Expose throughput and heartbeat settings

[jespersmith]

We use the ros1 to ros2 bridge to send large point clouds around over WiFi. Because of the data size, the flood of UDP packets results in dropped packets. With the default heartbeat settings, this results in quite a big delay using RELIABLE and using BEST_EFFORT we would lose a large number of packets.

Is it possible to set the maximum throughput and configure the hearbeat settings?

[mikaelarguedas]

This is unfortunately not possible on a per node / per topic basis at the moment. This is on the wishlist though.
Right now these settings are using the default provided by Fast-RTPS and can be overriden here.
Note: modifying these values in rmw_fastrtps_cpp will impact all created topics.

Hope this helps

[jespersmith]

That could get us working, as we do not use ROS2 directly (we are working on a Java RTPS implementation with support for ROS2 message format). Is it a possibility to make these settings user changeable after compilation so we don't have to recompile but can just set ENV variables or edit a config file?

That way it might also be possible to set them on a per process basis.

[mikaelarguedas]

Follow-up of this discussion on rmw_fastrtps ros2/rmw_fastrtps#95

[mikaelarguedas]

@jespersmith FYI since ros2/rmw_fastrtps#153 it is possible to override vendor's default QoS settings using xml files

[jespersmith]

That sounds like a good solution to us. I'm closing this issue.