HttpListener BeginGetContext does not seem to handle more than 2 request simultaneously

Kunal · Dec 21, 2006

Hi Friends,

I'm trying to host a webservice that will receive/process multiple
client requests simultaneously. For this purpose, I wrote the following
code, but it does not seem to be handling more than two at a time. I
put in a few console prints and have also attached the output. Here it
goes -

public void serverStart() {

HttpListener _listener = new HttpListener();

_listener.Prefixes.Add(.......);

_listener.Start();

while (true)

ProcessRequest();

}

public void ProcessRequest()

{

Console.WriteLine("PR " + ++count); //count initialized to 0 in
beginning

IAsyncResult result = _listener.BeginGetContext(new AsyncCallback
ListenerCallback),this._listener);

result.AsyncWaitHandle.WaitOne();

}

protected void ListenerCallback(IAsyncResult result)

{

if (this._listener == null) return;

HttpListenerContext context = this._listener.EndGetContext(result);

Console.WriteLine("LC " + count);

this.ProcessRequest2(context);

}

public void ProcessRequest2(HttpListenerContext ctx)

{

Console.WriteLine("PR2 " + count);

string str = ctx.Request.HttpMethod;

HttpListenerWorkerRequest workerRequest =

new HttpListenerWorkerRequest(ctx,_virtualDir, _physicalDir,
_logCallback, _pxeb);

HttpRuntime.ProcessRequest(workerRequest);

}

The output this gives me looks like this -

PR 1
PR 2
LC 2
PR2 2
LC 2
PR2 3
PR 3
LC 3
PR2 4
PR 4
LC 4
PR2 5
PR 5
PR 6
LC 6
PR2 6
LC 6
PR2 7
PR 7
PR 8
LC 8
PR2 8
PR 9
LC 9
PR2 9
LC 9

Can someone point out what's happening ? The Microsoft documentation
does not say anything about the no. of connections this model can
handle or has a limit to. Any developers who have used this may please
enlighten me !

Thanks and Regards,

Kunal

Vadym Stetsyak · Dec 22, 2006

Hello, Kunal!

line "result.AsyncWaitHandle.WaitOne();"
blocks in ProcessRequest method thus breaking the async execution.

Try to comment that line an repeat your tests.

You wrote on 21 Dec 2006 14:41:15 -0800:

K> Hi Friends,

K> I'm trying to host a webservice that will receive/process multiple
K> client requests simultaneously. For this purpose, I wrote the
K> following
K> code, but it does not seem to be handling more than two at a time. I
K> put in a few console prints and have also attached the output. Here
K> it
K> goes -

K> public void serverStart() {

K> HttpListener _listener = new HttpListener();

K> _listener.Prefixes.Add(.......);

K> _listener.Start();

K> while (true)

K> ProcessRequest();

K> }

K> public void ProcessRequest()

K> {

K> Console.WriteLine("PR " + ++count); //count initialized to 0 in
K> beginning

K> IAsyncResult result = _listener.BeginGetContext(new AsyncCallback
K> ListenerCallback),this._listener);

K> result.AsyncWaitHandle.WaitOne();

K> }

K> protected void ListenerCallback(IAsyncResult result)

K> {

K> if (this._listener == null) return;

K> HttpListenerContext context =
K> this._listener.EndGetContext(result);

K> Console.WriteLine("LC " + count);

K> this.ProcessRequest2(context);

K> }

K> public void ProcessRequest2(HttpListenerContext ctx)

K> {

K> Console.WriteLine("PR2 " + count);

K> string str = ctx.Request.HttpMethod;

K> HttpListenerWorkerRequest workerRequest =

K> new HttpListenerWorkerRequest(ctx,_virtualDir, _physicalDir,
K> _logCallback, _pxeb);

K> HttpRuntime.ProcessRequest(workerRequest);

K> }

K> The output this gives me looks like this -

K> PR 1
K> PR 2
K> LC 2
K> PR2 2
K> LC 2
K> PR2 3
K> PR 3
K> LC 3
K> PR2 4
K> PR 4
K> LC 4
K> PR2 5
K> PR 5
K> PR 6
K> LC 6
K> PR2 6
K> LC 6
K> PR2 7
K> PR 7
K> PR 8
K> LC 8
K> PR2 8
K> PR 9
K> LC 9
K> PR2 9
K> LC 9

K> Can someone point out what's happening ? The Microsoft documentation
K> does not say anything about the no. of connections this model can
K> handle or has a limit to. Any developers who have used this may
K> please
K> enlighten me !

