Merge pull request #205660 from zr-msft/zr-aks-fix-hpa-interval

[AKS] update HPA sync details for consistency

Author: PRMerger17

articles/aks/concepts-scale.md

@@ -27,7 +27,7 @@ To get started with manually scaling pods and nodes see [Scale applications in A
 
 ## Horizontal pod autoscaler
 
-Kubernetes uses the horizontal pod autoscaler (HPA) to monitor the resource demand and automatically scale the number of replicas. By default, the horizontal pod autoscaler checks the Metrics API every 60 seconds for any required changes in replica count. When changes are required, the number of replicas is increased or decreased accordingly. Horizontal pod autoscaler works with AKS clusters that have deployed the Metrics Server for Kubernetes 1.8+.
+Kubernetes uses the horizontal pod autoscaler (HPA) to monitor the resource demand and automatically scale the number of replicas. By default, the horizontal pod autoscaler checks the Metrics API every 15 seconds for any required changes in replica count, but the Metrics API retrieves data from the Kubelet every 60 seconds. Effectively, the HPA is updated every 60 seconds. When changes are required, the number of replicas is increased or decreased accordingly. Horizontal pod autoscaler works with AKS clusters that have deployed the Metrics Server for Kubernetes 1.8+.
 
 ![Kubernetes horizontal pod autoscaling](media/concepts-scale/horizontal-pod-autoscaling.png)
 
@@ -37,7 +37,7 @@ To get started with the horizontal pod autoscaler in AKS, see [Autoscale pods in
 
 ### Cooldown of scaling events
 
-As the horizontal pod autoscaler checks the Metrics API every 30 seconds, previous scale events may not have successfully completed before another check is made. This behavior could cause the horizontal pod autoscaler to change the number of replicas before the previous scale event could receive application workload and the resource demands to adjust accordingly.
+As the horizontal pod autoscaler is effectively updated every 60 seconds, previous scale events may not have successfully completed before another check is made. This behavior could cause the horizontal pod autoscaler to change the number of replicas before the previous scale event could receive application workload and the resource demands to adjust accordingly.
 
 To minimize race events, a delay value is set. This value defines how long the horizontal pod autoscaler must wait after a scale event before another scale event can be triggered. This behavior allows the new replica count to take effect and the Metrics API to reflect the distributed workload. There is [no delay for scale-up events as of Kubernetes 1.12](https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/#support-for-cooldown-delay), however the delay on scale down events is defaulted to 5 minutes.