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HPA stabilization window

In Kubernetes Horizontal Pod Autoscaler (HPA) configurations, the stabilization window is a parameter used to control the timing of scaling down operations.^[400-devops__06-Kubernetes__k8s-ithelp__Day26__README.md]

Behavior and Algorithm

When Metrics indicate that a target should be scaled down, the autoscaler does not immediately reduce the replica count to the calculated lower value. Instead, the algorithm reviews previously calculated desired states.^[400-devops__06-Kubernetes__k8s-ithelp__Day26__README.md]

Specifically, it looks at the states calculated within the time interval defined by the stabilization window. The system selects the maximum value among these historical desired states to be the effective target.^[400-devops__06-Kubernetes__k8s-ithelp__Day26__README.md]

Purpose

The primary function of the stabilization window is to prevent the replica count from fluctuating too frequently, a phenomenon often referred to as "thrashing" or jitter.^[400-devops__06-Kubernetes__k8s-ithelp__Day26__README.md] By enforcing a wait period where the highest recent demand is preserved, it ensures that brief drops in load do not trigger an immediate scale-down that might be premature.

Configuration

The stabilization window is defined within the behavior field of an HPA resource, specifically under scaleDown.^[400-devops__06-Kubernetes__k8s-ithelp__Day26__README.md]

  • Field: spec.behavior.scaleDown.stabilizationWindowSeconds
  • Default: A common default value (often used in examples) is 300 seconds (5 minutes).^[400-devops__06-Kubernetes__k8s-ithelp__Day26__README.md]

Sources

^[400-devops__06-Kubernetes__k8s-ithelp__Day26__README.md]