[Iron] Add new node interface TypeDescriptionsInterface to provide GetTypeDescription service (backport #2224)

rclcpp/CMakeLists.txt

@@ -92,6 +92,7 @@ set(${PROJECT_NAME}_SRCS
   src/rclcpp/node_interfaces/node_time_source.cpp
   src/rclcpp/node_interfaces/node_timers.cpp
   src/rclcpp/node_interfaces/node_topics.cpp
+  src/rclcpp/node_interfaces/node_type_descriptions.cpp
   src/rclcpp/node_interfaces/node_waitables.cpp
   src/rclcpp/node_options.cpp
   src/rclcpp/parameter.cpp

rclcpp/include/rclcpp/node.hpp

@@ -56,6 +56,7 @@
 #include "rclcpp/node_interfaces/node_time_source_interface.hpp"
 #include "rclcpp/node_interfaces/node_timers_interface.hpp"
 #include "rclcpp/node_interfaces/node_topics_interface.hpp"
+#include "rclcpp/node_interfaces/node_type_descriptions_interface.hpp"
 #include "rclcpp/node_interfaces/node_waitables_interface.hpp"
 #include "rclcpp/node_options.hpp"
 #include "rclcpp/parameter.hpp"
@@ -1454,6 +1455,11 @@ class Node : public std::enable_shared_from_this<Node>
   rclcpp::node_interfaces::NodeTimeSourceInterface::SharedPtr
   get_node_time_source_interface();
 
+  /// Return the Node's internal NodeTypeDescriptionsInterface implementation.
+  RCLCPP_PUBLIC
+  rclcpp::node_interfaces::NodeTypeDescriptionsInterface::SharedPtr
+  get_node_type_descriptions_interface();
+
   /// Return the sub-namespace, if this is a sub-node, otherwise an empty string.
   /**
    * The returned sub-namespace is either the accumulated sub-namespaces which
@@ -1591,6 +1597,11 @@ class Node : public std::enable_shared_from_this<Node>
   const rclcpp::NodeOptions node_options_;
   const std::string sub_namespace_;
   const std::string effective_namespace_;
+
+  /// Static map(s) containing extra member variables for Node without changing its ABI.
+  // See node.cpp for more details.
+  class BackportMembers;
+  static BackportMembers backport_members_;
 };
 
 }  // namespace rclcpp

rclcpp/include/rclcpp/node_interfaces/node_interfaces.hpp

@@ -30,6 +30,7 @@
   rclcpp::node_interfaces::NodeTimeSourceInterface, \
   rclcpp::node_interfaces::NodeTimersInterface, \
   rclcpp::node_interfaces::NodeTopicsInterface, \
+  rclcpp::node_interfaces::NodeTypeDescriptionsInterface, \
   rclcpp::node_interfaces::NodeWaitablesInterface
 
 
@@ -118,6 +119,7 @@ class NodeInterfaces
    *   - rclcpp::node_interfaces::NodeTimeSourceInterface
    *   - rclcpp::node_interfaces::NodeTimersInterface
    *   - rclcpp::node_interfaces::NodeTopicsInterface
+   *   - rclcpp::node_interfaces::NodeTypeDescriptionsInterface
    *   - rclcpp::node_interfaces::NodeWaitablesInterface
    *
    * Or you use custom interfaces as long as you make a template specialization

rclcpp/include/rclcpp/node_interfaces/node_type_descriptions.hpp

@@ -0,0 +1,63 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__NODE_INTERFACES__NODE_TYPE_DESCRIPTIONS_HPP_
+#define RCLCPP__NODE_INTERFACES__NODE_TYPE_DESCRIPTIONS_HPP_
+
+#include <memory>
+
+#include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/node_base_interface.hpp"
+#include "rclcpp/node_interfaces/node_logging_interface.hpp"
+#include "rclcpp/node_interfaces/node_parameters_interface.hpp"
+#include "rclcpp/node_interfaces/node_services_interface.hpp"
+#include "rclcpp/node_interfaces/node_topics_interface.hpp"
+#include "rclcpp/node_interfaces/node_type_descriptions_interface.hpp"
+#include "rclcpp/visibility_control.hpp"
+
+namespace rclcpp
+{
+namespace node_interfaces
+{
+
+/// Implementation of the NodeTypeDescriptions part of the Node API.
+class NodeTypeDescriptions : public NodeTypeDescriptionsInterface
+{
+public:
+  RCLCPP_SMART_PTR_ALIASES_ONLY(NodeTypeDescriptions)
+
+  RCLCPP_PUBLIC
+  explicit NodeTypeDescriptions(
+    NodeBaseInterface::SharedPtr node_base,
+    NodeLoggingInterface::SharedPtr node_logging,
+    NodeParametersInterface::SharedPtr node_parameters,
+    NodeServicesInterface::SharedPtr node_services);
+
+  RCLCPP_PUBLIC
+  virtual
+  ~NodeTypeDescriptions();
+
+private:
+  RCLCPP_DISABLE_COPY(NodeTypeDescriptions)
+
+  // Pimpl hides helper types and functions used for wrapping a C service, which would be
+  // awkward to expose in this header.
+  class NodeTypeDescriptionsImpl;
+  std::unique_ptr<NodeTypeDescriptionsImpl> impl_;
+};
+
+}  // namespace node_interfaces
+}  // namespace rclcpp
+
+#endif  // RCLCPP__NODE_INTERFACES__NODE_TYPE_DESCRIPTIONS_HPP_

