The operation was canceled. at System.Threading.CancellationToken.ThrowIfCancellationRequested()

Question

I am using latest version of WebAPI. My WebAPI return RSS feed data. I did a load testing with blitz and below are its results.

This rush generated 115,908 successful hits in 300 seconds and we transferred 1.91 GB of data in and out of your app. The average hit rate of 386.36/second translates to about 33,381,504 hits/day. The average response time was 410 ms. You've got bigger problems, though: 0.87% of the users during this rush experienced timeouts or errors!

The Code for WebAPI which returns RSS is as below. It uses OutPutCache lib from https://github.com/filipw/AspNetWebApi-OutputCache

[AllowAnonymous]
        [CacheOutput(ServerTimeSpan = 14400)]
        [HttpGet]
        public async Task<HttpResponseMessage> GetRssData()
        {

            string responseFromServer = string.Empty;
            WebRequest request = WebRequest.Create("URL FOR MY RSS FEED HERE");


            using (WebResponse response = await request.GetResponseAsync())
            {
                using (Stream dataStream = response.GetResponseStream())
                {
                    using (StreamReader reader = new StreamReader(dataStream))
                    {
                        responseFromServer = await reader.ReadToEndAsync();
                    }
                }
            }

            return new HttpResponseMessage() { Content = new StringContent(responseFromServer, Encoding.UTF8, "application/rss+xml") };

        }

Below is the error log for same

Exception information: Exception type: OperationCanceledException Exception message: The operation was canceled. at System.Threading.CancellationToken.ThrowIfCancellationRequested()
at System.Web.Http.WebHost.HttpControllerHandler.d__1b.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.WebHost.HttpControllerHandler.d__7.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.WebHost.HttpControllerHandler.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.TaskAsyncHelper.EndTask(IAsyncResult ar) at System.Web.HttpApplication.CallHandlerExecutionStep.OnAsyncHandlerCompletion(IAsyncResult ar)

Thread information:

Stack trace:    at System.Threading.CancellationToken.ThrowIfCancellationRequested()   

at System.Web.Http.WebHost.HttpControllerHandler.d__1b.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.WebHost.HttpControllerHandler.d__7.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.WebHost.HttpControllerHandler.d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.TaskAsyncHelper.EndTask(IAsyncResult ar) at System.Web.HttpApplication.CallHandlerExecutionStep.OnAsyncHandlerCompletion(IAsyncResult ar)

Answer 1

This looks like cancelled requests, being automatically cancelled by Web API. You can typically ignore these errors (and they will not show up on global error handling starting with Web API 5.2).