Why WCF custom ServiceHostFactory getting called every time? - wcf

Question

I have a WCF service (hosted in IIS 7.5) which has SVC file less activation using the following
<serviceHostingEnvironment>
<serviceActivations>
<add factory="String"
service="String"/>
</serviceActivations>
</serviceHostingEnvironment>
I am using a custom host factory not the default one.
And the service is WSTrustServiceContract. Now if you see the declaration of this class
[ServiceBehaviorAttribute(Name = "SecurityTokenService", Namespace = "http://schemas.microsoft.com/ws/2008/06/identity/securitytokenservice",
InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)]
[AspNetCompatibilityRequirementsAttribute(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class WSTrustServiceContract : IWSTrustFeb2005SyncContract,
IWSTrust13SyncContract, IWSTrustFeb2005AsyncContract, IWSTrust13AsyncContract, IWsdlExportExtension, IContractBehavior
So we can infer that
The custom host factory will be called to create instance of the service.
Once the service instance is created, it will be there for all the requests (InstanceContextMode.Single)
My questions are
Why the instance of custom host factory is getting created per call (I have a breakpoint in the constructor of this factory. I am debugging by attaching to w3wc instance) ?
Why instance of my service is getting created per call?

Answer 1

As I said, I created simple application and it worked correctly. So try to compare that:
ServiceHost
Public Class MyServiceHost
Inherits ServiceHost
Public Sub New(serviceType As Type, baseAddresses As Uri())
MyBase.New(serviceType, baseAddresses)
End Sub
End Class
Public Class MyServiceHostFactory
Inherits ServiceHostFactory
Public Sub New()
Trace.TraceInformation("MyServiceHost instance created.")
End Sub
Protected Overrides Function CreateServiceHost(serviceType As Type, baseAddresses As Uri()) As ServiceHost
Return New MyServiceHost(serviceType, baseAddresses)
End Function
End Class
Service
<ServiceContract>
Public Interface IService
<OperationContract()>
Function SayHello(name As String) As String
End Interface
<ServiceBehavior(InstanceContextMode:=InstanceContextMode.Single, ConcurrencyMode:=ConcurrencyMode.Multiple)>
<AspNetCompatibilityRequirements(RequirementsMode:=AspNetCompatibilityRequirementsMode.Allowed)>
Public Class Service
Implements IService
Public Sub New()
Trace.TraceInformation("Service instance created.")
End Sub
Public Function SayHello(name As String) As String Implements IService.SayHello
Trace.TraceInformation("Calling Service.SayHello({0}).", name)
Return "Hello " & name
End Function
End Class
Public Class Global_asax
Inherits HttpApplication
Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
Trace.TraceInformation("Application started")
End Sub
End Class
Web.config
<system.serviceModel>
<behaviors>
<serviceBehaviors>
<behavior>
<serviceMetadata httpGetEnabled="true" />
</behavior>
</serviceBehaviors>
</behaviors>
<serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true">
<serviceActivations>
<add factory="FileLessActivationWithCustomServiceHost.MyServiceHostFactory"
service="FileLessActivationWithCustomServiceHost.Service"
relativeAddress="Service.svc"/>
</serviceActivations>
</serviceHostingEnvironment>
</system.serviceModel>
<system.diagnostics>
<trace autoflush="true" indentsize="4">
<listeners>
<remove name="Default" />
<add name="Default"
type="System.Diagnostics.XmlWriterTraceListener"
initializeData="log.svclog" />
</listeners>
</trace>
</system.diagnostics>
I started web application, made several calls of SayHello function and as you can see bellow, it behaves correctly: