WCF - Informing about the progress to client (Can I use one-way call back methods within a request/reply operation)

问题

My contract has request-reply operation which performs multiple tasks. So I would like to inform about the progress of the operation to the client as its a long running operation. So Duplex is the ideal choice as I can use call back methods. But my operation returns results at the end of the operations. So what is the recommendation to solve this problem?

Reuest-reply operation and one-way call back method for the progress messaages from the service within the operation?
Blocking (request-reply) operation and blocking (sync) progress messages from service
Will the call back method uses same channel, so will my blocking (request-reply) method assumes its its result?
- If yes, should I perform my service operation asynchronously.
Will the call back method will come in another worker thread or will be returned to the same thread which has given the instance context?

I think blocking service operation and blocking call back method for progress message (if it can return on another thread) will be ideal and easy solution.

But I am not sure how much WCF provides me out of box.

In Other words I want to do something similar to the below code(psuedo). Its working. Do you see any issues with this approach? (The idea is to calling a callback method within a blocking call. Service runs in multiple concurencymode. So i declared callback UseSynchronizationContext = false) to avoid deadlock.any issues are there with the below approach?

[ServiceContract(CallbackContract(typeof(IServiceCallback)]]
public interfact IService
{
     //A long (timetaken) request-reply operation
     string LonggggWork();
}

public interface IServiceCallback
{
     void Report(string msg);
}

[CallbackBehavior(ConcuerencyMode.Multiple, UseSynchronizationContext=false)]
public ClientCallback : IServiceCallback
{
public void Report(string msg)
{
     Console.WriteLine(msg);
}
}
[ServiceBehavior(ConcurencyMode.Multiple, InstanceMode.PerSession)]
publci Service : IService
{
     IServiceCallback callback = ....;
     public string LongggWork()
     {
          callback.Report("task1");
          task1();
          callback.Report("task2");
          task2();
           ...
               ...
     }
}

Eventhough if i set it UseSynchronizationContext to true, WCF is invoking the report method in worker thread itself. So looks like I dont need to set it to false. Will it make sense only for UI thread becasue I am invoking operation already in a another thread?

回答1:

[ServiceContract(CallbackContract = typeof(ISubscriber))]
public interface IJobProcessor
{
    [OperationContract(IsOneWay = true)]
    void ProcessJob();
}



[ServiceContract]
public interface ISubscriber
{
    //This would be the operation using which the server would notify the client about the status.
    [OperationContract]
    void UpdateStatus(string statusMessage);
}

class Program
{
    static void Main(string[] args)
    {
        ServiceHost host = new ServiceHost(typeof(JobProcessor), new Uri[] { new Uri("net.tcp://localhost:10000") });
        host.AddServiceEndpoint(typeof(IJobProcessor), new NetTcpBinding(), "jobprocessor");
        host.Open();
        Console.WriteLine("Server  running. Press enter to quit!");
        Console.Read();
    }
}

[ServiceBehavior(ConcurrencyMode=ConcurrencyMode.Reentrant)]
public class JobProcessor : IJobProcessor
{
    public void ProcessJob()
    {
        ISubscriber subscriber = OperationContext.Current.GetCallbackChannel<ISubscriber>();
        for (int i = 0; i < 5; i++)
        {
            Thread.Sleep(1000 * 10);
            subscriber.UpdateStatus(String.Format("{0} % complete", (i + 1) * 20));
        }

    }
}

//Client would look something like this...

class Program
{
    static void Main(string[] args)
    {
        var proxy = DuplexChannelFactory<IJobProcessor>.CreateChannel(new InstanceContext(new Subscriber()), new NetTcpBinding(), new EndpointAddress("net.tcp://localhost:10000/jobprocessor"));
        proxy.ProcessJob();
        Console.Write("Client proceeding with other work...");
        Console.Read();
    }
}

public class Subscriber : ISubscriber
{
    public void UpdateStatus(string statusMessage)
    {
        Console.WriteLine(statusMessage);
    }
}

来源：https://stackoverflow.com/questions/7865537/wcf-informing-about-the-progress-to-client-can-i-use-one-way-call-back-method

标签

wcf

wcf-client