ROS 2: Improve the discovery methods used by nodes to prevent conflicts and accidental discoveries

[gbiggs]

See this Discourse thread.

EDIT(eric): Removed text to minimize redundancy w.r.t. discourse post. Let's have as few sources of truth as possible!

[EricCousineau-TRI]

Thanks! Posted initial impression and requests here:
https://discourse.ros.org/t/proposed-changes-to-how-ros-performs-discovery-of-nodes/27640/17?u=ericcousineau-tri

[IanTheEngineer]

Agreed on removing the text from this ticket. However, it would be nice to see a meta-ticket on one of the relevant repositories that describes the different areas of improvement (preferably with check-boxes) to serve as a central point to link against when its eventually time to create PR's.

[EricCousineau-TRI]

Centralized issue: ros2/ros2#1359

[mxgrey]

Note that there has been significant progress in making a testbed for the behaviors in this PR: osrf/iron_irwini_discovery_modes_prototype#2

[mxgrey]

Relevant PRs:

• [rmw] Improve handling of dynamic discovery ros2/rmw#338
• [rcl] Improve handling of dynamic discovery  ros2/rcl#1023
• [rmw_fastrtps] Improve handling of dynamic discovery ros2/rmw_fastrtps#653
• [rmw_cyclonedds] Improve handling of dynamic discovery ros2/rmw_cyclonedds#429
• [rmw_connextdds] New RMW discovery options ros2/rmw_connextdds#108
• Sloretz/test discovery ros2/system_tests#512

[EricCousineau-TRI]

Closed per our TRI SoW