问题描述
在使用App Service的过程中，发现应用频繁出现503错误，通过Kudu站点获取到Logfiles。
在 Eventlog.xml 文件中，发现大量的 Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener 异常，并且引起 w3wp.exe 进程终止。
<Event> <System> <Provider Name=".NET Runtime"/> <EventID>1026</EventID> <Level>1</Level> <Task>0</Task> <Keywords>Keywords</Keywords> <TimeCreated SystemTime="2022-09-22T09:52:50Z"/> <EventRecordID>421882843</EventRecordID> <Channel>Application</Channel> <Computer>RD0003FF0C13B3</Computer> <Security/> </System> <EventData> <Data>Application: w3wp.exe Framework Version: v4.0.30319 Description: The process was terminated due to an unhandled exception. Exception Info: System.Configuration.ConfigurationErrorsException at System.Diagnostics.TraceUtils.GetRuntimeObject(System.String, System.Type, System.String) at System.Diagnostics.TypedElement.BaseGetRuntimeObject() at System.Diagnostics.ListenerElement.GetRuntimeObject() at System.Diagnostics.ListenerElementsCollection.GetRuntimeObject() at System.Diagnostics.TraceInternal.get_Listeners() at System.Diagnostics.TraceInternal.WriteLine(System.String) at System.Diagnostics.Debug.WriteLine(System.String) at Microsoft.Web.Compilation.Snapshots.SnapshotHelper.TakeSnapshotTimerCallback(System.Object) at System.Threading.TimerQueueTimer.CallCallbackInContext(System.Object) at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean) at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean) at System.Threading.TimerQueueTimer.CallCallback() at System.Threading.TimerQueueTimer.Fire() at System.Threading.TimerQueue.FireNextTimers() at System.Threading.TimerQueue.AppDomainTimerCallback(Int32) </Data> </EventData> </Event> <Event> <System> <Provider Name="ASP.NET 4.0.30319.0"/> <EventID>1325</EventID> <Level>1</Level> <Task>0</Task> <Keywords>Keywords</Keywords> <TimeCreated SystemTime="2022-09-22T10:02:53Z"/> <EventRecordID>422485625</EventRecordID> <Channel>Application</Channel> <Computer>RD0003FF0C13B3</Computer> <Security/> </System> <EventData> <Data>An unhandled exception occurred and the process was terminated. Application ID: /LM/W3SVC/152666399/ROOT Process ID: 6092 Exception: System.Configuration.ConfigurationErrorsException Message: Couldn't find type for class Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Version=2.8.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35. StackTrace: at System.Diagnostics.TraceUtils.GetRuntimeObject(String className, Type baseType, String initializeData) at System.Diagnostics.TypedElement.BaseGetRuntimeObject() at System.Diagnostics.ListenerElement.GetRuntimeObject() at System.Diagnostics.ListenerElementsCollection.GetRuntimeObject() at System.Diagnostics.TraceInternal.get_Listeners() at System.Diagnostics.TraceInternal.WriteLine(String message) at System.Diagnostics.Debug.WriteLine(String message) at Microsoft.Web.Compilation.Snapshots.SnapshotHelper.TakeSnapshotTimerCallback(Object stateInfo) at System.Threading.TimerQueueTimer.CallCallbackInContext(Object state) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.TimerQueueTimer.CallCallback() at System.Threading.TimerQueueTimer.Fire() at System.Threading.TimerQueue.FireNextTimers() at System.Threading.TimerQueue.AppDomainTimerCallback(Int32 id)</Data> </EventData> </Event>在启用了 Proactive Crash Monitoring in Azure App Service 后，当应用再次应为没有处理的异常(24小时内发生3次)就会自动抓取Memory DUMP进行分析。完整的异常日志为：
======================================================== Dump Analysis for w3wp__xxxxxxxx__PID__9644__Date__09_22_2022__Time_02_59_27AM__239__Second_Chance_Exception_E0434352.dmp ======================================================== Thread 7984 ExitCode E0434352 ExitCodeString CLR EXCEPTION DefaultHostName xxxxxxxxxx.chinacloudsites.cn Managed Exception = System.Configuration.ConfigurationErrorsException:Couldn't find type for class Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Version=2.8.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35. CallStack - Managed Exception ======================================================== 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) CallStack - Crashing Thread ======================================================== 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 Native Call Stack ======================================================== KERNELBASE!RaiseException clr!RaiseTheExceptionInternalOnly clr!IL_Throw mscorlib_ni mscorlib_ni mscorlib_ni mscorlib_ni mscorlib_ni mscorlib_ni clr!CallDescrWorkerInternal clr!CallDescrWorkerWithHandler clr!MethodDescCallSite::CallTargetWorker clr!AppDomainTimerCallback_Worker clr!ManagedThreadBase_DispatchInner clr!ManagedThreadBase_DispatchMiddle clr!ManagedThreadBase_DispatchOuter clr!ManagedThreadBase_DispatchInCorrectAD clr!Thread::DoADCallBack clr!ManagedThreadBase_DispatchInner clr!ManagedThreadBase_DispatchMiddle clr!ManagedThreadBase_DispatchOuter clr!ManagedThreadBase_FullTransitionWithAD clr!AppDomainTimerCallback clr!ThreadpoolMgr::AsyncTimerCallbackCompletion clr!UnManagedPerAppDomainTPCount::DispatchWorkItem clr!ThreadpoolMgr::ExecuteWorkRequest clr!ThreadpoolMgr::WorkerThreadStart clr!Thread::intermediateThreadProc kernel32!BaseThreadInitThunk ntdll!__RtlUserThreadStart ntdll!_RtlUserThreadStart
这个问题是什么原因呢？
问题解答
在Eventlog.xml文件中，已经发现了此异常的根本原因是：Couldn’t find type for class Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Culture=neutral, PublicKeyToken=31bf3856ad364e35
这个问题发生的原因是在项目中使用了 ”Microsoft.WindowsAzure.Diagnostics.dll“， 这个 dll 可以在云服务(Azure Cloud Service)中使用，但是它与App Service不相容，不能在App Service中使用。否则，就不停的引发异常导致W3WP.EXE重启。
通过下面两方面来解决这个问题：
1）检查应用项目文件，移除全部 Microsoft.WindowsAzure.Diagnostics.dll 的引用
2）检查应用的 web.config 文件，如果存在 system.diagnostics 中含有 DiagnosticMonitorTraceListener 内容，则全部移除
<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>操作以上两步骤后，希望能解决因为Couldn’t find type for class Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener 问题。
参考资料
Preventing crashes due to DiagnosticMonitorTraceListener ：https://azure.github.io/AppService/2021/06/09/Apps-on-App-Services-crash-due-to-DiagnosticMonitorTraceListener.html
Proactive Crash Monitoring in Azure App Service ： https://azure.github.io/AppService/2021/03/01/Proactive-Crash-Monitoring-in-Azure-App-Service