rclcpp/include/rclcpp/node_interfaces/node_type_descriptions_interface.hpp

@@ -0,0 +1,44 @@
+// Copyright 2023 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCLCPP__NODE_INTERFACES__NODE_TYPE_DESCRIPTIONS_INTERFACE_HPP_
+#define RCLCPP__NODE_INTERFACES__NODE_TYPE_DESCRIPTIONS_INTERFACE_HPP_
+
+#include "rclcpp/macros.hpp"
+#include "rclcpp/node_interfaces/detail/node_interfaces_helpers.hpp"
+#include "rclcpp/visibility_control.hpp"
+
+namespace rclcpp
+{
+namespace node_interfaces
+{
+
+/// Pure virtual interface class for the NodeTypeDescriptions part of the Node API.
+class NodeTypeDescriptionsInterface
+{
+public:
+  RCLCPP_SMART_PTR_ALIASES_ONLY(NodeTypeDescriptionsInterface)
+
+  RCLCPP_PUBLIC
+  virtual
+  ~NodeTypeDescriptionsInterface() = default;
+};
+
+}  // namespace node_interfaces
+}  // namespace rclcpp
+
+RCLCPP_NODE_INTERFACE_HELPERS_SUPPORT(
+  rclcpp::node_interfaces::NodeTypeDescriptionsInterface, type_descriptions)
+
+#endif  // RCLCPP__NODE_INTERFACES__NODE_TYPE_DESCRIPTIONS_INTERFACE_HPP_

rclcpp/src/rclcpp/node.cpp

@@ -17,7 +17,10 @@
 #include <limits>
 #include <map>
 #include <memory>
+#include <mutex>
+#include <shared_mutex>
 #include <string>
+#include <unordered_map>
 #include <utility>
 #include <vector>
 
@@ -36,6 +39,7 @@
 #include "rclcpp/node_interfaces/node_time_source.hpp"
 #include "rclcpp/node_interfaces/node_timers.hpp"
 #include "rclcpp/node_interfaces/node_topics.hpp"
+#include "rclcpp/node_interfaces/node_type_descriptions.hpp"
 #include "rclcpp/node_interfaces/node_waitables.hpp"
 #include "rclcpp/qos_overriding_options.hpp"
 
@@ -109,6 +113,72 @@ create_effective_namespace(const std::string & node_namespace, const std::string
 
 }  // namespace
 
+/// \brief Associate new extra member variables with instances of Node without changing ABI.
+/**
+ * It is used only for bugfixes or backported features that require new members.
+ * Atomically constructs/destroys all extra members.
+ * Node instance will register and remove itself, and use its methods to retrieve members.
+ * Note for performance consideration that accessing these members uses a map lookup.
+ */
+class Node::BackportMembers
+{
+public:
+  BackportMembers() = default;
+  ~BackportMembers() = default;
+
+  /// \brief Add all backported members for a new Node.
+  /**
+   * \param[in] key Raw pointer to the Node instance that will use new members.
+   */
+  void add(Node * key)
+  {
+    // Adding a new instance to the maps requires exclusive access
+    std::unique_lock lock(map_access_mutex_);
+    type_descriptions_map_.emplace(
+      key,
+      std::make_shared<rclcpp::node_interfaces::NodeTypeDescriptions>(
+        key->get_node_base_interface(),
+        key->get_node_logging_interface(),
+        key->get_node_parameters_interface(),
+        key->get_node_services_interface()));
+  }
+
+  /// \brief Remove the members for an instance of Node
+  /**
+   * \param[in] key Raw pointer to the Node
+   */
+  void remove(const Node * key)
+  {
+    // Removing an instance from the maps requires exclusive access
+    std::unique_lock lock(map_access_mutex_);
+    type_descriptions_map_.erase(key);
+  }
+
+  /// \brief Retrieve the NodeTypeDescriptionsInterface for a Node.
+  /**
+   * \param[in] key Raw pointer to an instance of Node.
+   * \return A shared ptr to this Node's NodeTypeDescriptionsInterface instance.
+   */
+  rclcpp::node_interfaces::NodeTypeDescriptionsInterface::SharedPtr
+  get_node_type_descriptions_interface(const Node * key) const
+  {
+    // Multiple threads can retrieve from the maps at the same time
+    std::shared_lock lock(map_access_mutex_);
+    return type_descriptions_map_.at(key);
+  }
+
+private:
+  /// \brief Map that stored TypeDescriptionsInterface members
+  std::unordered_map<
+    const Node *, rclcpp::node_interfaces::NodeTypeDescriptionsInterface::SharedPtr
+  > type_descriptions_map_;
+
+  /// \brief Controls access to all private maps
+  mutable std::shared_mutex map_access_mutex_;
+};
+// Definition of static member declaration
+Node::BackportMembers Node::backport_members_;
+
 Node::Node(
   const std::string & node_name,
   const NodeOptions & options)
@@ -211,6 +281,8 @@ Node::Node(
   sub_namespace_(""),
   effective_namespace_(create_effective_namespace(this->get_namespace(), sub_namespace_))
 {
+  backport_members_.add(this);
+
   // we have got what we wanted directly from the overrides,
   // but declare the parameters anyway so they are visible.
   rclcpp::detail::declare_qos_parameters(
@@ -272,6 +344,7 @@ Node::Node(
 Node::~Node()
 {
   // release sub-interfaces in an order that allows them to consult with node_base during tear-down
+  backport_members_.remove(this);
   node_waitables_.reset();
   node_time_source_.reset();
   node_parameters_.reset();
@@ -591,6 +664,12 @@ Node::get_node_topics_interface()
   return node_topics_;
 }
 
+rclcpp::node_interfaces::NodeTypeDescriptionsInterface::SharedPtr
+Node::get_node_type_descriptions_interface()
+{
+  return backport_members_.get_node_type_descriptions_interface(this);
+}
+
 rclcpp::node_interfaces::NodeServicesInterface::SharedPtr
 Node::get_node_services_interface()
 {