Elixir / Phoenix containerized development environment

This repo contains simple boilerplate files that can be added to any Phoenix application so you may run it and its database inside Docker containers using Docker Compose.

What you get

• One-line dev environment setup: docker-compose up. This command creates the database, does the Dialyzer pre-work (if the project has Dialyxer installed), and everything else.
• Developer-friendly setup: Source code is mounted so that changes in the container appear on the host and vice-versa.
• Fast re-builds because the Dockerfile is written to help Docker cache the images.
• Syncing with Postgres startup delay.
• All the crappy little dependencies installed.
• No weird hacks.

Uses Elixir 1.9.4 (compatible with Phoenix 1.4), and latest Postgres.

Instructions

1. Copy the three files (Dockerfile, docker-compose.yml, and run.sh) to an existing Phoenix project which you want to Dockerize.
2. Make run.sh executable, e.g. chmod +x run.sh
3. Edit the database connection settings for the environments which will use this setup (usually dev.exs and test.exs). You can hard-code the credentials for the relevant environment(s) to reference the hostname of db, a username of postgres, and an empty password, or you can specify environment-variable overrides like the following:

# Inside config/dev.ex and/or config/test.exs
config :my_app, MyApp.Repo,
  hostname: System.get_env("DB_HOST", "localhost"),
  password: System.get_env("DB_PASS", "postgres"),
  # ... etc...

4. Spin it up with docker-compose up.

Usage

Tests can be run in the container like so:

docker-compose run web mix test

Or, for a slightly faster startup time,

docker-compose exec web mix test

... I haven't found a disadvantage of re-using the running container this way.