CloudWatch Alarms

  • Alarms are used to trigger notifications for any metric.

  • Alarms cab be raised for various options such as sampling, max, min etc.

  • Alarm States

    • OK

    • INSUFFICIENT_DATA

    • ALARM

  • Period

    • Length of time in seconds to evaluate the metric.

    • High resolution cutom metrics can be collected for periods like 10 secs, 30 secs or multiple of 60 secs.

  • Targets

    • Alarms have a targets such as stop, restart or recover an EC2 instance.

    • Trigger Auto Scaling Action.

    • Send notifications to SNS

Composite Alarms

  • CloudWatch Alarms are on a single metrics

  • Composite Alarms are monitoring the states of multiple other alarms, basically AND and OR conditions.

  • This helps creating complex composite alarms, so as to reduce alarm noise.

EC2 Instance Recovery

  • ClouWatch Alarms can be created on following EC2 instance status Check,

    • Instance status -> Check EC2 VM

    • System status -> Check underlying hardware

    • Attached EBS status -> Check attached EBS volumes

  • On breach of these alarms, one can start EC2 Instance Recovery, which moves an EC2 instance from one host to another.

  • On recovery of EC2 instance, we get same private, public, elastic IP, metadata, Placement group as with previous host.

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