ROS Galactic groot monitoring

[kribe48]

Bug report

In ROS galactic, an additional action server has been added (navigate through poses). However, both servers use the same groot_zmq_publisher/server_port parameter values. This makes it impossible for me to monitor the behavior trees in groot. Am I using it wrong, or is it a bug that needs to be updated?

• Operating System:
  ubuntu 20.04
• ROS2 Version:
  Galactic
• Version or commit hash:
  From source

Expected behavior

Able to monitor both navigate through poses and navigate to pose in groot

Actual behavior

Not possible to monitor either of them

[SteveMacenski]

This is a known issue with Groot, that it only allows a single instance per process. I'd welcome a PR to help resolve this, but as I alluded to this ticket, if this isn't resolved relatively soon, my tentative plan is to strip support for groot out of Nav2 since it seems to be causing issues with critically needed features.

Destroying and replacing Groot objects every time the navigator changes turns out to not be as straight forward as I thought it would be, so you'd be correct that right now it only works with NavigateToPose actions, not NavigateThroughPoses.

I have no issue with Groot, but this seems to be causing us a number of different issues. I'd really appreciate a PR with a fix to this if you have the cycles. That would greatly increase the likelihood it stays in the stack if this is something you rely on!

[SteveMacenski]

I believe #2409 would resolve these concerns @kribe48. Do you agree?

[kribe48]

Yes, I agree!