Why AWS CloudWatch does not have Memory usage metric for Autoscaling group

Question

I am trying to create a graph for memory usage of an autoscaling group but I discovered that there is no such metric. Although there is Memory usage metric but it is for individual instances. It is useless since instances keep on changing in autoscaling group. I want to know the technical reason why AWS cloudwatch didn't provide it. Moreover I want to know the work around to achieve it.

Answer 1

The metrics that AWS provides can be collected at the hypervisor level. But memory metrics (like disk metrics) is from the OS level. So it is a custom metric that you have to periodically push to CloudWatch.

Monitoring Memory and Disk Metrics for Amazon EC2 Linux Instances shows how to push your metrics to CloudWatch. Install the scripts (along with credentials if you are not using IAM role) before creating your AMI and you are set. Each instance in AS will start pushing its memory metric to CloudWatch. Not sure how useful it will be for you.