记录MongoDb连接错误System.TimeoutException: A timeout occured after 30000ms selecting a server
网站使用MongoDb数据库，网站发布后运行出错，提示数据库连接超时异常(System.TimeoutException)。其实一般只要仔细阅读错误信息，都能找到问题的源头，这里记录下我曾遇到的情况。
先贴下我遇到的错误截图：
详细的错误信息如下：
Error Details
System.TimeoutException: A timeout occured after 30000ms selecting a server using CompositeServerSelector{ Selectors = WritableServerSelector, LatencyLimitingServerSelector{ AllowedLatencyRange = 00:00:00.0150000 } }. Client view of cluster state is { ClusterId : "1", ConnectionMode : "Automatic", Type : "Unknown", State : "Disconnected", Servers : [{ ServerId: "{ ClusterId : 1, EndPoint : "192.168.1.113:27017" }", EndPoint: "192.168.1.113:27017", State: "Disconnected", Type: "Unknown", HeartbeatException: "MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. ---> System.Net.Sockets.SocketException: 由于连接方在一段时间后没有正确答复或连接的主机没有反应，连接尝试失败。 192.168.1.113:27017
at System.Net.Sockets.Socket.EndConnect(IAsyncResult asyncResult)
at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Connections.TcpStreamFactory.d__7.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Connections.TcpStreamFactory.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()
at MongoDB.Driver.Core.Connections.BinaryConnection.d__47.MoveNext()
--- End of inner exception stack trace ---
at MongoDB.Driver.Core.Connections.BinaryConnection.d__47.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Servers.ClusterableServer.d__42.MoveNext()" }] }.
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.Core.Bindings.WritableServerBinding.GetWriteChannelSource(CancellationToken cancellationToken)
at MongoDB.Driver.Core.Operations.BulkMixedWriteOperation.Execute(IWriteBinding binding, CancellationToken cancellationToken)
at MongoDB.Driver.MongoCollectionImpl`1.ExecuteWriteOperation[TResult](IWriteOperation`1 operation, CancellationToken cancellationToken)
at MongoDB.Driver.MongoCollectionImpl`1.BulkWrite(IEnumerable`1 requests, BulkWriteOptions options, CancellationToken cancellationToken)
at MongoDB.Driver.MongoCollectionBase`1.InsertOne(TDocument document, InsertOneOptions options, CancellationToken cancellationToken)
at CallSite.Target(Closure , CallSite , IMongoCollection`1 , Object )
at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1)
at System.Net.Sockets.Socket.EndConnect(IAsyncResult asyncResult)
at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Connections.TcpStreamFactory.d__7.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Connections.TcpStreamFactory.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()
at MongoDB.Driver.Core.Connections.BinaryConnection.d__47.MoveNext()
--- End of inner exception stack trace ---
at MongoDB.Driver.Core.Connections.BinaryConnection.d__47.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Servers.ClusterableServer.d__42.MoveNext()" }] }.
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.Core.Bindings.WritableServerBinding.GetWriteChannelSource(CancellationToken cancellationToken)
at MongoDB.Driver.Core.Operations.BulkMixedWriteOperation.Execute(IWriteBinding binding, CancellationToken cancellationToken)
at MongoDB.Driver.MongoCollectionImpl`1.ExecuteWriteOperation[TResult](IWriteOperation`1 operation, CancellationToken cancellationToken)
at MongoDB.Driver.MongoCollectionImpl`1.BulkWrite(IEnumerable`1 requests, BulkWriteOptions options, CancellationToken cancellationToken)
at MongoDB.Driver.MongoCollectionBase`1.InsertOne(TDocument document, InsertOneOptions options, CancellationToken cancellationToken)
at CallSite.Target(Closure , CallSite , IMongoCollection`1 , Object )
at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1)
要注意MongoDb错误信息的格式问题，有的web框架有自己的错误页面模板，会导致浏览器出现横向的滚动条，如果不注意会忽略掉重要的错误信息！仔细查阅错误详情，一般都可以看出问题的关键点！我遇到的情况就是项目在部署时，没有调整正确的数据库IP地址，在内部引发了System.Net.Sockets.SocketException异常，才导致提示连接超时。
我平时在使用mongodb过程中，也常常遇到遇到类似的错误，大部分都是数据库无法正确连接上导致的，归纳下大概有这几种情况：
- 项目连接mongodb数据库的IP地址/连接语句设置错误，需要检查项目部署时是否有修改正确的数据库地址。
- mongodb所在服务器防火墙相关端口未开启，只要开启对应的端口即可。
- 网络影响，例如项目是部署在香港，数据库部署在北京，网络传输跨度大，一旦出现网络波动很容易造成链接超时以及System.TimeoutException。
另外还有可能是数据库版本所造成的BUG，也有框架驱动的BUG，这方面我只在网上有看到过。有很多外国猿类也遇到相同问题，情况也各不相同，如果有其他情况只能在网络上找找了。
由于MongoDb目前的中文资料比较少，在网上找的大部分资料都是英文的，所以对英文不太熟悉的就比较蛋疼了。
这两个网页也有提到相同的问题，可以参考参考：
- https://jira.mongodb.org/browse/CSHARP-1435
- https://stackoverflow.com/questions/29832622/mongodb-c-sharp-2-0-timeoutexception
作者：十有三
出处：https://shiyousan.com/post/636177837177647637
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