docker - 在 docker-compose.yml 中重用环境变量

Question

是否可以重复使用在多个容器之间共享的环境变量？

这个想法是为了避免重复，如下例所示:

version: '2'

services:

  db:
    image: example/db
    ports:
      - "8443:8443" 
    container_name: db
    hostname: db
    environment:
      - USER_NAME = admin 
      - USER_PASSWORD = admin 

svc:
  image: example/svc
  depends_on:
    - db
  ports:
    - "9443:9443"
  container_name: svc
  hostname: svc
  environment:
    - DB_URL = https://db:8443
    - DB_USER_NAME = admin
    - DB_USER_PASSWORD = admin 

Answer 1

extends 选项可能不错，但它是 not supported在 3.x 中编写文件。其他方法是:

1. Extension fields (撰写文件 3.4+)

   如果您可以使用 3.4+ 撰写文件，扩展字段可能是最佳选择:

   docker-compose.yml

    version: '3.4'
   
    x-common-variables: &common-variables
      VARIABLE: some_value
      ANOTHER_VARIABLE: another_value
   
    services:
      some_service:
        image: someimage
        environment: *common-variables
   
      another_service:
        image: anotherimage
        environment:
          <<: *common-variables
          NON_COMMON_VARIABLE: 'non_common_value'
   

2. env_file指令

   docker-compose.yml

    version: '3.2'
   
    services:
      some_service:
        image: someimage
        env_file:
          - 'variables.env'
   
      another_service:
        image: anotherimage
        env_file:
          - 'variables.env'
   

   variables.env

    VARIABLE=some_value
    ANOTHER_VARIABLE=another_value
   

3. .env file在项目根目录(或实际撰写环境中的变量)

   .env 文件中的变量可以在服务配置中引用:

   docker-compose.yml

    version: '3.2'
   
    services:
      some_service:
        image: someimage
        environment:
          - VARIABLE
   
      another_service:
        image: anotherimage
        environment:
          - VARIABLE
          - ANOTHER_VARIABLE
   

   .env

    VARIABLE=some_value
    ANOTHER_VARIABLE=another_value