An exception was thrown by a TaskScheduler

Question

I am using Tasks to perform the heavy tasks in the background so that the front-end application won't be blocked, while doing so I get this "An exception was thrown by a TaskScheduler" error randomly. The complete stack trace is as followed

Message: "An exception was thrown by a TaskScheduler.", Data: [], InnerException: OutOfMemoryException { TargetSite: Void StartInternal(), StackTrace: "   at System.Threading.Thread.StartInternal()
   at System.Threading.Thread.Start()
   at System.Threading.Thread.Start(Object parameter)
   at System.Threading.Tasks.ThreadPoolTaskScheduler.QueueTask(Task task)
   at System.Threading.Tasks.TaskScheduler.InternalQueueTask(Task task)
   at System.Threading.Tasks.Task.ScheduleAndStart(Boolean needsProtection)", Message: "Exception of type 'System.OutOfMemoryException' was thrown.", Data: [], InnerException: null, HelpLink: null, Source: "System.Private.CoreLib", HResult: -2147024882 }, HelpLink: null, Source: "System.Private.CoreLib", HResult: -2146233088 }

Below is the code snippet which shows How I use the tasks.

public async Task<bool> Method1()
{
  //Do something
  Task task = new Task(() => ProcessHeavyTaskInTheBackground(), TaskCreationOptions.LongRunning);
  task.Start(); //The above exception occurred on this line
  return true;
}

Method1() is called by the API

My application is hosted on Azure app service, when I checked the Metrics in the monitoring section for the metric type "Memory working set" and Aggregation is set to max, I could see max 20-30% memory was utilized from 14GB which I have for my app service.

After seeing this I thought the problem is not with the RAM of the app service it is with the task scheduler as we can see in the exception.

Has anybody known what is the fix for this? Many thanks in advance

Maybe a related question: https://stackoverflow.com/questions/6271463/taskfactory-startnew-system-outofmemoryexception/8061407 — Kayndarr, Jul 20 '21 at 04:39
If you don't want to wait for the result, It's better to make your Method [Fire&Forget](https://stackoverflow.com/questions/5613951/simplest-way-to-do-a-fire-and-forget-method-in-c-sharp-4-0/20364016). If not, you may use a Task scheduler Like [Quartz](https://www.quartz-scheduler.net/) — Matt Qafouri, Jul 20 '21 at 07:49
What happens if you invoke the `ProcessHeavyTaskInTheBackground()` method directly? — Theodor Zoulias, Jul 20 '21 at 07:51
Sure, but does it throw `System.OutOfMemoryException`, or completes successfully? — Theodor Zoulias, Jul 20 '21 at 08:14
How many threads are you using? Does removing `LongRunning` make any difference? — JonasH, Jul 20 '21 at 09:58
You should probably share with us the code of the `ProcessHeavyTaskInTheBackground` method, otherwise it will be hard to offer any specific advice. — Theodor Zoulias, Jul 20 '21 at 13:32
Check if running the task with Task.Run() would change anything (safer defaults will be used) — Maciek Świszczowski, Jul 20 '21 at 13:57

An exception was thrown by a TaskScheduler

0 Answers0