Container Optimized OS Graceful Shutdown of Celery - docker

Question

Running COS on GCE
Any ideas on how to get COS to do a graceful docker shutdown?
My innermost process is celery, which says he wants a SIGTERM to stop gracefully
http://docs.celeryproject.org/en/latest/userguide/workers.html#stopping-the-worker
My entrypoint is something like
exec celery -A some_app worker -c some_concurrency
On COS I am running my docker a service, something like
write_files:
- path: /etc/systemd/system/servicename.service
permissions: 0644
owner: root
content: |
[Unit]
Description=Some service
[Service]
Environment="HOME=/home/some_home"
RestartSec=10
Restart=always
ExecStartPre=/usr/share/google/dockercfg_update.sh
ExecStart=/usr/bin/docker run -u 2000 --name=somename --restart always some_image param_1 param_2
ExecStopPost=/usr/bin/docker stop servicename
KillMode=processes
KillSignal=SIGTERM
But ultimately when my COS instance it shut down, it just yanks the plug.
Do I need to add a shutdown script to do a docker stop? Do I need to do something more advanced?

Answer 1

What is the expected exit status of your container process when when it receives SIGTERM?
Running systemctl stop <service> then systemctl status -l <service> should show the exit code of the main process. Example:
Main PID: 21799 (code=exited, status=143)
One possibility is that the process does receive SIGTERM and shuts down gracefully, but returns non-zero exit code.
This would make the systemd believe that it didn't shutdown correctly. If that is the case, adding
SuccessExitStatus=143
to your systemd service should help. (Replace 143 with the actual exit code of your main process.)