Preventing crashes due to DiagnosticMonitorTraceListener

Azure App Services has the proactive crash monitoring feature, which checks for process crashes and collects diagnostic data that helps you determine the root cause of the crash. After looking at this feature’s telemetry, we identified a common exception that is causing a lot of apps hosted on Azure App Service to crash with this call-stack:

HelperMethodFrame
System.Diagnostics.TraceUtils.GetRuntimeObject(System.String, System.Type, System.String)
System.Diagnostics.TypedElement.BaseGetRuntimeObject()
System.Diagnostics.ListenerElement.GetRuntimeObject()
System.Diagnostics.ListenerElementsCollection.GetRuntimeObject()
System.Diagnostics.TraceInternal.get_Listeners()
System.Diagnostics.TraceInternal.WriteLine(System.String)
System.Diagnostics.Debug.WriteLine(System.String)
Microsoft.Web.Compilation.Snapshots.SnapshotHelper.TakeSnapshotTimerCallback(System.Object)
System.Threading.TimerQueueTimer.CallCallbackInContext(System.Object)
System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
System.Threading.TimerQueueTimer.CallCallback()
System.Threading.TimerQueueTimer.Fire()
System.Threading.TimerQueue.FireNextTimers()
System.Threading.TimerQueue.AppDomainTimerCallback(Int32)
DebuggerU2MCatchHandlerFrame
ContextTransitionFrame
DebuggerU2MCatchHandlerFrame

The underlying exception message is Couldn’t find type for class Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Culture=neutral, PublicKeyToken=31bf3856ad364e35

This issue can happen if you have migrated your application from Azure Cloud Services. Azure Cloud services uses the DiagnosticMonitorTraceListener class and this class is designed for cloud services and is not compabtible with Azure App Services. To address this issue, please follow these steps :

1. Remove references to Microsoft.WindowsAzure.Diagnostics.dll from the project.

2. Remove the following section from the application web.config file (if it exists)

    <system.diagnostics>
      <trace>
        <listeners>
          <add type="Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="AzureDiagnostics">
          <filter type="" />
          </add>
        </listeners>
      </trace>
    </system.diagnostics>
   

We hope this information helps in preventing crashes within your application.

Happy Debugging !