datastore returns `exited with code 0`

[chansuke]

• docker for mac(Version:1.12.3-beta30
• docker-compose(Version:1.9.0-rc4, build 181a4e9)

I am running docker-compose with the file below,but always fail with datastore.It returns sampleapp_datastore_1 exited with code 0.

version: "2"
services:

  datastore:
    image: busybox
    volumes:
      - postgres-data:/var/lib/postgres/data

  postgres:
    image: postgres
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: password
    ports:
      - '5432:5432'
    volumes_from:
      - datastore
  app:
    build: .
    ports:
      - '3000:3000'
    links:
      - postgres
    volumes_from:
      - datastore
    command: bundle exec rails s -b "0.0.0.0"

volumes:
  postgres-data:
    driver: local

[shin-]

You don't need a datastore service. Simply reference the named volume directly in your postgres service definition (see below).

version: "2"
services:
  postgres:
    image: postgres
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: password
    ports:
      - '5432:5432'
    volumes:
      - postgres-data:/var/lib/postgres/data
  app:
    build: .
    ports:
      - '3000:3000'
    links:
      - postgres
    command: bundle exec rails s -b "0.0.0.0"

volumes:
  postgres-data:
    driver: local

[shin-]

But to answer the original question, the reason datastore exits with code 0 is because you don't define a command to be run. It's not an error, just means the container doesn't have anything to run and terminates as result.