WaWorkerHost.exe crashes role: CallbackException

Question

When I run my WorkerRole C# application on Azure, after a while waworkerhost.exe crashes due the following exception:

Application: WaWorkerHost.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.Runtime.CallbackException
Stack:
   at System.Runtime.Fx+IOCompletionThunk.UnhandledExceptionFrame(UInt32, UInt32, System.Threading.NativeOverlapped*)
   at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32, UInt32, System.Threading.NativeOverlapped*)

I have an application that generates load to a webserver. I don't care about the actual response, but i want to control the number of requests made per second. Therefore i have a Timer that fires every second and generates a number of requests. I have tried the following options:

• Parallel.For with WebRequests
• For loop with ASync WebRequests
• For loop with ThreadPool.QueueUserWorkItem(do webrequest)

When the number of requests increase, the exception occurs (8+ req/sec). The same exception for all three options. When I run the role in local DevelopmentFabric all three options work just fine. If someone could give me some pointers on what might be going wrong I appreciate it. If you have other ideas to generate this type of load from Azure and C#, please share your thoughts.

Answer 1

The author answered the question in the comment to the original post, but for better visibility, I'm reporting it to here:

Turn out to be an IntelliTrace issue, see http://social.msdn.microsoft.com/Forums/en-ZA/windowsazuretroubleshooting/thread/543da280-2e5c-4e1a-b416-9999c7a9b841:

...

After redeploying my solution with Intellitrace disabled, the issues where resolved, and my WorkerRole stayed healthy.