diff --git a/rclcpp/include/rclcpp/callback_group.hpp b/rclcpp/include/rclcpp/callback_group.hpp
index efa8352206..94bceced81 100644
--- a/rclcpp/include/rclcpp/callback_group.hpp
+++ b/rclcpp/include/rclcpp/callback_group.hpp
@@ -138,6 +138,14 @@ class CallbackGroup
   const CallbackGroupType &
   type() const;
 
+  RCLCPP_PUBLIC
+  void collect_all_ptrs(
+    std::function<void(const rclcpp::SubscriptionBase::SharedPtr &)> sub_func,
+    std::function<void(const rclcpp::ServiceBase::SharedPtr &)> service_func,
+    std::function<void(const rclcpp::ClientBase::SharedPtr &)> client_func,
+    std::function<void(const rclcpp::TimerBase::SharedPtr &)> timer_func,
+    std::function<void(const rclcpp::Waitable::SharedPtr &)> waitable_func) const;
+
   /// Return a reference to the 'associated with executor' atomic boolean.
   /**
    * When a callback group is added to an executor this boolean is checked
diff --git a/rclcpp/include/rclcpp/memory_strategy.hpp b/rclcpp/include/rclcpp/memory_strategy.hpp
index 0993c223c9..fb5ba2a63f 100644
--- a/rclcpp/include/rclcpp/memory_strategy.hpp
+++ b/rclcpp/include/rclcpp/memory_strategy.hpp
@@ -100,52 +100,52 @@ class RCLCPP_PUBLIC MemoryStrategy
 
   static rclcpp::SubscriptionBase::SharedPtr
   get_subscription_by_handle(
-    std::shared_ptr<const rcl_subscription_t> subscriber_handle,
+    const std::shared_ptr<const rcl_subscription_t> & subscriber_handle,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 
   static rclcpp::ServiceBase::SharedPtr
   get_service_by_handle(
-    std::shared_ptr<const rcl_service_t> service_handle,
+    const std::shared_ptr<const rcl_service_t> & service_handle,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 
   static rclcpp::ClientBase::SharedPtr
   get_client_by_handle(
-    std::shared_ptr<const rcl_client_t> client_handle,
+    const std::shared_ptr<const rcl_client_t> & client_handle,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 
   static rclcpp::TimerBase::SharedPtr
   get_timer_by_handle(
-    std::shared_ptr<const rcl_timer_t> timer_handle,
+    const std::shared_ptr<const rcl_timer_t> & timer_handle,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 
   static rclcpp::node_interfaces::NodeBaseInterface::SharedPtr
   get_node_by_group(
-    rclcpp::CallbackGroup::SharedPtr group,
+    const rclcpp::CallbackGroup::SharedPtr & group,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 
   static rclcpp::CallbackGroup::SharedPtr
   get_group_by_subscription(
-    rclcpp::SubscriptionBase::SharedPtr subscription,
+    const rclcpp::SubscriptionBase::SharedPtr & subscription,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 
   static rclcpp::CallbackGroup::SharedPtr
   get_group_by_service(
-    rclcpp::ServiceBase::SharedPtr service,
+    const rclcpp::ServiceBase::SharedPtr & service,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 
   static rclcpp::CallbackGroup::SharedPtr
   get_group_by_client(
-    rclcpp::ClientBase::SharedPtr client,
+    const rclcpp::ClientBase::SharedPtr & client,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 
   static rclcpp::CallbackGroup::SharedPtr
   get_group_by_timer(
-    rclcpp::TimerBase::SharedPtr timer,
+    const rclcpp::TimerBase::SharedPtr & timer,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 
   static rclcpp::CallbackGroup::SharedPtr
   get_group_by_waitable(
-    rclcpp::Waitable::SharedPtr waitable,
+    const rclcpp::Waitable::SharedPtr & waitable,
     const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes);
 };
 
