[launch_ros] node_name overrides for a multi-node rclpy process

[stonier]

Feature description

A means of setting node_name overrides for a multi-node rclpy process such as that given in ros2/launch#204.

Implementation considerations

This also brings into question the naming of the class launch_ros.actions.Node since it currently can launch a multi-node process. Perhaps that should fail on trying to launch a multi-node process and for that, use a launch_ros.actions.MultiNode action.

Note: This is a different problem to the composable node launch. Here the nodes are brought into the same process via ... the process, not the launcher. I suspect the same situation would arise linking two c++ classes with nodes and instantiating them in the same application.

[stonier]

FYI @IanTheEngineer

[wjwwood]

https://answers.ros.org/question/316870/ros2-composition-and-node-names-with-launch-files/?answer=316925#post-id-316925

[masynthetic]

is there a workaround/fix for this? remapping the rclpy.create_node() parameter does not seem to do anything, any use of the name= parameter in the launch file seems to cause the issue

[hidmic]

any use of the name= parameter in the launch file seems to cause the issue

@masynthetic launch_ros.actions.Node is not a multi-node aware action, so yes, it won't work as you intend in that case.

If you can't use components, a possible workaround is to launch your process as a plain process using launch.actions.ExecuteProcess and configure your nodes through command line arguments.

Alternatively, contributions are most welcome. A multi-node aware action proposal would be great.

[jbohren]

This also brings into question the naming of the class launch_ros.actions.Node since it currently can launch a multi-node process.
@stonier

This is what brought me here.

Since even a single-node executable is an executable which owns a node and not the node itself, it feels like launch_ros.actions.Node is a misnomer and could lead to confusion and unexpected behavior. Something like ExecuteSingleNodeProcess would definitely reduce the likelihood of that occurring.

Also is it weird that some actions are written as imperative statements while others are noun phrases?