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Auto Scaling Group (ASG) For Solution Architects

Auto Scaling Groups For Solutions ArchitectsΒΆ

  • [[ASG Default Termination Policy]] (simplified version)
    • Find the AZ which has the most number of instances
    • If there are multiple instances in the Availability Zones to choose from, delete the one with the oldest configuration

  • ASG tries the balance the number of instances across Availability Zones by default

  • The [[cool-down period]] helps to ensure that your Auto Scaling group doesn't launch or terminate additional instances before the previous scaling activity takes effect.

  • In addition to default cool-down for Auto Scaling Group (ASG), we can create cool-downs that apply to a specific [[simple scaling policy]]
  • A scaling-specific cool-down period overrides the [[default cool-down period]]
  • One common use for scaling-specific cool-downs is with a [[scale-in policy]] - a policy that terminates instances based on a specific criteria or metric. Because this policy terminates instances, [[Amazon EC2 Auto Scaling]] needs less time to determine whether to terminate additional instances.
  • If the default cool-down period of 300 seconds is too long - you can reduce costs by applying a scaling-specific cool-down period of 180 seconds to the [[scale-in policy]].
  • If your application is scaling up and down multiple times each hour, modify the auto scaling groups cool-down timers and the cloud watch alarm period that triggers the [[Scale in]]