在docker-compose yml

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

extends选项可能不错，但在3.x撰写文件时为not supported。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：

   <强>搬运工-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

   <强>搬运工-compose.yml

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

   <强> variables.env

   VARIABLE=some_value
   ANOTHER_VARIABLE=another_value
   

项目根目录中的

3. .env file （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：

   <强>搬运工-compose.yml

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

   <强> .ENV

   VARIABLE=some_value
   ANOTHER_VARIABLE=another_value
   

Answer 2

您可以使用extends指令让多个容器从基础服务描述继承environment配置。例如，将以下内容放在名为base.yml的文件中：

version: '2'

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

然后在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container1内，你会看到：

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

在container2内，你会看到：

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

显然，您可以将extends用于environment指令之外的其他内容;这是使用docker-compose时避免重复的好方法。

Answer 3

您可以在docker-compose文件中引用本地环境变量。假设您要做的是USER_NAME与DB_USER_NAME相同：

<强>搬运工-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，运行docker-compose，如：

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

或者，对于更持久的内容，并且更容易定期打字：

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