K> Thanks and Regards,

K> Kunal

With best regards, Vadym Stetsyak.
Blog: http://vadmyst.blogspot.com

Kunal · Dec 27, 2006

Hi Vadym,

Thanks for your suggestion. This change seems to work for me.
However, what is the best way of determining how many concurrent
connections
my server is handling at any instant ? And how to make sure any
connections
are not being refused or dropped ?

In my code, there's one change I tried but that threw an exception.
Instead of
calling ProcessRequest in the infinite while loop, I call it just once.
Then within
the ListenerCallback, I setup a new BeginGetContext just after the call
to
EndGetContext, to set up a loop. But I got an exception related to a
thread
exit at the time of call.

Do you think the current while loop is just fine and I need not try out
this new
way ? I saw this implementation technique somewhere and was curious to
try
it out.

Thanks for all your time,

Regards,
Kunal

Kunal · Dec 29, 2006

Hi Vadym,

After the change you suggested, my server ran just fine and seemed to
be aceepting/processing multiple requests simultaneously. However,
after a few hours of operation (when there are about 15 clients coming
in per second) the
server crashed with the followin exception -

System.OutOfMemoryException: Exception of type
'System.OutOfMemoryException' was thrown.

Server stack trace:
at System.Net.RequestContextBase.SetBuffer(Int32 size)
at System.Net.AsyncRequestContext.Allocate(UInt32 size)
at System.Net.HttpListener.BeginGetContext(AsyncCallback callback,
Object state)
at HttpListenerLibrary.HttpListenerWrapper.ProcessRequest() in
C:\StarTeam\easycare\Software\Release\SimulatorsDev\AcsSim\HttpListenerLibrary\HttpListenerLibrary.cs:line
260
at
System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr
md, Object[] args, Object server, Int32 methodPtr, Boolean
fExecuteInContext, Object[]& outArgs)
at
System.Runtime.Remoting.Messaging.StackBuilderSink.PrivateProcessMessage(RuntimeMethodHandle
md, Object[] args, Object server, Int32 methodPtr, Boolean
fExecuteInContext, Object[]& outArgs)
at
System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage
msg, Int32 methodPtr, Boolean fExecuteInContext)

Exception rethrown at [0]:
at
System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage
reqMsg, IMessage retMsg)
at
System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData&
msgData, Int32 type)
at HttpListenerLibrary.HttpListenerWrapper.ProcessRequest()
at HttpListenerLibrary.HttpListenerController.Pump() in
C:\StarTeam\easycare\Software\Release\SimulatorsDev\AcsSim\HttpListenerLibrary\HttpListenerLibrary.cs:line
166

There was this event also in the event log -

Exception information:
Exception type: OutOfMemoryException
Exception message: Exception of type 'System.OutOfMemoryException'
was thrown.

Thread information:
Thread ID: 7
Thread account name: CPEPR1\Administrator
Is impersonating: False
Stack trace: at System.Web.HttpRequest.GetEntireRawContent()
at System.Web.HttpRequest.get_InputStream()
at System.Web.Services.Protocols.SoapServerProtocol.Initialize()
at System.Web.Services.Protocols.ServerProtocolFactory.Create(Type
type, HttpContext context, HttpRequest request, HttpResponse response,
Boolean& abortProcessing)
at
System.Web.Services.Protocols.WebServiceHandlerFactory.CoreGetHandler(Type
type, HttpContext context, HttpRequest request, HttpResponse response)
at
System.Web.Services.Protocols.WebServiceHandlerFactory.GetHandler(HttpContext
context, String verb, String url, String filePath)
at System.Web.HttpApplication.MapHttpHandler(HttpContext context,
String requestType, VirtualPath path, String pathTranslated, Boolean
useAppConfig)
at
System.Web.HttpApplication.MapHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step,
Boolean& completedSynchronously)

Do you think the server is not getting enough memory to process further
requests ? from the exception it looks like while trying to allocate
buffers for storing the incoming request it fails. But this is within
the stack area. How can this be debugged ? How can I find out what are
the resources occupying memory at that time ?

Thanks,
Kunal

Vadym Stetsyak · Jan 3, 2007

Hello, Kunal!

I think there is a memory leak some where in your code.

