Hosting in Windows Services

Hosting a WCF service in a Windows service is a logical choice. Windows services shouldn't be confused with WCF services. They both use the word service, but they have different meanings. A Windows service is a process managed by the operating system. Windows comes with the Service Control Manager, which controls the services installed on the operating system. Windows uses services to support operating system features such as networking, USB, remote access, message queuing, and so on. You can use Visual Studio 2005 to create a Windows service using the Windows Service project template shown in Figure 5-2.

The Windows Service project template generates a project that contains two files: the service1.cs that contains the service implementation and the program.cs file that instantiates and essentially hosts the Windows service. To host your WCF service inside a Windows service, you merely need to implement the Start() and Stop() methods of the Windows service, as shown in Listing 5-2. Since the paradigm of starting Windows services is similar to starting your services inside WCF ServiceHost, you end up tying the lifetime of your WCF service to the lifetime of your Windows service.

Visual Studio 2005 Windows Service project template

Example. Windows Service Hosting the WCF ServiceHost

using System;
using System.ServiceModel;
using System.ServiceProcess;
using QuickReturns.StockTrading.ExchangeService;

namespace QuickReturns.StockTrading.ExchangeService.Hosts
{
    public partial class ExchangeWindowsService : ServiceBase
    {
        ServiceHost host;

        public ExchangeWindowsService()
        {
            InitializeComponent();
        }

protected override void OnStart(string[] args)
						{
						   Type serviceType = typeof(TradeService);
						 host = new ServiceHost(serviceType);
						 host.Open();
						}
						 protected override void OnStop()
						    {
						  if(host != null)
						 host.Close();
						        }
						  }
						}

If you want to debug your start-up (or shutdown) code, just insert the following line in your code: System.Diagnostics.Debugger.Break(); (potentially surrounded by some logic to do this only in debug builds).

So, writing a Windows service that hosts your WCF service is pretty easy and comes with several benefits when compared to the self-hosting scenario from earlier in this chapter. On the other hand, writing a Windows service that hosts your WCF service also comes with some disadvantages that you need to understand.

The following are the advantages:

Automatic starting

The Windows Service Control Manager allows you to set the start-up type to automatic so that as soon as Windows boots, the service will be started, without an interactive login on the machine.

Recovery

The Windows Service Control Manager has built-in support to restart services when failures occur.

Security identity

The Windows Service Control Manager allows you to choose a specific security identity under which you want the service to run including built-in system or network service accounts.

Manageability

In general, Windows operators know a lot about the Service Control Manager and other management tools that can work with Windows service installation and configuration. This will improve the acceptance of Windows services in production environments; however, to make services maintainable, you would probably have to add some instrumentation and logging features.

Support for all bindings and transports

Self-hosting doesn't limit you in using any of the out-of-the-box bindings and transports whatsoever. On Windows XP and Windows Server 2003, IIS limits you to HTTP only.

The following are some of the disadvantages of Windows services:

Deployment

Services need to be installed with the .NET Framework Installutil.exe utility or through a custom action in an installer package.

Limited features

Windows services still have a limited set of out-of-the-box features to support high availability, easy manageability, versioning, and deployment scenarios. Essentially you have to cover these requirements yourself through custom code while, for example, IIS comes with several of these features by default. Windows services do add recoverability and some security features, but you still have to do some work yourself.

To be able to install a service in the Service Control Manager, you have to add an installer to the project. Visual Studio 2005 allows you to do this easily:

To be able create a setup that can be used to install your Windows service, you need to add a Visual Studio setup and deployment project to the solution. The following steps describe how to add a setup and deployment project to your solution:

This adds a project item for the primary output of your Windows service to the setup project. Now add a custom action to install the executable file. To add a custom action to the setup project, follow these steps:

When you compile the project, the output is a Microsoft Installer file (.msi) that you can use to install the service into the Windows Service Control Manager.