Docker compose file with a data container for the Elixir/Phoenix "deps" folder

docker-compose.yml

version: '2'

services:
  # Application database
  db:
    image: postgres
    ports:
      - "5432:5432"
    volumes:
      - ./db:/var/lib/postgresql
  # Dependencies caching
  app_deps:
    image: <name of your image here>
    command: echo Mix data container
    volumes:
      - /deps
  # Elixir Phoenix application
  app:
    build: .
    command: mix phx.server
    environment:
      - PORT=4000
      - PG_HOST=db
      - PG_USERNAME=postgres
    ports:
      - 4000:4000
    links:
      - db
    volumes_from:
      - app_deps