[ros2component] List occasionally fails to retrieve components

[jubeira]

Bug report

Required Info:

• Operating System:
  • Ubuntu 18.04
• Installation type:
  • Source
• Version or commit hash:
  • Hash 930dea5c8de47d47ac0b3814ee1c08bac8a70c22 (Fix component arguments to be inline with service. (#220)) + rclcpp_components from binaries version 0.7.0.
• DDS implementation:
  • RTI Connext
• Client library (if applicable):
  • N/A

Steps to reproduce issue

1. From a terminal, run rclcpp_components:

ros2 run rclcpp_components component_container

2. From a second terminal, add some components (tested with 2 talkers and 2 listeners):

ros2 component load /ComponentManager composition composition::Talker
ros2 component load /ComponentManager composition composition::Listener
ros2 component load /ComponentManager composition composition::Talker
ros2 component load /ComponentManager composition composition::Listener

The interaction between talkers and listeners should be displayed in the first terminal, e.g:

[INFO] [talker]: Publishing: 'Hello World: 114'
[INFO] [listener]: I heard: [Hello World: 114]
[INFO] [listener]: I heard: [Hello World: 114]
[INFO] [talker]: Publishing: 'Hello World: 29'
[INFO] [listener]: I heard: [Hello World: 29]
[INFO] [listener]: I heard: [Hello World: 29]

3. List the components:

ros2 component list

Expected behavior

Components should be listed like this:

/ComponentManager
    1  /talker
    2  /listener
    3  /talker
    4  /listener

Actual behavior

~20% of the times, no component is listed.

Additional information

This doesn't seem to happen in fastrtps nor opensplice.

[dirk-thomas]

Does the problem disappear when passing --spin-time N with a long enough period to ensure the node started by ros2 component list has enough time to complete discovery?

[jubeira]

I need to rebuild by workspace with the current packages to retest properly; right now it is heppening to me even with --spin-time 10, but I want to make sure it's not a local issue. I'll try again and post the results here.

[jubeira]

@dirk-thomas I can't reproduce this issue anymore using an up-to-date workspace from source.
For completion I tried listing the components 20 times in a row with FastRTPS, OpenSplice and Connext and it didn't fail even a single time. --spin-time N option wasn't required.

I think this issue is safe to close.