There's a similar question here, but I think I want different thing. For those who familiar with docker-compose, there's a brilliant command which runs command in container just once, this insanely helps for launching migrations before each deploy:
docker-compose -f docker-compose.prod.yml run web npm run migrateAlso because this is a one line command it's comfortable for automation purpose: like using Makefile or ansible/chef/saltstack.
The only thing I've found is kubectl run which is more similar to docker run. But docker-compose run allows us to use config file, where docker-run does not:
kubectl run rp2migrate --command -- npm run migrateThis would probably work, but I need to list 20 environment variables, and really don't want to do this in command line.. instead I'd like to pass a flag which would specify yaml config like this:
kubectl run rp2migrate -f k8s/rp2/rp2-deployment.yaml --command -- npm run migrateEdit:
Kubernetes also got init containers as a beta feature (as of now) - http://kubernetes.io/docs/user-guide/production-pods/#handling-initialization
You should probably leverage Kubernetes PostStart hook. Something like below:
lifecycle:
postStart:
exec:
command:
- "npm"
- "run"
- "migrate"http://kubernetes.io/docs/user-guide/container-environment/
The environment variables specified for your pod will be available too:
Additionally, user-defined environment variables from the pod definition, are also available to the container, as are any environment variables specified statically in the Docker image
I'm using kubernetes batch jobs to execute one time commands and having a yaml config.