Liquibase无法连接MySQL数据库，请求排查Docker Compose配置

报错信息 #

liquibase_1  | Starting Liquibase at 21:40:22 (version 4.23.1 #12042 built at 2023-08-10 13:48+0000)
liquibase_1  | Liquibase Version: 4.23.1
liquibase_1  | Liquibase Open Source 4.23.1 by Liquibase
liquibase_1  | 
liquibase_1  | Unexpected error running Liquibase: Connection could not be created to jdbc:mysql://mysql_db:3307/patshala with driver com.mysql.cj.jdbc.Driver.  Communications link failure
liquibase_1  | 
liquibase_1  | The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
liquibase_1  |   - Caused by: Connection refused

Docker Compose配置 #

version: '3.8'

services:
  mysql_db:
    image: mysql:5.7
    environment:
      MYSQL_ROOT_PASSWORD: password
      MYSQL_DATABASE: patshala
      MYSQL_USER: mysql
      MYSQL_PASSWORD: password
    volumes:
      - ./db:/docker-entrypoint-initdb.d/
    ports:
      - "3307:3306"
    networks:
      - app-network

  liquibase:
    image: liquibase/liquibase:latest
    command: ["--url=jdbc:mysql://mysql_db:3307/patshala", "--username=mysql", "--password=password", "--changeLogFile=/db/changelog/db.changelog.xml", "update"]
    volumes:
      - ./db:/liquibase/changelog
      - ./mysql-connector-j-8.1.0.jar:/liquibase/lib/mysql-connector-j-8.1.0.jar
    depends_on:
      - mysql_db
    networks:
      - app-network


networks:
  app-network:
    driver: bridge

问题分析与修复步骤 #

1. 错误的数据库端口配置 #

Docker容器间通信时，不能使用宿主机映射的端口（3307），而是要使用MySQL容器内部的默认端口3306。ports: "3307:3306"仅用于宿主机访问容器，容器之间通过服务名mysql_db通信时，直接用内部端口3306即可。

修改Liquibase的JDBC URL：

--url=jdbc:mysql://mysql_db:3306/patshala

2. 数据库就绪检测缺失 #

depends_on仅保证Liquibase在MySQL容器之后启动，但不保证MySQL服务已完成初始化、可以接受连接。需要添加健康检查，让Liquibase等待MySQL就绪后再运行。

修改mysql_db服务配置，添加健康检查：

mysql_db:
  # ... 原有配置
  healthcheck:
    test: ["CMD", "mysqladmin", "ping", "-h", "localhost", "-u", "root", "-ppassword"]
    interval: 5s
    timeout: 5s
    retries: 5

同时修改liquibase服务的depends_on，依赖MySQL的健康状态：

liquibase:
  # ... 原有配置
  depends_on:
    mysql_db:
      condition: service_healthy

3. 驱动兼容与连接参数补充 #

MySQL 5.7与新版JDBC驱动配合时，建议添加兼容参数避免连接异常：

--url=jdbc:mysql://mysql_db:3306/patshala?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC

4. ChangeLog文件路径修正 #

你挂载了./db:/liquibase/changelog，但命令中指定的路径/db/changelog/db.changelog.xml与容器内实际路径不匹配。调整挂载和路径：

修改liquibase的挂载配置：

liquibase:
  volumes:
    - ./db:/liquibase/db
    - ./mysql-connector-j-8.1.0.jar:/liquibase/lib/mysql-connector-j-8.1.0.jar

同步修改命令中的changeLogFile路径：

--changeLogFile=/liquibase/db/changelog/db.changelog.xml

修复后的完整Docker Compose配置 #

version: '3.8'

services:
  mysql_db:
    image: mysql:5.7
    environment:
      MYSQL_ROOT_PASSWORD: password
      MYSQL_DATABASE: patshala
      MYSQL_USER: mysql
      MYSQL_PASSWORD: password
    volumes:
      - ./db:/docker-entrypoint-initdb.d/
    ports:
      - "3307:3306"
    networks:
      - app-network
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "localhost", "-u", "root", "-ppassword"]
      interval: 5s
      timeout: 5s
      retries: 5

  liquibase:
    image: liquibase/liquibase:latest
    command: ["--url=jdbc:mysql://mysql_db:3306/patshala?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC", "--username=mysql", "--password=password", "--changeLogFile=/liquibase/db/changelog/db.changelog.xml", "update"]
    volumes:
      - ./db:/liquibase/db
      - ./mysql-connector-j-8.1.0.jar:/liquibase/lib/mysql-connector-j-8.1.0.jar
    depends_on:
      mysql_db:
        condition: service_healthy
    networks:
      - app-network


networks:
  app-network:
    driver: bridge

内容的提问来源于stack exchange，提问作者Mabel Oza