Allow ActionClient to get_status() of Goal from Server side

[dcconner]

Feature request

Seeing #1072, comments on https://answers.ros.org/question/406766/ros2-actions-publish-status-messages-that-get-exponentially-more-expensive/, and issue on FlexBE/flexbe_behavior_engine#3

I'd like the ActionClient to be able to report the GoalStatus from the server side.

In ROS 1, we were able to monitor the goal status separately from the "feedback" topic.

Is there a reason this was dropped for ROS 2?

Should the server publish the status topic as a regular topic?

I'm happy to develop a proposal and PR, but I'd like to understand the larger history and any known issues.

[dcconner]

@clalancette Wondering if you can give some feedback on this issues? I've gotten another ping on FlexBE/flexbe_behavior_engine#3 , but have not seen any updates to #1072 or action server.

I see there is a status_pub_qos_profile, but it does not appear to be used in server code.

[fujitatomoya]

I'd like the ActionClient to be able to report the GoalStatus from the server side.

rclpy/rclpy/rclpy/action/client.py

Lines 68 to 70 in 220d714

	@property
	def status(self):
	return self._status

this does not work???

I see there is a status_pub_qos_profile, but it does not appear to be used in server code.

rcl_action_server_init takes it and used?

rclpy/rclpy/src/rclpy/action_server.cpp

Line 101 in 220d714

&action_server_ops);

[dcconner]

@fujitatomoya the status propery belongs to the GoalHandle. I've been using an async call that returns a future

`
future = client.send_goal_async(new_goal,
feedback_callback=lambda f: ProxyActionClient._feedback_callback(topic, f)
)
ProxyActionClient._result_status[topic] = GoalStatus.STATUS_ACCEPTED
future.add_done_callback(partial(ProxyActionClient._done_callback, topic=topic))

@classmethod
def _done_callback(cls, future, topic):
    ProxyActionClient._current_goal[topic] = future
    result = future.result().get_result_async()
    result.add_done_callback(partial(ProxyActionClient._result_callback, topic=topic))

@classmethod
def _result_callback(cls, future, topic):
    result = future.result().result
    result_status = future.result().status

`
Which lets me get the final status properly.

Can I query "STATUS_ACCEPTED", "EXECUTING", and "CANCELING" while waiting on the future using the Python client?