refactor(perception_rviz_plugin): apply thread pool to manage detached thread

common/autoware_auto_perception_rviz_plugin/include/object_detection/predicted_objects_display.hpp

@@ -24,9 +24,11 @@
 
 #include <condition_variable>
 #include <list>
+#include <queue>
 #include <set>
 #include <string>
 #include <unordered_map>
+#include <utility>
 #include <vector>
 
 namespace autoware
@@ -45,10 +47,31 @@ class AUTOWARE_AUTO_PERCEPTION_RVIZ_PLUGIN_PUBLIC PredictedObjectsDisplay
   using PredictedObjects = autoware_auto_perception_msgs::msg::PredictedObjects;
 
   PredictedObjectsDisplay();
+  ~PredictedObjectsDisplay()
+  {
+    {
+      std::unique_lock<std::mutex> lock(queue_mutex);
+      should_terminate = true;
+    }
+    condition.notify_all();
+    for (std::thread & active_thread : threads) {
+      active_thread.join();
+    }
+    threads.clear();
+  }
 
 private:
   void processMessage(PredictedObjects::ConstSharedPtr msg) override;
 
+  void queueJob(std::function<void()> job)
+  {
+    {
+      std::unique_lock<std::mutex> lock(queue_mutex);
+      jobs.push(std::move(job));
+    }
+    condition.notify_one();
+  }
+
   boost::uuids::uuid to_boost_uuid(const unique_identifier_msgs::msg::UUID & uuid_msg)
   {
     const std::string uuid_str = uuid_to_string(uuid_msg);
@@ -100,6 +123,8 @@ class AUTOWARE_AUTO_PERCEPTION_RVIZ_PLUGIN_PUBLIC PredictedObjectsDisplay
     PredictedObjects::ConstSharedPtr msg);
   void workerThread();
 
+  void messageProcessorThreadJob();
+
   void update(float wall_dt, float ros_dt) override;
 
   std::unordered_map<boost::uuids::uuid, int32_t, boost::hash<boost::uuids::uuid>> id_map;
@@ -108,6 +133,14 @@ class AUTOWARE_AUTO_PERCEPTION_RVIZ_PLUGIN_PUBLIC PredictedObjectsDisplay
   int32_t marker_id = 0;
   const int32_t PATH_ID_CONSTANT = 1e3;
 
+  // max_num_threads: number of threads created in the thread pool, hard-coded to be 1;
+  int max_num_threads;
+
+  bool should_terminate{false};
+  std::mutex queue_mutex;
+  std::vector<std::thread> threads;
+  std::queue<std::function<void()>> jobs;
+
   PredictedObjects::ConstSharedPtr msg;
   bool consumed{false};
   std::mutex mutex;

common/autoware_auto_perception_rviz_plugin/src/object_detection/predicted_objects_display.cpp

@@ -25,27 +25,44 @@ namespace object_detection
 {
 PredictedObjectsDisplay::PredictedObjectsDisplay() : ObjectPolygonDisplayBase("tracks")
 {
-  std::thread worker(&PredictedObjectsDisplay::workerThread, this);
-  worker.detach();
+  max_num_threads = 1;  // hard code the number of threads to be created
+
+  for (int ii = 0; ii < max_num_threads; ++ii) {
+    threads.emplace_back(std::thread(&PredictedObjectsDisplay::workerThread, this));
+  }
 }
 
 void PredictedObjectsDisplay::workerThread()
-{
+{  // A standard working thread that waiting for jobs
   while (true) {
-    std::unique_lock<std::mutex> lock(mutex);
-    condition.wait(lock, [this] { return this->msg; });
+    std::function<void()> job;
+    {
+      std::unique_lock<std::mutex> lock(queue_mutex);
+      condition.wait(lock, [this] { return !jobs.empty() || should_terminate; });
+      if (should_terminate) {
+        return;
+      }
+      job = jobs.front();
+      jobs.pop();
+    }
+    job();
+  }
+}
 
-    auto tmp_msg = this->msg;
-    this->msg.reset();
+void PredictedObjectsDisplay::messageProcessorThreadJob()
+{
+  // Receiving
+  std::unique_lock<std::mutex> lock(mutex);
+  auto tmp_msg = this->msg;
+  this->msg.reset();
+  lock.unlock();
 
-    lock.unlock();
+  auto tmp_markers = createMarkers(tmp_msg);
 
-    auto tmp_markers = createMarkers(tmp_msg);
-    lock.lock();
-    markers = tmp_markers;
+  lock.lock();
+  markers = tmp_markers;
 
-    consumed = true;
-  }
+  consumed = true;
 }
 
 std::vector<visualization_msgs::msg::Marker::SharedPtr> PredictedObjectsDisplay::createMarkers(
@@ -188,7 +205,7 @@ void PredictedObjectsDisplay::processMessage(PredictedObjects::ConstSharedPtr ms
   std::unique_lock<std::mutex> lock(mutex);
 
   this->msg = msg;
-  condition.notify_one();
+  queueJob(std::bind(&PredictedObjectsDisplay::messageProcessorThreadJob, this));
 }
 
 void PredictedObjectsDisplay::update(float wall_dt, float ros_dt)