services:
  a:
    image:  nginx:alpine
    ports: [80]
    healthcheck:
      test: wget --spider -S -T1 http://localhost:80
      interval: 1s
      timeout: 1s
  b:
    image:  nginx:alpine
    ports: [80]
    depends_on:
      - a
    healthcheck:
      test: wget --spider -S -T1 http://localhost:80
      interval: 1s
      timeout: 1s