Docker-compose运行正常，docker run启动容器时Mongo连接超时

问题现象 #

执行docker-compose up时Denex.Backend项目可正常运行，但执行docker run denexbackend_denex-service单独启动容器时，出现MongoDB连接超时错误，核心报错为：

System.Net.Internals.SocketExceptionFactory+ExtendedSocketException (00000005, 0xFFFDFFFF): Name or service not known

即无法解析mongodb-service主机名。

原因分析 #

Docker Compose会自动为项目创建专属网络（无论是默认网络还是自定义的samplenetwork），在这个网络内的容器可以通过服务名称（如mongodb-service）互相访问。但单独使用docker run启动的容器默认加入Docker的公共bridge网络，该网络与Compose创建的项目网络不互通，因此无法解析仅在项目网络内有效的服务主机名。

解决方案 #

方案1：将容器加入Compose项目网络 #

1. 先查看Compose创建的网络名称：

   docker network ls
   

   找到对应项目的网络（例如自定义的samplenetwork，或默认的<项目目录名>_default）

2. 启动容器时指定该网络：

   docker run --network samplenetwork denexbackend_denex-service
   

方案2：修改连接字符串为宿主机IP（测试场景） #

1. 修改appsettings.json中的MongoDB连接字符串，将mongodb-service替换为宿主机的IP地址：

   "MongoDbSettings": {
     "ConnectionString": "mongodb://<宿主机IP>:27018",
     "Database": "DenexDB"
   }
   

2. 重新构建镜像：

   docker-compose build denex-service
   

3. 再用docker run启动容器即可连接到宿主机映射的MongoDB端口。

方案3：使用docker-compose run启动容器 #

直接通过Compose命令启动服务容器，它会自动加入项目网络：

docker-compose run denex-service

相关配置参考 #

appsettings.json #

"MongoDbSettings": {
    "ConnectionString": "mongodb://mongodb-service:27017",
    "Database": "DenexDB"
  },

调整后的docker-compose.yml #

version: '3.8'
services:
  mongodb-service:
    image: mongo
    ports:
      - 27018:27017
    volumes:
      - denex-data:/data/db
    networks:
      - samplenetwork
  denex-service:
    container_name: denex-backend
    build: .
    ports:
      - 3003:80
    depends_on:
      - mongodb-service
    networks:
      - samplenetwork
volumes:
  denex-data:

networks:
  samplenetwork:
    driver: bridge

完整错误信息 #

Unhandled exception. System.TimeoutException: A timeout occurred after 30000ms selecting a server using CompositeServerSelector{ Selectors = MongoDB.Driver.MongoClient+AreSessionsSupportedServerSelector, LatencyLimitingServerSelector{ AllowedLatencyRange = 00:00:00.0150000 }, OperationsCountServerSelector }. Client view of cluster state is { ClusterId : "1", Type : "Unknown", State : "Disconnected", Servers : [{ ServerId: "{ ClusterId : 1, EndPoint : "Unspecified/mongodb-service:27017" }", EndPoint: "Unspecified/mongodb-service:27017", ReasonChanged: "Heartbeat", State: "Disconnected", ServerVersion: , TopologyVersion: , Type: "Unknown", HeartbeatException: "MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server.
 ---> System.Net.Internals.SocketExceptionFactory+ExtendedSocketException (00000005, 0xFFFDFFFF): Name or service not known
   at System.Net.Dns.GetHostEntryOrAddressesCore(String hostName, Boolean justAddresses, AddressFamily addressFamily, ValueStopwatch stopwatch)
   at System.Net.Dns.GetHostAddresses(String hostNameOrAddress, AddressFamily family)
   at MongoDB.Driver.Core.Connections.TcpStreamFactory.ResolveEndPoints(EndPoint initial)
   at MongoDB.Driver.Core.Connections.TcpStreamFactory.CreateStream(EndPoint endPoint, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken)
   --- End of inner exception stack trace ---
   at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Connections.BinaryConnection.Open(CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Servers.ServerMonitor.InitializeConnection(CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Servers.ServerMonitor.Heartbeat(CancellationToken cancellationToken)", LastHeartbeatTimestamp: "2022-11-13T19:16:54.6844686Z", LastUpdateTimestamp: "2022-11-13T19:16:54.6844692Z" }] }.
   at MongoDB.Driver.Core.Clusters.Cluster.ThrowTimeoutException(IServerSelector selector, ClusterDescription description)
   at MongoDB.Driver.Core.Clusters.Cluster.WaitForDescriptionChangedHelper.HandleCompletedTask(Task completedTask)
   at MongoDB.Driver.Core.Clusters.Cluster.WaitForDescriptionChanged(IServerSelector selector, ClusterDescription description, Task descriptionChangedTask, TimeSpan timeout, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Clusters.Cluster.SelectServer(IServerSelector selector, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoClient.AreSessionsSupportedAfterServerSelection(CancellationToken cancellationToken)
   at MongoDB.Driver.MongoClient.AreSessionsSupported(CancellationToken cancellationToken)
   at MongoDB.Driver.MongoClient.StartImplicitSession(CancellationToken cancellationToken)
   at MongoDB.Driver.OperationExecutor.StartImplicitSession(CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabaseImpl.UsingImplicitSession[TResult](Func`2 func, CancellationToken cancellationToken)
   at MongoDB.Driver.MongoDatabaseImpl.ListCollectionNames(ListCollectionNamesOptions options, CancellationToken cancellationToken)
   at Denex.Persistance.Extensions.MongoImportExtension.AddMongoImport(IConfiguration configuration) in /app/src/Infrastructure/Denex.Persistance/Extensions/MongoImportExtension.cs:line 19
   at Program.<Main>$(String[] args) in /app/src/WebApi/Denex.WebApi/Program.cs:line 24

内容的提问来源于stack exchange，提问作者Mevlüt Gür