wb_robot_cleanup fix for python plugins

[angel-ayala]

trying to solve #476 by adding a stop() method in python plugins

[angel-ayala]

I was able to handle the SIGINT inside the drive, however the ros2_supervisor.py process cannot end properly, present an exit code 1.

[ygoumaz]

Very nice! Thank you for the contribution. Could you please add an entry in both related changelogs?

I will further investigate if we can terminate cleanly the supervisor node too.

[ygoumaz]

Have you tried to run some examples on Iron distribution (I am not sure if the following error is also on Humble), because I found a problem in examples that don't use Python plugins, namely webots_ros2_tiago.

If I start it:

ros2 launch webots_ros2_tiago robot_launch.py 

and then interrupt it with Ctrl+C, I get the following logs:

[webots_controller_Tiago_Lite-5] Warning: class_loader.ClassLoader: SEVERE WARNING!!! Attempting to unload library while objects created by this loader exist in the heap! You should delete your objects before attempting to unload the library or destroying the ClassLoader. The library will NOT be unloaded.
[webots_controller_Tiago_Lite-5]          at line 127 in ./src/class_loader.cpp
[webots_controller_Tiago_Lite-5] Warning: class_loader.ClassLoader: SEVERE WARNING!!! Attempting to unload library while objects created by this loader exist in the heap! You should delete your objects before attempting to unload the library or destroying the ClassLoader. The library will NOT be unloaded.
[webots_controller_Tiago_Lite-5]          at line 127 in ./src/class_loader.cpp
[webots_controller_Tiago_Lite-5] [ros2run]: Segmentation fault
[ERROR] [webots_controller_Tiago_Lite-5]: process has died [...]

It is not related to the changes of this PR but I wonder if we should not try to fix this issue at the same time. What do you think?

[angel-ayala]

I have not been able to test it in Iron, I will run it in Humble to see if it also happens.

[angel-ayala]

I was checking, that maybe the problem is related to the return added in WebotsNode.step()

webots_ros2/webots_ros2_driver/src/WebotsNode.cpp

Line 257 in 2ce3fb2

int WebotsNode::step() {

inside the condition when the signal is captured, I'm returning -1 without calling wb_robot_step (code diff)

if (gShutdownSignalReceived && !mWaitingForUrdfRobotToBeRemoved) {
  mRemoveUrdfRobotPublisher->publish(mRemoveUrdfRobotMessage);
  mWaitingForUrdfRobotToBeRemoved = true;
  return -1
}

once the SIGINT is received, should it call wb_robot_step? this is the only changed behavior that affects both Python and C++ plugins, what do you think @ygoumaz?

Anyway, I will check it out

[ygoumaz]

This error also occurs in the master branch, so it doesn't seem to be related to the changes of this PR. We can already merge this to fix the termination of Python plugins and I will open an issue for C++ plugins on Iron.

[ygoumaz]

@angel-ayala, can you update the changelogs, so that we can merge this PR before releasing 2023.1.1?

[angel-ayala]

yeah sure, I was finishing some issues with my project's code. I will update this today.

[ygoumaz]

Thank you!