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WCF-based communication stack for Reliable Services

  • Стаття

The Reliable Services framework allows service authors to choose the communication stack that they want to use for their service. They can plug in the communication stack of their choice via the ICommunicationListener returned from the CreateServiceReplicaListeners or CreateServiceInstanceListeners methods. The framework provides an implementation of the communication stack based on the Windows Communication Foundation (WCF) for service authors who want to use WCF-based communication.

WCF Communication Listener

The WCF-specific implementation of ICommunicationListener is provided by the Microsoft.ServiceFabric.Services.Communication.Wcf.Runtime.WcfCommunicationListener class.

Lest say we have a service contract of type ICalculator

[ServiceContract]
public interface ICalculator
{
    [OperationContract]
    Task<int> Add(int value1, int value2);
}

We can create a WCF communication listener in the service the following manner.


protected override IEnumerable<ServiceReplicaListener> CreateServiceReplicaListeners()
{
    return new[] { new ServiceReplicaListener((context) =>
        new WcfCommunicationListener<ICalculator>(
            wcfServiceObject:this,
            serviceContext:context,
            //
            // The name of the endpoint configured in the ServiceManifest under the Endpoints section
            // that identifies the endpoint that the WCF ServiceHost should listen on.
            //
            endpointResourceName: "WcfServiceEndpoint",

            //
            // Populate the binding information that you want the service to use.
            //
            listenerBinding: WcfUtility.CreateTcpListenerBinding()
        )
    )};
}

Writing clients for the WCF communication stack

For writing clients to communicate with services by using WCF, the framework provides WcfClientCommunicationFactory, which is the WCF-specific implementation of ClientCommunicationFactoryBase.


public WcfCommunicationClientFactory(
    Binding clientBinding = null,
    IEnumerable<IExceptionHandler> exceptionHandlers = null,
    IServicePartitionResolver servicePartitionResolver = null,
    string traceId = null,
    object callback = null);

The WCF communication channel can be accessed from the WcfCommunicationClient created by the WcfCommunicationClientFactory.


public class WcfCommunicationClient : ServicePartitionClient<WcfCommunicationClient<ICalculator>>
   {
       public WcfCommunicationClient(ICommunicationClientFactory<WcfCommunicationClient<ICalculator>> communicationClientFactory, Uri serviceUri, ServicePartitionKey partitionKey = null, TargetReplicaSelector targetReplicaSelector = TargetReplicaSelector.Default, string listenerName = null, OperationRetrySettings retrySettings = null)
           : base(communicationClientFactory, serviceUri, partitionKey, targetReplicaSelector, listenerName, retrySettings)
       {
       }
   }

Client code can use the WcfCommunicationClientFactory along with the WcfCommunicationClient which implements ServicePartitionClient to determine the service endpoint and communicate with the service.

// Create binding
Binding binding = WcfUtility.CreateTcpClientBinding();
// Create a partition resolver
IServicePartitionResolver partitionResolver = ServicePartitionResolver.GetDefault();
// create a  WcfCommunicationClientFactory object.
var wcfClientFactory = new WcfCommunicationClientFactory<ICalculator>
    (clientBinding: binding, servicePartitionResolver: partitionResolver);

//
// Create a client for communicating with the ICalculator service that has been created with the
// Singleton partition scheme.
//
var calculatorServiceCommunicationClient =  new WcfCommunicationClient(
                wcfClientFactory,
                ServiceUri,
                ServicePartitionKey.Singleton);

//
// Call the service to perform the operation.
//
var result = calculatorServiceCommunicationClient.InvokeWithRetryAsync(
                client => client.Channel.Add(2, 3)).Result;

Note

The default ServicePartitionResolver assumes that the client is running in same cluster as the service. If that is not the case, create a ServicePartitionResolver object and pass in the cluster connection endpoints.

Next steps