.NET应用通过Docker Compose连接PostgreSQL失败求助

问题详情 #

运行基于.NET的应用和PostgreSQL的Docker Compose栈时，出现数据库连接错误，报错信息：

appdemo-service  |       System.InvalidOperationException: An exception has been raised that is likely due to a transient failure. appdemo-service  |        ---> Npgsql.NpgsqlException (0x80004005): Failed to connect to [::1]:5433 appdemo-service  |        ---> System.Net.Sockets.SocketException (99): Cannot assign requested address appdemo-service  |          at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.CreateException(SocketError error, Boolean forAsyncThrow)

使用的Docker Compose配置：

version: '3.4'

networks:
  dev:
    driver: bridge

services:
  app-demo:
    image: docker.io/library/appdemo
    depends_on:
     - "app_db"
    container_name: appdemo-service
    ports:
      - "5009:80"
    build:
      context: .
      dockerfile: Dockerfile
    environment:
      - ConnectionStrings__DefaultConnection=User ID =postgres;Password=postgres;Server=localhost;Port=5433;Database=SampleDriverDb; Integrated Security=true;Pooling=true;
      - ASPNETCORE_URLS=http://+:80
    networks:
      - dev

  app_db:
    image: postgres:latest
    container_name: app_db
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres
      - POSTGRES_DB=SampleDriverDb
    ports:
      - "5433:5432"
    restart: always
    volumes:
      - app_data:/var/lib/postgresql/data
    networks:
      - dev
volumes:
  app_data:

错误原因及修复步骤 #

1. 容器间访问不能用localhost #

Docker Compose自定义网络中，容器需通过服务名互相访问。app-demo容器内的localhost指向容器自身，而非数据库容器。

• 修复：将连接字符串中的Server=localhost改为Server=app_db（对应PostgreSQL服务的名称）

2. 端口使用错误 #

数据库容器内部PostgreSQL默认端口为5432，ports: "5433:5432"是宿主机端口到容器端口的映射，容器间访问直接用容器内部端口即可。

• 修复：将连接字符串中的Port=5433改为Port=5432

3. 移除无效参数 #

PostgreSQL不支持Integrated Security=true（该参数属于SQL Server），会干扰连接逻辑。

• 修复：删除连接字符串中的Integrated Security=true;

4. 可选：处理数据库启动延迟 #

depends_on仅保证容器启动顺序，不确保数据库服务就绪。可添加健康检查或启动脚本，让应用等待数据库就绪：

app_db:
  # ... 其他配置
  healthcheck:
    test: ["CMD-SHELL", "pg_isready -U postgres"]
    interval: 5s
    timeout: 5s
    retries: 5

app-demo:
  # ... 其他配置
  depends_on:
    app_db:
      condition: service_healthy

修改后的连接字符串 #

最终app-demo服务的环境变量应改为：

environment:
  - ConnectionStrings__DefaultConnection=User ID=postgres;Password=postgres;Server=app_db;Port=5432;Database=SampleDriverDb;Pooling=true;
  - ASPNETCORE_URLS=http://+:80

内容的提问来源于stack exchange，提问作者wandos