Always use Releases

[cjbottaro]

@benwilson512

Releases have no issue with environment variables. REPLACE_OS_VARS=true, and then in your config just foo: “${FOO}”. We use identical images in staging and production, and do all config changes by specifying environment variables in our docker containers.

We have a configuration database instead of environment vars. This is what I ended up doing:

use Mix.Config

Mix.Task.run "loadpaths"
{:ok, _} = Application.ensure_all_started(:config_db)

config :indexer_spike, Repo,
  adapter: Ecto.Adapters.Postgres,
  database: ConfigDb.get!("/postgresql/database")

So then our builder server can build a single Docker image that can be run in any environment via mix run --no-halt.