Changing IIS 6 Application Pools for a Web App Project

Question

Following recent hardware problems, I attempted to switch a couple of our websites to use new, individual application pools. A test run on our staging server worked fine, and has had no visible negative consequences.

Unfortunately, trying the same operation on our live machine left one of our key applications struggling - my best guess is with some kind of mismatch in Session state. I could log in fine, but a few clicks later would be presented with a screen that was part login screen, but with all menus visible. This indicates to me that part of the system thinks the session had been lost (redirect to login page), but IIS itself had not lost the session (hence the menus showing on the master page).

I tried recycling all the Application Pools (new and old), and each website using IIS Manager. I also tried a single-space change to the web.config file, and a full release of the dll's. Still, I could intermittently use the system for a few clicks, do some useful stuff, then maybe find myself at a login screen again or similar. We have some logging and on some occasions I could see that the session was being timed-out after a couple of seconds, substantially less than the settings on the App-pool (default 20mins).

As soon as I switched the web site's app-pool back to the default, everything was ok again.

What have I missed? Any suggestions gratefully received!

EDIT:

Just thought... on the staging environment I did name the App-pool differently from the website name (e.g. Xxxx_Dev, Xxx_Test etc) but on live I just called it the same name as the website. Could this cause an issue?

Answer 1

do your various applications all use Forms Authentication? Have you specified unique path attributes in each form tag in the web.config under the Authentication tag?

Answer 2

OK. I think I've found the problem.

I was actually using an Application Pool that had been set up by someone else - of the expected name - but they had set it up with the Properties, Performance tab | Web Garden option to use 4 worker processes. I have now changed that to 1.

As the session state was being stored 'In Process' (the default), each time the connection hit a new thread it also essentially lost any stored session variables, as I now understand things.

Its early days, but a simple switch to the newly altered Application Pool (no restarts or web.config saves necessary thus far) and everything appears to be behaving normally.