Added ROS2 ActionClient w/ limited functionality

[danmartzla]

Added the roslibpy.ActionClient object to send actions goals to ROS2-based systems.
This implementation has limited capabilities (related to RobotWebTools/rosbridge_suite#909) such as:

• Goal cancelation is not functional.
• Goal rejection/acceptance are not being notified to the Action client.

What type of change is this?

• Bug fix in a backwards-compatible manner.
• New feature in a backwards-compatible manner.
• Breaking change: bug fix or new feature that involve incompatible API changes.
• Other (e.g. doc update, configuration, etc)

Checklist

• I added a line to the CHANGELOG.rst file in the Unreleased section under the most fitting heading (e.g. Added, Changed, Removed).
• I ran all tests on my computer and it's all green (i.e. invoke test).
• I ran lint on my computer and there are no errors (i.e. invoke check).
• I have added tests that prove my fix is effective or that my feature works.
• I have added necessary documentation (if appropriate)

[sea-bass]

This all looks great to me -- just a few minor formatting things and I think this V1 support will be a great addition. Thank you!

[danmartzla]

This all looks great to me -- just a few minor formatting things and I think this V1 support will be a great addition. Thank you!

Hi! I already fixed your suggested minor changes. Thanks.

[sea-bass]

Sorry, but I'm not a maintainer of this repo so I can't actually approve your changes. I was just looking because I implemented the rosbridge side of this work.

[sea-bass]

Sorry @danmartzla, I forgot to mention that I recently landed a small change to the protocol that allows for cleaner action cancellation. It may require a small change since now the action_result message also contains a status field telling you whether the action was successful, canceled, aborted, etc.: RobotWebTools/rosbridge_suite#953

Also @gonzalocasas Would you be able to review this PR?

[danmartzla]

I've adapted this minor change to work with the latest rosbridge_suite updates.

However, sending a cancelation request from a roslibpy "Action Client" seems not to be working. The "rosbridge_server" debug logs do not report any cancelation request (or any other received message). The JSON message seems to be correct based on the documentation:

https://github.com/danmartzla/roslibpy/blob/bcd403c12f32da1118a6c71d84602a237592bf72/src/roslibpy/core.py#L598-L604

[sea-bass]

It does look right... I wonder if you need the send_action_goals_in_new_thread parameter in the server set to True for this to work?

[danmartzla]

It does look right... I wonder if you need the send_action_goals_in_new_thread parameter in the server set to True for this to work?

OK. I was totally unaware about this parameter of the "rosbridge_server". I can confirm that it is working well when launching the server this way:
ros2 launch rosbridge_server rosbridge_websocket_launch.xml send_action_goals_in_new_thread:="true"

I'm adding this as a comment in the example code : https://github.com/danmartzla/roslibpy/blob/13ae184e691f3024c15bcc1e6a3f857c89affb65/docs/files/ros2-action-client.py#L41-L42

[sea-bass]

Awesome, great to hear!

There is also an equivalent call_services_in_new_thread which allows multiple service calls to be processed concurrently.

Not necessary for this example, of course, but just noting.

[sea-bass]

@gonzalocasas this has been around a while and seems to work well. Please consider merging this great contribution.