WCF Service Memory Leaks

Question

I have a very small wcf service hosted in a console app.

[ServiceContract]
public interface IService1
{
    [OperationContract]
    void DoService();
}

[ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall)]
public class Service1 : IService1
{
    public void DoService()
    {

    }
}

and its being called as

using (ServiceReference1.Service1Client client = new ServiceReference1.Service1Client())
{
    client.DoService(new DoServiceRequest());
    client.Close();
} 

Please remember that service is published on basicHttpBindings.

Problem

Now when i performed above client code in a loop of 1000 i found big difference between "All Heap bytes" and "Private Bytes" performance counters (i used .net memory profiler). After investigation i found some of the objects are not properly disposed following are the list of those objects (1000 undisposed instance were found --> equals to the client calls)

(namespace for all of them is System.ServiceModel.Channels)

HttpOutput.ListenerResponseHttpOutput.ListenerResponseOutputStream
BodyWriterMessage
BufferedMessage
HttpRequestContext.ListenerHttpContext.ListenerContextHttpInput.ListenerContextInputStream
HttpRequestContext.ListenerHttpContext 

Questions Why do we have lot of undisposed objects and how to control them.

Please Help

Answer 1

You're requesting a new instance per call (InstanceContextMode=InstanceContextMode.PerCall). If there is no GC happening in the 1000 calls then the service instances will be uncollected. WCF requires you implement IDisposable

From MSDN : Discover Mighty Instance Management Techniques For Developing WCF Apps

Per-Call Services Per-call services are the Windows Communication Foundation default instantiation mode. When the service type is configured for per-call activation, a service instance, a common language runtime (CLR) object, exists only while a client call is in progress. Every client request gets a new dedicated service instance. Figure 2 illustrates how this single-call activation works.

_{(source: microsoft.com)}

1. The client calls the proxy and the proxy forwards the call to the service.
2. Windows Communication Foundation creates a service instance and calls the method on it.
3. After the method call returns, if the object implements IDisposable, then Windows Communication Foundation calls IDisposable.Dispose on it.

Answer 2

Did you by any chance enable performance counters? Like below?

<system.serviceModel>
  <diagnostics performanceCounters="All" />
  ..
</system.serviceModel>

In paragraph "Increasing Memory Size for Performance Counters", from this link: http://msdn.microsoft.com/en-us/library/ms735098.aspx

there's mention of a "rogue" Private Bytes count when WCF performance counters are enabled. Changing it into ServiceOnly or completely disabling it (Off) may do the trick.