@wip

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

rclcpp/CMakeLists.txt

@@ -64,7 +64,6 @@ set(${PROJECT_NAME}_SRCS
   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

rclcpp/include/rclcpp/callback_group.hpp

@@ -180,14 +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,

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.
 /**
@@ -402,17 +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.
@@ -497,6 +486,11 @@ protected:
   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.
@@ -508,62 +502,6 @@ protected:
   void
   wait_for_work(std::chrono::nanoseconds timeout = std::chrono::nanoseconds(-1));
 
-  /// Find node associated with a callback group
-  /**
-   * \param[in] weak_groups_to_nodes map of callback groups to nodes
-   * \param[in] group callback group to find assocatiated node
-   * \return Pointer to associated node if found, else nullptr
-   */
-  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.
-  /**
-   * \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
-   */
-  RCLCPP_PUBLIC
-  bool
-  has_node(
-    const rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-    const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes) const;
-
-  /// Find the callback group associated with a timer
-  /**
-   * \param[in] timer Timer to find associated callback group
-   * \return Pointer to callback group node if found, else nullptr
-   */
-  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_);
-
   /// Check for executable in ready state and populate union structure.
   /**
    * \param[out] any_executable populated union structure of ready executable
@@ -574,33 +512,6 @@ protected:
   bool
   get_next_ready_executable(AnyExecutable & any_executable);
 
-  /// Check for executable in ready state and populate union structure.
-  /**
-   * This is the implementation of get_next_ready_executable that takes into
-   * account the current state of callback groups' association with nodes and
-   * executors.
-   *
-   * This checks in a particular order for available work:
-   *   * Timers
-   *   * Subscriptions
-   *   * Services
-   *   * Clients
-   *   * Waitable
-   *
-   * If the next executable is not associated with this executor/node pair,
-   * then this method will return false.
-   *
-   * \param[out] any_executable populated union structure of ready executable
-   * \param[in] weak_groups_to_nodes mapping of callback groups to nodes
-   * \return true if an executable was ready and any_executable was populated,
-   *   otherwise false
-   */
-  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
@@ -618,21 +529,6 @@ protected:
     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;
 
@@ -642,16 +538,8 @@ protected:
   /// 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_;
 
@@ -661,42 +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_;
 
-  typedef std::map<rclcpp::CallbackGroup::WeakPtr,
-      const rclcpp::GuardCondition *,
-      std::owner_less<rclcpp::CallbackGroup::WeakPtr>>
-    WeakCallbackGroupsToGuardConditionsMap;
+  std::atomic_bool entities_need_rebuild_;
 
-  /// maps nodes to guard conditions
-  WeakNodesToGuardConditionsMap
-  weak_nodes_to_guard_conditions_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+  /// Collector used to associate executable entities from nodes and guard conditions
+  rclcpp::executors::ExecutorEntitiesCollector collector_;
 
-  /// maps callback groups to guard conditions
-  WeakCallbackGroupsToGuardConditionsMap
-  weak_groups_to_guard_conditions_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
+  /// Waitset to be waited on.
+  rclcpp::WaitSet wait_set_ RCPPUTILS_TSA_GUARDED_BY(mutex_);
 
-  /// maps callback groups associated to nodes
-  WeakCallbackGroupsToNodesMap
-  weak_groups_associated_with_executor_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_);
 
-  /// maps callback groups to nodes associated with executor
-  WeakCallbackGroupsToNodesMap
-  weak_groups_to_nodes_associated_with_executor_ 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_);
 
-  /// maps all callback groups to nodes
-  WeakCallbackGroupsToNodesMap
-  weak_groups_to_nodes_ 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 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/executor_entities_collection.hpp

@@ -198,14 +198,15 @@ build_entities_collection(
  *
  * \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.
- * \return A queue of executables that have been marked ready by the waitset.
+ * \param[inout] queue of executables to append new ready executables to
+ * \return number of new ready executables
  */
-std::deque<rclcpp::AnyExecutable>
+size_t
 ready_executables(
   const ExecutorEntitiesCollection & collection,
-  rclcpp::WaitResult<rclcpp::WaitSet> & wait_result
+  rclcpp::WaitResult<rclcpp::WaitSet> & wait_result,
+  std::deque<rclcpp::AnyExecutable> & executables
 );
-
 }  // namespace executors
 }  // namespace rclcpp
 

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/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/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

@@ -56,6 +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,

rclcpp/src/rclcpp/executor.cpp

@@ -13,6 +13,8 @@
 // limitations under the License.
 
 #include <algorithm>
+#include <chrono>
+#include <iterator>
 #include <memory>
 #include <map>
 #include <string>
@@ -22,13 +24,14 @@
 
 #include "rcl/allocator.h"
 #include "rcl/error_handling.h"
+#include "rclcpp/executors/executor_notify_waitable.hpp"
+#include "rclcpp/subscription_wait_set_mask.hpp"
 #include "rcpputils/scope_exit.hpp"
 
 #include "rclcpp/dynamic_typesupport/dynamic_message.hpp"
 #include "rclcpp/exceptions.hpp"
 #include "rclcpp/executor.hpp"
 #include "rclcpp/guard_condition.hpp"
-#include "rclcpp/memory_strategy.hpp"
 #include "rclcpp/node.hpp"
 #include "rclcpp/utilities.hpp"
 
@@ -38,14 +41,25 @@
 
 using namespace std::chrono_literals;
 
-using rclcpp::exceptions::throw_from_rcl_error;
 using rclcpp::Executor;
+class rclcpp::ExecutorImplementation {};
+
+/// Mask to indicate to the waitset to only add the subscription.
+/// The events and intraprocess waitable are already added via the callback group.
+static constexpr rclcpp::SubscriptionWaitSetMask kDefaultSubscriptionMask = {true, false, false};
 
 Executor::Executor(const rclcpp::ExecutorOptions & options)
 : spinning(false),
   interrupt_guard_condition_(std::make_shared<rclcpp::GuardCondition>(options.context)),
   shutdown_guard_condition_(std::make_shared<rclcpp::GuardCondition>(options.context)),
-  memory_strategy_(options.memory_strategy)
+  notify_waitable_(std::make_shared<rclcpp::executors::ExecutorNotifyWaitable>(
+      [this]() {
+        this->entities_need_rebuild_.store(true);
+      })),
+  collector_(notify_waitable_),
+  wait_set_({}, {}, {}, {}, {}, {}, options.context),
+  current_notify_waitable_(notify_waitable_),
+  impl_(std::make_unique<rclcpp::ExecutorImplementation>())
 {
   // Store the context for later use.
   context_ = options.context;
@@ -58,74 +72,56 @@ Executor::Executor(const rclcpp::ExecutorOptions & options)
       }
     });
 
-  // The number of guard conditions is always at least 2: 1 for the ctrl-c guard cond,
-  // and one for the executor's guard cond (interrupt_guard_condition_)
-  memory_strategy_->add_guard_condition(*shutdown_guard_condition_.get());
-
-  // Put the executor's guard condition in
-  memory_strategy_->add_guard_condition(*interrupt_guard_condition_.get());
-  rcl_allocator_t allocator = memory_strategy_->get_allocator();
-
-  rcl_ret_t ret = rcl_wait_set_init(
-    &wait_set_,
-    0, 2, 0, 0, 0, 0,
-    context_->get_rcl_context().get(),
-    allocator);
-  if (RCL_RET_OK != ret) {
-    RCUTILS_LOG_ERROR_NAMED(
-      "rclcpp",
-      "failed to create wait set: %s", rcl_get_error_string().str);
-    rcl_reset_error();
-    throw_from_rcl_error(ret, "Failed to create wait set in Executor constructor");
-  }
+  notify_waitable_->add_guard_condition(interrupt_guard_condition_);
+  notify_waitable_->add_guard_condition(shutdown_guard_condition_);
 }
 
