Seamless deployment in ASP.NET (IIS kills worker process before new worker process is ready)

Question

I am trying to deploy a .NET Web application to IIS (7.5) without any hassle for the users. I have made sure that Disable Overlapped Recycle is False b

Answer 1

Whilst Smirkin's answer provides a nice seamless way for an Admin to deploy a site with little or no downtime, and should resolve your issue with missing assemblies/references, if you have breaking changes in your code-base (i.e. removing old pages, changes to forms, etc.), then using this method could still result in some "hassle" for any users who start a process before the switch and complete it after the switch (i.e., they request a page before you switch over, start filling it in, and then submit the page after you've switched over to the new directory).

I know you don't want me to say this, but without a load-balancer with Sticky-Sessions enabled, you won't be able to allow people to continue using the old version of the site until they've finished while handling new sessions on the new version - by changing the home directory of the application, IIS will perform a re-compile of the app and restart the processes. This way you can set the old server to continue serving its current connections, but tell the load-balance not to send any new connections to it.

There is however another step you can take to help mitigate the issues often seen around this:

Configure the MachineKey to be a constant value rather than AutoGenerate - this means that when the AppPool recycles it will use the same key, and so be able to decrypt session cookies, viewstate, etc.