Configuration a web application for Application Warmup in IIS

Further to one of my previous blog posts about how to configure an ASP.NET web application for Application Initialization (warmup), here's the follow up: a powershell script for configuring the corresponding IIS application for warmup:


<# .SYNOPSIS Sets the required settings in the applicationHost.config file for an application to be able to automatically initialize. .PARAMETER WebSitePath The name of the web application that's to have it's settings configured for application warmup. .PARAMETER RestartService A switch to indicate that the W3SVC (IIS) service should be restarted after the change. #> function Set-WebApplicationInitialization { [CmdletBinding(SupportsShouldProcess = $true)] Param( [Parameter(Mandatory = $true)][ValidateNotNullOrEmpty()][string] $WebSitePath, [Parameter(Mandatory = $false)][switch] $RestartService ) $pathElements = $WebSitePath.Split('/') $site = $pathElements[0] $appSubPath = @($pathElements | select -Skip 1) -join '/' $webApp = Get-WebApplication -Site $site -Name $appSubPath if ($webApp -eq $null) { throw "Failed to find application '$appSubPath' under web site '$site'" } if ($PSCmdlet.ShouldProcess($WebSitePath, "Update application to use Application Initialization settings")) { $appPoolPath = "IIS:\AppPools\$($webApp.applicationPool)" Set-ItemProperty -Path $appPoolPath -Name 'autoStart' -Value 'true' Set-ItemProperty -Path $appPoolPath -Name 'startMode' -Value 'AlwaysRunning' Set-ItemProperty -Path $appPoolPath -Name 'processModel.idleTimeout' -Value '00:00:00' $applicationPath = "IIS:\Sites\$($WebSitePath)" Set-ItemProperty -Path $applicationPath -Name 'preloadEnabled' -Value $true Write-Verbose "Updated properties for web application '$appSubPath' running on pool '$($webApp.applicationPool)'" if ($RestartService.ToBool()) { if ($PSCmdlet.ShouldProcess("W3SVC", "Restart web service")) { Restart-Service W3SVC } } } }

Implementing Application Warmup with IIS 7.5 on Windows Server 2008 R2

In order to be able to support certain features of some of our applications, we've found the need to enable application warmup. However, this isn't built-in to IIS 7.5, but rather it's available as the Application Initialization module provided by Microsoft. In order to get this working, you'll need to do the following:

1. Install the Application Initialization 1.0 module available from Microsoft here.
2. You'll need to edit the applicationHost.config file on your server to enable Application Initialization. To do this, you'll need to open the file at %WINDIR%\System32\inetsrv\config\applicationHost.config in your text editor of choice and make the following changes:
• Find the 'application' element that you wish to enable for Application Initialization, which you can do with an XPath similar to "/configuration/system.applicationHost/sites/site/application" and once found, set the preloadEnabled="true" attribute on the XML element. Add the element if it's not already there.
• While on the 'application' element, take note of the 'applicationPool' value, because that's the Application Pool in which the application runs. Find the configuration node for that application pool (XPath: /configuration/system.applicationHost/applicationPools) and then set the following attributes on the <add> element for the application pool and its child 'processModel' element:
• <add .... startMode="AlwaysRunning">
• <processModel ... idleTimeout="0">
3. In your application's web.config file, you'll need to add the following elements:

<system.webServer>
<applicationInitialization remapManagedRequestsTo="/InitializationProxyPage.txt" skipManagedModules="true" doAppInitAfterRestart="true">

            <add initializationPage="/Services/MyCustomService.svc" hostName="localhost" />

        </applicationInitialization>

        <directoryBrowse enabled="true" />
</system.webServer>

You'll need to have the "InitializationProxyPage.txt" file in the root of your web application.

4. Enable "Anonymous" authentication in the Authentication panel of your application in IIS. This is necessary so that the warmup page can successfully execute a GET request for your initialization page to kick off the warmup.

5. If you use the system.webServer/security/authorization or system.webServer/security/authentication sections in your web.config to control access to the application, you'll also need to add the following under the /configuration element as a sibling to the system.webServer element:

<configuration>
<location path="InitializationProxyPage.txt">
        <system.webServer>
            <security>
                <authorization>
                    <clear />
                    <add accessType="Allow" users="*"/>
                </authorization>
            </security>
        </system.webServer>
    </location>
</configuration>
This will grant explicit access to the InitializationProxyPage.txt file to all users (including the App Pool Identity user) so that application warmup is guaranteed to have access to that file and can bootstrap your services.

Using the Azure Key Vault: an experiment

So, I've found this article on MSDN about how to use the Azure Key Vault for storing secrets, e.g. encryption keys. Let's see how it goes.

**UPDATE** : So, apparently we won't be able to use the Key Vault because use of the key vault at this time requires that your application be used in conjunction with Azure Active Directory, which ours does not. That's unfortunate.