System.Threading.Tasks.TaskCancelledException:

[colindooley11]

System.Threading.Tasks.TaskCanceledException: at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Web.Http.Controllers.ApiControllerActionInvoker+d0.MoveNext (System.Web.Http, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35) at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Web.Http.Controllers.ActionFilterResult+d2.MoveNext (System.Web.Http, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35) at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Web.Http.Filters.AuthorizationFilterAttribute+d2.MoveNext (System.Web.Http, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35) at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Web.Http.Dispatcher.HttpControllerDispatcher+d1.MoveNext (System.Web.Http, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35) at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Web.Http.HttpServer+d0.MoveNext (System.Web.Http, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35) at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Web.Http.Owin.HttpMessageHandlerAdapter+d0.MoveNext (System.Web.Http.Owin, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35) at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089) at ApplicationInsights.OwinExtensions.HttpRequestTrackingMiddleware+d__4.MoveNext (ApplicationInsights.OwinExtensions, Version=0.5.1.0, Culture=neutral, PublicKeyToken=null)

This exception appears to be occurring perhaps 1 in every 1000 requests, on the back of a POST ( which is likely immaterial here) .

In relation to a previous similar bug, you suggested a forceful client disconnection.
Is there anyway I can get any more logging around this?

[colindooley11]

The accompanying call on the client application that observes this error is actually quite useful and may serve to suggest how to log the exception

A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread. Response status code does not indicate success: 500 (Internal Server Error)

[colindooley11]

This may be my only hope without changing the code:

https://stackoverflow.com/questions/7883052/a-tasks-exceptions-were-not-observed-either-by-waiting-on-the-task-or-accessi

[marcinbudny]

Hi Colin,

Could you please say something more about your scenario. Do you control the client? Is the A Task's exception(s) were not observed... error something you see on the client when TaskCanceledException is logged in application insights? Do you also observe this problem when owin extensions are not used?

[colindooley11]

Hi Marcin, Yes we control the client too. I was reluctant to remove the middleware as our CI pipeline and getting us into our PerfTest environment is a little cumbersome (but I agree its a good test) . The "good thing" is that this really is a drop in the ocean and its a fraction of 1 percent of calls. I was just keen to get understanding of what the issue was. (I could fork and add additional logging, but I was reluctant to do this too as "in the main" the middleware works)

I am understanding that our architecture protects us from these failures anyway and will confirm this today, which makes this a known issue but a non issue "as it were".

[marcinbudny]

Let me know if you are able to confirm that the middleware is causing the issues.

[vinmeet84]

@marcinbudny Any fix for this issue. we are still getting Task Cancelled exception. Any pointers would be really helpfull.

[marcinbudny]

Moving all discussions to #20