RMF map not loaded when use_sim_time:=false

[RValner]

Hi,

I recently updated the RMF submodules in my project (after ~3 months) and now the traffic map in rviz is not loaded on a physical setup. All works fine in the simulation but if I set the use_sim_time:=false in the top-level launch file, the map will not come up. This bug/behavior is really hard to isolate but that's as close I could get, i.e., here's a simple launch file that reproduces the bug with the latest RMF setup (note that use_sim_time arg is not even defined nor used!):

<launch>

  <arg name="viz_config_file"/>
  <arg name="config_file"/>

  <!-- Traffic Schedule - LEAVE THAT ONE OUT AND NO MAP  -->
  <node pkg="rmf_traffic_ros2" exec="rmf_traffic_schedule" output="both"/>

  <!-- Building Map  -->
  <node pkg="rmf_building_map_tools" exec="building_map_server" args="$(var config_file)"/>

  <!-- Visualizer -->
  <include file="$(find-pkg-share rmf_visualization)/visualization.launch.xml">
    <arg name="viz_config_file" value ="$(var viz_config_file)"/>
  </include>

</launch>

and I launch it via

ros2 launch rmf_test test.launch viz_config_file:=/path/to/viz/config config_file:=/path/to/building/yaml use_sim_time:=true

If I set use_sim_time:=true, the map will appear and use_sim_time:=false the map will not appear. To make the case even weirder I ran all these three components in a separate terminal with use_sim_time:=false and the map did appear (but I had to launch the visualization.launch.xml last, otherwise no map, go figure) ... I seriously have no clue with this one. The way how use_sim_time argument is implicitly there in the launch file and affects RMF is odd. Any help very highly appreciated!

[youliangtan]

Sorry, I am a bit confused about your description. As what u have described in the last paragraph, it seems that when use_sim_time:=true the map appears; however when false the map will fail to show. I briefly tested it with the example rmf_demos office world, it does work. Maybe you can provide us with an example launch file along with instructions to recreate the issue.

Anyway, just for your info. the use_sim_time param acts slightly different while compare to ros1. In ros1, use_sim_time is a "global" rosparam, which will be applied to all running nodes if enabled/disabled. For ros2 case, use_sim_time is a private rosparam within a ros2 node. Therfore, you will need to ensure that all nodes' use_sim_time are equally enabled or disabled at the same time. This might be the cause of the issue you have stated here.

[youliangtan]

After testing out the launch file above, I am still able to view the map and lanes on rviz, with both true and false for use_sim_time. Just for a sanity check, you can try to echo the topic /map with qos transient_local.

[RValner]

Just to be clear, based on your request I:

1. launched the above described launch file
   ros2 launch rmf_test test.launch viz_config_file:=/path/to/viz/config config_file:=/path/to/building/yaml use_sim_time:=false/true
2. in a separate terminal:
   ros2 topic echo --qos-durability transient_local /map

Regardless whether the use_sim_time is true or false, nothing is echoed on the /map topic with or without the transient_local qos setting. BUT now if I keep the /map subscriber running and restart the launch file (step 1), then the map is echoed. Am I missing something here?

[mxgrey]

When you echo you should also set --qos-reliability reliable to make sure that DDS doesn't let the packet get dropped.

If that doesn't work, then it might be worth trying out a different DDS implementation just to figure out if the issue you're experiencing is caused by the DDS level. In theory if the publisher and subscriber both use transient local and reliable QoS settings then the message should definitely make it, but maybe there's an issue in one of the DDS implementations.

You can find a list of supported DDS implementations here. For Foxy the default is rwm_fastrtps_cpp while for Galactic the default is rmw_cyclonedds_cpp. Those are the two free open source DDS implementations that ROS2 has full support for. You can use

$ export RMW_IMPLEMENTATION=rmw_<selection>_cpp

to select a different implementation. Just make sure to apply that to all the terminals that you're running ROS2 from.

[RValner]

Looks like issue is indeed originating from the DDS level. When I switched from the default rwm_fastrtps_cpp to rmw_cyclonedds_cpp on my Foxy setup and ran the above described launch file again with use_sim_time=false, the map did appear in rviz. Also with the default rwm_fastrtps_cpp the /map subscriber was able to receive the message after I added the --qos-reliability reliable flag along with --qos-durability transient_local flag. Seems that switching the DDS will do the trick. Very peculiar bug.

Thank you both!

[mxgrey]

It may be the case that fastrtps can work but only if the subscriber in rviz has a "reliable" QoS (the "reliable" setting only works if both the punisher AND subscriber have it turned on).

We should check if there's a way to tell rviz to use a reliable connection for the map topic.