Add tini as PID 1 process in front of entrypoint

[lreiher]

Problem

• containers take long to shut down
• reason is that docker stop sends SIGTERM signal
• ROS listens for SIGINT
• after 10s, container is killed via SIGKILL

Solution

• use tini as init process: Why tini?
• Why Your Dockerized Application Isn’t Receiving Signals
• correctly forwards signals and speeds up container shutdown
• alternatives
  • stop_signal: SIGINT in Docker Compose: works for speeding up shutdown of ROS apps, but doesn't bring tini benefits
  • docker run --init: automatically starts containers with tini; works for speeding up shutdown, but is easily forgotten

---

Shutdown Evaluation

services:

  current:
    image: ghcr.io/ika-rwth-aachen/mqtt_client:ros2

  stop-signal:
    image: ghcr.io/ika-rwth-aachen/mqtt_client:ros2
    stop_signal: SIGINT

  tini-by-docker:
    image: ghcr.io/ika-rwth-aachen/mqtt_client:ros2
    init: true

  tini:
    image: mqtt_client # image built by this version of docker-ros

time docker stop $(basename $(pwd))-current-1
tmp-current-1
docker stop $(basename $(pwd))-current-1  0,05s user 0,04s system 0% cpu 10,316 total

time docker stop $(basename $(pwd))-stop-signal-1
tmp-stop-signal-1
docker stop $(basename $(pwd))-stop-signal-1  0,05s user 0,04s system 13% cpu 0,624 total

time docker stop $(basename $(pwd))-tini-by-docker-1
tmp-tini-by-docker-1
docker stop $(basename $(pwd))-tini-by-docker-1 0,05s user 0,04s system 27% cpu 0,310 total

time docker stop $(basename $(pwd))-tini-1
tmp-tini-1
docker stop $(basename $(pwd))-tini-1  0,05s user 0,03s system 31% cpu 0,262 total

[lreiher]

@TillBeemelmanns