ASP.NET Single Worker Thread? (In Memory Session)

Answer 1

Your application receives multiple requests at a time. Based on your edits and comments here you are looking for information on Web Gardens and sessions, as opposed to threads and session state.

Web Gardens use multiple processes and act like a load balancer when it comes to session state. Each process will have a separate in memory session store. IIS will send requests to any available process. Since the processes do not share session state then session usage will only really work if your session provider is shared between all the web garden processes.

Web Gardens only make sense if you use something like SQL Server for session state, and want to have affinity with a particular CPU/core. Since you can increase the number of threads this may be a more appropriate optimization for some users than using web gardens. However some applications may perform better with web gardens due to a particular work load or application characteristic. Use of web gardens in testing could also help work out some potential issues present under load balancing.

I believe it uses the .NET ThreadPool and has 20 threads by default. The each request coming into the server may be handled on a separate thread. The ASP.NET performance guidelines have some information on this topic.

Answer 2

In memory sessions means you should typically only have one front-end web server at a time, not a single worker thread :D

The reason being that any information stored in session on one machine is not available on the other. If you have two front-end web servers and your proxy or firewall does "load-balancing" whereby it will randomly assign requests to web servers, then you will have problems. That said, the problem is easily solved with so called "sticky sessions" where users are always sent to the same server.

-Oisin