 Executor::~Executor()
 {
-  // Disassociate all callback groups.
-  for (auto & pair : weak_groups_to_nodes_) {
-    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.
-  std::for_each(
-    weak_nodes_.begin(), weak_nodes_.end(), []
-      (rclcpp::node_interfaces::NodeBaseInterface::WeakPtr weak_node_ptr) {
-      auto shared_node_ptr = weak_node_ptr.lock();
-      if (shared_node_ptr) {
-        std::atomic_bool & has_executor = shared_node_ptr->get_associated_with_executor_atomic();
-        has_executor.store(false);
-      }
+  std::lock_guard<std::mutex> guard(mutex_);
+
+  notify_waitable_->remove_guard_condition(interrupt_guard_condition_);
+  notify_waitable_->remove_guard_condition(shutdown_guard_condition_);
+
+  std::cout << "Executor::~Executor" << std::endl;
+
+  current_collection_.timers.update(
+    {}, {},
+    [this](auto timer) {
+      std::cout << "remove_timer(" << timer.get() << ")" << std::endl;
+      wait_set_.remove_timer(timer);
     });
-  weak_nodes_.clear();
-  weak_groups_associated_with_executor_to_nodes_.clear();
-  weak_groups_to_nodes_associated_with_executor_.clear();
-  weak_groups_to_nodes_.clear();
-  for (const auto & pair : weak_groups_to_guard_conditions_) {
-    auto guard_condition = pair.second;
-    memory_strategy_->remove_guard_condition(guard_condition);
-  }
-  weak_groups_to_guard_conditions_.clear();
 
-  for (const auto & pair : weak_nodes_to_guard_conditions_) {
-    auto guard_condition = pair.second;
-    memory_strategy_->remove_guard_condition(guard_condition);
-  }
-  weak_nodes_to_guard_conditions_.clear();
+  current_collection_.subscriptions.update(
+    {}, {},
+    [this](auto subscription) {
+      std::cout << "remove_subscription(" << subscription.get() << ")" << std::endl;
+      wait_set_.remove_subscription(subscription, kDefaultSubscriptionMask);
+    });
 
-  // Finalize the wait set.
-  if (rcl_wait_set_fini(&wait_set_) != RCL_RET_OK) {
-    RCUTILS_LOG_ERROR_NAMED(
-      "rclcpp",
-      "failed to destroy wait set: %s", rcl_get_error_string().str);
-    rcl_reset_error();
-  }
-  // Remove and release the sigint guard condition
-  memory_strategy_->remove_guard_condition(shutdown_guard_condition_.get());
-  memory_strategy_->remove_guard_condition(interrupt_guard_condition_.get());
+  current_collection_.clients.update(
+    {}, {},
+    [this](auto client) {
+      std::cout << "remove_client(" << client.get() << ")" << std::endl;
+      wait_set_.remove_client(client);});
+
+  current_collection_.services.update(
+    {}, {},
+    [this](auto service) {
+      std::cout << "remove_service(" << service.get() << ")" << std::endl;
+      wait_set_.remove_service(service);});
+
+  current_collection_.guard_conditions.update(
+    {}, {},
+    [this](auto guard_condition) {
+      std::cout << "remove_guard_condition(" << guard_condition.get() << ")" << std::endl;
+        wait_set_.remove_guard_condition(guard_condition);});
+
+  current_collection_.waitables.update(
+    {}, {},
+    [this](auto waitable) {
+      std::cout << "remove_waitable(" << waitable.get() << ")" << std::endl;
+      wait_set_.remove_waitable(waitable);});
 
   // Remove shutdown callback handle registered to Context
   if (!context_->remove_on_shutdown_callback(shutdown_callback_handle_)) {
@@ -139,95 +135,39 @@ Executor::~Executor()
 std::vector<rclcpp::CallbackGroup::WeakPtr>
 Executor::get_all_callback_groups()
 {
-  std::vector<rclcpp::CallbackGroup::WeakPtr> groups;
-  std::lock_guard<std::mutex> guard{mutex_};
-  for (const auto & group_node_ptr : weak_groups_associated_with_executor_to_nodes_) {
-    groups.push_back(group_node_ptr.first);
-  }
-  for (auto const & group_node_ptr : weak_groups_to_nodes_associated_with_executor_) {
-    groups.push_back(group_node_ptr.first);
-  }
-  return groups;
+  this->collector_.update_collections();
+  return this->collector_.get_all_callback_groups();
 }
 
 std::vector<rclcpp::CallbackGroup::WeakPtr>
 Executor::get_manually_added_callback_groups()
 {
-  std::vector<rclcpp::CallbackGroup::WeakPtr> groups;
-  std::lock_guard<std::mutex> guard{mutex_};
-  for (auto const & group_node_ptr : weak_groups_associated_with_executor_to_nodes_) {
-    groups.push_back(group_node_ptr.first);
-  }
-  return groups;
+  this->collector_.update_collections();
+  return this->collector_.get_manually_added_callback_groups();
 }
 
 std::vector<rclcpp::CallbackGroup::WeakPtr>
 Executor::get_automatically_added_callback_groups_from_nodes()
 {
-  std::vector<rclcpp::CallbackGroup::WeakPtr> groups;
-  std::lock_guard<std::mutex> guard{mutex_};
-  for (auto const & group_node_ptr : weak_groups_to_nodes_associated_with_executor_) {
-    groups.push_back(group_node_ptr.first);
-  }
-  return groups;
+  this->collector_.update_collections();
+  return this->collector_.get_automatically_added_callback_groups();
 }
 
 void
-Executor::add_callback_groups_from_nodes_associated_to_executor()
-{
-  for (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())
-          {
-            this->add_callback_group_to_map(
-              shared_group_ptr,
-              node,
-              weak_groups_to_nodes_associated_with_executor_,
-              true);
-          }
-        });
-    }
-  }
-}
-
-void
-Executor::add_callback_group_to_map(
+Executor::add_callback_group(
   rclcpp::CallbackGroup::SharedPtr group_ptr,
   rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-  rclcpp::memory_strategy::MemoryStrategy::WeakCallbackGroupsToNodesMap & weak_groups_to_nodes,
   bool notify)
 {
-  // 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.");
-  }
+  (void) node_ptr;
+  this->collector_.add_callback_group(group_ptr);
 
-  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.");
-  }
-  // Also add to the map that contains all callback groups
-  weak_groups_to_nodes_.insert(std::make_pair(weak_group_ptr, node_ptr));
-
-  if (node_ptr->get_context()->is_valid()) {
-    auto callback_group_guard_condition = group_ptr->get_notify_guard_condition();
-    weak_groups_to_guard_conditions_[weak_group_ptr] = callback_group_guard_condition.get();
-    // Add the callback_group's notify condition to the guard condition handles
-    memory_strategy_->add_guard_condition(*callback_group_guard_condition);
+  if (!spinning.load()) {
+    std::lock_guard<std::mutex> guard(mutex_);
+    this->collect_entities();
   }
 
   if (notify) {
-    // Interrupt waiting to handle new node
     try {
       interrupt_guard_condition_->trigger();
     } catch (const rclcpp::exceptions::RCLError & ex) {
@@ -238,91 +178,23 @@ Executor::add_callback_group_to_map(
   }
 }
 
