Docker容器项目无法访问MySQL的问题排查与解决策略

Error: connect ECONNREFUSED 172.18.0.2:3306
dial tcp 172.17.0.1:3306: connect: connection timed out
Can't connect to MySQL server on 'localhost' (111)
Communications link failure

# 查看容器网络配置
docker network ls
docker inspect <container_id>

# 测试网络连通性
docker exec <app_container> ping <mysql_container>
docker exec <app_container> telnet <mysql_host> 3306
docker exec <app_container> nc -zv <mysql_host> 3306

# docker-compose.yml 错误示例
services:
  app:
    image: my-app
    depends_on:
      - mysql  # 仅保证容器启动，不保证服务就绪
  mysql:
    image: mysql:8.0

# 1. 创建自定义网络
docker network create app-network

# 2. 启动MySQL容器并加入网络
docker run -d \
  --name mysql-server \
  --network app-network \
  -e MYSQL_ROOT_PASSWORD=rootpass \
  -e MYSQL_DATABASE=myapp \
  mysql:8.0

# 3. 启动应用容器，使用容器名作为主机地址
docker run -d \
  --name myapp \
  --network app-network \
  -e DB_HOST=mysql-server \
  -e DB_PORT=3306 \
  -e DB_USER=root \
  -e DB_PASSWORD=rootpass \
  my-app-image

version: '3.8'
services:
  mysql:
    image: mysql:8.0
    container_name: mysql-server
    environment:
      MYSQL_ROOT_PASSWORD: rootpass
      MYSQL_DATABASE: myapp
    networks:
      - app-network
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "localhost"]
      interval: 10s
      timeout: 5s
      retries: 5
  app:
    image: my-app
    environment:
      DB_HOST: mysql-server  # 使用服务名作为主机名
      DB_PORT: 3306
    depends_on:
      mysql:
        condition: service_healthy  # 等待MySQL健康检查通过
    networks:
      - app-network
networks:
  app-network:
    driver: bridge

# 使用 host.docker.internal 特殊DNS（Docker 18.03+）
docker run -e DB_HOST=host.docker.internal my-app

# 或使用宿主机IP（Linux）
docker run -e DB_HOST=172.17.0.1 my-app  # 默认docker0网桥IP

services:
  mysql:
    image: mysql:8.0
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "localhost", "-u", "root", "-p$$MYSQL_ROOT_PASSWORD"]
      interval: 5s
      timeout: 3s
      retries: 10
      start_period: 30s  # 给MySQL初始化预留时间
  app:
    build: .
    depends_on:
      mysql:
        condition: service_healthy
    restart: unless-stopped  # 增加容错性

async function connectWithRetry(maxRetries = 10) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      await db.connect();
      console.log('Database connected successfully');
      return;
    } catch (err) {
      console.log(`Connection attempt ${i+1}/${maxRetries} failed, retrying in 5s...`);
      await new Promise(resolve => setTimeout(resolve, 5000));
    }
  }
  throw new Error('Failed to connect to database after maximum retries');
}

# 方案A：关闭防火墙（测试环境）
sudo ufw disable

# 方案B：精确放行Docker网段（生产环境）
sudo ufw allow from 172.22.0.0/16 to any port 3306

docker exec -it mysql-server mysql -uroot -p

-- 查看现有用户权限
SELECT Host, User FROM mysql.user;

-- 创建允许任意主机访问的用户（开发环境）
CREATE USER 'appuser'@'%' IDENTIFIED BY 'securepass';
GRANT ALL PRIVILEGES ON myapp.* TO 'appuser'@'%';
FLUSH PRIVILEGES;

-- 或修改root用户权限（不推荐生产环境）
UPDATE mysql.user SET Host='%' WHERE User='root' AND Host='localhost';

CREATE USER 'appuser'@'%' IDENTIFIED WITH mysql_native_password BY 'securepass';

docker run -d \
  --network host \
  --name mysql-server \
  -e MYSQL_ROOT_PASSWORD=rootpass \
  mysql:8.0

应用容器无法连接MySQL
    │
    ▼
┌─────────────────┐
│ 1. 检查容器状态  │──docker ps──► 容器是否Running?
└─────────────────┘
    │
    ▼
┌─────────────────┐
│ 2. 检查网络配置  │──docker network inspect──► 容器是否同网络?
└─────────────────┘
    │
    ▼
┌─────────────────┐
│ 3. 测试连通性   │──docker exec ping/telnet──► 网络是否通?
└─────────────────┘
    │
    ▼
┌─────────────────┐
│ 4. 检查MySQL状态 │──docker logs mysql──► MySQL是否就绪?
└─────────────────┘
    │
    ▼
┌─────────────────┐
│ 5. 验证连接参数  │──检查DB_HOST/PORT/USER/PASS──► 配置是否正确?
└─────────────────┘
    │
    ▼
┌─────────────────┐
│ 6. 检查权限与防火墙│──mysql.user表 + ufw/iptables──► 权限是否开放?
└─────────────────┘

volumes:
  - mysql_data:/var/lib/mysql