Calling services from other application in the cluster

Question

Is it possible to call services or actors from one application to another in a Service Fabric Cluster ? When I tryed (using ActorProxy.Create with the proper Uri), I got a \"No

Answer 1

Yes, it is possible. As long as you have the right Uri to the Service (or ActorService) and you have access to the assembly with the interface defining your service or actor the it should not be much different than calling the Service/Actor from within the same application. It you have enabled security for your service then you have to setup the certificates for the exchange as well.

If I have a simple service defined as:

public interface ICalloutService : IService
{
    Task<string> SayHelloAsync();
}

internal sealed class CalloutService : StatelessService, ICalloutService
{
    public CalloutService(StatelessServiceContext context)
        : base(context) { }

    protected override IEnumerable<ServiceInstanceListener> CreateServiceInstanceListeners()
    {
        yield return new ServiceInstanceListener(this.CreateServiceRemotingListener);
    }

    public Task<string> SayHelloAsync()
    {
        return Task.FromResult("hello");
    }
}

and a simple actor:

public interface ICalloutActor : IActor
{
    Task<string> SayHelloAsync();
}

[StatePersistence(StatePersistence.None)]
internal class CalloutActor : Actor, ICalloutActor
{
    public CalloutActor(ActorService actorService, ActorId actorId)
        : base(actorService, actorId) {}

    public Task<string> SayHelloAsync()
    {
        return Task.FromResult("hello");
    }
}

running in a application like this:

Then you can call it from another application within the same cluster:

        // Call the service
        var calloutServiceUri = new Uri(@"fabric:/ServiceFabric.SO.Answer._41655575/CalloutService");
        var calloutService = ServiceProxy.Create<ICalloutService>(calloutServiceUri);
        var serviceHello = await calloutService.SayHelloAsync();

        // Call the actor
        var calloutActorServiceUri = new Uri(@"fabric:/ServiceFabric.SO.Answer._41655575/CalloutActorService");
        var calloutActor = ActorProxy.Create<ICalloutActor>(new ActorId(DateTime.Now.Millisecond), calloutActorServiceUri);
        var actorHello = await calloutActor.SayHelloAsync();

You can find the right Uri in the Service Fabric Explorer if you click the service and look at the name. By default the Uri of a service is: fabric:/{applicationName}/{serviceName}.

The only tricky part is how do you get the interface from the external service to your calling service? You could simply reference the built .exe for the service you wish to call or you could package the assembly containing the interface as a NuGet package and put on a private feed.

If you don't do this and you instead just share the code between your Visual Studio solutions the Service Fabric will think these are two different interfaces, even if they share the exact same signature. If you do it for a Service you get an NotImplementedException saying "Interface id '{xxxxxxxx}' is not implemented by object '{service}'" and if you do it for an Actor you get an KeyNotfoundException saying "No MethodDispatcher is found for interface id '-{xxxxxxxxxx}'".

So, to fix your problem, make sure you reference the same assembly that is in the application you want to call in the external application that is calling.