-void
-Executor::add_callback_group(
-  rclcpp::CallbackGroup::SharedPtr group_ptr,
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr,
-  bool notify)
-{
-  std::lock_guard<std::mutex> guard{mutex_};
-  this->add_callback_group_to_map(
-    group_ptr,
-    node_ptr,
-    weak_groups_associated_with_executor_to_nodes_,
-    notify);
-}
-
 void
 Executor::add_node(rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr, bool notify)
 {
-  // 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.");
+  this->collector_.add_node(node_ptr);
+
+  if (!spinning.load()) {
+    std::lock_guard<std::mutex> guard(mutex_);
+    this->collect_entities();
   }
-  std::lock_guard<std::mutex> guard{mutex_};
-  node_ptr->for_each_callback_group(
-    [this, node_ptr, notify](rclcpp::CallbackGroup::SharedPtr group_ptr)
-    {
-      if (!group_ptr->get_associated_with_executor_atomic().load() &&
-      group_ptr->automatically_add_to_executor_with_node())
-      {
-        this->add_callback_group_to_map(
-          group_ptr,
-          node_ptr,
-          weak_groups_to_nodes_associated_with_executor_,
-          notify);
-      }
-    });
 
-  const auto gc = node_ptr->get_shared_notify_guard_condition();
-  weak_nodes_to_guard_conditions_[node_ptr] = gc.get();
-  // Add the node's notify condition to the guard condition handles
-  memory_strategy_->add_guard_condition(*gc);
-  weak_nodes_.push_back(node_ptr);
-}
-
-void
-Executor::remove_callback_group_from_map(
-  rclcpp::CallbackGroup::SharedPtr group_ptr,
-  rclcpp::memory_strategy::MemoryStrategy::WeakCallbackGroupsToNodesMap & weak_groups_to_nodes,
-  bool notify)
-{
-  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);
-    weak_groups_to_nodes_.erase(group_ptr);
-    std::atomic_bool & has_executor = group_ptr->get_associated_with_executor_atomic();
-    has_executor.store(false);
-  } 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_to_nodes_associated_with_executor_) &&
-    !has_node(node_ptr, weak_groups_associated_with_executor_to_nodes_))
-  {
-    auto iter = weak_groups_to_guard_conditions_.find(weak_group_ptr);
-    if (iter != weak_groups_to_guard_conditions_.end()) {
-      memory_strategy_->remove_guard_condition(iter->second);
-    }
-    weak_groups_to_guard_conditions_.erase(weak_group_ptr);
-
-    if (notify) {
-      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 remove: ") + ex.what());
-      }
+  if (notify) {
+    try {
+      interrupt_guard_condition_->trigger();
+    } catch (const rclcpp::exceptions::RCLError & ex) {
+      throw std::runtime_error(
+              std::string(
+                "Failed to trigger guard condition on node add: ") + ex.what());
     }
   }
 }
@@ -332,11 +204,21 @@ Executor::remove_callback_group(
   rclcpp::CallbackGroup::SharedPtr group_ptr,
   bool notify)
 {
-  std::lock_guard<std::mutex> guard{mutex_};
-  this->remove_callback_group_from_map(
-    group_ptr,
-    weak_groups_associated_with_executor_to_nodes_,
-    notify);
+  this->collector_.remove_callback_group(group_ptr);
+
+  if (!spinning.load()) {
+    std::lock_guard<std::mutex> guard(mutex_);
+    this->collect_entities();
+  }
+  if (notify) {
+    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 remove: ") + ex.what());
+    }
+  }
 }
 
 void
@@ -348,48 +230,22 @@ Executor::add_node(std::shared_ptr<rclcpp::Node> node_ptr, bool notify)
 void
 Executor::remove_node(rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr, bool notify)
 {
-  if (!node_ptr->get_associated_with_executor_atomic().load()) {
-    throw std::runtime_error("Node needs to be associated with an executor.");
+  this->collector_.remove_node(node_ptr);
+
+  if (!spinning.load()) {
+    std::lock_guard<std::mutex> guard(mutex_);
+    this->collect_entities();
   }
 
-  std::lock_guard<std::mutex> guard{mutex_};
-  bool found_node = false;
-  auto node_it = weak_nodes_.begin();
-  while (node_it != weak_nodes_.end()) {
-    bool matched = (node_it->lock() == node_ptr);
-    if (matched) {
-      found_node = true;
-      node_it = weak_nodes_.erase(node_it);
-    } else {
-      ++node_it;
+  if (notify) {
+    try {
+      interrupt_guard_condition_->trigger();
+    } catch (const rclcpp::exceptions::RCLError & ex) {
+      throw std::runtime_error(
+              std::string(
+                "Failed to trigger guard condition on node remove: ") + ex.what());
     }
   }
-  if (!found_node) {
-    throw std::runtime_error("Node needs to be associated with this executor.");
-  }
-
-  for (auto it = weak_groups_to_nodes_associated_with_executor_.begin();
-    it != weak_groups_to_nodes_associated_with_executor_.end(); )
-  {
-    auto weak_node_ptr = it->second;
-    auto shared_node_ptr = weak_node_ptr.lock();
-    auto group_ptr = it->first.lock();
-
-    // Increment iterator before removing in case it's invalidated
-    it++;
-    if (shared_node_ptr == node_ptr) {
-      remove_callback_group_from_map(
-        group_ptr,
-        weak_groups_to_nodes_associated_with_executor_,
-        notify);
-    }
-  }
-
-  memory_strategy_->remove_guard_condition(node_ptr->get_shared_notify_guard_condition().get());
-  weak_nodes_to_guard_conditions_.erase(node_ptr);
-
-  std::atomic_bool & has_executor = node_ptr->get_associated_with_executor_atomic();
-  has_executor.store(false);
 }
 
 void
@@ -456,21 +312,44 @@ Executor::spin_some_impl(std::chrono::nanoseconds max_duration, bool exhaustive)
     throw std::runtime_error("spin_some() called while already spinning");
   }
   RCPPUTILS_SCOPE_EXIT(this->spinning.store(false); );
-  bool work_available = false;
+
+  size_t work_in_queue = 0;
+  bool has_waited = false;
+
+  {
+    std::lock_guard<std::mutex> lock(mutex_);
+    work_in_queue = ready_executables_.size();
+  }
+  // The logic below is to guarantee that we:
+  // a) run all of the work in the queue before we spin the first time
+  // b) spin at least once
+  // c) run all of the work in the queue after we spin
+
   while (rclcpp::ok(context_) && spinning.load() && max_duration_not_elapsed()) {
     AnyExecutable any_exec;
-    if (!work_available) {
-      wait_for_work(std::chrono::milliseconds::zero());
-    }
-    if (get_next_ready_executable(any_exec)) {
-      execute_any_executable(any_exec);
-      work_available = true;
-    } else {
-      if (!work_available || !exhaustive) {
-        break;
+    if (work_in_queue > 0) {
+      // If there is work in the queue, then execute it
+      // This covers the case that there are things left in the queue from a
+      // previous spin.
+      if (get_next_ready_executable(any_exec)) {
+        execute_any_executable(any_exec);
+      }
+    } else if (!has_waited && !work_in_queue) {
+      // Once the ready queue is empty, then we need to wait at least once.
+      wait_for_work(std::chrono::milliseconds(0));
+      has_waited = true;
+    } else if (has_waited && !work_in_queue) {
+      // Once we have emptied the ready queue, but have already waited:
+      if (!exhaustive) {
+        // In the case of spin some, then we can exit
+        break;
+      } else {
+        // In the case of spin all, then we will allow ourselves to wait again.
+        has_waited = false;
       }
-      work_available = false;
     }
+    std::lock_guard<std::mutex> lock(mutex_);
+    work_in_queue = ready_executables_.size();
   }
 }
 
