Archive for January, 2011

IIS in depth

January 22, 2011 Leave a comment

Web server is used when we want to host the application on a centralized location and wanted to access from many locations. Web server is responsible for handle all the requests that are coming from clients, process them and provide the responses.


What is IIS ?

IIS (Internet Information Server) is one of the most powerful web servers from Microsoft that is used to host your ASP.NET Web application. IIS has it’s own ASP.NET Process Engine  to handle the ASP.NET request. So, when a request comes from client to server, IIS takes that request and  process it and send response back to clients.




Worker Process:  Worker Process (w3wp.exe) runs the ASP.Net application in IIS. This process is responsible to manage all the request and response that are coming from client system.  All the ASP.Net functionality runs under the scope of worker process.  When a request comes to the server from a client worker process is responsible to generate the request and response. In a single word we can say worker process is the heart of ASP.NET Web Application which runs on IIS.

Application Pool: Application pool is the container of worker process.  Application pools is used to separate sets of IIS worker processes that share the same configuration.  Application pools enables a better security, reliability, and availability for any web application.  The worker process serves as the process boundary that separates each application pool so that when one worker process or application is having an issue or recycles, other applications or worker processes are not affected. This makes sure that a particular web application doesn’t not impact other web application as they they are configured into different application pools.


Application Pool with multiple worker process is called “Web Garden”.


Now, I have covered all the basic stuff like Web server, Application Pool, Worker process. Now let’s have look how IIS process the request when a new request comes up from client.

If we look into the IIS 6.0 Architecture, we can divided them into Two Layer


1.    Kernel Mode

2.    User Mode


Now, Kernel mode is introduced with IIS 6.0, which contains the HTTP.SYS.  So whenever a request comes from Client to Server, it will hit HTTP.SYS First.



Now, HTTP.SYS is Responsible for pass the request to particular Application pool. Now here is one question, How HTTP.SYS comes to know where to send the request?  This is not a random pickup. Whenever we creates a new Application Pool, the ID of the Application Pool is being generated and it’s registered with the HTTP.SYS. So whenever HTTP.SYS Received the request from any web application, it checks for the Application Pool and based on the application pool it send the request.


So, this was the first steps of IIS Request Processing.

Till now, Client Requested for some information and request came to the Kernel level of IIS means at HTTP.SYS. HTTP.SYS has been identified the name of the application pool where to send. Now, let’s see how this request moves from HTTP.SYS to Application Pool.

In User Level of IIS, we have Web Admin Services (WAS) which takes the request from HTTP.SYS and pass it to the respective application pool.


When Application pool receive the request, it simply pass the request to worker process (w3wp.exe) . The worker process “w3wp.exe” looks up the URL of the request in order to load the correct ISAPI extension. ISAPI extensions are the IIS way to handle requests for different resources. Once ASP.NET is installed, it installs its own ISAPI extension (aspnet_isapi.dll) and adds the mapping into IIS.  

Note : Sometimes if we install IIS after installing, we need to register the extension with IIS using aspnet_regiis command.

When Worker process loads the aspnet_isapi.dll, it start an HTTPRuntime, which is the entry point of an application. HTTPRuntime is a class which calls the ProcessRequest method to start Processing.

When this methods called, a new instance of HTTPContext is been created.  Which is accessible using HTTPContext.Current  Properties. This object still remains alive during life time of object request.  Using HttpContext.Current we can access some other objects like Request, Response, Session etc.

After that HttpRuntime load an HttpApplication object with the help of  HttpApplicationFactory class.. Each and every request should pass through the corresponding HTTPModule to reach to HTTPHandler, this list of module are configured by the HTTPApplication.

Now, the concept comes called “HTTPPipeline“. It is called a pipeline because it contains a set of HttpModules ( For Both Web.config and Machine.config level) that intercept the request on its way to the HttpHandler. HTTPModules are classes that have access to the incoming request. We can also create our own HTTPModule if we need to handle anything during upcoming request and response.