diff --git a/rclcpp/include/rclcpp/strategies/allocator_memory_strategy.hpp b/rclcpp/include/rclcpp/strategies/allocator_memory_strategy.hpp
index d0bb9c7df2..88698179d4 100644
--- a/rclcpp/include/rclcpp/strategies/allocator_memory_strategy.hpp
+++ b/rclcpp/include/rclcpp/strategies/allocator_memory_strategy.hpp
@@ -164,30 +164,22 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
       if (!group || !group->can_be_taken_from().load()) {
         continue;
       }
-      group->find_subscription_ptrs_if(
+
+      group->collect_all_ptrs(
         [this](const rclcpp::SubscriptionBase::SharedPtr & subscription) {
           subscription_handles_.push_back(subscription->get_subscription_handle());
-          return false;
-        });
-      group->find_service_ptrs_if(
+        },
         [this](const rclcpp::ServiceBase::SharedPtr & service) {
           service_handles_.push_back(service->get_service_handle());
-          return false;
-        });
-      group->find_client_ptrs_if(
+        },
         [this](const rclcpp::ClientBase::SharedPtr & client) {
           client_handles_.push_back(client->get_client_handle());
-          return false;
-        });
-      group->find_timer_ptrs_if(
+        },
         [this](const rclcpp::TimerBase::SharedPtr & timer) {
           timer_handles_.push_back(timer->get_timer_handle());
-          return false;
-        });
-      group->find_waitable_ptrs_if(
+        },
         [this](const rclcpp::Waitable::SharedPtr & waitable) {
           waitable_handles_.push_back(waitable);
-          return false;
         });
     }
 
@@ -204,7 +196,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
 
   bool add_handles_to_wait_set(rcl_wait_set_t * wait_set) override
   {
-    for (auto subscription : subscription_handles_) {
+    for (const std::shared_ptr<const rcl_subscription_t> & subscription : subscription_handles_) {
       if (rcl_wait_set_add_subscription(wait_set, subscription.get(), NULL) != RCL_RET_OK) {
         RCUTILS_LOG_ERROR_NAMED(
           "rclcpp",
@@ -213,7 +205,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
       }
     }
 
-    for (auto client : client_handles_) {
+    for (const std::shared_ptr<const rcl_client_t> & client : client_handles_) {
       if (rcl_wait_set_add_client(wait_set, client.get(), NULL) != RCL_RET_OK) {
         RCUTILS_LOG_ERROR_NAMED(
           "rclcpp",
@@ -222,7 +214,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
       }
     }
 
-    for (auto service : service_handles_) {
+    for (const std::shared_ptr<const rcl_service_t> & service : service_handles_) {
       if (rcl_wait_set_add_service(wait_set, service.get(), NULL) != RCL_RET_OK) {
         RCUTILS_LOG_ERROR_NAMED(
           "rclcpp",
@@ -231,7 +223,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
       }
     }
 
-    for (auto timer : timer_handles_) {
+    for (const std::shared_ptr<const rcl_timer_t> & timer : timer_handles_) {
       if (rcl_wait_set_add_timer(wait_set, timer.get(), NULL) != RCL_RET_OK) {
         RCUTILS_LOG_ERROR_NAMED(
           "rclcpp",
@@ -244,7 +236,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
       detail::add_guard_condition_to_rcl_wait_set(*wait_set, *guard_condition);
     }
 
