1. 阐明

本博客目标：解释 docker compose 两个不同 level 的 networks 作用，不便初学者。
注: 本文探讨的 Compose file format >= 3.0

2. 定义两级 networks

version: "3.9"

services:
  proxy:
    build: ./proxy
    networks:  ## Service-level networks key
      - frontend
  app:
    build: ./app
    networks:  ## Service-level networks key
      - frontend
      - backend
  db:
    image: postgres
    networks:
      - backend

networks:  ## Top-level networks key
  frontend:
    driver: brige
  backend:
    # Use a custom driver which takes special options
    driver: brige

3. Top-level networks key

3.1 作用

指定 将要创立 的 networks.
(The top-level networks key lets you specify networks to be created.)
能够指定的 networks 信息：driver(比方 bridge, overlay)，driver_opts 等

4. Service-level networks key

4.1 作用

指定要退出的 top-level networks key.
(Networks to join, referencing entries under the top-level networks key.)

O. 参考资料

<1> Networking in Compose
<2> top-level networks
<3> service-level networks key