Recommended approach for running `rails console` or rolling back?

[ramontayag]

This is neither a bug report or feature request, but I don't know where else to ask.

What is the recommended approach for running things like rails console or rails db:rollback? I was looking at the task-runner, but it seems that it isn't meant to be deploying a specific version of the app, but rather be a container running a more generic environment to do general tasks.

[dturn]

I don't know that we have a recommended approach for either but there are options.

If you can't exec into a running container (e.g it crashes on boot and the logs aren't providing enough information to debug). One option would be to create a pod with your app image, but change the command to ["sleep", "8000"]. You could then exec into the sleeping container to run rails console.

[KnVerey]

Re: rails console, this gem doesn't including any tools for running interactive commands, but I agree with Danny that the usual approach is to deploy a long-running pod with your app image and kubectl exec into it.

Re: rails db:rollback, although I haven't tried it for this purpose myself, I think kubernetes-run should work for something like that. Basically, you include a pod template that uses your app image in your regular deploy (so that it always references the latest image), and then the command to launch a rollback pod from that template would be something like kubernetes-run $namespace $context bundle exec rails db:rollback (the exact command depends on the structure of your image).

[ramontayag]

Ok, thank you for the recommendations! Will check out how to implement rollback using kubernetes-run.

[yfxie]

For anyone finding this later: I wrote kran, a thin wrapper around krane, and it covers the console side of this. kran console runs kubectl exec -it into an app pod picked by a label selector from config/kran.yml, and kran exec bin/rails db:rollback runs a one-off command in a pod the same way. Nothing kubectl can't already do, just fewer flags to remember each time.

https://github.com/yfxie/kran