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[this has previously been posted buy raymondr at Nullreference exception in
Asynchronous webservice call (.Net 2.0)]


Hi,

First a brief description of out application:
We have a webapplication which calls a couple of webservices during one
request (postback). These calls to the webservices are made concurrent using
asynchronous webservices calls. The number of webservices called concurrent
is between 1 and 18.
The webservice calls are made using SSL with a X509 clientcertificate.
The application is underhigh load

The problem:
After migration to the .Net Framework 2.0 we once in a while get a
nullreferenceexception during the asynchronous call. The exception seems to
occur somewhere in the framework. It only occurs on our production
environment.

Maybe someone got a clue? See the stacktrace below

The stacktrace is :
NullreferenceException
at
System.Web.Services.Protocols.WebClientProtocol.Re adAsyncResponse(WebClientAsyncResult client)
at
System.Web.Services.Protocols.WebClientProtocol.Ge tResponseAsyncCallback(IAsyncResult asyncResult)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
at System.Net.ContextAwareResult.CompleteCallback(Obj ect state)
at System.Threading.ExecutionContext.runTryCode(Objec t userData)
at
System.Runtime.CompilerServices.RuntimeHelpers.Exe cuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
at System.Threading.ExecutionContext.RunInternal(Exec utionContext
executionContext, ContextCallback callback, Object state)
at System.Threading.ExecutionContext.Run(ExecutionCon text
executionContext, ContextCallback callback, Object state)
at System.Net.ContextAwareResult.Complete(IntPtr userToken)
at System.Net.LazyAsyncResult.ProtectedInvokeCallback (Object result,
IntPtr userToken)
at System.Net.HttpWebRequest.SetResponse(Exception E)
at System.Net.HttpWebRequest.CheckWriteSideResponsePr ocessing()
at System.Net.ConnectStream.ProcessWriteCallDone(Conn ectionReturnResult
returnResult)
at System.Net.HttpWebRequest.WriteCallDone(ConnectStr eam stream,
ConnectionReturnResult returnResult)
at System.Net.ConnectStream.CallDone(ConnectionReturn Result returnResult)
at System.Net.ConnectStream.ResubmitWrite(ConnectStre am oldStream,
Boolean suppressWrite)
at System.Net.HttpWebRequest.EndWriteHeaders_Part2()
at System.Net.HttpWebRequest.EndWriteHeaders(Boolean async)
at System.Net.HttpWebRequest.WriteHeadersCallback(Web ExceptionStatus
errorStatus, ConnectStream stream, Boolean async)
at System.Net.ConnectStream.WriteHeadersCallback(IAsy ncResult ar)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
at System.Net.LazyAsyncResult.ProtectedInvokeCallback (Object result,
IntPtr userToken)
at System.Net.Security._SslStream.StartWriting(Byte[] buffer, Int32
offset, Int32 count, AsyncProtocolRequest asyncRequest)
at System.Net.Security._SslStream.WriteCallback(IAsyn cResult
transportResult)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
at System.Net.ContextAwareResult.CompleteCallback(Obj ect state)
at System.Threading.ExecutionContext.runTryCode(Objec t userData)
at
System.Runtime.CompilerServices.RuntimeHelpers.Exe cuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
at System.Threading.ExecutionContext.RunInternal(Exec utionContext
executionContext, ContextCallback callback, Object state)
at System.Threading.ExecutionContext.Run(ExecutionCon text
executionContext, ContextCallback callback, Object state)
at System.Net.ContextAwareResult.Complete(IntPtr userToken)
at System.Net.LazyAsyncResult.ProtectedInvokeCallback (Object result,
IntPtr userToken)
at
System.Net.Sockets.BaseOverlappedAsyncResult.Compl etionPortCallback(UInt32
errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
at
System.Threading._IOCompletionCallback.PerformIOCo mpletionCallback(UInt32
errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)

Best Regards,
Raymond

www.VECOZO.nl

Hello Raymond,

I never saw similiar issue reported before. Did the exception always occur
with one web service\web method, or totally random? Can it be repeated
after you find one in the system?

