I have a server running windows server 2008 R2, recently my websites have becoming unresponsive at least once a day, seemingly at random intervals.

I have installed some monitoring software and noticed that the anonymous user count spikes when this happens, it normally averages around 100-200 users, but the spikes are jumping to around 400-700 users.

This has only recently started to happen in the last few weeks, a restart of my IIS Server fixes almost immediately.

What should i be doing to investigate this further, what could be causing these spikes?

My initial thought was it being a spider crawling my site at a ridiculous rate, but i'm not sure how to determine if this is true or not.

Any advice is appreciated.


Does your monitoring software not show you what pages are being hit? That might help show you if it's a spider.

At any rate, it's either of :

  1. Too much load for the plain ol' web server (IIS) and OS to handle, in which case you need to rate-limit your visitors (probably at your internet connection), or scale up to more servers, or scale out with a bigger server.

  2. The visitors are hitting a dynamically-generated page that isn't dealing with the load well - in which case, you could either do one of the above solutions, or fix the code so it deals with more load better.

  3. You have some mis-configuration in the OS. Have you confirmed that it's a web-server-related process that's driving the load high? Are you running SQL on the same machine, perhaps?

With the minimal amount of information given, that's about the most that I can say.

  • 1) Well a few weeks ago with the same load, everything was just fine. 2) same as 1, nothing has changed that could affect performance. 3) No sql server, there is a database server called RavenDb, but it won't be adding connections to my IIS server. I'm not sure what other information i can tell you that will help. I think my question really at this stage is how to get a list of IP addresses from my IIS logs to see where the connections are coming from when it spikes... – Paul Hinett Dec 27 '12 at 16:39
  • @paul-hinett - If you are using 2008 R2, then it should be IIS 7.5. Open IIS Manager. Go to your site properties and click Logging. In the Log file section under Format click Select Fields and check Client IP Address(c-ip). If you already have c-ip logging in your logs, then use logparser to get the ip. – Muhammad Dec 28 '12 at 4:30

Ok i found the answer, it was down to a bug in our NoSql Database software which has now been fixed. It was taking all available memory and killing the server.

Not sure why the anonymous user count was increasing at the same time though, but this no longer happens now.

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