Add caching to build_component_topic_map with graph invalidation

src/ros2_medkit_gateway/include/ros2_medkit_gateway/native_topic_sampler.hpp

@@ -278,18 +278,24 @@ class NativeTopicSampler {
    * @param topic_name Full topic path
    * @return true if this is a system topic that should be filtered
    */
-  static bool is_system_topic(const std::string & topic_name);
+    static bool is_system_topic(const std::string & topic_name);
 
- private:
-  /**
-   * @brief Get the message type for a topic from the graph
-   */
-  std::string get_topic_type(const std::string & topic_name);
+    private:
+    std::string get_topic_type(const std::string & topic_name);
 
   rclcpp::Node * node_;
 
-  /// Native JSON serializer for topic deserialization
   std::shared_ptr<ros2_medkit_serialization::JsonSerializer> serializer_;
+
+  // Getter for cached component-topic map
+  // Returns a copy to avoid exposing internal data while the mutex is released.
+  std::map<std::string, ComponentTopics>
+  get_component_topic_map();
+
+  // --- Component topic map cache ---
+  std::map<std::string, ComponentTopics> topic_map_cache_;
+  size_t cached_graph_change_count_{0};
+  mutable std::mutex topic_map_mutex_;
 };
 
 }  // namespace ros2_medkit_gateway

src/ros2_medkit_gateway/src/native_topic_sampler.cpp

@@ -486,11 +486,43 @@ std::map<std::string, ComponentTopics> NativeTopicSampler::build_component_topic
   RCLCPP_DEBUG(node_->get_logger(), "Built topic map for %zu components", component_map.size());
   return component_map;
 }
+std::map<std::string, ComponentTopics>
+NativeTopicSampler::get_component_topic_map()
+{
+  std::lock_guard<std::mutex> lock(topic_map_mutex_);
+
+  // Compute a lightweight fingerprint of the ROS graph (topics+types)
+  // Note: ROS 2 does not expose a simple graph change counter; using
+  // get_topic_names_and_types() and hashing the result is a reliable
+  // way to detect graph changes that affect topic/component mapping.
+  auto all_topics = node_->get_topic_names_and_types();
+
+  size_t current_graph_fingerprint = 1469598103934665603ULL;  // FNV-1a seed-ish
+  std::hash<std::string> hasher;
+  // Incorporate topic count
+  current_graph_fingerprint ^= all_topics.size() + 0x9e3779b97f4a7c15ULL + (current_graph_fingerprint << 6) + (current_graph_fingerprint >> 2);
+  for (const auto & kv : all_topics) {
+    const auto & topic = kv.first;
+    const auto & types = kv.second;
+    current_graph_fingerprint ^= hasher(topic) + 0x9e3779b97f4a7c15ULL + (current_graph_fingerprint << 6) + (current_graph_fingerprint >> 2);
+    if (!types.empty()) {
+      current_graph_fingerprint ^= hasher(types[0]) + 0x9e3779b97f4a7c15ULL + (current_graph_fingerprint << 6) + (current_graph_fingerprint >> 2);
+    }
+  }
+
+  if (topic_map_cache_.empty() || cached_graph_change_count_ != current_graph_fingerprint) {
+    topic_map_cache_ = build_component_topic_map();
+    cached_graph_change_count_ = current_graph_fingerprint;
+  }
+
+  // Return a copy to avoid callers holding a reference to internal cache
+  return topic_map_cache_;
+}
+
 
 ComponentTopics NativeTopicSampler::get_component_topics(const std::string & component_fqn) {
   // Build full map and extract for this component
-  // TODO(optimization): Cache the map and invalidate on graph changes
-  auto full_map = build_component_topic_map();
+  const auto full_map = get_component_topic_map();
 
   auto it = full_map.find(component_fqn);
   if (it != full_map.end()) {