How do I run delayed_jobs in Kubernetes?

Running multiple processes in one docker container is problematic as you cannot easily observe lifetime of particular process - every container need one process which is "main" and when it exit, container also exit.

As looking on Github (https://github.com/collectiveidea/delayed_job#user-content-running-jobs) I would strongly suggest to change a little your starting command to run it in foreground because now when you are starting Kubernetes job with daemons - job is ending immediately as docker container lifetime is directly related to "main" foreground process lifetime so when you run only background process your main process exit immediately and your container too.

Change your command to:

RAILS_ENV=production script/delayed_job run

What start worker in foreground so your Kubernetes Job won't exit. Please note also that Kubernetes Jobs are not intended to such infinitive tasks (job should has start and end) so I would suggest to use ReplicaSet for that

Now I am doing this:

this_pid=$$(while [[ $(ps -ef | grep delayed_job | grep -v -e grep -e tail | head -c1 | wc -c) -ne 0 ]]; do sleep 10; done; kill -- -$this_pid) &

after starting multiple workers. And after this I tail -f the logs so that those go to the standard output of the container. I am quite crazy, so I am also running logrotate to keep the logs in check. The rails environment is pretty big anyway, so the container needs to be pretty big, and we need to be able to run many jobs and I don't want many pods running to do so. This seems to be efficient and will stop and restart if the workers die for some reason.