.NET 3.5, VS2008, WCF service using BasicHttpBinding
I have a WCF service hosted in a Windows service. When the Windows service shuts down, due to upgrades, scheduled maintenance, etc, I need to gracefully shut down my WCF service. The WCF service has methods that can take up to several seconds to complete, and typical volume is 2-5 method calls per second. I need to shut down the WCF service in a way that allows any previously call methods to complete, while denying any new calls. In this manner, I can reach a quiet state in ~ 5-10 seconds and then complete the shutdown cycle of my Windows service.
Calling ServiceHost.Close seems like the right approach, but it closes client connections right away, without waiting for any methods in progress to complete. My WCF service completes its method, but there is no one to send the response to, because the client has already been disconnected. This is the solution suggested by this question.
Here is the sequence of events:
- Client calls method on service, using the VS generated proxy class
- Service begins execution of service method
- Service receives a request to shut down
- Service calls ServiceHost.Close (or BeginClose)
- Client is disconnected, and receives a System.ServiceModel.CommunicationException
- Service completes service method.
- Eventually service detects it has no more work to do (through application logic) and terminates.
What I need is for the client connections to be kept open so the clients know that their service methods completed sucessfully. Right now they just get a closed connection and don't know if the service method completed successfully or not. Prior to using WCF, I was using sockets and was able to do this by controlling the Socket directly. (ie stop the Accept loop while still doing Receive and Send)
It is important that the host HTTP port is closed so that the upstream firewall can direct traffic to another host system, but existing connections are left open to allow the existing method calls to complete.
Is there a way to accomplish this in WCF?
Things I have tried:
- ServiceHost.Close() - closes clients right away
- ServiceHost.ChannelDispatchers - call Listener.Close() on each - doesn't seem to do anything
- ServiceHost.ChannelDispatchers - call CloseInput() on each - closes clients right away
- Override ServiceHost.OnClosing() - lets me delay the Close until I decide it is ok to close, but new connections are allowed during this time
- Remove the endpoint using the technique described here. This wipes out everything.
- Running a network sniffer to observe ServiceHost.Close(). The host just closes the connection, no response is sent.
Thanks
Edit: Unfortunately I cannot implement an application-level advisory response that the system is shutting down, because the clients in the field are already deployed. (I only control the service, not the clients)
Edit: I used the Redgate Reflector to look at Microsoft's implementation of ServiceHost.Close. Unfortunately, it calls some internal
helper classes that my code can't access.
Edit: I haven't found the complete solution I was looking for, but Benjamin's suggestion to use the IMessageDispatchInspector to reject requests prior to entering the service method came closest.