Why does my Wcf Duplex service gets in faulted state after first call to the service?

Question

What I am trying to do is have a wcf duplex service that multiple clients register to. When a client calls the service, the other clients are notified of the call.

Right now, I have a Silverlight app that calls a wcf duplex service. On the first call everything is working correctly including duplex communication. On the second call to the service I am getting a :

The communication object, System.ServiceModel.Channels.ClientPollingDuplexSessionChannel, cannot be used for communication because it is in the Faulted state.

My service has 2 different methods; RegisterClient and ReassignOwner. If I call the same method twice or both method once in any order I am still getting this error.

After researching on the subject I thought it might be a timeout problem. I checked what the default timeout value was and it's 10 minutes. I do both calls within the span of 2-3 minutes tops. I have also increased the Inactivity timeout and the Receive timeout to 4 hours just to be sure and I am still getting this problem.

Next, I thought my service might be generating an exception which would cause the client to go in a faulted state. To test this, I have put try/catch statements in the 2 methods of my service and ran the program in debug mode. I did not catch any exception. I also tried commenting out all the code from those 2 methods (so no exception can be generated) and just calling those 2 empty methods and I still got the exception.

By reading other related post here on SO, I decided to try WCF tracing. I enabled it in my web.config and set the switch value to Warning. I get 2 warnings:

Description Faulted System.ServiceModel.Channels.ServicePollingDuplexSessionChannel
Description Faulted System.ServiceModel.Channels.ServiceChannel

Here is how my service is defined in the code behind .svc.cs file:

[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Single, AutomaticSessionShutdown = false)] 
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class NotificationService : BaseService, INotificationDuplexService

In my service contract my methods both have the following attributes:

[OperationContract(AsyncPattern = true, IsOneWay = true,
                   Action = "http://www.abc.org/NotificationDuplex/INotificationDuplexService/MethodName")]

Both my methods are implemented in an async fashion with a Begin and an End method.

Here is how I invoke my methods

base.InvokeAsync(this.onBeginRegisterClientDelegate, new object[] {
                    id}, this.onEndRegisterClientDelegate, this.onRegisterClientCompletedDelegate, userState);

Anybody know why this is happening or have any clue to how I could continue trying to solve this problem ?

score 2 · Answer 1 · answered Mar 02 '11 at 14:09

2

Does your ServiceContract require a CallbackContract? If so, I suggest that you read about callback reentrancy here - it's a good description of how WCF can proactively fault your communication channels to prevent a deadlock when you are using callbacks, and what you should do to prevent it.

answered Mar 02 '11 at 14:09

PaulF

1,085
7
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My ServiceContract does indeed require a CallBackContract. I read the article you linked. I changed my ConcurencyMode to reentrant as sugested but it did not have any effect to the problem at hand. The article also mentioned another solution which I am currently investigating. – Gilles Mar 03 '11 at 13:55
Did you specify both `ServiceBehavior` and `CallbackBehavior` as `ConcurrencyMode.Reentrant`? – PaulF Mar 03 '11 at 16:07

score 1 · Answer 2 · answered Dec 08 '11 at 14:09

Another solution which I have seen referenced and I implemented myself is to set up a "heartbeat." I have my configuration set to MultipleMessagesPerPoll, and the service keeps running without a problem because I have the client pinging the server at least once every 9 seconds. That seemed to be a bit of a magic number -- after nine seconds the channel times out and goes into a faulted state. Just set up a thread to ping the service (using a method called ping or something) and the service can respond back to the client with a "pong."

Agree that this problem does not seem to be a problem on Chrome or other browsers.

score 0 · Accepted Answer · edited May 23 '17 at 12:10

Finally I have found the awnser in a similar question : Silverlight PollingDuplex InnerChannel faulted with multipleMessagesPerPoll (serverPollTimeout)

It seems there is a bug when you set the PollingDuplexHttpBinding to PollingDuplexMode.MultipleMessagesPerPoll and you run your application under IE 8 (other browsers aren't affected).

The solution is to put the PollingDuplexMode to SingleMessagePerPoll which is less performant but focntionnal in IE8.

Why does my Wcf Duplex service gets in faulted state after first call to the service?

3 Answers3