@@ -505,22 +384,13 @@ Executor::cancel()
   }
 }
 
-void
-Executor::set_memory_strategy(rclcpp::memory_strategy::MemoryStrategy::SharedPtr memory_strategy)
-{
-  if (memory_strategy == nullptr) {
-    throw std::runtime_error("Received NULL memory strategy in executor.");
-  }
-  std::lock_guard<std::mutex> guard{mutex_};
-  memory_strategy_ = memory_strategy;
-}
-
 void
 Executor::execute_any_executable(AnyExecutable & any_exec)
 {
   if (!spinning.load()) {
     return;
   }
+
   if (any_exec.timer) {
     TRACEPOINT(
       rclcpp_executor_execute,
@@ -542,16 +412,10 @@ Executor::execute_any_executable(AnyExecutable & any_exec)
   if (any_exec.waitable) {
     any_exec.waitable->execute(any_exec.data);
   }
+
   // Reset the callback_group, regardless of type
-  any_exec.callback_group->can_be_taken_from().store(true);
-  // Wake the wait, because it may need to be recalculated or work that
-  // was previously blocked is now available.
-  try {
-    interrupt_guard_condition_->trigger();
-  } catch (const rclcpp::exceptions::RCLError & ex) {
-    throw std::runtime_error(
-            std::string(
-              "Failed to trigger guard condition from execute_any_executable: ") + ex.what());
+  if (any_exec.callback_group) {
+    any_exec.callback_group->can_be_taken_from().store(true);
   }
 }
 
@@ -720,228 +584,117 @@ Executor::execute_client(
     [&]() {client->handle_response(request_header, response);});
 }
 
+void
+Executor::collect_entities()
+{
+  // Get the current list of available waitables from the collector.
+  rclcpp::executors::ExecutorEntitiesCollection collection;
+  this->collector_.update_collections();
+  auto callback_groups = this->collector_.get_all_callback_groups();
+  rclcpp::executors::build_entities_collection(callback_groups, collection);
+
+  // Make a copy of notify waitable so we can continue to mutate the original
+  // one outside of the execute loop.
+  // This prevents the collection of guard conditions in the waitable from changing
+  // while we are waiting on it.
+  if (notify_waitable_) {
+    current_notify_waitable_ = std::make_shared<rclcpp::executors::ExecutorNotifyWaitable>(
+      *notify_waitable_);
+    auto notify_waitable = std::static_pointer_cast<rclcpp::Waitable>(current_notify_waitable_);
+    collection.waitables.insert({notify_waitable.get(), {notify_waitable, {}}});
+  }
+
+  std::cout << "current_collection.timers: " << current_collection_.timers.size() << std::endl;
+  std::cout << "next_collection.timers: " << collection.timers.size() << std::endl;
+  // Update each of the groups of entities in the current collection, adding or removing
+  // from the wait set as necessary.
+  current_collection_.timers.update(
+    collection.timers,
+    [this](auto timer) {
+        std::cout << "add_timer(" << timer << ")" << std::endl;
+        wait_set_.add_timer(timer);},
+    [this](auto timer) {
+        std::cout << "remove_timer(" << timer << ")" << std::endl;
+        wait_set_.remove_timer(timer);});
+
+  std::cout << "current_collection.subscriptions: " << current_collection_.subscriptions.size() << std::endl;
+  std::cout << "next_collection.subscriptions: " << collection.subscriptions.size() << std::endl;
+  current_collection_.subscriptions.update(
+    collection.subscriptions,
+    [this](auto subscription) {
+      std::cout << "add_subscription(" << subscription << ")" << std::endl;
+      wait_set_.add_subscription(subscription, kDefaultSubscriptionMask);
+    },
+    [this](auto subscription) {
+      std::cout << "remove_subscription(" << subscription << ")" << std::endl;
+      wait_set_.remove_subscription(subscription, kDefaultSubscriptionMask);
+    });
+
+  current_collection_.clients.update(
+    collection.clients,
+    [this](auto client) {wait_set_.add_client(client);},
+    [this](auto client) {wait_set_.remove_client(client);});
+
+  current_collection_.services.update(
+    collection.services,
+    [this](auto service) {wait_set_.add_service(service);},
+    [this](auto service) {wait_set_.remove_service(service);});
+
+  current_collection_.guard_conditions.update(
+    collection.guard_conditions,
+    [this](auto guard_condition) {wait_set_.add_guard_condition(guard_condition);},
+    [this](auto guard_condition) {wait_set_.remove_guard_condition(guard_condition);});
+
+  current_collection_.waitables.update(
+    collection.waitables,
+    [this](auto waitable) {
+      wait_set_.add_waitable(waitable);
+    },
+    [this](auto waitable) {wait_set_.remove_waitable(waitable);});
+
+  this->entities_need_rebuild_.store(false);
+}
+
 void
 Executor::wait_for_work(std::chrono::nanoseconds timeout)
 {
   TRACEPOINT(rclcpp_executor_wait_for_work, timeout.count());
-  {
-    std::lock_guard<std::mutex> guard(mutex_);
 
-    // Check weak_nodes_ to find any callback group that is not owned
-    // by an executor and add it to the list of callbackgroups for
-    // collect entities. Also exchange to false so it is not
-    // allowed to add to another executor
-    add_callback_groups_from_nodes_associated_to_executor();
-
-    // Collect the subscriptions and timers to be waited on
-    memory_strategy_->clear_handles();
-    bool has_invalid_weak_groups_or_nodes =
-      memory_strategy_->collect_entities(weak_groups_to_nodes_);
-
-    if (has_invalid_weak_groups_or_nodes) {
-      std::vector<rclcpp::CallbackGroup::WeakPtr> invalid_group_ptrs;
-      for (auto pair : weak_groups_to_nodes_) {
-        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);
-          auto node_guard_pair = weak_nodes_to_guard_conditions_.find(weak_node_ptr);
-          if (node_guard_pair != weak_nodes_to_guard_conditions_.end()) {
-            auto guard_condition = node_guard_pair->second;
-            weak_nodes_to_guard_conditions_.erase(weak_node_ptr);
-            memory_strategy_->remove_guard_condition(guard_condition);
-          }
-        }
-      }
-      std::for_each(
-        invalid_group_ptrs.begin(), invalid_group_ptrs.end(),
-        [this](rclcpp::CallbackGroup::WeakPtr group_ptr) {
-          if (weak_groups_to_nodes_associated_with_executor_.find(group_ptr) !=
-          weak_groups_to_nodes_associated_with_executor_.end())
-          {
-            weak_groups_to_nodes_associated_with_executor_.erase(group_ptr);
-          }
-          if (weak_groups_associated_with_executor_to_nodes_.find(group_ptr) !=
-          weak_groups_associated_with_executor_to_nodes_.end())
-          {
-            weak_groups_associated_with_executor_to_nodes_.erase(group_ptr);
-          }
-          auto callback_guard_pair = weak_groups_to_guard_conditions_.find(group_ptr);
-          if (callback_guard_pair != weak_groups_to_guard_conditions_.end()) {
-            auto guard_condition = callback_guard_pair->second;
-            weak_groups_to_guard_conditions_.erase(group_ptr);
-            memory_strategy_->remove_guard_condition(guard_condition);
-          }
-          weak_groups_to_nodes_.erase(group_ptr);
-        });
-    }
-
-    // clear wait set
-    rcl_ret_t ret = rcl_wait_set_clear(&wait_set_);
-    if (ret != RCL_RET_OK) {
-      throw_from_rcl_error(ret, "Couldn't clear wait set");
-    }
-
-    // The size of waitables are accounted for in size of the other entities
-    ret = rcl_wait_set_resize(
-      &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_from_rcl_error(ret, "Couldn't resize the wait set");
-    }
-
-    if (!memory_strategy_->add_handles_to_wait_set(&wait_set_)) {
-      throw std::runtime_error("Couldn't fill wait set");
-    }
+  std::lock_guard<std::mutex> guard(mutex_);
+  if (current_collection_.empty() || this->entities_need_rebuild_.load()) {
+    this->collect_entities();
   }
 
