web:
  build: .
  command: npm start
  ports:
    - "4000:4000"
  links:
    - mongo
mongo:
  image: mongo:latest
  expose:
    - "27017"

version: "2.0"

services:
  web:
    build: .
    command: npm start
    ports:
      - "4000:4000"
    links:
      - mongo
  mongo:
    image: mongo:latest
    expose:
      - "27017"

Use new Compose file format
Use new Compose file format

  * need docker-compose 1.6.0+
  * need docker-engine 1.10.0+
  * https://docs.docker.com/compose/compose-file/#version-2
