[SignalR] Java Client NullPointerException

[JMaroz]

Describe the bug

When start the connection the SignalR HubConnection class throw an Exception

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.microsoft.signalr.HubConnection$ConnectionState.cancelOutstandingInvocations(java.lang.Exception)' on a null object reference at com.microsoft.signalr.HubConnection.stopConnection(HubConnection.java:6) at com.microsoft.signalr.HubConnection.lambda$start$6(HubConnection.java:1) at com.microsoft.signalr.s.invoke(Unknown Source:2) at com.microsoft.signalr.WebSocketTransport.onClose(WebSocketTransport.java:4) at com.microsoft.signalr.WebSocketTransport.lambda$start$1(WebSocketTransport.java:3) at com.microsoft.signalr.A.invoke(Unknown Source:2) at com.microsoft.signalr.OkHttpWebSocketWrapper$SignalRWebSocketListener.onFailure(OkHttpWebSocketWrapper.java:3) at okhttp3.internal.ws.RealWebSocket.failWebSocket(RealWebSocket.java:84) at okhttp3.internal.ws.RealWebSocket$2.onFailure(RealWebSocket.java:1) at okhttp3.RealCall$AsyncCall.execute(RealCall.java:8) at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:3) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636) at java.lang.Thread.run(Thread.java:764)

To Reproduce

Unable to reproduce the behavior, the crash happen randomly

Expected behavior

SignalR must catch the exception or not throw the exception

[jkotalik]

@mikaelm12 @BrennanConroy

[mikaelm12]

I'll investigate. Thanks!

[bradygaster]

@JMaroz are you connecting to a traditional server-side Hub or are you connecting through the SignalR Service? Just curious.

[mikaelm12]

So I believe that I was running into this bug during my work on the LongPolling transport and I fixed it in that pr which is still under review #6856. The issue I believe was
the connection state wasn't being set until we received the Handshake response so if the connection is stopped before it has been fully set up you could null ref in stop. This should be fixed in the LongPolling pr. https://github.com/aspnet/AspNetCore/blob/a6f4a27abb2db0dcd65d1595c43bcde048b85228/src/SignalR/clients/java/signalr/src/main/java/com/microsoft/signalr/HubConnection.java#L326

[imperugo]

@bradygaster let me share some information about server side. The problem explained by @JMaroz happens with this configuration:

• ASP.NET Core 2.2.0
• SignalR 1.1.0
• Hosting on Docker over ECS on AWS Cloud Platform (no reverse proxy, just kestrel behind the balancer)

The client connects to simple Hub service that looks like this (more or less)

public class MySuperHub : HubBase
{
   public async Task DoSomethingSpecial(string param1, Guid param2, dynamic param3 = null)
   {
      // await ....
   }
}

Let me add another error we get server side in another mobile application (maybe could be helpful).

Error message: Failed connection handshake.

HttpHeaders: [Connection, upgrade], [Upgrade, websocket], [Accept-Encoding, gzip], [Host, mydomain.mycompany.com], [User-Agent, okhttp/3.10.0], [Origin, https://mydomain.mycompany.com/], [X-Original-Proto, https], [X-Forwarded-Port, 443], [X-Amzn-Trace-Id, Root=1-5c47e65a-d7286a28e44316b8c5463ea0], [Sec-WebSocket-Key, G9xa4kZDUhAyfAgF8iypFg==], [Sec-WebSocket-Version, 13], [X-Original-For, 10.202.3.196:51446]

SourceContext: Microsoft.AspNetCore.SignalR.HubConnectionContext

Didn't understand exactly when it happens because I don't have any stack (it happens not in my code but is logged as error).

Let me know if you need more info.
Thanks

[bradygaster]

@mikaelm12 and @muratg would this be ready (or is it already in) for 2.2.3?

[muratg]

@bradygaster To get this in 2.2.3, we'll need a PR with the fix with the label servicing-consider. It'll show up in the next shiproom then.

[mikaelm12]

I don't think that that would be critical to get into 2.2.3. It's an error that happens in a failure in the close logic of the Java client. Happy to discuss it more though if people have other opinions.

[JMaroz]

@mikaelm12 is there a release date w/ the fix for the java client?

[mikaelm12]

The fix for the null ref will be coming in Preview3, but that is not why your HubConnection fails to start. The exception you posted is the result of you HubConnection failing to start, not the cause of it I believe. Do you have any more logs or a repro app we can look at?