Automatically Run Database Migrations

[dstufft]

Right now there's no way to automatically run our database migrations, however it would be great if there were (I think?). At the moment whenever there is a migration to apply I have to manually run it. Given that we're on Heroku and we're using pipelines I'm not sure we have very many options to run our migrations. The only idea I can think of is to run them as part of the application starting up, which has problems with the fact we have multiple Dynos running in production.

So I guess the question is, should we run them automatically and if we should, is there anyplace better to run them than on application startup?

[dstufft]

After talking to @ewdurbin I think the way we're going to go with this, is we'll have auto migrations only when the staging site deploys because that deploys from Github automatically. On top of that, we'll add a wrapper around the heroku pipeline:promote command that won't allow you to trigger a promotion if there is a pending database migration to run.

This will require us to run our migrations remotely, which means we'll need to be careful with how our migrations are handled. We don't want to make any migrations that will remove or alter something that the currently running copy of code will require, nor add anything that the code won't be setup to handle.