CloudWatch Essentials:

  • CloudWatch is used to monitor AWS services, such as EC2, ELB and S3.
  • You monitor your environment by configuring and viewing CloudWatch metrics.
  • Metrics are specific to each AWS service or resource, and include such metrics as:
    • EC2 per-instance metrics:
      • CPUUtilization
      • CPUCreditUsage
    • S3 metrics:
      • NumberOfObjects
      • BucketSizeBytes
    • ELB metrics:
      • RequestCount
      • UnhealthyHostCount
  • Detailed vs. Basic level monitoring
    • Basic: Data is available automatically in 5-minute periods at no charge.
    • Detailed: Data is available in 1-minute periods.
  • CloudWatch Alarms can be created to trigger alerts (or other actions in your AWS accounts, such as an SNS topic), based on threshold you set on CloudWatch metrics.
  • Auto Scaling heavily utilizes CloudWatch - relying on threshold and alarms to trigger the addition (or removal) of instances from an auto scaling group.

CloudWatch Alarms:

  • CloudWatch Alarms allow for you (or the system admin) to be notified when certain defined threshold are met on CloudWatch metrics.
  • For example, you can setup an alarm to be triggered whenever the CPUUtilization metric on an EC2 instance goes above 70%.
  • Alarm can also be used to trigger other events in AWS like publishing to an SNS topic or triggering auto scaling.

CloudWatch EC2 Monitoring:

  • System Status Checks: (things that our outside of our control)

    • Loss of network connectivity.
    • Loss of system power.
    • Software issues on the physical host.
    • Hardware issues on the physical host.
    • How to solve: Generally stopping and restarting the instance will fix the issue. This causing the instance to launch on a different physical hardware device.

  • Instance Status Checks: (software issues that we do control)

    • Failed system status checks.
    • Misconfigured networking or startup configuration.
    • Exhausted memory.
    • Corrupted file system.
    • Incompatible kernel.
    • How to solve: Generally a reboot, or solving the file system configuration issue.

  • By default, CloudWatch will automatically monitor metrics that can be viewed at the host level (NOT the software level), such as:

    • CPUUtilization

    • Network in/out

    • CPUCreditBalance

    • CPUCreditUsage

  • OS level metrics that required a third party script (perl) to be installed (provided by AWS)

    • Memory utilization, memory used, and memory available.

    • Disk swap utilization

    • Disk space utilization, disk space used, disk space, available.

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