Question

I create a WCF SOAP server with an operation that takes some time to perform:

[ServiceContract]
public interface IMyService
{
    [OperationContract]
    string LongRunningOperation();
}

[ServiceBehavior(
    ConcurrencyMode = ConcurrencyMode.Multiple,
    UseSynchronizationContext = false,
    InstanceContextMode = InstanceContextMode.Single)]
class MyService : IMyService
{
    public string LongRunningOperation()
    {
        Thread.Sleep(20000);
        return "Hey!";
    }
}

class Program
{
    static void Main(string[] args)
    {
        MyService instance = new MyService();
        ServiceHost serviceHost = new ServiceHost(instance);
        BasicHttpBinding binding = new BasicHttpBinding();
        serviceHost.AddServiceEndpoint(typeof(IMyService), binding, "http://localhost:9080/MyService");
        serviceHost.Open();
        Console.WriteLine("Service running");
        Thread.Sleep(10000);
        serviceHost.Close();
        Console.WriteLine("Service closed");
        Thread.Sleep(30000);
        Console.WriteLine("Exiting");
    }
}

The ServiceHost is opened, and after 10 seconds I close it.

When calling serviceHost.Close(), all clients currently connected, waiting for LongRunningOperation to finish, are inmediately disconnected.

Is there a wait of closing the ServiceHost in a cleaner way? That is, I want to disable the service listeners, but also wait for all currently connected clients to finish (or specify a maximum timeout).

Answer 1

In principle, I think something like the following should be possible, though I haven’t implemented it to confirm all the details:

• Implement a custom IOperationInvoker
  wrapping the Dispatcher’s normal
  OperationInvoker (you’ll want an IServiceBehavior to install the wrapped invoker when the service dispatcher runtime is built)
• the custom invoker would mostly delegate to the real one, but would also provide
  “gate-keeper” functionality to turn away
  new requests (e.g. raise a some kind of exception) when the service host is about
  to be shut down.
• it would also keep track of operation invocations still in
  progress and set an event when the last operation invocation finishes or times out.
• the main hosting thread would then wait on the invoker’s “all finished” event before calling serviceHost.Close().