A SignalR backplane implemented in Orleans

When running SignalR on more than one web server (a common scenario in the cloud) you need a backplane to connect together each of the servers. This allows messages broadcast from a user connected to one server, to reach the users on the other servers.

There are already some backplane options in Azure:

• SQL Server
• Service Bus Topics/Subscriptions
• Redis (you should probably use this)

I thought it would be interesting to implement a backplane in Orleans.

The projects required to implement a system:

• OrleansR.GrainInterfaces The Oreans grain interfaces.
• OrleansR.Grains The Orleans grain implementations.
• OrleansR.MessageBus The IMessageBus implementation which plugs into SignalR, and connects to the Orleans Silos.

Sample/test projects included in the solution:

• OrleansR.Cloud A sample project to deploy the solution to Azure.
• OrleansR.UnitTests Unit tests for the grains.
• OrleansR.Web A sample web application.
• OrleansR.WorkerRoleSiloHost A sample Worker Role to host the Orleans Silo.

Configure Orleans in the usual way, by starting up a Silo, and connecting a web application to it as described here.

When configuring SignalR in the Startup class of your web application, register the OrleanMessageBus class like this:

using Microsoft.AspNet.SignalR;
using Microsoft.AspNet.SignalR.Messaging;
using OrleansR.MessageBus;
using Owin;

namespace OrleansR.Web
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
 			// configure the OrleansR message bus
            var config = new ScaleoutConfiguration { MaxQueueLength = 10, QueueBehavior = QueuingBehavior.Always };
            var omb = new OrleansMessageBus(GlobalHost.DependencyResolver, config);
            GlobalHost.DependencyResolver.Register(typeof(IMessageBus), () => omb);

            // register SignalR as ususal
            app.MapSignalR();
        }
    }
}

MIT