-  rcl_ret_t status =
-    rcl_wait(&wait_set_, std::chrono::duration_cast<std::chrono::nanoseconds>(timeout).count());
-  if (status == RCL_RET_WAIT_SET_EMPTY) {
+  auto wait_result = wait_set_.wait(timeout);
+  if (wait_result.kind() == WaitResultKind::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");
+      "empty wait set received in wait(). This should never happen.");
   }
-
-  // check the null handles in the wait set and remove them from the handles in memory strategy
-  // for callback-based entities
-  std::lock_guard<std::mutex> guard(mutex_);
-  memory_strategy_->remove_null_handles(&wait_set_);
-}
-
-rclcpp::node_interfaces::NodeBaseInterface::SharedPtr
-Executor::get_node_by_group(
-  const rclcpp::memory_strategy::MemoryStrategy::WeakCallbackGroupsToNodesMap &
-  weak_groups_to_nodes,
-  rclcpp::CallbackGroup::SharedPtr group)
-{
-  if (!group) {
-    return nullptr;
-  }
-  rclcpp::CallbackGroup::WeakPtr weak_group_ptr(group);
-  const auto finder = weak_groups_to_nodes.find(weak_group_ptr);
-  if (finder != weak_groups_to_nodes.end()) {
-    rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr = finder->second.lock();
-    return node_ptr;
-  }
-  return nullptr;
-}
-
-rclcpp::CallbackGroup::SharedPtr
-Executor::get_group_by_timer(rclcpp::TimerBase::SharedPtr timer)
-{
-  std::lock_guard<std::mutex> guard{mutex_};
-  for (const auto & pair : weak_groups_associated_with_executor_to_nodes_) {
-    auto group = pair.first.lock();
-    if (!group) {
-      continue;
-    }
-    auto timer_ref = group->find_timer_ptrs_if(
-      [timer](const rclcpp::TimerBase::SharedPtr & timer_ptr) -> bool {
-        return timer_ptr == timer;
-      });
-    if (timer_ref) {
-      return group;
-    }
-  }
-
-  for (const auto & pair : weak_groups_to_nodes_associated_with_executor_) {
-    auto group = pair.first.lock();
-    if (!group) {
-      continue;
-    }
-    auto timer_ref = group->find_timer_ptrs_if(
-      [timer](const rclcpp::TimerBase::SharedPtr & timer_ptr) -> bool {
-        return timer_ptr == timer;
-      });
-    if (timer_ref) {
-      return group;
-    }
-  }
-  return nullptr;
+  rclcpp::executors::ready_executables(current_collection_, wait_result, ready_executables_);
 }
 
 bool
 Executor::get_next_ready_executable(AnyExecutable & any_executable)
-{
-  bool success = get_next_ready_executable_from_map(any_executable, weak_groups_to_nodes_);
-  return success;
-}
-
-bool
-Executor::get_next_ready_executable_from_map(
-  AnyExecutable & any_executable,
-  const rclcpp::memory_strategy::MemoryStrategy::WeakCallbackGroupsToNodesMap &
-  weak_groups_to_nodes)
 {
   TRACEPOINT(rclcpp_executor_get_next_ready);
-  bool success = false;
-  std::lock_guard<std::mutex> guard{mutex_};
-  // Check the timers to see if there are any that are ready
-  memory_strategy_->get_next_timer(any_executable, weak_groups_to_nodes);
-  if (any_executable.timer) {
-    success = true;
-  }
-  if (!success) {
-    // Check the subscriptions to see if there are any that are ready
-    memory_strategy_->get_next_subscription(any_executable, weak_groups_to_nodes);
-    if (any_executable.subscription) {
-      success = true;
-    }
-  }
-  if (!success) {
-    // Check the services to see if there are any that are ready
-    memory_strategy_->get_next_service(any_executable, weak_groups_to_nodes);
-    if (any_executable.service) {
-      success = true;
-    }
-  }
-  if (!success) {
-    // Check the clients to see if there are any that are ready
-    memory_strategy_->get_next_client(any_executable, weak_groups_to_nodes);
-    if (any_executable.client) {
-      success = true;
-    }
-  }
-  if (!success) {
-    // Check the waitables to see if there are any that are ready
-    memory_strategy_->get_next_waitable(any_executable, weak_groups_to_nodes);
-    if (any_executable.waitable) {
-      any_executable.data = any_executable.waitable->take_data();
-      success = true;
-    }
-  }
-  // At this point any_executable should be valid with either a valid subscription
-  // or a valid timer, or it should be a null shared_ptr
-  if (success) {
-    rclcpp::CallbackGroup::WeakPtr weak_group_ptr = any_executable.callback_group;
-    auto iter = weak_groups_to_nodes.find(weak_group_ptr);
-    if (iter == weak_groups_to_nodes.end()) {
-      success = false;
-    }
+
+  std::lock_guard<std::mutex> guard(mutex_);
+  if (ready_executables_.size() == 0) {
+    return false;
   }
 
-  if (success) {
-    // If it is valid, check to see if the group is mutually exclusive or
-    // not, then mark it accordingly ..Check if the callback_group belongs to this executor
-    if (any_executable.callback_group && any_executable.callback_group->type() == \
-      CallbackGroupType::MutuallyExclusive)
-    {
-      // It should not have been taken otherwise
-      assert(any_executable.callback_group->can_be_taken_from().load());
-      // Set to false to indicate something is being run from this group
-      // This is reset to true either when the any_executable is executed or when the
-      // any_executable is destructued
-      any_executable.callback_group->can_be_taken_from().store(false);
-    }
+  any_executable = ready_executables_.front();
+  ready_executables_.pop_front();
+
+  if (any_executable.callback_group &&
+    any_executable.callback_group->type() == CallbackGroupType::MutuallyExclusive)
+  {
+    assert(any_executable.callback_group->can_be_taken_from().load());
+    any_executable.callback_group->can_be_taken_from().store(false);
   }
-  // If there is no ready executable, return false
-  return success;
+
+  return true;
 }
 
 bool
@@ -964,22 +717,6 @@ Executor::get_next_executable(AnyExecutable & any_executable, std::chrono::nanos
   return success;
 }
 
-// Returns true iff the weak_groups_to_nodes map has node_ptr as the value in any of its entry.
-bool
-Executor::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();
-}
-
 bool
 Executor::is_spinning()
 {

rclcpp/src/rclcpp/executors/executor_entities_collection.cpp

@@ -20,12 +20,13 @@ namespace executors
 {
 bool ExecutorEntitiesCollection::empty() const
 {
-  return subscriptions.empty() &&
-         timers.empty() &&
-         guard_conditions.empty() &&
-         clients.empty() &&
-         services.empty() &&
-         waitables.empty();
+  return
+    subscriptions.empty() &&
+    timers.empty() &&
+    guard_conditions.empty() &&
+    clients.empty() &&
+    services.empty() &&
+    waitables.empty();
 }
 
 void ExecutorEntitiesCollection::clear()
@@ -38,7 +39,6 @@ void ExecutorEntitiesCollection::clear()
   waitables.clear();
 }
 
