I have 3 applications on the same web server. Two of them are configured in separate ASP.NET 4 application pools and and one of them is on an ASP.NET 2 application pool.
I'm experiencing intermitent timeouts when accessing those apps during the day. To track down this timeouts, I have setup a ping monitoring service (motive.com). Here is a sample of the timeout ocurrencies log:
app date downtime main reason APP2 19-September-2012, at 14:51 4 mins 50 secs connect() timed out! APP1 19-September-2012, at 14:51 4 mins 50 secs connect() timed out! APP2 19-September-2012, at 14:11 2 mins 50 secs couldn't connect to host APP1 19-September-2012, at 14:11 2 mins 50 secs couldn't connect to host APP2 19-September-2012, at 9:17 2 mins 41 secs couldn't connect to host APP1 19-September-2012, at 9:17 2 mins 41 secs couldn't connect to host ...
As you can see, both ASP.net 4 pools are timing out simultaneously. I'm also monitoring the ASP.NET 2.0 app pool web site and I haven't have one single timeout!
There's no pattern whatsoever related to the time of the day that it occurs (both day/night). Intervals between timeouts don't follow a pattern either, sometimes they happen after 40 minutes, others take some hours in between.
The timeout never lasts more than 5 minutes, but they also vary from 2 to 5 minutes randomly.
At first I thought it might have something to do with application pool recycling but I've checked and recycling is set to occur after 24 hours and disabled for other events (memory peaks, etc.).
The site is infrequently accessed (it's in beta test), so there are no huge number of access, workers demand, memory consumption, etc.
I've also checked the IIS log and there are 2 to 5 minutes gaps during the hours of downtime reported by the monitoring service, but no error message. I also checked the Windows event log and haven't found anything unusual in system and application events.
I'm really desperate right now. If someone could help me out, I'd be really thankful.
Best Regards.
Eduardo de Freitas
Best Answer
If an external host has periods where it cannot establish a TCP connection or the connection times out, then your issue is perhaps network-related, rather than application-related. IIS wouldn't log anything, because it's oblivious to any external network issues - it just services requests it receives.
If you're monitoring service is also showing that ping tests are timing out, this would indicate a definite network connectivity problem. You need to start troubleshooting that.