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From Yun Feng Chua <>
Subject RE: isapi_redirect.dll fail in SSO on high cpu load
Date Fri, 23 Jul 2010 07:18:30 GMT

Yes it is a IIS issue. 
and i think i just solve it. 

I increase the "Max number of Worker Processes" from 1 to 3 in the Default Application Pool.

and it works.

It will not prompt for authentication immediately anymore, but will just try to serve the
page when the cpu is not 100%.

I should say that the web application is very SQL intensive.

 If the application makes a large number of long blocking calls (e.g. long SQL/Oracle Queries),
more worker 

will help (assuming that the backend can handle the connection load).

> From:
> To:
> Date: Wed, 21 Jul 2010 09:41:10 -0400
> Subject: RE: isapi_redirect.dll fail in SSO on high cpu load
> I am going to guess that some policy in Windows rejects the high volume of logons, too
many connections or something of that kind. It's most likely not a Tomcat problem. Andre suggestions
are pretty good in terms of isolating it. I would start by stressing IIS alone with a static
page in it.
> Since you're running on Windows, you might as well get rid of IIS and replace it with
a Waffle filter - 
> dB. @ 
> Moscow|Geneva|Seattle|New York
> -----Original Message-----
> From: Yun Feng Chua [] 
> Sent: Wednesday, July 21, 2010 3:07 AM
> To:
> Subject: isapi_redirect.dll fail in SSO on high cpu load
> Hi, 
> Currently using Tomcat 5.5 and isapi_redirect.dll 1.2.14 in IIS 6.0
> Configure with IIS integrated authentication for SSO.
> Notice that under high cpu load in the server, 100% util, the website prompt for authentication.
> When the cpu load subsided, the SSO is working. 
> Any ideas why it prompt for authentication under heavy cpu load?
> thank you 
> yun feng, chua
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