Why is my IIS 7 App Pool creating multiple Sessions for each request?

I am supporting a legacy Asp.Net web site that is heavily using Microsoft AJAX and the Ajax Control Toolkit. I have run into an issue where when a user logs in successfully and the Session times out, the user is logged out but cannot log back in because the Session variables that I use t开发者_如何转开发o determine an active Session are null.

I got a minidump from the customer and it shows that when this issue occurrs there are multiple Sessions being created in rapid succession. All of the Sessions have a timeout of either 0 or 1. When I dig into them I see that there is usually only one value set.

I have read that App Pool recycling has caused this issue for others. The thing that puzzles me is that for only 4 HttpContexts being created there are 311 sessions.

Has anyone seen anything similar to this?

---

For AJAX stuffs, dumps are not as useful as Fiddler trace,

http://www.fiddlertool.com/fiddler2/version.asp

Reproduce the problem with Fiddler capturing the packets. Then you should be able to analyze the sessions one by one and identify more useful symptoms, so as to know the root cause.