow to interfere with the thread running
+  if (running_) {
+    throw std::runtime_error(
+            "execute_head_timer() can't be used while timers thread is running");
+  }
+
+  std::unique_lock<std::mutex> lock(timers_mutex_);
+
+  TimersHeap timers_heap = weak_timers_heap_.validate_and_lock();
+
+  // Nothing to do if we don't have any timer
+  if (timers_heap.empty()) {
+    return false;
+  }
+
+  TimerPtr head_timer = timers_heap.front();
+
+  const bool timer_ready = head_timer->is_ready();
+  if (timer_ready) {
+    // NOTE: here we always execute the timer, regardless of whether the
+    // on_ready_callback is set or not.
+    head_timer->call();
+    head_timer->execute_callback();
+    timers_heap.heapify_root();
+    weak_timers_heap_.store(timers_heap);
+  }
+
+  return timer_ready;
+}
+
+void TimersManager::execute_ready_timer(const rclcpp::TimerBase * timer_id)
+{
+  TimerPtr ready_timer;
+  {
+    std::unique_lock<std::mutex> lock(timers_mutex_);
+    ready_timer = weak_timers_heap_.get_timer(timer_id);
+  }
+  if (ready_timer) {
+    ready_timer->execute_callback();
+  }
+}
+
+std::chrono::nanoseconds TimersManager::get_head_timeout_unsafe()
+{
+  // If we don't have any weak pointer, then we just return maximum timeout
+  if (weak_timers_heap_.empty()) {
+    return std::chrono::nanoseconds::max();
+  }
+  // Weak heap is not empty, so try to lock the first element.
+  // If it is still a valid pointer, it is guaranteed to be the correct head
+  TimerPtr head_timer = weak_timers_heap_.front().lock();
+
+  if (!head_timer) {
+    // The first element has expired, we can't make other assumptions on the heap
+    // and we need to entirely validate it.
+    TimersHeap locked_heap = weak_timers_heap_.validate_and_lock();
+    // NOTE: the following operations will not modify any element in the heap, so we
+    // don't have to call `weak_timers_heap_.store(locked_heap)` at the end.
+
+    if (locked_heap.empty()) {
+      return std::chrono::nanoseconds::max();
+    }
+    head_timer = locked_heap.front();
+  }
+
+  return head_timer->time_until_trigger();
+}
+
+void TimersManager::execute_ready_timers_unsafe()
+{
+  // We start by locking the timers
+  TimersHeap locked_heap = weak_timers_heap_.validate_and_lock();
+
+  // Nothing to do if we don't have any timer
+  if (locked_heap.empty()) {
+    return;
+  }
+
+  // Keep executing timers until they are ready and they were already ready when we started.
+  // The two checks prevent this function from blocking indefinitely if the
+  // time required for executing the timers is longer than their period.
+
+  TimerPtr head_timer = locked_heap.front();
+  const size_t number_ready_timers = locked_heap.get_number_ready_timers();
+  size_t executed_timers = 0;
+  while (executed_timers < number_ready_timers && head_timer->is_ready()) {
+    head_timer->call();
+    if (on_ready_callback_) {
+      on_ready_callback_(head_timer.get());
+    } else {
+      head_timer->execute_callback();
+    }
+
+    executed_timers++;
+    // Executing a timer will result in updating its time_until_trigger, so re-heapify
+    locked_heap.heapify_root();
+    // Get new head timer
+    head_timer = locked_heap.front();
+  }
+
+  // After having performed work on the locked heap we reflect the changes to weak one.
+  // Timers will be already sorted the next time we need them if none went out of scope.
+  weak_timers_heap_.store(locked_heap);
+}
+
+void TimersManager::run_timers()
+{
+  // Make sure the running flag is set to false when we exit from this function
+  // to allow restarting the timers thread.
+  RCPPUTILS_SCOPE_EXIT(this->running_.store(false); );
+
+  while (rclcpp::ok(context_) && running_) {
+    // Lock mutex
+    std::unique_lock<std::mutex> lock(timers_mutex_);
+
+    std::chrono::nanoseconds time_to_sleep = get_head_timeout_unsafe();
+
+    // No need to wait if a timer is already available
+    if (time_to_sleep > std::chrono::nanoseconds::zero()) {
+      if (time_to_sleep != std::chrono::nanoseconds::max()) {
+        // Wait until timeout or notification that timers have been updated
+        timers_cv_.wait_for(lock, time_to_sleep, [this]() {return timers_updated_;});
+      } else {
+        // Wait until notification that timers have been updated
+        timers_cv_.wait(lock, [this]() {return timers_updated_;});
+      }
+    }
+
+    // Reset timers updated flag
+    timers_updated_ = false;
+
+    // Execute timers
+    this->execute_ready_timers_unsafe();
+  }
+}
+
+void TimersManager::clear()
+{
+  {
+    // Lock mutex and then clear all data structures
+    std::unique_lock<std::mutex> lock(timers_mutex_);
+
+    TimersHeap locked_heap = weak_timers_heap_.validate_and_lock();
+    locked_heap.clear_timers_on_reset_callbacks();
+
+    weak_timers_heap_.clear();
+
+    timers_updated_ = true;
+  }
+
+  // Notify timers thread such that it can re-compute its timeout
+  timers_cv_.notify_one();
+}
+
+void TimersManager::remove_timer(TimerPtr timer)
+{
+  bool removed = false;
+  {
+    std::unique_lock<std::mutex> lock(timers_mutex_);
+    removed = weak_timers_heap_.remove_timer(timer);
+
+    timers_updated_ = timers_updated_ || removed;
+  }
+
+  if (removed) {
+    // Notify timers thread such that it can re-compute its timeout
+    timers_cv_.notify_one();
+    timer->clear_on_reset_callback();
+  }
+}

