WCF not properly cleaning up pending secure conversations

Question

Hi,

I recently received an HTTP 500 saying "There are too many pending secure conversations on the server."

A pending secure conversation should be one that has been established but not used by an operation call.

However, even if a client closes its channel/client properly, the pending conversions is not cleaned up and the server goes down eventually.

The following sample demonstrates this. It will crash a standard "Hello world!" service created by the Visual Studio template.

            while(true)

            {

                Console.WriteLine("OPEN");



                var client = new ServiceReference2.Service2Client();


                client.Open();


                // As soon as I call the DoWork operation here, the service stays healthy.


                client.Close();

            }

Someone sharing the opniniion that this is a WCF f*** up? Or am I missing something?

Thanks,
Alex

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Alex

Answer 1

Additional question:

The default limit for those pending sessions is 128. Which is pretty low in my opinion.

Imaging an intranet scenario and a new client component gets deployed. Certainly I would like to survive the event of a buggy client being shipped. I would tend to set this value to pretty high number and hope that the cleanup timeout catches up quickly enough. Let's say more like 65k. Memory consumption wouldn't be the problem.

Is there a severe performance penalty in increasing this value? Or what are other reasons that this limit is so low?

Cheers,
Alex

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Alex

Answer 2

Hi,

I guess you need to up your maxPendingSessions. Are you using wsHttpBinding?

Answer 3

Yes, I do. That's my second post about why this value is so low by default and what performance impact is has.

However, as I am explicitly closing the client in my test code, the problem shouldn't occur at all.

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Alex

Answer 4

Hi,

You probably need to create a custom bindings to increase the maxPendingSessions property value, see the discussion here:

http://www.dotnetmonster.com/Uwe/Forum.aspx/dotnet-web-services/5594/Too-many-pending-secure-conversations

Thanks
Binze

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Answer 5

Hi Binze,

thanks for your reply!

However, I don't agree with that article you reference. It says " The default number of secure connections allowed is 128 on a 2 minute timeout". Of course, a service does allow more then 128 secure connections/conversations per two minutes.

It also doesn't answer the questions on the impact that a change on the maxPendingSessions setting has:

>> Is there a severe performance penalty in increasing this value? Or what are other reasons that this limit is so low?

Do you have further information more precise information on that?

Thanks in advance,
Alex

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Alex

Answer 6

Hi,

The maxPendingSessions is a property of LocalServiceSecuritySettings of SymmetricSecurityBindingElement, you can change this value programmatically through :

            WSHttpBinding b = new WSHttpBinding();

            // Get the binding element collection.
            BindingElementCollection bec = b.CreateBindingElements();

            // Find the SymmetricSecurityBindingElement in the colllection.
            // Important: Cast to the SymmetricSecurityBindingElement when using the Find
            // method.
            SymmetricSecurityBindingElement sbe = (SymmetricSecurityBindingElement)bec.Find<SecurityBindingElement>();

            LocalServiceSecuritySettings lss = sbe.LocalServiceSettings;
            lss.MaxPendingSessions = 500;

Then pass the binding to your service endpoint or the alternative way is create a custom binding with this SymmetricSecurityBindingElement and change the MaxPendingSessions value to appropriated number, then register this custom binding to your service endpoint.

<customBinding>
        <binding name="cutom">
          <security>
            <localServiceSettings maxPendingSessions="500"/>
          </security>
        </binding>
      </customBinding>

Thanks
Binze

---

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Answer 7

Thanks Binzen for the comprehesinve description regarding the workaround!

Alex

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Alex

Answer 8

Microsoft confirmed this to be a known issue in .NET 3 framework.

https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=499859&wa=wsignin1.0

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Alex

Answer 9

This is NOT FIXED!!!!!!!

I spent 4 days investigating this in .NET 4.0 to realise it is NOT fixed.

Repro is easy:

ChannelFactory<IFoo> foo = new ChannelFactory<IFoo>("binding");
foo.Open();
foo.Close();

After 128 calls you get the error

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Ali Kheyrollahi