Running the ROS2 driver with intra-process communication when using composition

[tanelikor]

Describe your question
Is there a way - or plans to implement one - to allow using intra-process communication the component nodes of the ROS 2 driver?

Currently, it is not possible to enable intra-process communication on the driver nodes because rclcpp doesn't yet support using it with transient local topics, see ros2/rclcpp#752 and ros2/rclcpp#1753 for some of the discussion on rclcpp side. Of the ouster nodes, os_sensor currently publishes the metadata topic with transient local QoS, and os_cloud does the same with transforms between the lidar frames.

I would think that disabling the tf_static publishing should not be a big problem if desired: the user should just take care to broadcast the transforms separately from somewhere else. I also vaguely remember seeing an issue/suggestion about parameter for publishing of the transforms, but can't seem to find it now, so perhaps I was dreaming about that.

About the metadata, I don't really know. Would it be possible to disable that publisher and still have the driver work correctly, or alternatively change the QoS of it to have a volatile durability?

The support for the transient local QoS with intra-process communication on the rclcpp side seems to be progressing extremely slowly, so the options are either to work around the issue for now or just not use the intra-process communication. I would be very interested to try it out, though I do not have any metrics to say how big of a reduction to latency etc. this might provide. The difference should be between copying the data and just passing a pointer, but how much this would affect actual performance is, at the moment, unknown to me.

Platform (please complete the following information):

• Ouster Sensor: N/A
• Ouster Firmware Version: N/A
• ROS version/distro: Humble
• Operating System: N/A
• Machine Architecture: N/A

[tanelikor]

Edit: Never mind, I just realized that there are open PRs about allowing the disabling of the tf publisher and explicitly excluding the metadata publisher from intra-process communication. These, to my knowledge, should fix the problem described above, so I will go ahead and close this issue.