rclcpp/src/rclcpp/generic_subscription.cpp

@@ -25,17 +25,20 @@
 namespace rclcpp
 {
 
-std::shared_ptr<void> GenericSubscription::create_message()
+std::shared_ptr<void>
+GenericSubscription::create_message()
 {
   return create_serialized_message();
 }
 
-std::shared_ptr<rclcpp::SerializedMessage> GenericSubscription::create_serialized_message()
+std::shared_ptr<rclcpp::SerializedMessage>
+GenericSubscription::create_serialized_message()
 {
   return std::make_shared<rclcpp::SerializedMessage>(0);
 }
 
-void GenericSubscription::handle_message(
+void
+GenericSubscription::handle_message(
   std::shared_ptr<void> &,
   const rclcpp::MessageInfo &)
 {
@@ -51,7 +54,8 @@ GenericSubscription::handle_serialized_message(
   callback_(message);
 }
 
-void GenericSubscription::handle_loaned_message(
+void
+GenericSubscription::handle_loaned_message(
   void * message, const rclcpp::MessageInfo & message_info)
 {
   (void) message;
@@ -60,16 +64,69 @@ void GenericSubscription::handle_loaned_message(
           "handle_loaned_message is not implemented for GenericSubscription");
 }
 
-void GenericSubscription::return_message(std::shared_ptr<void> & message)
+void
+GenericSubscription::return_message(std::shared_ptr<void> & message)
 {
   auto typed_message = std::static_pointer_cast<rclcpp::SerializedMessage>(message);
   return_serialized_message(typed_message);
 }
 
-void GenericSubscription::return_serialized_message(
+void
+GenericSubscription::return_serialized_message(
   std::shared_ptr<rclcpp::SerializedMessage> & message)
 {
   message.reset();
 }
 
+
+// DYNAMIC TYPE ====================================================================================
+// TODO(methylDragon): Reorder later
+rclcpp::dynamic_typesupport::DynamicMessageType::SharedPtr
+GenericSubscription::get_shared_dynamic_message_type()
+{
+  throw rclcpp::exceptions::UnimplementedError(
+          "get_shared_dynamic_message_type is not implemented for GenericSubscription");
+}
+
+rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr
+GenericSubscription::get_shared_dynamic_message()
+{
+  throw rclcpp::exceptions::UnimplementedError(
+          "get_shared_dynamic_message is not implemented for GenericSubscription");
+}
+
+rclcpp::dynamic_typesupport::DynamicSerializationSupport::SharedPtr
+GenericSubscription::get_shared_dynamic_serialization_support()
+{
+  throw rclcpp::exceptions::UnimplementedError(
+          "get_shared_dynamic_serialization_support is not implemented for GenericSubscription");
+}
+
+rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr
+GenericSubscription::create_dynamic_message()
+{
+  throw rclcpp::exceptions::UnimplementedError(
+          "create_dynamic_message is not implemented for GenericSubscription");
+}
+
+void
+GenericSubscription::return_dynamic_message(
+  rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr & message)
+{
+  (void) message;
+  throw rclcpp::exceptions::UnimplementedError(
+          "return_dynamic_message is not implemented for GenericSubscription");
+}
+
+void
+GenericSubscription::handle_dynamic_message(
+  const rclcpp::dynamic_typesupport::DynamicMessage::SharedPtr & message,
+  const rclcpp::MessageInfo & message_info)
+{
+  (void) message;
+  (void) message_info;
+  throw rclcpp::exceptions::UnimplementedError(
+          "handle_dynamic_message is not implemented for GenericSubscription");
+}
+
 }  // namespace rclcpp