IIS Hang Troubleshooting

Question

I'm running a website on IIS 6 (Windows Server 2003) that hangs occasionally.

Timeline:

Released to the wild, website ran fine for 3 days.

Website hangs on every request until the website is stopped and started.

Website runs for 2 weeks with no problem.

Website hangs on every request until site is restarted.

We see a few application log entries before hang starts: Faulting application w3wp.exe, faulting module unknown, version 0.0.0.0 fault address -------.

The application installed on the website is written in .Net 2.0.

Can anyone please guide me on troubleshooting this issue? Thanks!

Answer 1

Your best bet might be to use adplus to capture a memory dump of the hanging w3wp process, and then use windbg + the sos extension to try to determine the cause of the hang.

You can get adplus and Windbg here: http://www.microsoft.com/whdc/devtools/debugging/default.mspx

Also, Tess Ferrandez' blog is an absolute goldmine of information on learning how to analyze memory dumps with Windbg. She even has a set of labs you can go through targeted toward specific scenarios.

http://blogs.msdn.com/tess/default.aspx

Answer 2

There are many reasons why this could happen. A couple of years ago, I had this happen on web project in production, and it took a call to Microsoft to fix it. I wish I could give you specific details but this is what I remember.

.NET caches the folders in your web application. There is a registry key on the server (cannot remember where ) that sets a folder limit (believe it or not). The limit was set to 150 folders by default. If you had more than this many folders in your web application, and you tried to access the 151st folder, it would crash IIS.

Yes this sounds crazy but trust me, I spent weeks with Microsoft until we found out the cause of the crash. The answer at the time was to up the limit in the registry and reboot the server. This was a couple of years ago, and I hope that this was fixed in later updates, but I offer this to you just in case you are using an older version of Server 2003.

I am sorry I cannot provide more specific details, but I just want to let you know my experiences just in case this sounds like your issue.

Answer 3

make sure IIS is set to be able to recycle its process automaticly, might help to fix the issue if it is a memory leak. (well ok cope with the problem not fix)

My advice is to give you app its own application pool, so you are 100% sure that its the appication you think pulling the server down, what dose the application log say when this happens?

From the information you have given it sounds like its a memory leak or open db connection / thread issue.

P.s If you are using N2 there was a known issue that when IIS recycled it wouldnt come back up.