How to Host ASP.NET in a Windows Service

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Today, I’ll be showing how you can finally host ASP.NET in a Windows service. Yes, with ASP.NET 5, it is possible to host ASP.NET in a Windows service. This article builds on a previous one which shows you how to run a DNX (.NET Execution Environment) application in a Windows Service. It’s a quick one, so go read it now.

Project Dependencies

Once you’ve got the shell project set up using the previous article, you’ll need to add in some dependencies.

Open up project.json and add in a dependencies property with the following entries:

  • "Microsoft.AspNet.Hosting": "1.0.0-beta7" – Bootstraps the web server
  • "Microsoft.AspNet.Server.Kestrel": "1.0.0-beta7" – Web server implementation
  • "Microsoft.AspNet.StaticFiles": "1.0.0-beta7" – Hosts static files
  • "Microsoft.AspNet.Mvc": "6.0.0-beta7" – Includes all the MVC packages

Your project.json should now look like this:

{
    "version": "1.0.0-*",
    "description": "MyDnxService Console Application",
    "commands": {
        "run": "MyDnxService"
    },
    "frameworks": {
        "dnx451": {
            "frameworkAssemblies": {
                "System.ServiceProcess": "4.0.0.0"
            }
        }
    },
    "dependencies": {
        "Microsoft.AspNet.Hosting": "1.0.0-beta7",
        "Microsoft.AspNet.Server.Kestrel": "1.0.0-beta7",
        "Microsoft.AspNet.StaticFiles": "1.0.0-beta7",
        "Microsoft.AspNet.Mvc": "6.0.0-beta7"
    }
}

Run in Visual Studio or Command Line

It would really be a pain to develop and debug your application while running as a Windows service. That’s not to say you can’t, but if you are currently developing an application, you probably want to run it from Visual Studio or the command line. To do this, you need some sort of switch in the Main method that will either call ServiceBase.Run or just call directly into OnStart and OnStop. Let’s do this by writing our Main method as follows:

public void Main(string[] args)
{
    if (args.Contains("--windows-service"))
    {
        Run(this);
        return;
    }

    OnStart(null);
    Console.ReadLine();
    OnStop();
}

Simply check for the presence of the --windows-service argument, call ServiceBase.Run and you are good to go. Now you can just run and debug your application from Visual Studio by hitting F5. When you want to install the application as a Windows service, don’t forget to pass --windows-service at the end of the binPath= argument.

sc.exe create <service-name> binPath= "\"<dnx-exe-path>\" \"<project-path>\" run --windows-service"

Configure and Start the Server and ASP.NET

Let’s add some namespaces:

using Microsoft.AspNet.Builder;
using Microsoft.AspNet.Hosting;
using Microsoft.AspNet.Hosting.Internal;
using Microsoft.Framework.Configuration;
using Microsoft.Framework.Configuration.Memory;
using Microsoft.Framework.DependencyInjection;
using System;
using System.Diagnostics;
using System.Linq;
using System.ServiceProcess;

Before we start the server, we need to set up a few fields and a constructor on the Program class. We need to store the hosting engine, its shutdown function and a service provider that we will use soon. The IServiceProvider instance will be injected by the DNX runtime.

private readonly IServiceProvider _serviceProvider;
private IHostingEngine _hostingEngine;
private IDisposable _shutdownServerDisposable;

public Program(IServiceProvider serviceProvider)
{
    _serviceProvider = serviceProvider;
}

To get the server up and running, we will use the WebHostBuilder class. Your Program.OnStart method should look as follows:

protected override void OnStart(string[] args)
{
    var configSource = new MemoryConfigurationSource();
    configSource.Add("server.urls", "http://localhost:5000");

    var config = new ConfigurationBuilder(configSource).Build();
    var builder = new WebHostBuilder(_serviceProvider, config);
    builder.UseServer("Microsoft.AspNet.Server.Kestrel");
    builder.UseServices(services => services.AddMvc());
    builder.UseStartup(appBuilder =>
    {
        appBuilder.UseDefaultFiles();
        appBuilder.UseStaticFiles();
        appBuilder.UseMvc();
    });

    _hostingEngine = builder.Build();
    _shutdownServerDisposable = _hostingEngine.Start();
}

There are several steps involved here:

  1. Create and populate the server configuration. (lines 3-6)
  2. Create the builder and tell it what server implementation to use. (lines 7-8)
  3. Configure services using the built-in dependecy injection support. (line 9)
  4. Configure the ASP.NET middleware pipeline. (lines 10-15)
  5. Build and start the server. (lines 17-18)

The previous code is oversimplified for the purposes of this article. We are hardcoding the server URL into an in memory config store, but you can set this up in other ways. See the ASP.NET Configuration repo on Github for other options.

To gracefully shut down the server, implement Program.OnStop as follows:

protected override void OnStop()
{
    if (_shutdownServerDisposable != null)
        _shutdownServerDisposable.Dispose();
}

Getting Down to Business

Now that we have a server set up and running ASP.NET with static files and MVC, let’s add some content and a controller.