-    for (auto waitable : waitable_handles_) {
+    for (const std::shared_ptr<Waitable> & waitable : waitable_handles_) {
       waitable->add_to_wait_set(wait_set);
     }
     return true;
@@ -402,7 +394,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
   {
     auto it = waitable_handles_.begin();
     while (it != waitable_handles_.end()) {
-      auto waitable = *it;
+      std::shared_ptr<Waitable> & waitable = *it;
       if (waitable) {
         // Find the group for this handle and see if it can be serviced
         auto group = get_group_by_waitable(waitable, weak_groups_to_nodes);
@@ -438,7 +430,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
   size_t number_of_ready_subscriptions() const override
   {
     size_t number_of_subscriptions = subscription_handles_.size();
-    for (auto waitable : waitable_handles_) {
+    for (const std::shared_ptr<Waitable> & waitable : waitable_handles_) {
       number_of_subscriptions += waitable->get_number_of_ready_subscriptions();
     }
     return number_of_subscriptions;
@@ -447,7 +439,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
   size_t number_of_ready_services() const override
   {
     size_t number_of_services = service_handles_.size();
-    for (auto waitable : waitable_handles_) {
+    for (const std::shared_ptr<Waitable> & waitable : waitable_handles_) {
       number_of_services += waitable->get_number_of_ready_services();
     }
     return number_of_services;
@@ -456,7 +448,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
   size_t number_of_ready_events() const override
   {
     size_t number_of_events = 0;
-    for (auto waitable : waitable_handles_) {
+    for (const std::shared_ptr<Waitable> & waitable : waitable_handles_) {
       number_of_events += waitable->get_number_of_ready_events();
     }
     return number_of_events;
@@ -465,7 +457,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
   size_t number_of_ready_clients() const override
   {
     size_t number_of_clients = client_handles_.size();
-    for (auto waitable : waitable_handles_) {
+    for (const std::shared_ptr<Waitable> & waitable : waitable_handles_) {
       number_of_clients += waitable->get_number_of_ready_clients();
     }
     return number_of_clients;
@@ -474,7 +466,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
   size_t number_of_guard_conditions() const override
   {
     size_t number_of_guard_conditions = guard_conditions_.size();
-    for (auto waitable : waitable_handles_) {
+    for (const std::shared_ptr<Waitable> & waitable : waitable_handles_) {
       number_of_guard_conditions += waitable->get_number_of_ready_guard_conditions();
     }
     return number_of_guard_conditions;
@@ -483,7 +475,7 @@ class AllocatorMemoryStrategy : public memory_strategy::MemoryStrategy
   size_t number_of_ready_timers() const override
   {
     size_t number_of_timers = timer_handles_.size();
-    for (auto waitable : waitable_handles_) {
+    for (const std::shared_ptr<Waitable> & waitable : waitable_handles_) {
       number_of_timers += waitable->get_number_of_ready_timers();
     }
     return number_of_timers;
diff --git a/rclcpp/src/rclcpp/callback_group.cpp b/rclcpp/src/rclcpp/callback_group.cpp
index 6b38578ba9..4b11156cf9 100644
--- a/rclcpp/src/rclcpp/callback_group.cpp
+++ b/rclcpp/src/rclcpp/callback_group.cpp
@@ -40,6 +40,51 @@ CallbackGroup::type() const
   return type_;
 }
 
+void CallbackGroup::collect_all_ptrs(
+  std::function<void(const rclcpp::SubscriptionBase::SharedPtr &)> sub_func,
+  std::function<void(const rclcpp::ServiceBase::SharedPtr &)> service_func,
+  std::function<void(const rclcpp::ClientBase::SharedPtr &)> client_func,
+  std::function<void(const rclcpp::TimerBase::SharedPtr &)> timer_func,
+  std::function<void(const rclcpp::Waitable::SharedPtr &)> waitable_func) const
+{
+  std::lock_guard<std::mutex> lock(mutex_);
+
+  for (const rclcpp::SubscriptionBase::WeakPtr & weak_ptr : subscription_ptrs_) {
+    rclcpp::SubscriptionBase::SharedPtr ref_ptr = weak_ptr.lock();
+    if (ref_ptr) {
+      sub_func(ref_ptr);
+    }
+  }
+
+  for (const rclcpp::ServiceBase::WeakPtr & weak_ptr : service_ptrs_) {
+    rclcpp::ServiceBase::SharedPtr ref_ptr = weak_ptr.lock();
+    if (ref_ptr) {
+      service_func(ref_ptr);
+    }
+  }
+
+  for (const rclcpp::ClientBase::WeakPtr & weak_ptr : client_ptrs_) {
+    rclcpp::ClientBase::SharedPtr ref_ptr = weak_ptr.lock();
+    if (ref_ptr) {
+      client_func(ref_ptr);
+    }
+  }
+
+  for (const rclcpp::TimerBase::WeakPtr & weak_ptr : timer_ptrs_) {
+    rclcpp::TimerBase::SharedPtr ref_ptr = weak_ptr.lock();
+    if (ref_ptr) {
+      timer_func(ref_ptr);
+    }
+  }
+
+  for (const rclcpp::Waitable::WeakPtr & weak_ptr : waitable_ptrs_) {
+    rclcpp::Waitable::SharedPtr ref_ptr = weak_ptr.lock();
+    if (ref_ptr) {
+      waitable_func(ref_ptr);
+    }
+  }
+}
+
 std::atomic_bool &
 CallbackGroup::get_associated_with_executor_atomic()
 {
diff --git a/rclcpp/src/rclcpp/memory_strategy.cpp b/rclcpp/src/rclcpp/memory_strategy.cpp
index bd32bdb169..cb69dc0d26 100644
--- a/rclcpp/src/rclcpp/memory_strategy.cpp
+++ b/rclcpp/src/rclcpp/memory_strategy.cpp
@@ -19,7 +19,7 @@ using rclcpp::memory_strategy::MemoryStrategy;
 
