Troubleshooting with ROS

This page provides some common issues that can occur when working with ROS, and more specifically, writing tests with ROS.

Failing Tests Due to Non-allowable Exit Codes (ROS2 launch_testing)

It is relatively common to test that all nodes, processes etc. have shutdown gracefully. The example below shows how this can be done using launch_testing against a particular process (in this case the controller).

launch_testing.asserts.assertExitCodes(
    proc_info, [launch_testing.asserts.EXIT_OK], controller_process
)

If the process does not exit cleanly, you may get an error code of -6 and the line terminate called without an active exception. This error code typically indicates that the process was terminated due to an unhandled exception or signal.

You may be able to resolve this by making sure that not only rclpy is made to shutdown gracefully (if using Python), but also any threads that have been started. The below example demonstrates this:

import rclpy
from threading import Thread

...

def main(args=None):
    rclpy.init(args=args)
    my_node = MyNode()
    executor = rclpy.executors.MultiThreadedExecutor(4)
    executor.add_node(my_node)

    # Start the executor in a separate thread
    executor_thread = Thread(target=executor.spin, daemon=True)
    executor_thread.start()

    try:
        my_node.my_initiating_function()
    except KeyboardInterrupt:
        pass
    finally:
        # Shutdown the executor and wait for the thread to terminate
        executor.shutdown()
        executor_thread.join()
        rclpy.shutdown()

if __name__ == '__main__':
    main()

In this example:

• We initialize rclpy and add our node.
• We create a MultiThreadedExecutor and add the node to it.
• We start the executor in a separate thread.
• In the finally block, we ensure that the executor is shut down and the executor thread waits until it is terminated.