Auto Scaling Monitoring

Auto Scaling can monitor instances and groups by

• Health checks –
  • EC2 Auto Scaling periodically performs health checks on instances in Auto Scaling group
  • It identifies unhealthy instances
  • Auto Scaling finds health status using EC2 status checks, ELB health checks, or custom health checks.
• CloudWatch metrics
  • EC2 Auto Scaling publishes data points to Amazon CloudWatch
  • CloudWatch retrieve statistics about those data points as ordered set of time series data or metrics.
  • use these metrics to verify that system is working as expected.
• CloudWatch Events
  • EC2 Auto Scaling can also submit events to CloudWatch Events
  • Event submission is when
  • Auto Scaling groups launch or terminate instances,
  • lifecycle action occurs.
  • Can invoke Lambda function when event occurs.
• SNS notifications
  • EC2 Auto Scaling can send Amazon SNS notifications
  • SNS sent, when groups launch or terminate instances.
• CloudTrail logs
  • CloudTrail tracks calls to EC2 Auto Scaling API by
  • It stores information in log files in S3 bucket
  • Use log files to monitor activity of Auto Scaling groups.
  • Logs include
    • which requests were made,
    • source IP addresses of requests
    • who made request
    • when request was made

Instance Health Status

EC2 Auto Scaling finds health status of an instance using one or more of following:

• Status checks by EC2 and includes both instance and system status checks.
  • Health checks provided by Elastic Load Balancing.
  • custom health checks.
• Instance is considered unhealthy in any state other than running or if system status is impaired,
• unhealthy instance is terminated and replacement is launched
• Following states makes instance unhealthy
  • stopping
  • stopped
  • terminating
  • terminated

Auto Scaling Group Metrics

AWS/AutoScaling namespace includes following metrics.

CloudWatch Events

• It can automate AWS services and respond to system events as
  • application availability issues
  • resource changes
• Events from AWS services are delivered to CloudWatch Events in real time.
• Define rules to indicate actions to perform, against events
• EC2 Auto Scaling can send events to CloudWatch Events for events
  • EC2 Instance-launch Lifecycle Action
  • EC2 Instance Launch Successful
  • EC2 Instance Launch Unsuccessful
  • EC2 Instance-terminate Lifecycle Action
  • EC2 Instance Terminate Successful
  • EC2 Instance Terminate Unsuccessful

SNS Notifications

EC2 Auto Scaling can send SNS notifications against following events

message includes following information:

• Event — event.
• AccountId — AWS account ID.
• AutoScalingGroupName — name of Auto Scaling group.
• AutoScalingGroupARN — ARN of Auto Scaling group.
• EC2InstanceId — ID of EC2 instance.