IIS 7 SSO stops working during high CPU load? [migrated]

Posted by DanB on Pro Webmasters See other posts from Pro Webmasters or by DanB
Published on 2011-06-20T18:26:00Z Indexed on 2011/06/21 0:30 UTC
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iis7

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On our IIS7 site (Windows 2008 Server), we have set up single sign-on (SSO). It seems to work fine most of the time, but when the CPU load becomes high, SSO authentication completely stops working. I did some research and tried this suggestion to increase the max number of worker processes in the default app pool, but the increase did not help.

Some details:

The site is a WordPress blog.
The server has plenty of RAM (2 GB) and free disk space.
SSO is achieved by putting a copy of the WordPress login page (wp-login.php) into a subfolder below the root that has anonymous authentication disabled, and then redirecting the browser to it. This was the recommendation of Microsoft given to our consultants.

To increase CPU load for testing, I have three scripts hit the home page simultaneously, over and over. This drives CPU to 100%. When these scripts are running, SSO authentication simply doesn't happen. As soon as I stop the scripts, SSO works again.

(I should mention that the SSO problem also happens when many users visit the site at once....)

The WordPress database process (mysqld) is not stressed at all by the scripts.

I would be happy to provide further diagnostics. Any help appreciated!

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