HTTP Handlers are the endpoints in the HTTP pipeline. All request that are passing through the HTTPModule should reached to HTTPHandler.  Then  HTTP Handler  generates the output for the requested resource. So, when we requesting for any aspx web pages,   it returns the corresponding HTML output.

All the request now passes from  httpModule to  respective HTTPHandler then method and the ASP.NET Page life cycle starts.  This ends the IIS Request processing and start the ASP.NET Page Lifecycle.


When client request for some information from a web server, request first reaches to HTTP.SYS of IIS. HTTP.SYS then send the request to respective  Application Pool. Application Pool then forward the request to worker process to load the ISAPI Extension which will create an HTTPRuntime Object to Process the request via HTTPModule and HTTPHanlder. After that the ASP.NET Page LifeCycle events starts.

This was just overview of IIS Request Processing to let Beginner’s know how the request get processed in backend.  If you want to learn in details please check the link for Reference and further Study section.


Categories: IIS 7.0

The web server process that was being debugged has been terminated by Internet Information Services (IIS)

January 22, 2011 Leave a comment

By default, debugging a website or web project within Visual Studio bring up the built-in server of Visual Studio. But, we do have a problem to change the server to an IIS instance. I recently switched to debugging on IIS on my Windows 7. Debugging works fine. The only problem is that if your code hit some breakpoint and if you leave the program in ‘break’ mode for more than 90 seconds, Visual Studio shows the following message:




After a bit tweaking around in the new IIS interface, I got the solution:

  • Open Internet Information Services (IIS) Manager.
  • From the server tree (the item with the name as the server name), choose Application Pools.
  • Choose the Application Pool corresponding to your testing IIS website (usually it has the same name as your IIS website)
  • Right-click and choose Advanced Settings.
  • From the Process Model node, change the Ping Maximum Response Time (seconds) to a comfortably higher value (I have set the value to 900 seconds which is 15 minutes).


Alternatively, you can also set the Ping Enabled property to False.

Apparently what happens is that the server keeps pinging the worker process and waits for a response. When in debugging mode, the worker process is affectively suspended, which results in the ping not being responded.



Bypass specific IP from rendering google analytics code

January 13, 2011 Leave a comment

To bypass specific IP from rendering google analytics code, follow the following steps.

  1. List the IP which you wants to bypass from rendering into your web application, and add in web.config file

    e.g. <add key=ByPassUrl value=>

  2. Create a Usercontrol and named “GoogleAnalytics.ascx” replace your google analytics code with “<google analytics code here>“.

    <%@Control Language=”C#” AutoEventWireup=”true” CodeFile=”GoogleAnalytics.ascx.cs”

    <script type=”text/javascript”>

    <% if (ConfigurationManager.AppSettings[“showGoogleAnalytics”] == “True”) {%>

    <% if (!strByPassUrl.Contains(requestUrl)) {%>

    var _gaq = _gaq || [];

    _gaq.push([‘_setAccount’, <google analytics code here>]);


    (function() {

    var ga = document.createElement(‘script’); ga.type = ‘text/javascript’; ga.async = true;

    ga.src = (https: == document.location.protocol ? https://ssl : http://www) + ‘’;

    var s = document.getElementsByTagName(‘script’)[0]; s.parentNode.insertBefore(ga, s);


    <% } %>

    <% } %>



  3. Declare following 2 public variable in “GoogleAnalytics.ascx.cs” file

    public string requestUrl = HttpContext.Current.Request.UserHostAddress.ToString();
    string strByPassUrl = clsCommon.value(“ByPassUrl”);

  4. Add “GoogleAnalytics” user control in master page of the application within <Head></Head> tag.

    <head runat=”server”>

    <uc2:GoogleAnalytics ID=”GoogleAnalytics1″ runat=”server”/>


Note :- 1) Before Copying Google analytics code verify with google analytics script, provided in google analytics account.

2) check if “showGoogleAnalytics” key is present in web.config file.