Regards,

Luke Zhang
Microsoft Online Community Lead

==================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
==================================================

(This posting is provided "AS IS", with no warranties, and confers no
rights.)

You could try and register the AppDomain.UnhandledException and capture the
NullReference exception to see if it gives you any more clues.

Also ensure when you call the End method of the web service proxy class, the
IAsyncResult object is not null.

Regards
Simon.

<> wrote in message
news:74219720-52B1-403E-B31C-...
> [this has previously been posted buy raymondr at Nullreference exception
> in
> Asynchronous webservice call (.Net 2.0)]
>
>
> Hi,
>
> First a brief description of out application:
> We have a webapplication which calls a couple of webservices during one
> request (postback). These calls to the webservices are made concurrent
> using
> asynchronous webservices calls. The number of webservices called
> concurrent
> is between 1 and 18.
> The webservice calls are made using SSL with a X509 clientcertificate.
> The application is underhigh load
>
> The problem:
> After migration to the .Net Framework 2.0 we once in a while get a
> nullreferenceexception during the asynchronous call. The exception seems
> to
> occur somewhere in the framework. It only occurs on our production
> environment.
>
> Maybe someone got a clue? See the stacktrace below
>
> The stacktrace is :
> NullreferenceException
> at
> System.Web.Services.Protocols.WebClientProtocol.Re adAsyncResponse(WebClientAsyncResult
> client)
> at
> System.Web.Services.Protocols.WebClientProtocol.Ge tResponseAsyncCallback(IAsyncResult
> asyncResult)
> at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
> at System.Net.ContextAwareResult.CompleteCallback(Obj ect state)
> at System.Threading.ExecutionContext.runTryCode(Objec t userData)
> at
> System.Runtime.CompilerServices.RuntimeHelpers.Exe cuteCodeWithGuaranteedCleanup(TryCode
> code, CleanupCode backoutCode, Object userData)
> at System.Threading.ExecutionContext.RunInternal(Exec utionContext
> executionContext, ContextCallback callback, Object state)
> at System.Threading.ExecutionContext.Run(ExecutionCon text
> executionContext, ContextCallback callback, Object state)
> at System.Net.ContextAwareResult.Complete(IntPtr userToken)
> at System.Net.LazyAsyncResult.ProtectedInvokeCallback (Object result,
> IntPtr userToken)
> at System.Net.HttpWebRequest.SetResponse(Exception E)
> at System.Net.HttpWebRequest.CheckWriteSideResponsePr ocessing()
> at System.Net.ConnectStream.ProcessWriteCallDone(Conn ectionReturnResult
> returnResult)
> at System.Net.HttpWebRequest.WriteCallDone(ConnectStr eam stream,
> ConnectionReturnResult returnResult)
> at System.Net.ConnectStream.CallDone(ConnectionReturn Result
> returnResult)
> at System.Net.ConnectStream.ResubmitWrite(ConnectStre am oldStream,
> Boolean suppressWrite)
> at System.Net.HttpWebRequest.EndWriteHeaders_Part2()
> at System.Net.HttpWebRequest.EndWriteHeaders(Boolean async)
> at System.Net.HttpWebRequest.WriteHeadersCallback(Web ExceptionStatus
> errorStatus, ConnectStream stream, Boolean async)
> at System.Net.ConnectStream.WriteHeadersCallback(IAsy ncResult ar)
> at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
> at System.Net.LazyAsyncResult.ProtectedInvokeCallback (Object result,
> IntPtr userToken)
> at System.Net.Security._SslStream.StartWriting(Byte[] buffer, Int32
> offset, Int32 count, AsyncProtocolRequest asyncRequest)
> at System.Net.Security._SslStream.WriteCallback(IAsyn cResult
> transportResult)
> at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
> at System.Net.ContextAwareResult.CompleteCallback(Obj ect state)
> at System.Threading.ExecutionContext.runTryCode(Objec t userData)
> at
> System.Runtime.CompilerServices.RuntimeHelpers.Exe cuteCodeWithGuaranteedCleanup(TryCode
> code, CleanupCode backoutCode, Object userData)
> at System.Threading.ExecutionContext.RunInternal(Exec utionContext
> executionContext, ContextCallback callback, Object state)
> at System.Threading.ExecutionContext.Run(ExecutionCon text
> executionContext, ContextCallback callback, Object state)
> at System.Net.ContextAwareResult.Complete(IntPtr userToken)
> at System.Net.LazyAsyncResult.ProtectedInvokeCallback (Object result,
> IntPtr userToken)
> at
> System.Net.Sockets.BaseOverlappedAsyncResult.Compl etionPortCallback(UInt32
> errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
> at
> System.Threading._IOCompletionCallback.PerformIOCo mpletionCallback(UInt32
> errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)
>
> Best Regards,
> Raymond
>
> www.VECOZO.nl
>

