Raw topic subscription crashes node under Cyclone when subscriber leaves

Bug report

Required Info:

• Operating System:
  • Ubuntu 18.04
• Version or commit hash:
  • Foxy
• DDS implementation:
  • Cyclone
• Client library (if applicable):
  • rclpy

Steps to reproduce issue

Minimal subscriber example, slightly modified to use raw=True and output the raw msg instead of a string

import rclpy
from rclpy.node import Node

from std_msgs.msg import String


class MinimalSubscriber(Node):

    def __init__(self):
        super().__init__('minimal_subscriber')
        self.subscription = self.create_subscription(
            String,
            'topic',
            self.listener_callback,
            10,
            raw=True )
        self.subscription  # prevent unused variable warning

    def listener_callback(self, msg):
        self.get_logger().info(f'I got: {msg}')


def main(args=None):
    rclpy.init(args=args)

    minimal_subscriber = MinimalSubscriber()

    rclpy.spin(minimal_subscriber)

    # Destroy the node explicitly
    # (optional - otherwise it will be done automatically
    # when the garbage collector destroys the node object)
    minimal_subscriber.destroy_node()
    rclpy.shutdown()


if __name__ == '__main__':
    main()

Run this node under a Cyclone DDS setup. In a second terminal, publish to the topic, and then stop publishing

ros2 topic pub /topic std_msgs/msg/String
...
Ctrl+c

Expected behavior

The node stays up and happy

Actual behavior

Traceback (most recent call last):
  File "minimal_crash.py", line 38, in <module>
    main()
  File "minimal_crash.py", line 28, in main
    rclpy.spin(minimal_subscriber)
  File "/opt/ros/foxy/lib/python3.8/site-packages/rclpy/__init__.py", line 191, in spin
    executor.spin_once()
  File "/opt/ros/foxy/lib/python3.8/site-packages/rclpy/executors.py", line 711, in spin_once
    raise handler.exception()
  File "/opt/ros/foxy/lib/python3.8/site-packages/rclpy/task.py", line 239, in __call__
    self._handler.send(None)
  File "/opt/ros/foxy/lib/python3.8/site-packages/rclpy/executors.py", line 419, in handler
    arg = take_from_wait_list(entity)
  File "/opt/ros/foxy/lib/python3.8/site-packages/rclpy/executors.py", line 344, in _take_subscription
    msg_info = _rclpy.rclpy_take(capsule, sub.msg_type, sub.raw)
_rclpy.RCLError: Failed to take_serialized from a subscription: error not set

Additional information

Default dds, or removing raw=True fixes the crash

[clalancette]

Are there instructions on how to setup the necessary build environment?

https://docs.ros.org/en/foxy/Installation/Ubuntu-Development-Setup.html has the instructions on building from source for Foxy.

[suurjaak]

@fujitatomoya I suppose I could try.

Do I understand correctly that this should suffice in handling rcl_take_serialized_message result?

  ret = rcl_take_serialized_message(subscription, &msg, message_info, NULL);
  if (ret != RCL_RET_OK) {
    if (ret != RCL_RET_SUBSCRIPTION_TAKE_FAILED) {
      PyErr_Format(
        RCLError,
        "Failed to take_serialized from a subscription: %s", rcl_get_error_string().str);
      rcl_reset_error();
    }
    rmw_ret_t r_fini = rmw_serialized_message_fini(&msg);
    if (r_fini != RMW_RET_OK) {
      PyErr_Format(RCLError, "Failed to deallocate message buffer: %d", r_fini);
    }
    return NULL;
  }

Are there instructions on how to setup the necessary build environment?