SignalR 无法使用负载平衡

Question

我们已经有一个带有信号器集线器的服务器，客户端使用信号器进行连接。我们最近将它移到了两个带有负载均衡器的节点以实现可扩展性。但是在将其移动到负载平衡器之后，现在客户端无法使用信号器连接到服务器。客户端首先尝试使用 Web 套接字，它在信号器跟踪上给出以下错误。

   fae26beb-a806-4957-b52a-39b80856e492 - Auto: Failed to connect to using transport webSockets. System.Net.WebSockets.WebSocketException (0x80004005): Unable to connect to the remote server ---> System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
   at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)
   at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)
   --- End of inner exception stack trace ---
   at System.Net.Security._SslStream.EndRead(IAsyncResult asyncResult)
   at System.Net.TlsStream.EndRead(IAsyncResult asyncResult)
   at System.Net.PooledStream.EndRead(IAsyncResult asyncResult)
   at System.Net.Connection.ReadCallback(IAsyncResult asyncResult)
   --- End of inner exception stack trace ---
   at System.Net.HttpWebRequest.EndGetResponse(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 System.Net.WebSockets.ClientWebSocket.<ConnectAsyncCore>d__21.MoveNext()
   at System.Net.WebSockets.ClientWebSocket.<ConnectAsyncCore>d__21.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 Microsoft.AspNet.SignalR.Client.Transports.WebSocketTransport.<PerformConnect>d__1.MoveNext()

但经过几次尝试连接后，它设法使用 SSE（服务器发送事件）进行连接。

   fae26beb-a806-4957-b52a-39b80856e492 - SSE: OnMessage(Data: {"C":"s-0,BA9F","S":1,"M":[]})  
   fae26beb-a806-4957-b52a-39b80856e492 - ChangeState(Connecting, Connected)
   fae26beb-a806-4957-b52a-39b80856e492 - SSE: OnMessage(Data: {"C":"s-0,BAA0","M":[{"H":"PrintConnectorHub","M":"SignalRConnectedSuccessfully","A":[true]}]})  
   fae26beb-a806-4957-b52a-39b80856e492 - OnMessage({"R":false,"I":"3"}) 

但是当服务器试图将消息发送回客户端时，客户端并没有收到该消息。我们已经使用 SQL Server 实现了 SignalR 横向扩展，以下是服务器中的日志跟踪。

TRACE  SignalR.SqlMessageBus  Stream 0 : SqlReceiver last payload ID=47781, new payload ID=47782 (Microsoft.AspNet.SignalR.SqlServer.SqlReceiver.ProcessRecord) 
TRACE  SignalR.SqlMessageBus  Stream 0 : Updated receive reader initial payload ID parameter=47782 (Microsoft.AspNet.SignalR.SqlServer.SqlReceiver.ProcessRecord) 
TRACE  SignalR.SqlMessageBus  Stream 0 : Payload 47782 containing 1 message(s) received (Microsoft.AspNet.SignalR.SqlServer.SqlReceiver.ProcessRecord) 
TRACE  SignalR.SqlMessageBus  Stream 0 : 1 records received (Microsoft.AspNet.SignalR.SqlServer.ObservableDbOperation.ExecuteReaderWithUpdates) 
TRACE  SignalR.SqlMessageBus  Created DbCommand: CommandType=Text, CommandText=SELECT [PayloadId], [Payload], [InsertedOn] FROM [SignalR].[Messages_0] WHERE [PayloadId] > @PayloadId, Parameters= [Name=PayloadId, Value=47782] (Microsoft.AspNet.SignalR.SqlServer.DbOperation.TraceCommand)

在客户端初始化信号器

signalrHostUrl = "SignalR_Host"; 

try
{
    hubConnection = new HubConnection(signalrHostUrl);
    hubConnection.Error += ex =>
    {
        signalRlogger.Error(ex, "Exception from hubConnection");
    };

    hubConnection.ConnectionSlow += () => ConnectionSlow();
    hubConnection.Closed += () => SignalrConnectionConnectionClosed();
    hubConnection.StateChanged += signalRConnectionStateController.StateChanged;

    hubConnection.Start().Wait();
}
catch (Exception ex)
{
    signalRlogger.Error(ex, "initialzing hub connection");
}

在迁移到负载平衡器之前，客户端完全能够通过 Web 套接字进行连接和通信。但是在转移到负载均衡器之后，它完全无法通过 Web 套接字进行连接。我们甚至试图通过这个工具 (https://chrome.google.com/webstore/detail/simple-websocket-client/pfdhoblngboilpfeibdedpjgfnlcodoo?hl=en) 打开一个 Web 套接字连接，它也无法打开一个连接。尽管它设法通过 SSE 连接，但它仍然无法与客户端通信。在负载平衡中使用 Web 套接字有什么复杂性，在这种情况下，为什么 Signalr 无法与客户端建立连接？

Answer 1

当另一台机器尝试解密您在协商连接时获得的连接令牌时，它无法解密并且请求失败。您需要确保您使用的所有机器都具有相同的机器密钥。这样所有机器都可以解密其他机器创建的连接令牌。

您能否在负载平衡器上启用粘性？例如基于会话的粘性。这将确保客户端连接到同一台机器。缺点是如果机器出现故障，客户端将无法重新连接。