在docker-compose yml中重用环境变量

Question

是否可以重用多个容器之间共享的环境变量以避免重复,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

该extends选项可能很好,但在撰写文件中不支持3.x.其他方法是:

1. 扩展字段(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:

   泊坞窗,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

   泊坞窗,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. 项目根目录中的.env 文件(或实际撰写环境中的变量)

   来自.env文件的变量可以在服务配置中引用:

   泊坞窗,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
   

Answer 2

您可以使用extends指令让多个容器environment从底层服务描述继承配置.例如,将以下内容放在名为的文件中base.yml:

version: '2'

services:
  base:
    environment:
      DB_URL: https://db:8443
      DB_USER_NAME: admin
      DB_USER_PASSWORD: admin 

然后在你的docker-compose.yml:

version: '2'

services:
  container1:
    image: alpine
    command: sh -c "env; sleep 900"
    extends:
      file: base.yml
      service: base

  container2:
    image: alpine
    command: sh -c "env; sleep 900"
    extends:
      file: base.yml
      service: base
    environment:
      ANOTHERVAR: this is a test

然后在里面container1,你会看到:

DB_URL=https://db:8443
DB_USER_NAME=admin
DB_USER_PASSWORD=admin

在container2你内心会看到:

DB_URL=https://db:8443
DB_USER_NAME=admin
DB_USER_PASSWORD=admin
ANOTHERVAR=this is a test

显然extends,您可以使用environment指令以外的其他内容; 使用docker-compose时,这是避免重复的好方法.

Answer 3

您可以从 docker-compose 文件中引用本地环境变量。假设您想要做的是USER_NAME与以下内容相同DB_USER_NAME：

docker-compose.yml

version: '2'

services:
  db:
    image: example/db
    ports:
      - "8443:8443" 
    container_name: db
    hostname: db
    environment:
      - USER_NAME = ${USERNAME}
      - USER_PASSWORD = ${PASSWORD}

svc:
  image: example/svc
  depends_on:
    - db
  ports:
    - "9443:9443"
  container_name: svc
  hostname: svc
  environment:
    - DB_URL = https://db:8443
    - DB_USER_NAME = ${USERNAME}
    - DB_USER_PASSWORD = ${PASSWORD}

然后，像这样运行 docker-compose：

$ USERNAME="admin" PASSWORD="admin" docker-compose up

或者，对于更持久且更易于重复输入的内容：

$ printf '%s\n%s\n' 'export USERNAME="admin"' 'export PASSWORD="admin"' >> ~/.bash_profile
$ source ~/.bash_profile
$ docker-compose up