ColdFusion and IIS freeze

[michaelf83918231]

We are experiencing a strange issue with ColdFusion/IIS, which can’t crack and would need help with.

Our set up is 2x Windows 2008 R2 Servers, ColdFusion 9.01274733 Standard, IIS 7.5. The CF isn’t installed in high availability mode, instead we sync WWW directories across two servers, have identical CF and IIS settings and there is Barracuda Load Balancer in front of the two servers diverting the load.

The issue is that CF/IIS stops working from time to time and the server isn’t loading any cfm nor html files. It can happen once a day or 10 times a day. The “freeze” can lasts from 10 seconds to 3 minutes and eventually fixes itself. IIS or CF restart also fixes it. During the outage the web browser would just be waiting and trying  to load the page (or html file) without any error. When the server is back up again the page would eventually load fine. There are no errors on Windows event viewer and CF only shows time out error. This is affecting only one of the websites on IIS, while other sites are working fine. I was thinking it might be the application pool for the affected website but it’s not stopped during the outages. Perhaps it might be something else on the pool (see the setting in the screenshot)? The issue is affecting both servers.

It seems like the problem is related to how busy the server is as there aren’t any outages during quiet times. So it might be that something is hitting a connections/query/timeout limit? 

Please see the screenshot of cfstat output (frequency - every 10 seconds). The outage period is in red square. There are more than thousand connections on each server so high numbers during the normal operation are expected.

I ruled out networking or SQL server issues.

Any help or pointing to the right direction would be appreciated.

[Wilgeno1]

How much load is this server under? If it's heavy load it's possible that you need to tune the IIS connection in IIS.  See this article by Mark Kruger of CF Webtools.  https://www.coldfusionmuse.com/index.cfm/2011/11/4/iis7.constrain.simultaneous.requests 

I think it will help with your situation. It's also possible your ColdFusion JVM settings might need to be tuned. Are you sure it's IIS that is "freezing"? Actually it could be JVM tuning and potential Garbage Collection issues. Java GC can cause "stop the world" memory cleanups that can last a few seconds or much longer. Before you make changes I'd like to know what your JVM config looks like. We can add GC logging that will tell us what is happening with GC's and identify if the GC's are actually causing the freezes.

Regards,

Wil Genovese

Chief Systems Architect

CF Webtools