Running a background service in a Web Application (no Windows Service was involved during this process)

By | March 17, 2012

This is not something new but it might be helpful for someone who needs this solution, I am sharing this as I have a current project to create background services using my Web application like usual before I start some solution I check whether I had made something like it before and to my luck after checking my portable drive for past projects I did have and used it for batch emailing in a website I had made around 2005.  With some slight changes here is how its done.

Before we start you might ask why do I need to do this on the Web application when I can do it in the Windows service? well imagine you have your website hosted in on a shared hosting environment which you don’t have access to the operating system well you’re out of luck your only options at this time is to ask for server permission which in most cases wont be granted or you can run a background method that invokes every page request which is a bad practice that is why in this solution we will use HttpModule to act as your background service.


It is basically simple all you need to do is create a class for your Service and use Timers to invoke the process you want to achieve.  Below is a code to do such thing and I will explain to you how it works

public class Scheduler : IHttpModule
{
    protected static Timer timer;
    protected static object someAction;

    private static readonly ILog Log = LogManager.GetLogger(typeof(Scheduler).Name);

    static Scheduler()
    {
        someAction = new object();
    }
    void IHttpModule.Init(HttpApplication application)
    {
        //there should only be one timer otherwise it would be messy
        if (timer == null)
        {
            var timerCallback = new TimerCallback(ProcessSomething);
            var startTime = 0;
            var timerInterval = 5000; // 5 seconds
            timer = new Timer(timerCallback, null, startTime, timerInterval);
        }
    }

    protected void ProcessSomething(object state)
    {
        Log.Info("Invoked Normal Process - " + DateTime.Now);

        //this protects everthing inside from other threads that might be invoking this
        //which is good for long running processes on the background
        lock (someAction)
        {
            Log.Info("Invoked Protected Process - " + DateTime.Now);

            //To simulate long running process
            System.Threading.Thread.Sleep(20000);
        }

    }
    public void Dispose(){}

}

First you have your IHttpModule.Init where everything starts, basically you just need a Timer and a TimerCallback to call your process.  You can define the wait times or interval on how may seconds you want your process to be called.  We also added a line that checks whether the timer is null as having multiple timers in a Web application is not a good idea.

Next is that you have your method which in this case we call ProcessSomething, this is then being called by the TimerCallback every 5 seconds in our example.  You notice that we also start at 0 seconds which means it will immediately call one you website goes online or gets published.  Looking further inside ProcessSomething there is a lock which protects your process from being executed when the timer ticks again ahead of the running process.

Finally for that to work you have to place it in your web.config in between system.web tags inside httpModules like such

<system.web>
.
.
.
.
.
  <httpModules>
    <add type="YourNamespace.Scheduler" name="Scheduler"/>
  </httpModules>
</system.web>

Other than that all should be straightforward, the code is a working sample so here are my results.

If you notice we log everything in the event logs through that Log.Info line, and it that log it is visible that ticks happen every 5 seconds but the process only runs when ProcessSomething finishes (the yellow highlight) in this case after sleeping it for 20 seconds to simulate a long running process.


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