-
 void
 build_entities_collection(
   const std::vector<rclcpp::CallbackGroup::WeakPtr> & callback_groups,
@@ -94,110 +94,135 @@ build_entities_collection(
   }
 }
 
-template<typename EntityCollectionType>
-void check_ready(
-  EntityCollectionType & collection,
-  std::deque<rclcpp::AnyExecutable> & executables,
-  size_t size_of_waited_entities,
-  typename EntityCollectionType::Key * waited_entities,
-  std::function<bool(rclcpp::AnyExecutable &,
-  typename EntityCollectionType::EntitySharedPtr &)> fill_executable)
+size_t
+ready_executables(
+  const ExecutorEntitiesCollection & collection,
+  rclcpp::WaitResult<rclcpp::WaitSet> & wait_result,
+  std::deque<rclcpp::AnyExecutable> & executables
+)
 {
-  for (size_t ii = 0; ii < size_of_waited_entities; ++ii) {
-    if (!waited_entities[ii]) {continue;}
-    auto entity_iter = collection.find(waited_entities[ii]);
-    if (entity_iter != collection.end()) {
+  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 callback_group = entity_iter->second.callback_group.lock();
-      if (callback_group && !callback_group->can_be_taken_from().load()) {
+      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.callback_group = callback_group;
-      if (fill_executable(exec, entity)) {
-        executables.push_back(exec);
-      }
+      exec.timer = entity;
+      exec.callback_group = group_info;
+      executables.push_back(exec);
+      added++;
     }
   }
-}
 
-std::deque<rclcpp::AnyExecutable>
-ready_executables(
-  const ExecutorEntitiesCollection & collection,
-  rclcpp::WaitResult<rclcpp::WaitSet> & wait_result
-)
-{
-  std::deque<rclcpp::AnyExecutable> ret;
-
-  if (wait_result.kind() != rclcpp::WaitResultKind::Ready) {
-    return ret;
-  }
-  auto rcl_wait_set = wait_result.get_wait_set().get_rcl_wait_set();
-  check_ready(
-    collection.timers,
-    ret,
-    rcl_wait_set.size_of_timers,
-    rcl_wait_set.timers,
-    [](rclcpp::AnyExecutable & exec, auto timer) {
-      if (!timer->call()) {
-        return false;
+  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;
       }
-      exec.timer = timer;
-      return true;
-    });
+      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++;
+    }
+  }
 
-  check_ready(
-    collection.subscriptions,
-    ret,
-    rcl_wait_set.size_of_subscriptions,
-    rcl_wait_set.subscriptions,
-    [](rclcpp::AnyExecutable & exec, auto subscription) {
-      exec.subscription = subscription;
-      return 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;
+      }
+      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++;
+    }
+  }
 
-
-  check_ready(
-    collection.services,
-    ret,
-    rcl_wait_set.size_of_services,
-    rcl_wait_set.services,
-    [](rclcpp::AnyExecutable & exec, auto service) {
-      exec.service = service;
-      return true;
-    });
-
-  check_ready(
-    collection.clients,
-    ret,
-    rcl_wait_set.size_of_clients,
-    rcl_wait_set.clients,
-    [](rclcpp::AnyExecutable & exec, auto client) {
-      exec.client = client;
-      return 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;
+      }
+      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 && waitable->is_ready(&rcl_wait_set)) {
-      auto group = entry.callback_group.lock();
-      if (group && !group->can_be_taken_from().load()) {
-        continue;
-      }
-
-      rclcpp::AnyExecutable exec;
-      exec.waitable = waitable;
-      exec.callback_group = group;
-      ret.push_back(exec);
+    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 ret;
+  return added;
 }
-
 }  // namespace executors
 }  // namespace rclcpp

rclcpp/src/rclcpp/executors/executor_entities_collector.cpp

@@ -105,7 +105,8 @@ void
 ExecutorEntitiesCollector::remove_node(
   rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_ptr)
 {
-  if (!node_ptr->get_associated_with_executor_atomic().load()) {
+  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.");
@@ -161,7 +162,6 @@ ExecutorEntitiesCollector::remove_callback_group(rclcpp::CallbackGroup::SharedPt
     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;
@@ -314,7 +314,11 @@ ExecutorEntitiesCollector::process_queues()
     if (node_it != weak_nodes_.end()) {
       remove_weak_node(node_it);
     } else {
-      throw std::runtime_error("Node needs to be associated with this executor.");
+      // 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();

rclcpp/src/rclcpp/executors/executor_notify_waitable.cpp

@@ -46,20 +46,18 @@ 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) {
-      auto rcl_guard_condition = &guard_condition->get_rcl_guard_condition();
+    if (!guard_condition) {continue;}
 
-      rcl_ret_t ret = rcl_wait_set_add_guard_condition(
-        wait_set,
-        rcl_guard_condition, NULL);
+    rcl_guard_condition_t * cond = &guard_condition->get_rcl_guard_condition();
 
-      if (RCL_RET_OK != ret) {
-        rclcpp::exceptions::throw_from_rcl_error(
-          ret, "failed to add guard condition to wait set");
-      }
+    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");
     }
   }
 }

rclcpp/src/rclcpp/executors/multi_threaded_executor.cpp

@@ -99,6 +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()) {
-      weak_nodes_to_guard_conditions_[node_ptr] =
-        node_ptr->get_shared_notify_guard_condition().get();
-    }
-  }
-  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/test/benchmark/benchmark_executor.cpp

@@ -362,42 +362,3 @@ BENCHMARK_F(PerformanceTestExecutorSimple, spin_until_future_complete)(benchmark
     }
   }
 }
-
-BENCHMARK_F(
-  PerformanceTestExecutorSimple,
-  static_executor_entities_collector_execute)(benchmark::State & st)
-{
-  rclcpp::executors::StaticExecutorEntitiesCollector::SharedPtr entities_collector_ =
-    std::make_shared<rclcpp::executors::StaticExecutorEntitiesCollector>();
-  entities_collector_->add_node(node->get_node_base_interface());
-
-  rcl_wait_set_t wait_set = rcl_get_zero_initialized_wait_set();
-  rcl_allocator_t allocator = rcl_get_default_allocator();
-  auto shared_context = node->get_node_base_interface()->get_context();
-  rcl_context_t * context = shared_context->get_rcl_context().get();
-  rcl_ret_t ret = rcl_wait_set_init(&wait_set, 100, 100, 100, 100, 100, 100, context, allocator);
-  if (ret != RCL_RET_OK) {
-    st.SkipWithError(rcutils_get_error_string().str);
-  }
-  RCPPUTILS_SCOPE_EXIT(
-  {
-    rcl_ret_t ret = rcl_wait_set_fini(&wait_set);
-    if (ret != RCL_RET_OK) {
-      st.SkipWithError(rcutils_get_error_string().str);
-    }
-  });
-
-  auto memory_strategy = rclcpp::memory_strategies::create_default_strategy();
-  rclcpp::GuardCondition guard_condition(shared_context);
-
-  entities_collector_->init(&wait_set, memory_strategy);
-  RCPPUTILS_SCOPE_EXIT(entities_collector_->fini());
-
-  reset_heap_counters();
-
-  for (auto _ : st) {
-    (void)_;
-    std::shared_ptr<void> data = entities_collector_->take_data();
-    entities_collector_->execute(data);
-  }
-}

rclcpp/test/rclcpp/CMakeLists.txt

@@ -671,14 +671,6 @@ if(TARGET test_executors)
   target_link_libraries(test_executors ${PROJECT_NAME})
 endif()
 
