[ros2] Fix message duplication caused by bidirectional bridge (not for all rmw implementations)

[AndrejOrsula]

🦟 Bug fix

Fixes #143 (but not for all rmw implementations)

Summary

This PR adds ignore_local_publications option to ROS 2 subscriber of the bridge, which should fix duplication of Ignition messages (echoing). However, ROS 2 Design - Node to Participant mapping mentions that this feature is NOT part of all rmw implementations, and unfortunately, this feature is currently not implemented in the default FastRTPS rmw of ROS 2 Foxy. When using other rmw implementations like Cyclone DDS, the issue gets fixed by this PR, otherwise it persists.

I am aware that this way of fixing the issue is not robust enough, especially as it requires non-default configuration. If you know of a better solution to this problem, please close this PR. Else the documentation probably needs to be updated a bit.

To try out with FastRTPS (issue persists):

Shell 1:

ros2 run ros_ign_bridge parameter_bridge /chatter@std_msgs/msg/String@ignition.msgs.StringMsg

Shell 2:

ign topic -e -t /chatter

Shell 3:

ign topic -t /chatter -m ignition.msgs.StringMsg -p 'data:"This message should be received only once"'

To try out with Cyclone DDS (issue is fixed):

Install Cyclone DDS

sudo apt-get update && sudo apt-get install ros-${ROS_DISTRO}-rmw-cyclonedds-cpp

Shell 1:

export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp
ros2 run ros_ign_bridge parameter_bridge /chatter@std_msgs/msg/String@ignition.msgs.StringMsg

Shell 2:

ign topic -e -t /chatter

Shell 3:

ign topic -t /chatter -m ignition.msgs.StringMsg -p 'data:"This message should be received only once"'

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)

Note to maintainers: Remember to use Squash-Merge

[chapulina]

Thanks! I think this is good to get in because it solves the problem for some RMWs. Here's an issue for support on FastRTPS: ros2/rmw_fastrtps#76