Example real-time concurreny timer and subscription

[JanStaschulat]

See discussion in Slack https://micro-ros.slack.com/archives/CNC141G0N/p1675765402361599

The execution time of the subscription alternates (1ms, 900ms). It receives data every 1000ms. A slow timer with 100ms timeout is also defined. You can see from the results, that the timer events, while the subscription callback consumes 900ms, are lost and that there is no queue of timer events. That is, the there is no catch-up when there would be sufficient time when the subscription callback only needs 1ms.

Sample output:

$:~/github_ros_ws$ ros2 run rclc_examples example_short_timer_long_subscription 

[INFO] [1675775675.196181864] []: Created a timer with period 1000 ms.
Created timer with timeout 1000 ms.
[INFO] [1675775675.196259744] []: Created a timer with period 100 ms.
Created timer with timeout 100 ms.
Created subscriber topic_0:
Debug: number of DDS handles: 3

shorttimer 0
shorttimer 1
shorttimer 2
shorttimer 3
shorttimer 4
shorttimer 5
shorttimer 6
shorttimer 7
shorttimer 8
shorttimer 9
Callback: I heard: 1
shorttimer 10
shorttimer 11
Callback: I heard: 2
shorttimer 12
shorttimer 13
shorttimer 14
shorttimer 15
shorttimer 16
shorttimer 17
shorttimer 18
shorttimer 19
shorttimer 20
shorttimer 21
Callback: I heard: 3
shorttimer 22
shorttimer 23
Callback: I heard: 4

[codecov-commenter]

Codecov Report

Merging #329 (c5f85a6) into master (1d31f43) will decrease coverage by 0.15%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #329      +/-   ##
==========================================
- Coverage   69.20%   69.06%   -0.15%     
==========================================
  Files          16       16              
  Lines        2715     2715              
  Branches      765      765              
==========================================
- Hits         1879     1875       -4     
- Misses        450      452       +2     
- Partials      386      388       +2     

Impacted Files	Coverage Δ
rclc/src/rclc/action_goal_handle.c	58.59% <0.00%> (-2.55%)	⬇️

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[JanStaschulat]

@mergify backport humble foxy

[mergify]

backport humble foxy

✅ Backports have been created

• #330 Example real-time concurreny timer and subscription (backport #329) has been created for branch humble
• #331 Example real-time concurreny timer and subscription (backport #329) has been created for branch foxy