We have scaled-out some portions of our ASP.NET app to run on one server, and other portions to run on another server (& under a subdomain).
The two servers share (SQL Server) Session. We used this MS article to create a tiny HTTP Module to sync app domain name between the two servers (sans the cookie domain code, which can be configured in the web.config. I later found this CodeProject article which is essentially the same.)
Everything's working well, except for a small issue: deployment changes or web.config tweaks require a manual app pool recycle (the auto-recycle no longer works - instead we get the "web server is currently unavailable / hit refresh" error).
I tried moving the app domain naming code from the HTTP Module into the Application_Start section of the Global.asax (maybe this is a better place for it?) - but received the same problem.
I know that one solution is to hard-code the app name in one of the SQL Server Session stored procedures; but am a bit hesitant to do this.
Edit: The app is ASP.NET 3.5 under IIS 6.0 (thanks @Chris & @bzlm)