Helper module that can be used to easily ensure that Ecto database was migrated before rest of the application was started.

Rationale

There are many strategies how to deal with this issue, e.g. see https://hexdocs.pm/distillery/guides/running_migrations.html

However, if you have any workers that are relying on the DB schema that are launched upon boot with some methods, such as release post_start hooks you can easily enter race condition. Application may crash as these workers will not find tables or columns they expect and it will happen sooner than the post_start hook script will send the commands to the the application process.

In stateless environments such as Docker it is just sometimes more convenient to perform migration upon boot. This is exactly what this library does.

Currently it works only with PostgreSQL databases but that will be easy to extend.

Usage

defmodule MyApp do
  use Application

  def start(_type, _args) do
    import Supervisor.Spec, warn: false

    {:ok, _} = EctoBootMigration.migrate(:my_app)

    children = [
      supervisor(MyApp.Endpoint, []),
      worker(MyApp.Repo, []),
    ]
    Supervisor.start_link(children, [strategy: :one_for_one, name: MyApp.Supervisor])
  end
end

Credits

Inspired by https://github.com/bitwalker/distillery/blob/master/docs/Running Migrations.md