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I have a small asp.net website (using SQLServer express) on an T2.micro AWS EC2 instance running Windows Server 2012 R2. This is a very low volume site. It has been operational for 2 years without any issues.

I did Windows updates over the New Years and now everyday I am getting a CPU over 100% alert from Cloudwatch between 3:00 and 5:00am. This isn't users or usage, but likely some other automated process. My question is what is the best way to identify why this is occurring and if needed, stop it?

I look at the Event log and right before the alerts there are entries relating to "Windows Module Installer" under the source of "Service Control Manager". They are otherwise not descriptive.

I believe these could be related to automated updates. I did change the update setting to 'Download Updates But Let Me Choose to Install Them' so I was thinking that this process could be running during early morning hours.

Is there any better log or or way (through AWS perhaps) to identify what process is causing a CPU alarm?

Thank you for any guidance or suggestions!

vbuser2004
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  • Disable that update process and see if the alert keeps coming. Then you can rule this service out. – SPRBRN Jan 08 '16 at 15:22
  • Have you tried signing-in to the instance between 3am and 5am and checking Task Manager? – Matt Houser Jan 08 '16 at 16:18
  • @SPRBRN - thank you. I did just that (changed update to: let me choose when to download) and the alert did not come up so it was related to updates. Thanks. – vbuser2004 Jan 09 '16 at 13:12

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After disabling the update service for one night, the alarm is gone. This pretty much identifies the cause of this alert. Now that you know this, you can ask if this is a problem. I think not, but I might be wrong.

I guess Windows has logfiles that can show you the exact time this happens. You can stay up one night, and try to see if the website still works. If Windows handles this correctly, it gives the website priority while updating, and the website should work, although probably slower.

The fact that CPU usage is 100% is not a concern. Monitor your own laptop, do an update or some photo editing, and you'll see the same effect. If this happens for hours, it's a concern and something to look at. If the harddisk usage was at 100%, that would be a concern for immediate action.

You can probably disable the alert for these hours, or set it to go off only after longer high usage. We use Nagios, and it checks for various things, like webserver response time. If it finds a slow reaction, it checks after five minutes again, then once again later, and then gives an alert. So you could set Cloudwatch for less frequent alerts during 3-5AM.

SPRBRN
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After updating my windows 10, it start a problem in my pc, High CPU usage. I am just fedup with a lot of windows versions and updates. I suffer few days with this problem. By studying online I found the problem is related with Windows Modules Installer Worker. I followed instructions of an article and it solved my issue. In my opinion, Microsoft should have control releasing Windows versions randomly and to be serious about releasing its updates.

Belayet Hossain
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