First, create an index.html file and add “Hello world” as the content. Then create a controller file TimeController.cs with the file contents as follows:

using Microsoft.AspNet.Mvc;
using System;

namespace MyDnxService
{
    public class TimeController
    {
        [Route("time")]
        public DateTime GetTime()
        {
            return DateTime.Now;
        }
    }
}

That’s all there is to it. Now we can pull up http://localhost:5000 to see “Hello world” and http://localhost:5000/time to see the current time.

The Runtime User and Going to Production

When you install a Windows service, you have to specify a user under which to run the process. If you don’t, “Local System” is the default. Why is this important?

In the previous article we simply ran our Windows service as the default (Local System) user. It turns out we got lucky since we didn’t reference any package dependencies. If we try to do the same thing in this case, the service will quickly fail to start because “Local System” won’t be able to resolve any of the package dependencies we just added.

As you add package references to the project.json file, Visual Studio quietly runs dnu restore in the background and downloads the packages to your user profile (c:\users\<username>\.dnx\packages). When you run dnx.exe, it will resolve any dependencies from your user profile. (You’ll see how to override this in a bit.)

Since “Local System” doesn’t have Visual Studio helping it out, we need to somehow get those packages installed someplace that it can see. Running dnu restore as “Local System” will download the packages to c:\Windows\SysWOW64\config\systemprofile\.dnx\packages (on the 64-bit OS) since there’s no user profile for that account. How can you run dnu restore as “Local System”? This can be done by running psexec.exe -s cmd.exe from Sysinternals (runs a cmd.exe console as “Local System”) and then running dnu restore from the directory of your project. You can imagine that having to do this each time you want to deploy is a gigantic inconvenience.

While you’re IN DEVELOPMENT, you should run the Windows service under your own account. This allows you to install the service once and not have to manually run dnu restore under another account each time you modify your config (remember, Visual Studio is helping you out here). The service will be able to resolve the dependencies since it’s running under your account as well.

IN PRODUCTION, we can publish our project by running the following command (from the project’s root folder) and point the sc.exe create binPath= to its output:

dnu publish --out ..\publish-output --runtime active --no-source

This command builds and packages your code and copies it and all of its dependencies into an output folder. It will also add a global.json file in a sub-folder within the output directory that tells DNX to load the packages from the local folder and not the user’s profile. If that’s not enough, the command also packages the “active” DNX runtime. This means that the target machine doesn’t require DNX to be installed and doesn’t require you to run dnu restore on the target machine either. With this method, once you copy the published folder to the production machine, you can run the service under the account of your choosing and point to the run.cmd file within the root of the output folder.

sc.exe create <service-name> obj= <machine|domain>\<username> binPath= "\"<output-folder-path>\run.cmd\" --windows-service"

Now you have what you need to run ASP.NET in a Windows service in both development and production environments.

Get the Source

The source code and installation scripts for this article can be found in the aspnet-windows-service Github repo.

In Closing…

We can finally run ASP.NET in our Windows services. This is a big win for us as we host an admin site for our scheduler out of a Windows service. We currently do this using a custom-built static file server and WCF for web services.

There was a lot of information covered in this article, and there is still a lot more that could be covered. If you liked this article or have any questions, please feel free to leave a comment below. Thanks, and I hope you have enjoyed this post.

How to Run DNX Applications in a Windows Service

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Today I’m going to show you how you can run a DNX application in a Windows service because we recently needed to do this, and while there are many posts out there asking how to do it, the answers would lead you to believe it’s impossible. For this example we’re going to be using the beta6 version of ASP.NET 5. If you don’t yet have DNX, you should go here to get started.

Creating the Application

For demonstrative purposes, we’ll be creating a very simple DNX console application that will simply write to the event log when the service is started/stopped. To begin, create a new DNX Console Application (Package) in Visual Studio. You can find this template in the “Web” category, for some reason. Next we need to make a few tweaks to the project.json file:

  • First, remove the DNX Core reference, this is a windows service after all, so no point in trying to be cross platform today.
  • Under frameworks:dnx451, add a frameworkAssemblies reference to "System.ServiceProcess": "4.0.0.0"
  • Change your command key to something simple like “run” or “runservice”. You don’t have to do this, but it makes it more clear later what we’re doing.

