docker-compose.yml

# service configuration for our dockerized Rails app
app:
  # use the Dockerfile next to this file
  build: .
  # sources environment variable configuration for our app
  env_file: .env
  # rely on the RAILS_ENV value of the host machine
  environment:
    RAILS_ENV: $RAILS_ENV
  # makes the app container aware of the DB container
  links:
    - db
  # expose the port we configured Unicorn to bind to
  expose:
    - "3000"
# service configuration for our database
db:
  # use the preferred version of the official Postgres image
  # see https://hub.docker.com/_/postgres/
  image: postgres:9.4.5
  # persist the database between containers by storing it in a volume
  volumes:
    - myapp-pg:/var/lib/postgresql/data
    # service configuration for our web server
web:
  # set the build context to the root of the Rails app
  build: .
  # build with a different Dockerfile
  dockerfile: config/containers/Dockerfile-nginx
  # makes the web container aware of the app container
  links:
    - app
  # expose the port we configured Nginx to bind to
  ports:
    - "80:80"