Weird behavior with ASP.NET in a web farm

Question

We have 2 web servers in a web farm. We push files to web1 and have a schedule task running every 5 minutes that uses robocopy to copy the files over to web2. We have a website which uses some dlls and we changed one of dll recently to include new properties in a class. We also changed the website to consume those properties. We moved the changed files to web1 and they were then copied to web2 (I confirmed the files are identical). We also changed an appsetting in the web.config with a new value.

It looks like web2 has some kind of cache of the DLL and the web.config. For some requests we see errors that the new property that the webpage is trying to use doesn't exist, but sometimes it works fine (all in web2). Also, the web2 is still using the old appsetting value, although the new value is set. Web1 is working fine with the same codebase!

I made sure that the code was not caching anything in code and is not. I also restarted the servers and IIS 7 (Win Server 2008) a bunch of times. I deleted the Temp ASP.NET Folders and the problem still persists.

Do you guys know what could be causing this problem?

Thanks...

Answer 1

it turns out there was a second web1 which should have been deprovisioned by our hosting company that also had the replication task running. Since the server was never updated because it was out of the web farm rotation (it should have been off) both servers kept overwriting eachother by replicating to web2 back and forth, which explains why sometimes web2 worked and sometimes it didn't.