Web-server – ‘Server Application Unavailable’ in IIS7 after switching to .net 4.0

.net-4.0asp.netautomationiis-7web-server

We recently upgraded to .Net 4.0 and wrote a custom deployment script for our application that uses the Microsoft.Web.Administration library to do things like create websites and setup app pools. We started testing the code on developer boxes and it seemed to work. Then we noticed that if the dev re-built the application it would stop running and IIS7 would give us this (practically useless) error message:

Server Application Unavailable

The web application you are attempting to access on this web
server is currently unavailable.
Please hit the "Refresh" button in
your web browser to retry your
request.

Administrator Note: An error message detailing the cause of this
specific request failure can be found
in the application event log of the
web server. Please review this log
entry to discover what caused this
error to occur.

If we manually recycle the application pool the app will start right back up. We don't see any events or errors in the Application Log. The pool is set to automatically start and recycle on configuration changes.

We have tried every combination of setting in the app pool, application and ASP.net settings. We have tried running the app pool as different user accounts. We have tried deleting the app pool and the application and re-creating both by hand through the UI and the problem still persists.

It's as if using the Microsoft.Web.Administration library poisons the machine so it will never automatically restart app pools again??!!

We would appreciate any insight or debugging advice. We cant run this on any production systems until we understand what caused this to happen.

Best Answer

I found this thread while searching for the exact same error description. And I found what was causing it in my case.

I was converting an application from .net 3.5 to 4.0 and after I changed the app-pool from 2.0 to 4.0 this started. It only happened in classic mode not integrated.

In my case I had wildcard http handlers in web.config:

<add name="Wildcard .net 64 bit" path="*" verb="*" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework64\v2.0.50727\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="None" preCondition="bitness64"/>    
<add name="Wildcard .net 32 bit" path="*" verb="*" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="None" preCondition="bitness32"/>

But I had forgotten to change the path to the .net 4.0 directory

so after changing \v2.0.50727\aspnet_isapi.dll to \v4.0.30319\aspnet_isapi.dll the website started behaving normally.

Hope this helps someone.

Related Solutions

IIS gives 503 after updating .NET 4.0 to beta 2

Try running aspnet_regiis /i from the 21006 framework folder. That should re-register it with IIS7.

How to assign permissions to ApplicationPoolIdentity account

Update: The original question was for Windows Server 2008, but the solution is easier for Windows Server 2008 R2 and Windows Server 2012 (and Windows 7 and 8). You can add the user through the NTFS UI by typing it in directly. The name is in the format of IIS APPPOOL\{app pool name}. For example: IIS APPPOOL\DefaultAppPool.

IIS APPPOOL\{app pool name}

Note: Per comments below, there are two things to be aware of:

Enter the string directly into the "Select User or Group" and not in the search field.
In a domain environment you need to set the Location to your local computer first.

Reference to Microsoft Docs article: Application Pool Identities > Securing Resources

Original response: (for Windows Server 2008) This is a great feature, but as you mentioned it's not fully implemented yet. You can add the app pool identity from the command prompt with something like icacls, then you can manage it from the GUI. For example, run something like this from the command prompt:

icacls c:\inetpub\wwwroot /grant "IIS APPPOOL\DefaultAppPool":(OI)(CI)(RX)

Then, in Windows Explorer, go to the wwwroot folder and edit the security permissions. You will see what looks like a group (the group icon) called DefaultAppPool. You can now edit the permissions.

However, you don't need to use this at all. It's a bonus that you can use if you want. You can use the old way of creating a custom user per app pool and assigning the custom user to disk. That has full UI support.

This SID injection method is nice because it allows you to use a single user but fully isolate each site from each other without having to create unique users for each app pool. Pretty impressive, and it will be even better with UI support.

Note: If you are unable to find the application pool user, check to see if the Windows service called Application Host Helper Service is running. It's the service that maps application pool users to Windows accounts.

Best Answer

Related Solutions

IIS gives 503 after updating .NET 4.0 to beta 2

How to assign permissions to ApplicationPoolIdentity account

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