Expose node options to controller manager

[methylDragon]

Description and Scope

This PR exposes an options argument to the ControllerManager constructor to allow for users to configure NodeOptions to be given to the class.

It also exposes the get_cm_node_options() function for downstream use.

The default behavior doesn't change, this just adds a way for users to configure the manager. It shouldn't affect anyone downstream, but enables more configuration, and opens the path to fixing node name duplications down the line.

Context

The ControllerManager as its being used in this package doesn't need this functionality, but since it is a Node, downstream users (or more saliently, myself 😬) might want to instantiate it independently in a separate process.

This might lead to a case where there is more than one Node in the process, which can cause global node name remaps to forcibly change the ControllerManager's node name, leading to duplicate node names.

Design

The fix for this situation is to either:

• Globally in the CLI/launch, target the node name for remaps;
  

Or:

• Specify another node name remap rule in the NodeOptions passed to a node (causing it to ignore the global rule)

The former case requires users to be made aware of the constraint when writing launchfiles/starting the node up in CLI.
Whereas the latter case avoids that downside, but requires a NodeOptions to get passed to the node.

This change I'm proposing not only benefits my use case (fixing the node name remap issue), but also allows users to further configure the ControllerManager's node options if needed.

The intended use of this change would be for users to either ignore the NodeOptions arg, (i.e. nothing changes)

  auto cm = std::make_shared<controller_manager::ControllerManager>(executor, manager_node_name);

Or create a NodeOptions object using get_cm_node_options() and then configure it.

  auto options = controller_manager::get_cm_node_options();
  options.arguments({
    "--ros-args",
    "--remap", "_target_node_name:__node:=dst_node_name",
    // "--remap", "__node:=dst_node_name",  // (This should also work)
    "--log-level", "info"});
  
  auto cm = std::make_shared<controller_manager::ControllerManager>(executor, "_target_node_name", "some_optional_namespace", options);

There aren't any alternative solutions for this other than telling users downstream to change the way they use CLI/launch, and that's kinda fragile. So it would be good to get this in.

[methylDragon]

I'd also like this backported to humble when it's ready!

[destogl]

I agree! Thanks for this extension!

and.... WOW! this is a great explanation! Thanks for this. Would you mind adding at least parts of the explanation into documentation describing your use case of adding controller manager into other nodes. In doc folder are documentation files generated for control.ros.org

[destogl]

I'd also like this backported to humble when it's ready!

@bmagyar this is a API braking change... How many users would actually feel it?

[methylDragon]

I agree! Thanks for this extension!

and.... WOW! this is a great explanation! Thanks for this. Would you mind adding at least parts of the explanation into documentation describing your use case of adding controller manager into other nodes. In doc folder are documentation files generated for control.ros.org

I've updated the docs!
I'm not sure if I did it right though...

[bmagyar]

Thanks!

[bmagyar]

I don't think many would notice the API change since it's handled w default values for parameters.

The ABI change may pose a small issue but also it's mostly within the same package so I wouldn't worry too much. I think this PR is good for a backport

[destogl]

@Mergifyio backport humble

[mergify]

backport humble

✅ Backports have been created

• #946 Expose node options to controller manager (backport #942) has been created for branch humble