Have a look at (
http://msdn.microsoft.com/msdnmag/issues/06/11/CLRInsideOut/default.aspx?loc=en )
to do the memory issue investigation.

You wrote on 29 Dec 2006 12:53:40 -0800:

K> Hi Vadym,

K> After the change you suggested, my server ran just fine and seemed to
K> be aceepting/processing multiple requests simultaneously. However,
K> after a few hours of operation (when there are about 15 clients
K> coming
K> in per second) the
K> server crashed with the followin exception -

K> System.OutOfMemoryException: Exception of type
K> 'System.OutOfMemoryException' was thrown.

K> Server stack trace:
K> at System.Net.RequestContextBase.SetBuffer(Int32 size)
K> at System.Net.AsyncRequestContext.Allocate(UInt32 size)
K> at System.Net.HttpListener.BeginGetContext(AsyncCallback callback,
K> Object state)
K> at HttpListenerLibrary.HttpListenerWrapper.ProcessRequest() in
K> C:\StarTeam\easycare\Software\Release\SimulatorsDev\AcsSim\
K> HttpListenerLibrary\HttpListenerLibrary.cs:line
K> 260
K> at
K> System.Runtime.Remoting.Messaging.StackBuilderSink._
K> PrivateProcessMessage(IntPtr
K> md, Object[] args, Object server, Int32 methodPtr, Boolean
K> fExecuteInContext, Object[]& outArgs)
K> at
K> System.Runtime.Remoting.Messaging.StackBuilderSink.
K> PrivateProcessMessage(RuntimeMethodHandle
K> md, Object[] args, Object server, Int32 methodPtr, Boolean
K> fExecuteInContext, Object[]& outArgs)
K> at
K> System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(
K> IMessage
K> msg, Int32 methodPtr, Boolean fExecuteInContext)

K> Exception rethrown at [0]:
K> at
K> System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(
K> IMessage
K> reqMsg, IMessage retMsg)
K> at
K> System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData&
K> msgData, Int32 type)
K> at HttpListenerLibrary.HttpListenerWrapper.ProcessRequest()
K> at HttpListenerLibrary.HttpListenerController.Pump() in
K> C:\StarTeam\easycare\Software\Release\SimulatorsDev\AcsSim\
K> HttpListenerLibrary\HttpListenerLibrary.cs:line
K> 166

K> There was this event also in the event log -

K> Exception information:
K> Exception type: OutOfMemoryException
K> Exception message: Exception of type
K> 'System.OutOfMemoryException'
K> was thrown.

K> Thread information:
K> Thread ID: 7
K> Thread account name: CPEPR1\Administrator
K> Is impersonating: False
K> Stack trace: at System.Web.HttpRequest.GetEntireRawContent()
K> at System.Web.HttpRequest.get_InputStream()
K> at System.Web.Services.Protocols.SoapServerProtocol.Initialize()
K> at System.Web.Services.Protocols.ServerProtocolFactory.Create(Type
K> type, HttpContext context, HttpRequest request, HttpResponse
K> response,
K> Boolean& abortProcessing)
K> at
K> System.Web.Services.Protocols.WebServiceHandlerFactory.CoreGetHandler(
K> Type
K> type, HttpContext context, HttpRequest request, HttpResponse
K> response)
K> at
K> System.Web.Services.Protocols.WebServiceHandlerFactory.GetHandler(
K> HttpContext
K> context, String verb, String url, String filePath)
K> at System.Web.HttpApplication.MapHttpHandler(HttpContext context,
K> String requestType, VirtualPath path, String pathTranslated, Boolean
K> useAppConfig)
K> at
K> System.Web.HttpApplication.MapHandlerExecutionStep.System.Web.
K> HttpApplication.IExecutionStep.Execute()
K> at System.Web.HttpApplication.ExecuteStep(IExecutionStep step,
K> Boolean& completedSynchronously)

K> Do you think the server is not getting enough memory to process
K> further
K> requests ? from the exception it looks like while trying to allocate
K> buffers for storing the incoming request it fails. But this is within
K> the stack area. How can this be debugged ? How can I find out what
K> are
K> the resources occupying memory at that time ?

K> Thanks,
K> Kunal

With best regards, Vadym Stetsyak.
Blog: http://vadmyst.blogspot.com

ssmilind · Dec 6, 2011

Hello, Kunal!

Did you get any solution for this? I am facing the same issue.

Regards,
ssmilind