-ament_add_gtest(test_static_single_threaded_executor executors/test_static_single_threaded_executor.cpp
-  APPEND_LIBRARY_DIRS "${append_library_dirs}")
-if(TARGET test_static_single_threaded_executor)
-  ament_target_dependencies(test_static_single_threaded_executor
-    "test_msgs")
-  target_link_libraries(test_static_single_threaded_executor ${PROJECT_NAME} mimick)
-endif()
-
 ament_add_gtest(test_multi_threaded_executor executors/test_multi_threaded_executor.cpp
   APPEND_LIBRARY_DIRS "${append_library_dirs}")
 if(TARGET test_multi_threaded_executor)
@@ -687,15 +679,6 @@ if(TARGET test_multi_threaded_executor)
   target_link_libraries(test_multi_threaded_executor ${PROJECT_NAME})
 endif()
 
-ament_add_gtest(test_static_executor_entities_collector executors/test_static_executor_entities_collector.cpp
-  APPEND_LIBRARY_DIRS "${append_library_dirs}" TIMEOUT 120)
-if(TARGET test_static_executor_entities_collector)
-  ament_target_dependencies(test_static_executor_entities_collector
-    "rcl"
-    "test_msgs")
-  target_link_libraries(test_static_executor_entities_collector ${PROJECT_NAME} mimick)
-endif()
-
 ament_add_gtest(test_entities_collector executors/test_entities_collector.cpp
   APPEND_LIBRARY_DIRS "${append_library_dirs}" TIMEOUT 120)
 if(TARGET test_entities_collector)

rclcpp/test/rclcpp/executors/test_executors.cpp

@@ -83,8 +83,6 @@ public:
   int callback_count;
 };
 
-// spin_all and spin_some are not implemented correctly in StaticSingleThreadedExecutor, see:
-// https://github.com/ros2/rclcpp/issues/1219 for tracking
 template<typename T>
 class TestExecutorsStable : public TestExecutors<T> {};
 
@@ -126,15 +124,6 @@ public:
 // is updated.
 TYPED_TEST_SUITE(TestExecutors, ExecutorTypes, ExecutorTypeNames);
 
-// StaticSingleThreadedExecutor is not included in these tests for now, due to:
-// https://github.com/ros2/rclcpp/issues/1219
-using StandardExecutors =
-  ::testing::Types<
-  rclcpp::executors::SingleThreadedExecutor,
-  rclcpp::executors::MultiThreadedExecutor,
-  rclcpp::experimental::executors::EventsExecutor>;
-TYPED_TEST_SUITE(TestExecutorsStable, StandardExecutors, ExecutorTypeNames);
-
 // Make sure that executors detach from nodes when destructing
 TYPED_TEST(TestExecutors, detachOnDestruction)
 {
@@ -158,10 +147,7 @@ TYPED_TEST(TestExecutors, detachOnDestruction)
 }
 
 // Make sure that the executor can automatically remove expired nodes correctly
-// Currently fails for StaticSingleThreadedExecutor so it is being skipped, see:
-// https://github.com/ros2/rclcpp/issues/1231
-TYPED_TEST(TestExecutorsStable, addTemporaryNode)
-{
+TYPED_TEST(TestExecutors, addTemporaryNode) {
   using ExecutorType = TypeParam;
   // rmw_connextdds doesn't support events-executor
   if (
@@ -271,14 +257,17 @@ TYPED_TEST(TestExecutors, spinWhileAlreadySpinning)
   ExecutorType executor;
   executor.add_node(this->node);
 
-  bool timer_completed = false;
-  auto timer = this->node->create_wall_timer(1ms, [&]() {timer_completed = true;});
+  std::atomic_bool timer_completed = false;
+  auto timer = this->node->create_wall_timer(
+    1ms, [&]() {
+      timer_completed.store(true);
+    });
 
   std::thread spinner([&]() {executor.spin();});
   // Sleep for a short time to verify executor.spin() is going, and didn't throw.
 
   auto start = std::chrono::steady_clock::now();
-  while (!timer_completed && (std::chrono::steady_clock::now() - start) < 10s) {
+  while (!timer_completed.load() && (std::chrono::steady_clock::now() - start) < 10s) {
     std::this_thread::sleep_for(1ms);
   }
 

rclcpp/test/rclcpp/test_executor.cpp

@@ -46,23 +46,6 @@ public:
   {
     spin_node_once_nanoseconds(node, std::chrono::milliseconds(100));
   }
-
-  rclcpp::memory_strategy::MemoryStrategy * memory_strategy_ptr()
-  {
-    return memory_strategy_.get();
-  }
-
-  rclcpp::node_interfaces::NodeBaseInterface::SharedPtr local_get_node_by_group(
-    rclcpp::CallbackGroup::SharedPtr group)
-  {
-    std::lock_guard<std::mutex> guard_{mutex_};  // only to make the TSA happy
-    return get_node_by_group(weak_groups_to_nodes_, group);
-  }
-
-  rclcpp::CallbackGroup::SharedPtr local_get_group_by_timer(rclcpp::TimerBase::SharedPtr timer)
-  {
-    return get_group_by_timer(timer);
-  }
 };
 
 class TestExecutor : public ::testing::Test
@@ -130,7 +113,7 @@ TEST_F(TestExecutor, constructor_bad_wait_set_init) {
   auto mock = mocking_utils::patch_and_return("lib:rclcpp", rcl_wait_set_init, RCL_RET_ERROR);
   RCLCPP_EXPECT_THROW_EQ(
     static_cast<void>(std::make_unique<DummyExecutor>()),
-    std::runtime_error("Failed to create wait set in Executor constructor: error not set"));
+    std::runtime_error("Failed to create wait set: error not set"));
 }
 
 TEST_F(TestExecutor, add_callback_group_twice) {
@@ -142,7 +125,7 @@ TEST_F(TestExecutor, add_callback_group_twice) {
   cb_group->get_associated_with_executor_atomic().exchange(false);
   RCLCPP_EXPECT_THROW_EQ(
     dummy.add_callback_group(cb_group, node->get_node_base_interface(), false),
-    std::runtime_error("Callback group was already added to executor."));
+    std::runtime_error("Callback group has already been added to this executor."));
 }
 
 TEST_F(TestExecutor, add_callback_group_failed_trigger_guard_condition) {
@@ -168,9 +151,15 @@ TEST_F(TestExecutor, remove_callback_group_null_node) {
 
   node.reset();
 
+
+  /**
+   * TODO(mjcarroll): Assert this when we are enforcing that nodes must be destroyed
+   * after their created callback groups.
   RCLCPP_EXPECT_THROW_EQ(
     dummy.remove_callback_group(cb_group, false),
     std::runtime_error("Node must not be deleted before its callback group(s)."));
+   */
+  EXPECT_NO_THROW(dummy.remove_callback_group(cb_group, false));
 }
 
 TEST_F(TestExecutor, remove_callback_group_failed_trigger_guard_condition) {
@@ -197,7 +186,7 @@ TEST_F(TestExecutor, remove_node_not_associated) {
 
   RCLCPP_EXPECT_THROW_EQ(
     dummy.remove_node(node->get_node_base_interface(), false),
-    std::runtime_error("Node needs to be associated with an executor."));
+    std::runtime_error("Node '/ns/node' needs to be associated with an executor."));
 }
 
 TEST_F(TestExecutor, remove_node_associated_with_different_executor) {
@@ -211,7 +200,7 @@ TEST_F(TestExecutor, remove_node_associated_with_different_executor) {
 