When you’re all done, your project.json should look something like this:

{
    "version": "1.0.0-*",
    "description": "MyDnxService Console Application",
    "commands": {
        "run": "MyDnxService"
    },
    "frameworks": {
        "dnx451": {
            "frameworkAssemblies": {
                "System.ServiceProcess": "4.0.0.0"
            }
        }
    }
}

Next, make the Program class inherit from System.ServiceProcess.ServiceBase. This lets us create overrides for OnStart and OnStop service methods. We’re going to use these methods to simply log out messages to the event log. Finally, in the Main(string[] args) method of the Program class we add Run(this); in order to bootstrap the Windows service. Here is our program.cs file in it’s entirety:

using System.Diagnostics;
using System.ServiceProcess;

namespace MyDnxService
{
    public class Program : ServiceBase
    {
        private readonly EventLog _log = 
            new EventLog("Application") { Source = "Application" };

        public void Main(string[] args)
        {
            _log.WriteEntry("Test from MyDnxService.", EventLogEntryType.Information, 1);
            Run(this);
        }

        protected override void OnStart(string[] args)
        {
            _log.WriteEntry("MyDnxService started.");
        }

        protected override void OnStop()
        {
            _log.WriteEntry("MyDnxService stopped.");
        }
    }
}

Installing the Service

Once our application is written and building successfully we can install it as a service. To do this, open a command prompt in administrator mode and enter the following command:

sc.exe create <service-name> binPath= "\"<dnx-exe-path>\" \"<project-path>\" run"

UPDATE
If you’re targeting beta8 or beyond, the way we tell dnx.exe where to find our project has changed to include a –project (-p for short) argument. So the above command changes to:
sc.exe create <service-name> binPath= "\"<dnx-exe-path>\" -p \"<project-path>\" run"

sc.exe is a built-in tool that lets us perform a number of operations on a Windows service. Here we’re using it to create a new service. The very first argument that the create operation needs is the service name. This is the name that will show up in the services snap in. You can set this to any value, but since our example application is called MyDnxService we put our adventurous nature aside and simply used that.

The binPath= parameter is the only other parameter we’re specifying to sc.exe, even though it looks like three separate parameters. We’re basically telling sc.exe what command to execute when starting the service, which is DNX. The other parameters after that are actually parameters to dnx.exe, not sc.exe. Because there are spaces in the argument value, we are wrapping the entire argument in quotes (I’ll explain the escaped quotes in a minute). One gotcha to keep in mind when working with sc.exe is that the “=” you see after “binPath” is actually part of the parameter name for sc.exe, so that space you see between binPath= and the value is necessary as it tells sc.exe that we’re moving from the parameter name to the value. Now let’s look at the three components in that binPath= argument:

  • Since dnx.exe is the application that runs a DNX application, we’re going to need to point to it via its full path. If you install DNX via DNVM the default install directory (at least on our machines) is c:\users\\.dnx\runtimes\\bin\dnx.exe but if you aren’t sure where on your machine it is just open a command prompt and run where.exe dnx.exe and it should tell you where to find it. Since the path to DNX could have spaces, we’re wrapping that parameter in quotes too, but since these quotes are inside the quotes we specified for the binPath= parameter to sc.exe, we need to escape them.
  • Next we need to tell DNX where to find our application. If you use dnu publish to publish your application it will generate a .cmd file for you that you normally would use to launch your application. You cannot use that .cmd file when running your application in a Windows service but if you open that .cmd file you’ll see a path for --appbase and that’s the one we want. Again, escape the quotes around this path for safety.
  • Finally we tell DNX what command within our application to run. Remember above in the project.json file we named our command key “run”? that’s what this value specifies. So if you named your command key something else, just replace the “run” parameter to DNX with whatever command key name you chose in your project.json.

So putting all of that together, the complete sc.exe command we used for the application above (without the generic tokens) was:
sc.exe create MyDnxService binpath= "\"C:\Users\dave\.dnx\runtimes\dnx-clr-win-x86.1.0.0-beta6\bin\dnx.exe\" \"C:\Users\dave\Desktop\DnxWindowsService\src\MyDnxService\" run"

UPDATE
As mentioned above, if you’re targeting beta8 or beyond, the way we tell dnx.exe where to find our project has changed to include a –project (-p for short) argument. So the above command changes to:
sc.exe create MyDnxService binpath= "\"C:\Users\dave\.dnx\runtimes\dnx-clr-win-x86.1.0.0-beta8\bin\dnx.exe\" -p \"C:\Users\dave\Desktop\DnxWindowsService\src\MyDnxService\" run"

Running the Service

Now that our application has been installed as a service, it’s time to revel in the fruits of our labor. To run the service, open the Services MMC Snap-in, find the service we installed by its name and start it. Open Event Viewer, go to the Application log and you should see the text that we output from our OnStart() override in our application. Stopping the service and refreshing the event log will show the stop message. As I said earlier, this is a super basic demonstration of functionality, but it’s the basis for running any DNX application in the context of a Windows service.

Why Do This?

Taskmatics Scheduler currently hosts the administration website from inside one of the Windows services that are installed. In its current implementation we couldn’t support ASP.NET applications because only IIS would provide the environment necessary to properly run each request through the pipeline. With ASP.NET 5, the game changes, and you can host ASP.NET applications from a console application without being dependent on IIS. After some headbanging we are successfully running our MVC 6 web application inside of a Windows service, which you can now read about here.

Update!

Check out Erez’s follow up post showing you how to host a fully functional ASP.NET site from a Windows service, which has just been posted!