Limiting asp.net sessions in IIS7

Question

Is there a way of limiting the number of asp.net (in-process) sessions from within IIS7? I am thinking along the lines of the existing setting that allows this for classic asp. Basically we want to be able to limit the number of concurrent sessions on a server and once reached redirect other traffic to a "we are busy" type page. On previous systems (classic asp) we have done this by redirecting the 503 response to a holding page.

I realise this could potentially be done from within the asp.net code but monitoring the session start & ends isn't ideal. Is there an extension for IIS that could limit the sessions, or maybe one that is flexible that can use any Perfmon counter?

Many thanks.

Answer 1

There isn't a way to do this out of the box by configuring any Session State configuration settings.

You could write your own provider to do this:

Implementing a Session-State Store Provider
Sample Session-State Store Provider

The example uses SQL but you could modify to create your own in-memory store.

Limiting sessions at the Session State provider level may not be the best way to tackle this problem. The problem you're going to encounter is when you have the scenario where your site has maxed out the number of available sessions but then you have a drop in visitors. Because there is a session state timeout there will be unused session state instances and until these sessions time out you can't accept any more visitors. If your timeout is set to the default (20 minutes) and 20 or 30 users "go away" then it'll be 20 minutes before you can accept new sessions.