How best to run one-off migration tasks in a kubernetes cluster

Question

I have database migrations which I\'d like to run before deploying a new version of my app into a Kubernetes cluster. I want these migrations to be run automatically as part of

Answer 1

blocking while waiting on the result of a queued-up job seems to require hand-rolled scripts

This isn't necessary anymore thanks to the kubectl wait command.

Here's how I'm running db migrations in CI:

kubectl apply -f migration-job.yml
kubectl wait --for=condition=complete --timeout=60s job/migration
kubectl delete job/migration

In case of failure or timeout, one of the two first CLI commands returns with an erroneous exit code which then forces the rest of the CI pipeline to terminate.

migration-job.yml describes a kubernetes Job resource configured with restartPolicy: Never and a reasonably low activeDeadlineSeconds.

You could also use the spec.ttlSecondsAfterFinished attribute instead of manually running kubectl delete but that's still in alpha at the time of writing and not supported by Google Kubernetes Engine at least.