   RCLCPP_EXPECT_THROW_EQ(
     dummy2.remove_node(node1->get_node_base_interface(), false),
-    std::runtime_error("Node needs to be associated with this executor."));
+    std::runtime_error("Node '/ns/node1' needs to be associated with this executor."));
 }
 
 TEST_F(TestExecutor, spin_node_once_nanoseconds) {
@@ -328,42 +317,14 @@ TEST_F(TestExecutor, cancel_failed_trigger_guard_condition) {
     std::runtime_error("Failed to trigger guard condition in cancel: error not set"));
 }
 
-TEST_F(TestExecutor, set_memory_strategy_nullptr) {
-  DummyExecutor dummy;
-
+TEST_F(TestExecutor, create_executor_fail_wait_set_clear) {
+  auto mock = mocking_utils::patch_and_return("lib:rclcpp", rcl_wait_set_clear, RCL_RET_ERROR);
   RCLCPP_EXPECT_THROW_EQ(
-    dummy.set_memory_strategy(nullptr),
-    std::runtime_error("Received NULL memory strategy in executor."));
+    DummyExecutor dummy,
+    std::runtime_error("Couldn't clear the wait set: error not set"));
 }
 
-TEST_F(TestExecutor, set_memory_strategy) {
-  DummyExecutor dummy;
-  rclcpp::memory_strategy::MemoryStrategy::SharedPtr strategy =
-    std::make_shared<
-    rclcpp::memory_strategies::allocator_memory_strategy::AllocatorMemoryStrategy<>>();
-
-  dummy.set_memory_strategy(strategy);
-  EXPECT_EQ(dummy.memory_strategy_ptr(), strategy.get());
-}
-
-TEST_F(TestExecutor, spin_once_failed_trigger_guard_condition) {
-  DummyExecutor dummy;
-  auto node = std::make_shared<rclcpp::Node>("node", "ns");
-  auto timer =
-    node->create_wall_timer(std::chrono::milliseconds(1), [&]() {});
-
-  dummy.add_node(node);
-  // Wait for the wall timer to have expired.
-  std::this_thread::sleep_for(std::chrono::milliseconds(50));
-  auto mock = mocking_utils::patch_and_return(
-    "lib:rclcpp", rcl_trigger_guard_condition, RCL_RET_ERROR);
-  RCLCPP_EXPECT_THROW_EQ(
-    dummy.spin_once(std::chrono::milliseconds(1)),
-    std::runtime_error(
-      "Failed to trigger guard condition from execute_any_executable: error not set"));
-}
-
-TEST_F(TestExecutor, spin_some_fail_wait_set_clear) {
+TEST_F(TestExecutor, spin_all_fail_wait_set_clear) {
   DummyExecutor dummy;
   auto node = std::make_shared<rclcpp::Node>("node", "ns");
   auto timer =
@@ -371,9 +332,10 @@ TEST_F(TestExecutor, spin_some_fail_wait_set_clear) {
 
   dummy.add_node(node);
   auto mock = mocking_utils::patch_and_return("lib:rclcpp", rcl_wait_set_clear, RCL_RET_ERROR);
+
   RCLCPP_EXPECT_THROW_EQ(
-    dummy.spin_some(std::chrono::milliseconds(1)),
-    std::runtime_error("Couldn't clear wait set: error not set"));
+    dummy.spin_all(std::chrono::milliseconds(1)),
+    std::runtime_error("Couldn't clear the wait set: error not set"));
 }
 
 TEST_F(TestExecutor, spin_some_fail_wait_set_resize) {
@@ -401,7 +363,7 @@ TEST_F(TestExecutor, spin_some_fail_add_handles_to_wait_set) {
     RCL_RET_ERROR);
   RCLCPP_EXPECT_THROW_EQ(
     dummy.spin_some(std::chrono::milliseconds(1)),
-    std::runtime_error("Couldn't fill wait set"));
+    std::runtime_error("Couldn't fill wait set: error not set"));
 }
 
 TEST_F(TestExecutor, spin_some_fail_wait) {
@@ -417,71 +379,6 @@ TEST_F(TestExecutor, spin_some_fail_wait) {
     std::runtime_error("rcl_wait() failed: error not set"));
 }
 
-TEST_F(TestExecutor, get_node_by_group_null_group) {
-  DummyExecutor dummy;
-  ASSERT_EQ(nullptr, dummy.local_get_node_by_group(nullptr));
-}
-
-TEST_F(TestExecutor, get_node_by_group) {
-  DummyExecutor dummy;
-  auto node = std::make_shared<rclcpp::Node>("node", "ns");
-  rclcpp::CallbackGroup::SharedPtr cb_group = node->create_callback_group(
-    rclcpp::CallbackGroupType::MutuallyExclusive);
-  dummy.add_callback_group(cb_group, node->get_node_base_interface(), false);
-  ASSERT_EQ(node->get_node_base_interface().get(), dummy.local_get_node_by_group(cb_group).get());
-}
-
-TEST_F(TestExecutor, get_node_by_group_not_found) {
-  DummyExecutor dummy;
-  auto node = std::make_shared<rclcpp::Node>("node", "ns");
-  rclcpp::CallbackGroup::SharedPtr cb_group = node->create_callback_group(
-    rclcpp::CallbackGroupType::MutuallyExclusive);
-  ASSERT_EQ(nullptr, dummy.local_get_node_by_group(cb_group).get());
-}
-
-TEST_F(TestExecutor, get_group_by_timer_nullptr) {
-  DummyExecutor dummy;
-  ASSERT_EQ(nullptr, dummy.local_get_group_by_timer(nullptr));
-}
-
-TEST_F(TestExecutor, get_group_by_timer) {
-  DummyExecutor dummy;
-  auto node = std::make_shared<rclcpp::Node>("node", "ns");
-  rclcpp::CallbackGroup::SharedPtr cb_group = node->create_callback_group(
-    rclcpp::CallbackGroupType::MutuallyExclusive);
-  auto timer =
-    node->create_wall_timer(std::chrono::milliseconds(1), [&]() {}, cb_group);
-  dummy.add_node(node);
-
-  ASSERT_EQ(cb_group.get(), dummy.local_get_group_by_timer(timer).get());
-}
-
-TEST_F(TestExecutor, get_group_by_timer_with_deleted_group) {
-  DummyExecutor dummy;
-  auto node = std::make_shared<rclcpp::Node>("node", "ns");
-  rclcpp::CallbackGroup::SharedPtr cb_group = node->create_callback_group(
-    rclcpp::CallbackGroupType::MutuallyExclusive);
-  auto timer =
-    node->create_wall_timer(std::chrono::milliseconds(1), [&]() {}, cb_group);
-  dummy.add_node(node);
-
-  cb_group.reset();
-
-  ASSERT_EQ(nullptr, dummy.local_get_group_by_timer(timer).get());
-}
-
-TEST_F(TestExecutor, get_group_by_timer_add_callback_group) {
-  DummyExecutor dummy;
-  auto node = std::make_shared<rclcpp::Node>("node", "ns");
-  rclcpp::CallbackGroup::SharedPtr cb_group = node->create_callback_group(
-    rclcpp::CallbackGroupType::MutuallyExclusive);
-  auto timer =
-    node->create_wall_timer(std::chrono::milliseconds(1), [&]() {}, cb_group);
-  dummy.add_callback_group(cb_group, node->get_node_base_interface(), false);
-
-  ASSERT_EQ(cb_group.get(), dummy.local_get_group_by_timer(timer).get());
-}
-
 TEST_F(TestExecutor, spin_until_future_complete_in_spin_until_future_complete) {
   DummyExecutor dummy;
   auto node = std::make_shared<rclcpp::Node>("node", "ns");