Auto Scaling

Jump to

• Useful Libs and Tools
• Useful Articles and Blogs
• Scheduled scaling
• Pre-scaling

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Useful Libs and Tools

• AWS Auto Scaling Custom Resources - aws/aws-auto-scaling-custom-resource

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Useful Articles and Blogs

• Choosing the right health check with Elastic Load Balancing and EC2 Auto Scaling, AWS, 11 Apr 2023
  • There are three strategies to measure instance health:
    1. liveness checks,
    2. local health checks (or shallow health checks), and
    3. dependency health checks (or deep health checks).
  • See also Implementing health checks
• AWS scaling options - AWS Auto Scaling vs. Amazon EC2 Auto Scaling vs. Auto Scaling for Other Services
  • See "Q. How is AWS Auto Scaling different than the scaling capabilities for individual services?" in https://aws.amazon.com/autoscaling/faqs/

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Scheduled scaling

ℹ️ The cron expression formats used in AWS::AutoScaling::ScheduledAction and AWS::ApplicationAutoScaling::ScalableTarget are different.

• For ASG / AWS::AutoScaling::ScheduledAction (see details):

  [Minute] [Hour] [DayOfMonth] [MonthOfYear] [DayOfWeek]
  

• For Fargate / AWS::ApplicationAutoScaling::ScalableTarget (see details):

  cron(Minutes Hours DayOfMonth Month DayOfWeek Year)
  

ECS

• AWS::ApplicationAutoScaling::ScalableTarget
• CLI https://gist.github.com/toricls/fea9d8a4eb606a27f6666a1abc6a6fd8
• Doc https://docs.aws.amazon.com/autoscaling/application/userguide/application-auto-scaling-scheduled-scaling.html

ASG

• AWS::AutoScaling::ScheduledAction
• CLI https://docs.aws.amazon.com/autoscaling/ec2/userguide/ec2-auto-scaling-scheduled-scaling.html#create-sch-actions-aws-cli

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Pre-scaling

As desired = running + pending - terminating, but scaling calculates only use running, so it can get into race conditions when setting desired out of band.

Possible solutions:

• Include ScalingSuspend and ScalingResume calls around any pre-scaling tasks.
• Use scaling policy to scale up/down, instead of setting desired count.