Invert start discovery condition

Repeated calls to start_discovery should not start additional topics discovery tasks without stop_discovery calls

Signed-off-by: Øystein Sture <[email protected]>

rosbag2_transport/src/rosbag2_transport/recorder.cpp

@@ -143,7 +143,7 @@ class RecorderImpl
 
   std::mutex start_stop_transition_mutex_;
   std::mutex discovery_mutex_;
-  std::atomic<bool> stop_discovery_ = false;
+  std::atomic<bool> stop_discovery_ = true;
   std::atomic_uchar paused_ = 0;
   std::atomic<bool> in_recording_ = false;
   std::shared_ptr<KeyboardHandler> keyboard_handler_;
@@ -441,10 +441,10 @@ void RecorderImpl::start_discovery()
 {
   std::lock_guard<std::mutex> state_lock(discovery_mutex_);
   if (stop_discovery_.exchange(false)) {
-    RCLCPP_DEBUG(node->get_logger(), "Recorder topic discovery is already running.");
-  } else {
     discovery_future_ =
       std::async(std::launch::async, std::bind(&RecorderImpl::topics_discovery, this));
+  } else {
+    RCLCPP_DEBUG(node->get_logger(), "Recorder topic discovery is already running.");
   }
 }