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CloudWatch

https://aws.amazon.com/cloudwatch

To monitor services. The services send metrics to CloudWatch, and you can create alarms based on metrics.

Is a regional service.

AWS services that publish CloudWatch metrics - https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/aws-services-cloudwatch-metrics.html - Contains links to metrics for each service

Utilization Saturation and Errors (USE) Method - https://www.brendangregg.com/usemethod.html

info

CPU utilization usually gets problematic when crossing 80–90%, because the wait time explodes.

On a supermarket, the wait time for your customers is very high when your cashiers are used for 90% of the day, because customers don’t arrive at the same time at the queue.

Wait time is exponential to the utilization of a resource.

When you go from 0% utilization to 60%, wait time doubles. When you go to 80%, wait time has tripled. When you to 90%, wait time is six times higher, and so on. If your wait time is 100 ms during 0% utilization, you already have 300 ms wait time during 80% utilization, which is already slow for an e-commerce website.

(From AWS in Action p. 319.)

A CloudWatch metric has the following parameters:

  • Namespace: eg AWS/EC2, AWS/EKS or AWS/ECR.
  • Dimensions: eg AutoScalingGroupName (EC2), Cluster Name (EKS), TargetGroup (ALB), LoadBalancer (ALB) or QueueName (SQS).
  • MetricName: eg CPUUtilization (EC2), RequestCount (ALB) or APIServerRequests (EKS).

A CloudWatch alarm consists of the following:

  • Metric: CPU usage, health check...
  • Rule: a function that defines a threshold.
  • Actions: what to do when the alarm state changes.

The state can be OK, INSUFFICIENT_DATA or ALARM.

You can combine multiple alarms into one composite alarm, using boolean logic, see Combining alarms.

Detailed monitoring - https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/cloudwatch-metrics-basic-detailed.html

In different AWS services, detailed monitoring also has different names. For example, in Amazon EC2 it is called detailed monitoring, in AWS Elastic Beanstalk it is called enhanced monitoring, and in Amazon S3 it is called request metrics.

You are charged $0.10 per alarm metric month (first 10 alarm metrics are free). If you have alarms like TargetTracking-table/Customer-ProvisionedCapacityHigh-a53f2f67-9477-45a6-8197-788d2c7462b3 is because of DynamoDB auto scaling. To get rid of these alarms, go to the DynamoDB table and do Actions → Edit capacity, and at "Capacity mode", change from "Provisioned" to "On-demand". See Unexpected CloudWatch In The Billing Area.

Learning resources​

(Packt) Infrastructure Monitoring with Amazon CloudWatch - https://www.packtpub.com/product/infrastructure-monitoring-with-amazon-cloudwatch/9781800566057 - https://github.com/PacktPublishing/Infrastructure-Monitoring-with-Amazon-CloudWatch - https://www.youtube.com/playlist?list=PLeLcvrwLe186RQpGRXrruQ-zWFPYrFS5E

CloudTrail - https://mng.workshop.aws/cloudtrail/insights.html

https://workshops.aws/categories/Amazon%20CloudWatch