 rclcpp::SubscriptionBase::SharedPtr
 MemoryStrategy::get_subscription_by_handle(
-  std::shared_ptr<const rcl_subscription_t> subscriber_handle,
+  const std::shared_ptr<const rcl_subscription_t> & subscriber_handle,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   for (const auto & pair : weak_groups_to_nodes) {
@@ -40,7 +40,7 @@ MemoryStrategy::get_subscription_by_handle(
 
 rclcpp::ServiceBase::SharedPtr
 MemoryStrategy::get_service_by_handle(
-  std::shared_ptr<const rcl_service_t> service_handle,
+  const std::shared_ptr<const rcl_service_t> & service_handle,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   for (const auto & pair : weak_groups_to_nodes) {
@@ -61,7 +61,7 @@ MemoryStrategy::get_service_by_handle(
 
 rclcpp::ClientBase::SharedPtr
 MemoryStrategy::get_client_by_handle(
-  std::shared_ptr<const rcl_client_t> client_handle,
+  const std::shared_ptr<const rcl_client_t> & client_handle,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   for (const auto & pair : weak_groups_to_nodes) {
@@ -82,7 +82,7 @@ MemoryStrategy::get_client_by_handle(
 
 rclcpp::TimerBase::SharedPtr
 MemoryStrategy::get_timer_by_handle(
-  std::shared_ptr<const rcl_timer_t> timer_handle,
+  const std::shared_ptr<const rcl_timer_t> & timer_handle,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   for (const auto & pair : weak_groups_to_nodes) {
@@ -103,7 +103,7 @@ MemoryStrategy::get_timer_by_handle(
 
 rclcpp::node_interfaces::NodeBaseInterface::SharedPtr
 MemoryStrategy::get_node_by_group(
-  rclcpp::CallbackGroup::SharedPtr group,
+  const rclcpp::CallbackGroup::SharedPtr & group,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   if (!group) {
@@ -121,7 +121,7 @@ MemoryStrategy::get_node_by_group(
 
 rclcpp::CallbackGroup::SharedPtr
 MemoryStrategy::get_group_by_subscription(
-  rclcpp::SubscriptionBase::SharedPtr subscription,
+  const rclcpp::SubscriptionBase::SharedPtr & subscription,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   for (const auto & pair : weak_groups_to_nodes) {
@@ -143,7 +143,7 @@ MemoryStrategy::get_group_by_subscription(
 
 rclcpp::CallbackGroup::SharedPtr
 MemoryStrategy::get_group_by_service(
-  rclcpp::ServiceBase::SharedPtr service,
+  const rclcpp::ServiceBase::SharedPtr & service,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   for (const auto & pair : weak_groups_to_nodes) {
@@ -165,7 +165,7 @@ MemoryStrategy::get_group_by_service(
 
 rclcpp::CallbackGroup::SharedPtr
 MemoryStrategy::get_group_by_client(
-  rclcpp::ClientBase::SharedPtr client,
+  const rclcpp::ClientBase::SharedPtr & client,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   for (const auto & pair : weak_groups_to_nodes) {
@@ -187,7 +187,7 @@ MemoryStrategy::get_group_by_client(
 
 rclcpp::CallbackGroup::SharedPtr
 MemoryStrategy::get_group_by_timer(
-  rclcpp::TimerBase::SharedPtr timer,
+  const rclcpp::TimerBase::SharedPtr & timer,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   for (const auto & pair : weak_groups_to_nodes) {
@@ -209,7 +209,7 @@ MemoryStrategy::get_group_by_timer(
 
 rclcpp::CallbackGroup::SharedPtr
 MemoryStrategy::get_group_by_waitable(
-  rclcpp::Waitable::SharedPtr waitable,
+  const rclcpp::Waitable::SharedPtr & waitable,
   const WeakCallbackGroupsToNodesMap & weak_groups_to_nodes)
 {
   for (const auto & pair : weak_groups_to_nodes) {