.NET 4.8应用DiagnosticSourceEventSource参数不匹配致重复日志及性能下降

初始现象 #

在基于.NET 4.8的ASP.NET Web应用（重度使用Autofac）中出现严重性能下降，同时在VS2020的Debug Output中，每个HTTP请求都会生成上千条重复警告：

The parameters to the Event method do not match the parameters to the WriteEvent method. This may cause the event to be displayed incorrectly.

• 该问题并非ASP.NET独有，Windows WPF应用中也会出现
• 尝试禁用Task Parallel Library的ETW EventSource后无效果
• 无关联异常，仅在调试器下影响性能，捕获性能数据时问题消失

问题定位（更新1） #

通过单步调试，发现警告来自Autofac（v6.2）解析实例时的DiagnosticListener日志逻辑，调用堆栈如下：

EventSource.LogEventArgsMismatches() at EventSource.cs:line 1,036
EventSource.WriteEventVarargs() at EventSource.cs:line 935
EventSource.WriteEvent()
DiagnosticSourceEventSource.Event()
DiagnosticSourceEventSource.FilterAndTransform.<>c__DisplayClass2_1.<.ctor>b__2()
DiagnosticSourceEventSource.CallbackObserver<KeyValuePair<string, object>>.OnNext()
DiagnosticListener.Write()
DiagnosticSourceExtensions.OperationStart()
ResolveOperation.ExecuteOperation()
ResolveOperation.Execute()

当Autofac通过IContainer.DiagnosticSource记录解析调用时，若DiagnosticListener被订阅则会触发警告。触发订阅的堆栈如下：

DiagnosticListener.SubscribeInternal() at DiagnosticListener.cs:line 179
DiagnosticListener.Subscribe() at DiagnosticListener.cs:line 49
HttpHandlerDiagnosticListener.Subscribe()
DiagnosticSourceEventSource.FilterAndTransform.<>c__DisplayClass2_0.<.ctor>b__0()
DiagnosticSourceEventSource.CallbackObserver.OnNext() at DiagnosticSourceEventSource.cs:line 618
DiagnosticListener.AllListenerObservable.Subscribe()
new DiagnosticSourceEventSource.FilterAndTransform() at DiagnosticSourceEventSource.cs:line 316
DiagnosticSourceEventSource.FilterAndTransform.CreateFilterAndTransformList() at DiagnosticSourceEventSource.cs:line 216
DiagnosticSourceEventSource.OnEventCommand() at DiagnosticSourceEventSource.cs:line 155
EventSource.DoCommand() at EventSource.cs:line 1,462
EventSource.SendCommand() at EventSource.cs:line 1,383
EventSource.OverideEventProvider.OnControllerCommand() at EventSource.cs:line 2,950
EventProvider.EtwEnableCallBack() at EventProvider.cs:line 205

疑问：是什么触发了EtwEnableCallback，是否有相关配置？

根因确认（更新2） #

进一步调试发现，这是DiagnosticSourceEventSource的bug，而非Autofac问题——所有经过DiagnosticSourceEventSource的事件都会生成相同警告，例如HttpClientHandler的调用堆栈：

EventSource.WriteEventVarargs() at EventSource.cs:line 936
EventSource.WriteEvent() at EventSource.cs:line 696
DiagnosticSourceEventSource.Event()
DiagnosticSourceEventSource.FilterAndTransform.<>c__DisplayClass2_1.<.ctor>b__2()
DiagnosticSourceEventSource.CallbackObserver<KeyValuePair<string, object>>.OnNext()
DiagnosticListener.Write()
HttpHandlerDiagnosticListener.RaiseResponseEvent()
HttpHandlerDiagnosticListener.HttpWebRequestArrayList.RemoveAt()
Connection.ReadStartNextRequest()
ConnectStream.CallDone()
ConnectStream.EndReadWithoutValidation()
ConnectStream.EndRead()
HttpClientHandler.WebExceptionWrapperStream.EndRead()
StreamToStreamCopy.BufferReadCallback()
LazyAsyncResult.Complete()
ContextAwareResult.CompleteCallback()
ExecutionContext.RunInternal()
ExecutionContext.Run()
ExecutionContext.Run()
ContextAwareResult.Complete()
LazyAsyncResult.ProtectedInvokeCallback()
BaseOverlappedAsyncResult.CompletionPortCallback()
_IOCompletionCallback.PerformIOCompletionCallback()
[Native to Managed Transition]

注：Autofac是项目中唯一依赖System.Diagnostics.DiagnosticSource的包（已通过project.assets.json验证）。

目前找到的临时解决方案是通过反射释放DiagnosticSourceEventSource的EventSource实例，但该方法存在未知副作用：

var diagnosticsLib = Assembly.Load("System.Diagnostics.DiagnosticSource, Version=4.0.5.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51");
var diagnosticSourceEventSourceType = diagnosticsLib.GetType("System.Diagnostics.DiagnosticSourceEventSource");
object diagnosticSourceEventSource = diagnosticSourceEventSourceType.InvokeMember("Logger", BindingFlags.Static | BindingFlags.GetField | BindingFlags.Public, null, null, null);
        
if (diagnosticSourceEventSource is IDisposable disposable)
    disposable.Dispose();   

已知修复情况（更新3） #

该问题在.NET官方仓库已有相关记录，且已在.NET 5的System.Diagnostics.Tracing.EventSource中修复，但由于.NET Framework中该类属于mscorlib.dll，无法通过NuGet包更新，且修复未移植到.NET Framework，导致无法直接解决。

内容的提问来源于stack exchange，提问作者karmasponge