AWS CloudWatch Alarms

Eric Donaldson
Eric Donaldson used Ask the Experts™
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Have cloudwatch alarms keep going off on EC2 instance for high cpu.  Looks like it auto scales but then goes off again in another hour.  How can this be troubleshooted?
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Zephyr ICTCloud Architect
Commented:
What kind of scaling are you using? Dynamic probably, but at what settings?
Can you get more info on why the EC2 instance shows high cpu? Or is this expected behavior?

The more info you can give us the better we can help.

Author

Commented:
Its high cpu over 95 percent.  Im just trying to get the cpu down to normal.  How can I see on AWS what is causing this?
Zephyr ICTCloud Architect

Commented:
Is it a Linux or Windows instance? Can you log on and run an app to see what is taking up the CPU time? For Linux something like "top" and the "task manager" for Windows for example.

What type of instance is it? Is it a micro instance? If it is you might be looking at "cpu steal time" issues.

Author

Commented:
linux and m3.large
Zephyr ICTCloud Architect
Commented:
Well, the best way to start is to try and log onto the Linux instance and run top to see what's causing the high CPU. That's going to be the fastest way to find out what's happening.

Do you have Cloudwatch enabled for the log files of your instance?
Have you looked at your graph of CPU usage?

Check the following link to maybe get some help pinpointing what is causing your issue: https://www.datadoghq.com/blog/understanding-aws-stolen-cpu-and-how-it-affects-your-apps/

Depending on the EC2 instance type and the underlying hardware, you may not be paying for access to all of the underlying CPU cycles.

On EC2, steal doesn't depend on the activity of other virtual machine neighbors. It is simply a matter of EC2 making sure you are not getting more CPU cycles than you are paying for.

If your m3.large gets 50% of the underlying faster CPU, then for every bit of CPU you are using, you will see another equal percentage flagged as steal.

It would be nice if EC2 let you think your true available CPU was "100%" instead of teasing you with the rest of the CPU that you don't have access to, and then telling you that you can't have it when you try to use the CPU, but that's the way it works given the current VM and host setup.

Author

Commented:
Ok, thanks, but would this also be the case in a VPC?  I wasnt sure if the resources were still shared under that circumstance

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