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SignalR Scaleout with SQL Server

By Mike Wasson and Patrick Fletcher|

In this tutorial, you will use SQL Server to distribute messages across a SignalR application that is deployed in two separate IIS instances. You can also run this tutorial on a single test machine, but to get the full effect, you need to deploy the SignalR application to two or more servers. You must also install SQL Server on one of the servers, or on a separate dedicated server. Another option is to run the tutorial using VMs on Windows Azure.

Prerequisites

Microsoft SQL Server 2005 or later. The backplane supports both desktop and server editions of SQL Server. It does not support SQL Server Compact Edition or Windows Azure SQL Database. (If your application is hosted on Windows Azure, consider the Service Bus backplane instead.)

Overview

Before we get to the detailed tutorial, here is a quick overview of what you will do.

  1. Create a new empty database. The backplane will create the necessary tables in this database.
  2. Add these NuGet packages to your application:
  3. Create a SignalR application.
  4. Add the following code to Global.asax to configure the backplane:
protected void Application_Start()
{
    string sqlConnectionString = "Connecton string to your SQL DB";
    GlobalHost.DependencyResolver.UseSqlServer(sqlConnectionString);

    RouteTable.Routes.MapHubs();
    // ...
}

Configure the Database

Decide whether the application will use Windows authentication or SQL Server authentication to access the database. Regardless, make sure the database user has permissions to log in, create schemas, and create tables.

Create a new database for the backplane to use. You can give the database any name. You don’t need to create any tables in the database; the backplane will create the necessary tables.

Enable Service Broker

It is recommended to enable Service Broker for the backplane database. Service Broker provides native support for messaging and queuing in SQL Server, which lets the backplane receive updates more efficiently. (However, the backplane also works without Service Broker.)

To check whether Service Broker is enabled, query the is_broker_enabled column in the sys.databases catalog view.

SELECT [name], [service_broker_guid], [is_broker_enabled]
FROM [master].[sys].[databases]

To enable Service Broker, use the following SQL query:

ALTER DATABASE YOUR_DATABASE SET ENABLE_BROKER

If this query appears to deadlock, make sure there are no applications connected to the DB.

If you have enabled tracing, the traces will also show whether Service Broker is enabled.

Create a SignalR Application

Create a SignalR application by following either of these tutorials:

Next, we’ll modify the chat application to support scaleout with SQL Server. First, add the SignalR.SqlServer NuGet package to your project. In Visual Studio, from the Tools menu, select Library Package Manager, then select Package Manager Console. In the Package Manager Console window, enter the following command:

Install-Package Microsoft.AspNet.SignalR.SqlServer 

Next, open the Global.asax file. Add the following code to the Application_Start method:


protected void Application_Start()
{
        string sqlConnectionString = "<add your SQL connection string here>";
        GlobalHost.DependencyResolver.UseSqlServer(sqlConnectionString);

        RouteTable.Routes.MapHubs();
}

Deploy and Run the Application

Prepare your Windows Server instances to deploy the SignalR application.

Add the IIS role. Include “Application Development” features, including the WebSocket Protocol.

Also include the Management Service (listed under “Management Tools”).

Install Web Deploy 3.0. When you run IIS Manager, it will prompt you to install Microsoft Web Platform, or you can download the intstaller. In the Platform Installer, search for Web Deploy and install Web Deploy 3.0

Check that the Web Management Service is running. If not, start the service. (If you don’t see Web Management Service in the list of Windows services, make sure that you installed the Management Service when you added the IIS role.)

Finally, open port 8172 for TCP. This is the port that the Web Deploy tool uses.

Now you are ready to deploy the Visual Studio project from your development machine to the server. In Solution Explorer, right-click the solution and click Publish.

For more detailed documentation about web deployment, see Web Deployment Content Map for Visual Studio and ASP.NET.

If you deploy the application to two servers, you can open each instance in a separate browser window and see that they each receive SignalR messages from the other. (Of course, in a production environment, the two servers would sit behind a load balancer.)

After you run the application, you can see that SignalR has automatically created tables in the database:

SignalR manages the tables. As long as your application is deployed, don't delete rows, modify the table, and so forth.

Author Information

Mike Wasson

Mike Wasson – Mike Wasson is a programmer-writer at Microsoft.

Patrick Fletcher

Patrick Fletcher – Patrick Fletcher is a programmer-writer on the ASP.NET team, currently working on SignalR.