Docker网络中Spring Boot认证服务无法连接MySQL容器求助

问题详情 #

我是Docker新手，正在配置Spring Boot认证服务与MySQL数据库的网络连接。已通过application.yml用环境变量定义MySQL连接信息，同时使用docker-compose.yml将两者部署在同一自定义网络中，但认证服务始终无法连接MySQL。

application.yml配置 #

## application configuration
spring:
  application:
    name: ${APPLICATION_NAME:ignite-auth-service}
  datasource:
    url: jdbc:mysql://${MYSQL_HOST:localhost}:${MYSQL_PORT:3306}/auth_db?createDatabaseIfNotExist=true
    username: ${MYSQL_USER:root}
    password: ${MYSQL_PWD:password}
    driver-class-name: com.mysql.cj.jdbc.Driver
    initialization-mode: always

docker-compose.yml配置 #

version: '3.8'

# services
services:
  # mysql container
  mysql:
    container_name: mysql
    image: mysql
    ports:
      - 3307:3306
    environment:
      - MYSQL_ROOT_PASSWORD=password
    networks:
      ignite:

  # auth service container
  auth:
    container_name: auth
    build:
      context: ../ignite_project_auth_service-
      dockerfile: Dockerfile
    ports:
      - 8079:8079
    depends_on:
      - mysql
    environment:
      - MYSQL_HOST=mysql
      - MYSQL_PORT=3307
      - MYSQL_USER=root
      - MYSQL_PWD=password
    networks:
      ignite:

# network
networks:
  ignite:

报错日志 #

auth         | 2023-11-19 01:47:12.339  WARN 1 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'flywayInitializer' defined in class path resource [org/springframework/boot/autoconfigure/flyway/FlywayAutoConfiguration$FlywayConfiguration.class]: Invocation of init method failed; nested exception is org.flywaydb.core.internal.exception.FlywaySqlException: 
auth         | Unable to obtain connection from database (jdbc:mysql://mysql:3306/auth_db?createDatabaseIfNotExist=true) for user 'root': Communications link failure
auth         | 
auth         | The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
auth         | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
auth         | SQL State  : 08S01
auth         | Error Code : 0
auth         | Message    : Communications link failure
auth         | 
auth         | The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server

问题原因及修复方案 #

1. 端口配置错误（核心问题） #

容器间通信使用容器内部端口，而非宿主机映射的端口。当前auth服务的MYSQL_PORT设为3307（宿主机端口），但MySQL容器内部监听的是3306，导致连接失败。

修复：
修改docker-compose.yml中auth服务的环境变量：

environment:
  - MYSQL_HOST=mysql
  - MYSQL_PORT=3306  # 改为容器内部端口
  - MYSQL_USER=root
  - MYSQL_PWD=password

2. MySQL未完全就绪时服务发起连接 #

depends_on仅保证MySQL容器先启动，不保证MySQL服务完成初始化（比如数据库创建、权限配置）。此时Spring Boot服务提前发起连接会失败。

修复方案（二选一）：

• 方案一：添加健康检查与等待
  在docker-compose.yml中为MySQL添加健康检查，并让auth服务等待MySQL健康状态：

  mysql:
    container_name: mysql
    image: mysql
    ports:
      - 3307:3306
    environment:
      - MYSQL_ROOT_PASSWORD=password
    networks:
      ignite:
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "localhost", "-u", "root", "-ppassword"]
      interval: 5s
      timeout: 5s
      retries: 5
  
  auth:
    # ... 其他配置
    depends_on:
      mysql:
        condition: service_healthy  # 等待MySQL健康检查通过
  

• 方案二：在Spring Boot中添加重试机制
  在application.yml中配置连接重试，确保服务在MySQL就绪后再建立连接：

  spring:
    datasource:
      # ... 其他配置
      hikari:
        connection-test-query: SELECT 1
        maximum-pool-size: 5
        minimum-idle: 1
        connection-timeout: 30000
        validation-timeout: 5000
        idle-timeout: 600000
        max-lifetime: 1800000
    retry:
      enabled: true
    flyway:
      enabled: true
      baseline-on-migrate: true
  

  同时需添加Spring Retry依赖（Maven示例）：

  <dependency>
    <groupId>org.springframework.retry</groupId>
    <artifactId>spring-retry</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-aop</artifactId>
  </dependency>
  

3. 可选：MySQL版本兼容性优化 #

若使用MySQL 8.x版本，可能存在认证插件问题，可添加环境变量强制使用原生密码插件并提前创建目标数据库：

mysql:
  environment:
    - MYSQL_ROOT_PASSWORD=password
    - MYSQL_ROOT_HOST=%  # 允许root从任意主机连接
    - MYSQL_DATABASE=auth_db  # 提前创建目标数据库，避免权限问题

修复后完整docker-compose.yml示例 #

version: '3.8'

services:
  mysql:
    container_name: mysql
    image: mysql:8.0
    ports:
      - 3307:3306
    environment:
      - MYSQL_ROOT_PASSWORD=password
      - MYSQL_ROOT_HOST=%
      - MYSQL_DATABASE=auth_db
    networks:
      ignite:
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "localhost", "-u", "root", "-ppassword"]
      interval: 5s
      timeout: 5s
      retries: 5

  auth:
    container_name: auth
    build:
      context: ../ignite_project_auth_service-
      dockerfile: Dockerfile
    ports:
      - 8079:8079
    depends_on:
      mysql:
        condition: service_healthy
    environment:
      - MYSQL_HOST=mysql
      - MYSQL_PORT=3306
      - MYSQL_USER=root
      - MYSQL_PWD=password
    networks:
      ignite:

networks:
  ignite:

内容的提问来源于stack exchange，提问作者CleanCodeOnline