How to Run Ecto Migrations on Production

You’d think the answer to this question would be a simple Google search away. Unfortunately, that wasn’t the case for me this afternoon, working on a Phoenix project with a newly-added Ecto backend. In an effort to save others (and let’s be honest, future me) the same frustration, here’s the most straight-forward solutions I found.

What Doesn’t Work

Mix. Mix tasks aren’t compiled into your deployed release, and as evidenced in this exciting discussion, there’s no plans to change this any time soon.

So don’t try using your trusty local mix ecto.migrate task on production. Not gonna help you here.

What Does Work

1. Ecto.Migrator

Ecto ships with Ecto.Migrator, a first-class module for Ecto’s migration API.

Run it manually by ssh’ing onto your app server, attaching to your Phoenix app, and running the following:

path = Application.app_dir(:my_app, "priv/repo/migrations")

Ecto.Migrator.run(MyApp.Repo, path, :up, all: true)

Ideally, you’d wrap up the above in its own task that can be called during your build and deployment process. Check out Plataformatec’s blog for a nice example.

2. eDeliver

Our app uses edeliver for deployments, and it has a super handy command for manually running migrations:

mix edeliver migrate production

If we peek at the source, turns out this command actually just wraps up Ecto.Migrator for you, saving some precious keystrokes.

To run successfully, you’ll need to add ECTO_REPOSITORY="MyApp.Repo" to your .deliver/config file.

Again, Plataformatec has a nice blog post on deploying your Elixir app with eDeliver.

Summary

Hi future me! Hope this post was still helpful the nth time around.

References:

Written on July 6, 2017