Docker化FastAPI应用连接MySQL容器失败问题排查求助

我正在对一个使用MySQL和Selenium的FastAPI应用进行Docker化部署，但遇到FastAPI容器与MySQL容器连接失败的问题：

• 本地用MySQL Workbench以localhost为主机能成功连接MySQL容器
• FastAPI容器运行时抛出错误：

  sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'mysql' ([Errno -3] Temporary failure in name resolution)
  

当前docker-compose.yml配置 #

version: '3'

services:
  chrome:
    build: .
    image: selenium/node-chrome:3.141.59-20210929
    ports:
      - "4444:4444"
      - "5900:5900"
    volumes:
      - "/dev/shm:/dev/shm"
    networks:
      - selenium
    

  
  mysql:
     image: mysql:8.0
     command: --default-authentication-plugin=mysql_native_password 
     restart: always
     environment:
       - MYSQL_ROOT_PASSWORD=admin
       - MYSQL_DATABASE=autojob
       - MYSQL_USER=user
       - MYSQL_PASSWORD=4444
     healthcheck:
            test: ["CMD", "mysqladmin" ,"ping", "-h", "localhost"]
            timeout: 20s
            retries: 10
     volumes:
       - ./init:/docker-entrypoint-initdb.d
       - autojob:/var/lib/mysql
     ports:
       - "3307:3306"
     expose:
       - "3307"
     


  app:
    build: .
    restart: on-failure
    container_name: "autojobserve_container"
    command:
      uvicorn autojobserve.app:app --host 0.0.0.0 --port 8000 --reload
    ports:
      - 8000:8000
    volumes:
      - "./:/app"
    networks:
      - selenium
    depends_on:
      mysql:
          condition: service_healthy



volumes:
  autojob: {}

networks:
  selenium:

FastAPI数据库连接代码 #

engine = create_engine("mysql+pymysql://user:4444@mysql:3307/autojob")

MySQL容器就绪日志 #

2022-11-08T11:49:26.334069Z 0 [System] [MY-011323] [Server] X Plugin ready for connections. Bind-address: '::' port: 33060, socket: /var/run/mysqld/mysqlx.sock
2022-11-08T11:49:26.334869Z 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.31'  socket: '/var/run/mysqld/mysqld.sock'  port: 3306  MySQL Community Server - GPL.
2022-11-08 11:49:14+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 8.0.31-1.el8 started.
2022-11-08 11:49:14+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
2022-11-08 11:49:14+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 8.0.31-1.el8 started.
'/var/lib/mysql/mysql.sock' -> '/var/run/mysqld/mysqld.sock'

问题原因及修复方案 #

1. 网络隔离导致服务名解析失败 #

mysql服务未加入selenium网络，而FastAPI容器（app服务）在该网络内，同一网络外的服务无法通过服务名互相访问。

修复：给mysql服务添加网络配置：

mysql:
  # ... 原有配置
  networks:
    - selenium

2. 容器间通信端口错误 #

容器间通信应使用MySQL容器内部端口3306，而非宿主机映射的3307端口。端口映射3307:3306仅用于宿主机访问容器，容器间直接用内部端口即可。

修复：修改FastAPI连接字符串的端口：

engine = create_engine("mysql+pymysql://user:4444@mysql:3306/autojob")

3. 错误的expose配置 #

expose声明的是容器内部要暴露的端口，当前配置的3307是宿主机端口，不符合逻辑。MySQL镜像默认已暴露3306端口，可直接删除该配置。

修复：删除mysql服务中的expose: - "3307"，或改为expose: - "3306"。

4. 优化healthcheck检测逻辑 #

当前healthcheck用localhost仅检测容器内本地连接，改为0.0.0.0可确保服务对外（容器间）可访问，更准确反映服务就绪状态。

修复：更新healthcheck配置：

healthcheck:
  test: ["CMD", "mysqladmin" ,"ping", "-h", "0.0.0.0"]
  timeout: 20s
  retries: 10

内容的提问来源于stack exchange，提问作者OLUYELE SUNDAY ANTHONY