The need for programmatically executing an application pool recycle can arise for a number of reasons. It happened to me while I was managing lots of similar ASP.NET web applications, hosted on multiple IIS 6.0 web servers, and I had to find a way to reset their cache in a quick and easy way. In particular, I was using the WebSettings mechanism for storing my ASP.NET application configuration settings and, due to the number of web apps to be contacted on many web servers, the multiple calls to
GetWebSetting("", True) were becoming unmanageable. I found a "quick and easy way" to recycle application pools (hence, also, to reset the ASP.NET cache) through the
DirectoryEntry .NET Framework class, and now I'm sharing this with you.
Recycling the web from the web
I was looking for a way to recycle application pools without the need to connect to the web server (via a Terminal Server connection, or connecting remotely from my local IIS MMC console); as stated, this was useful, especially considering the lots of application pools distributed on more than ten web servers... My first thought was to develop a Windows Forms application (one of my famous "tools"), capable of interacting in some way with IIS or with its metabase, in order to execute an AppPool recycle with a single click. But, then I realized it was more natural to create this piece of code directly inside an ASP.NET application. So, I wrote a single, very "light", ASP.NET page.
This web page needs an XML data file (let's name it ApplicationPoolsList.xml) where the names and paths of all the desired application pools are listed; in fact, my goal was to recycle, at once, a set of "similar" AppPools. This is a sample of the XML data file:
AppPool" node contains the full path of an application pool to be recycled, including the web server machine name and the AppPool name as it appears on the IIS management console.
For example, in "IIS://SERVER00123/W3SVC/AppPools/Northwind":
- "SERVER00123" is the web server machine name (as returned by
System.Environment.MachineName when run on that machine);
- "Northwind" is the AppPool name as it appears on the IIS management console when looking at AppPools hosted on SERVER00123.
The ASP.NET page that does the magic is very simple, and it is coded as follows:
<%@ Page Language="vb" %>
<%@ Import Namespace="System.Xml" %>
<%@ Import Namespace="System.Management" %>
<%@ Import Namespace="System.DirectoryServices" %>
Dim AppPoolsList As New XmlDocument
Dim AppPool As XmlNode
For Each AppPool In AppPoolsList.SelectNodes("AppPoolsList/AppPool")
Dim AppPoolFullPath As String = AppPool.InnerText
Dim w3svc As New DirectoryEntry(AppPoolFullPath)
Response.Write(AppPoolFullPath & "<br />")
Response.Write(AppPoolFullPath & " [error]<br />")
Response.Write("<p />-- done --")
The heart of the execution consists of a call to the
Invoke method on the
DirectoryEntry class (be aware that this call could suffer restrictions depending upon the permission level of the ASP.NET account). I know: it's not a great and wonderful piece of code, but I found it very, very useful to reset the ASP.NET Cache of multiple applications on multiple servers.
Interesting note: you can also use this page to recycle the AppPool that hosts the web application that is serving the page itself. The AppPool is recycled immediately, after the execution of the page terminates.