Hello Luke,

We concurrently call different webservices endpoints which have implemented
the same wsdl. So it's always the same method but not the same webservice.
If a webservice doesn't respond in the time given, the asynchronous call is
aborted and the instance of the proxy class is disposed.

We have multiple servers in our cluster. It happens on all multiple servers.
The total number of requests made by our servers to the other webservers is
between 10.000 and 150.000 per hour.

Best Regards,

Raymond
"Luke Zhang [MSFT]" wrote:

> Hello Raymond,
>
> I never saw similiar issue reported before. Did the exception always occur
> with one web service\web method, or totally random? Can it be repeated
> after you find one in the system?
>
> Regards,
>
> Luke Zhang
> Microsoft Online Community Lead
>
> ==================================================
> When responding to posts, please "Reply to Group" via your newsreader so
> that others may learn and benefit from your issue.
> ==================================================
>
> (This posting is provided "AS IS", with no warranties, and confers no
> rights.)
>
>

Hell Raymond,

You may implement some exception handling code (like
AppDomain.UnhandledException as Simon suggested), record the server and web
method it happened with. And check if the server is connectable at that
time, or recall the web method, will it always failed if one exception
occurred?

Regards,

Luke Zhang
Microsoft Online Community Lead

==================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
==================================================

(This posting is provided "AS IS", with no warranties, and confers no
rights.)

Hello Luke,

The stacktrace in the first message is the Exception caught by the
AppDomain.UnhandledException event. The IAsyncResult object is not null, the
exception is not thrown in the End method of the webservice call.
It occurs somewhere in the framework when handling the asynchronous call. In
the exception is also not possible to detect which webservice is causing the
error.

Maybe this also did occure in the 1.1 framework but we didn't notice it
because we didn't handle the uncaught exceptions. We changed the
aspnet.config with legacyUnhandledExceptionPolicy enabled="true" so our
worker process isn't recycled when this occurs (it happens approx. each 5
minutes causing time out to our clients)

I think there's a bug in handling the asynchronous result. If something went
wrong with the webservice called I would expect this exception would be
caught and thrown when the End method of the webservice is called. The call
to the End Method is surrounded by a try/catch.
The way it's working now the exception is thrown in a separate thread
managed by the framework causing my application pool to crash.

Best regards,

Raymond Roelands
"Luke Zhang [MSFT]" wrote:

> Hell Raymond,
>
> You may implement some exception handling code (like
> AppDomain.UnhandledException as Simon suggested), record the server and web
> method it happened with. And check if the server is connectable at that
> time, or recall the web method, will it always failed if one exception
> occurred?
>
> Regards,
>
> Luke Zhang
> Microsoft Online Community Lead
>
> ==================================================
> When responding to posts, please "Reply to Group" via your newsreader so
> that others may learn and benefit from your issue.
> ==================================================
>
> (This posting is provided "AS IS", with no warranties, and confers no
> rights.)
>
>