【Docker基础】深入解析Docker-compose核心配置：Services服务配置详解

• 在定义服务时，首先需要指定容器使用的镜像，Docker-compose提供了两种方式来指定镜像

services:
  web:
    image: nginx:latest

• 这种方式直接从Docker Hub或其他镜像仓库拉取已构建好的镜像

services:
  webapp:
    build:
      context: .
      dockerfile: Dockerfile-alternate
      args:
        buildno: 1

• build配置项允许你指定构建上下文、自定义Dockerfile路径和构建参数

• 端口映射是将容器内部的端口绑定到宿主机的端口，使得外部可以访问容器服务

services:
  web:
    ports:
      - "80:80"           # 宿主机端口:容器端口
      - "443:443"
      - "8080:80"         # 不同宿主机端口映射到同一容器端口
      - "9000-9100:9000-9100" # 端口范围映射

• 环境变量是配置容器行为的常用方式，Docker-compose提供了两种设置方式

services:
  db:
    environment:
      MYSQL_ROOT_PASSWORD: secret
      MYSQL_DATABASE: appdb
      MYSQL_USER: appuser
      MYSQL_PASSWORD: apppass

services:
  db:
    env_file:
      - ./db.env
      - ./secrets.env

• 环境变量文件示例（db.env）：

MYSQL_ROOT_PASSWORD=secret
MYSQL_DATABASE=appdb
MYSQL_USER=appuser
MYSQL_PASSWORD=apppass

• 数据卷用于持久化容器数据或在容器间共享数据。Docker-compose支持多种挂载方式

services:
  db:
    volumes:
      - /var/lib/mysql                # 匿名卷
      - ./data:/var/lib/mysql         # 宿主机目录挂载
      - dbdata:/var/lib/mysql         # 命名卷挂载
      - ~/configs:/etc/configs/:ro   # 只读挂载

volumes:
  dbdata:                             # 命名卷定义

• depends_on用于控制服务启动顺序，确保依赖服务先启动

services:
  web:
    depends_on:
      - db
      - redis
  db:
    image: postgres
  redis:
    image: redis

• 重启策略定义了容器退出时Docker应采取的行动

services:
  web:
    restart: always
  worker:
    restart: on-failure
  cron:
    restart: unless-stopped

• 策略选项：

• command用于覆盖容器默认的启动命令

services:
  web:
    image: nginx
    command: ["nginx", "-g", "daemon off;"]
  app:
    image: myapp
    command: >
      sh -c "python manage.py migrate && 
      python manage.py runserver 0.0.0.0:8000"

• 通过扩展功能和环境变量实现多环境配置

# docker-compose.yml
services:
  app:
    image: myapp
    env_file:
      - .env.${ENV_MODE}

# 使用方式
ENV_MODE=prod docker-compose up

• 使用extends或YAML锚点复用配置

# 使用extends
services:
  base:
    image: mybase
    environment:
      COMMON_VAR: value
  service1:
    extends: base
    environment:
      SPECIFIC_VAR: value1

# 使用YAML锚点
services:
  base: &base
    image: mybase
    environment:
      COMMON_VAR: value
  service1:
    <<: *base
    environment:
      SPECIFIC_VAR: value1

services:
  web:
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 5s

services:
  db:
    deploy:
      resources:
        limits:
          cpus: '0.50'
          memory: 512M
        reservations:
          cpus: '0.25'
          memory: 256M

• 下面是一个包含多个服务的完整示例：

version: '3.8'

services:
  db:
    image: postgres:13
    env_file:
      - .env.db
    volumes:
      - db_data:/var/lib/postgresql/data
    ports:
      - "5432:5432"
    restart: unless-stopped
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 5s
      retries: 5

  redis:
    image: redis:6
    command: redis-server --requirepass ${REDIS_PASSWORD}
    volumes:
      - redis_data:/data
    ports:
      - "6379:6379"
    restart: always

  web:
    build: .
    depends_on:
      db:
        condition: service_healthy
      redis:
    ports:
      - "8000:8000"
    volumes:
      - .:/code
    environment:
      DEBUG: "true"
    restart: on-failure

  worker:
    build: .
    command: celery -A app worker -l info
    depends_on:
      - db
      - redis
    volumes:
      - .:/code
    restart: always

volumes:
  db_data:
  redis_data: