【茶包射手日記】w3wp.exe連續暴斃案

測試台ASP.NET 4.0網站在程式更新後，每隔一兩分鐘便出現Session遺失狀況。進行檢查，發現事件檢視器在每次Session遺失的當下，會連續出現三個錯誤事件:

** Event ID 1325 Source: ASP.NET 4.0.30319.0 **

Exception: System.Runtime.Serialization.SerializationException

Message: Type 'System.ServiceModel.Dispatcher.NetDispatcherFaultException' in Assembly 'System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' is not marked as serializable.

StackTrace:    at System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter, SerializationBinder binder)
   at System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Write(WriteObjectInfo objectInfo, NameInfo memberNameInfo, NameInfo typeNameInfo)
   at System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck)
   at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck)
   at System.Runtime.Remoting.Channels.CrossAppDomainSerializer.SerializeObject(Object obj, MemoryStream stm)
   at System.AppDomain.Serialize(Object o)
   at System.AppDomain.MarshalObject(Object o)

** Event ID 1026 Source: .NET Runtime **

Application: w3wp.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.Reflection.TargetInvocationException
Stack:
   at System.RuntimeMethodHandle._InvokeMethodFast(System.IRuntimeMethodInfo, System.Object, System.Object[], System.SignatureStruct ByRef, System.Reflection.MethodAttributes, System.RuntimeType)
   at System.RuntimeMethodHandle.InvokeMethodFast(System.IRuntimeMethodInfo, System.Object, System.Object[], System.Signature, System.Reflection.MethodAttributes, System.RuntimeType)
   at System.Reflection.RuntimeMethodInfo.Invoke(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo, Boolean)
   at System.Delegate.DynamicInvokeImpl(System.Object[])
   at Yuanta.Utility.Cache.CacheManagerInfo.SetCache()
   at System.Threading.ExecutionContext.runTryCode(System.Object)
   at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode, CleanupCode, System.Object)
   at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
   at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
   at System.Threading.ThreadHelper.ThreadStart()

** Event ID 1000 Source: Application Error **

Faulting application name: w3wp.exe, version: 7.5.7601.17514, time stamp: 0x4ce7afa2
Faulting module name: KERNELBASE.dll, version: 6.1.7601.17651, time stamp: 0x4e21213c
Exception code: 0xe0434352
Fault offset: 0x000000000000cacd
Faulting process id: 0x1330
Faulting application start time: 0x01ccfcc575dce2b0
Faulting application path: c:\windows\system32\inetsrv\w3wp.exe
Faulting module path: C:\Windows\system32\KERNELBASE.dll
Report Id: 58b53cc8-68b9-11e1-a5d0-005056ac0022

依訊息內容，可解讀為ASP.NET Process在試圖序列化NetDispatcherFaultException時，因該Exception物件未標註為Serializable出錯，但因未適當處理Exception導致整個w3wp.exe Process掛掉，而保存其中的Session資料也跟著消失；後續網頁存取時，IIS會重新建立w3wp.exe，功能依舊，但已無原先保存的Session內容，如此足以解釋Session遺失現象。

看到System.Runtime.Remoting.Channels.CrossAppDomainSerializer字眼，聯想到可能與ASP.NET網站在一啟動後就會呼叫另一台WCF服務取得資料有關(呼叫WCF算是Remoting、也一定會用到序列化)，而追查發現問題發生在今天更新ASP.NET程式後，而WCF並未更新換版，試著重新編譯部署新版WCF後，問題消失。

因測試期限壓力，沒再繼續挖掘這椿"WCF謀殺ASP.NET案件"的具體手法，只簡單歸納結論:

"ASP.NET 4.0在呼叫WCF的底層程式中似乎存在Bug，在遇到特定WCF錯誤時，會因NetDispatcherFaultException無法序列化而導致w3wp.exe整個Crash"

先筆記下來，未來遇到類似情境再併案調查。