“Service Unavailable” in IIS7 with 32 bit application pool

As sometime happens, while setting up a repro for a customer (I’m working with him on a completely different problem) I wanted to test my sample code on a 32 bit w3wp.exe instance (I am running Windows 2008 x64); nothing easier on IIS7, just create a new application pool and change its “Enable 32.Bit Applications” property to true in IIS Manager and you’re done:

 

But when I tried to run my code, I got this a “HTTP Error 503. The service is unavailable” message and the application pool was stopped. The Application event log contains a few entries like the following:

Log Name:      Application
Source:        Microsoft-Windows-IIS-W3SVC-WP
Date:          02/02/2009 14.19.05
Event ID:      2280
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      <computername>
Description: The Module DLL C:\Windows\system32\RpcProxy\RpcProxy.dll failed to load.  The data is the error.

I also got some of this warning:

Log Name:      System
Source:        Microsoft-Windows-WAS
Date:          03/02/2009 20.42.55
Event ID:      5139
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      <computername>
Description: A listener channel for protocol 'http' in worker process '4580' serving application pool '32bitPool' reported a listener channel failure.  The data field contains the error number

If I changed the application pool back to a 64 bit process, everything worked fine again.

I save you the tedious details, but the point is: RpcProxy.dll is 64 bit, obviously it cannot by loaded into a 32 bit process…

As I usually do as part of my “learning experience”, I installed all the available roles for IIS7 and one of them is “RPC over HTTP Proxy”:

This installs RpcProxy.dll (and other files) and changes applicationHost.config adding a new global module:

<add name="PasswordExpiryModule" image="C:\Windows\system32\RpcProxy\RpcProxy.dll" />

How can I prevent IIS from loading it? Easy, just add the preCondition=”bitness64” attribute as follows:

<add name="PasswordExpiryModule" image="C:\Windows\system32\RpcProxy\RpcProxy.dll" preCondition="bitness64" />

Bingo, I finally have my 32 bit worker process up and running!

 

 Carlo

Quote of the day:
We are born charming, fresh and spontaneous and must be civilized before we are fit to participate in society – Judith Martin