asyncio utils for ROS2 service and action

[Juliaj]

First, I wanted to thank you for taking the initiative to make asyncio easier to use for ROS2 developers. The APIs you've enabled under ros2 look very useful. On a side note, have you seen this alternative implementation at https://github.com/usnistgov/ariac_example_team/blob/main/example_team/example_team/utils.py? While it's way less comprehensive than what you've provided, I wanted to share it in case any parts might serve as pointers for future work.

[2lian]

Thanks for pointing out this other implementation. There are a few things that I forgot in my library that I noticed now haha. Notably:

• _ros_to_asyncio_future
• await_service_ready

The user can get those working given the tutorial and tools, but it would be better to have them available directly. I will get those in the next version in a few weeks.

Aside from this, the library you sent basically implements the ros_loop Method that is available using the afor.ros2.SyncExecutor, and I benchmarked it (it got the worse score, but honestly it's fast enough for most things).

I would actually welcome some PR about basic functionalities that are yet missing (_ros_to_asyncio_future, await_service_ready ...).

[2lian]

This has been implemented by: #7

To wait for an action server to be ready, there is no specific function, but you can take inspiration from the service implementation. I think it is simple enough to not warrant a function in the lib. I will make one once the Actions are fully implemented.

while not action_client.server_is_ready():
        await asyncio.sleep(polling_rate)

Also I find it funny that the busy while loop is the only way to do this. ROS 2 also does this in its source code ...