Kubernetes HPA disable scale down
I randomly stumbled upon this post, and it looks like you can disable scaledown. The documentation includes this example at the bottom. Potentially this feature wasn't available when the question was initially asked.
The selectPolicy value of Disabled turns off scaling the givendirection. So to prevent downscaling the following policy would beused:
behavior: scaleDown: selectPolicy: Disabled
NO, this is not possible.
1) you can delete HPA and create simple deployment with desired num of pods
2) you can use workaround provided on HorizontalPodAutoscaler: Possible to limit scale down?#65097 issue by user 'frankh':
I've made a very hacky workaround, I have a cronjob that runs every 3 minutes, and sets the minimum replicas on an HPA to $currentReplicas - $downscaleLimit. If anyone feels like using it it's here: https://gist.github.com/frankh/050943c72273cf639886b43e98bc3caa
apiVersion: batch/v1beta1kind: CronJobmetadata: name: hpa-downscale-limiter namespace: kube-systemspec: schedule: "*/3 * * * *" concurrencyPolicy: Forbid jobTemplate: spec: template: spec: serviceAccountName: hpa-downscale-limiter containers: - name: kubectl image: frankh/k8s-kubectl:1.10.3 command: ["/bin/bash", "-c"] args: - | set -xeuo pipefail namespaces=$(kubectl get hpa --no-headers --all-namespaces | cut -d' ' -f1 | uniq) for namespace in $namespaces; do hpas=$(kubectl get hpa --namespace=$namespace --no-headers | cut -d' ' -f1) for hpa in $hpas; do echo "$(kubectl get hpa --namespace=$namespace $hpa -o jsonpath="{.spec.minReplicas} {.status.desiredReplicas} {.metadata.annotations.originalMinimum} {.metadata.annotations.downscaleLimit}")" > tmpfile read -r minReplicas desiredReplicas originalMinimum downscaleLimit < tmpfile if [ -z "$originalMinimum" ]; then kubectl annotate hpa --namespace=$namespace $hpa originalMinimum="$minReplicas" originalMinimum=$minReplicas fi if [ -z "$downscaleLimit" ]; then downscaleLimit=1 fi target=$(( $desiredReplicas - $downscaleLimit )) target=$(( $target > $originalMinimum ? $target : $originalMinimum )) if [ "$minReplicas" -ne "$target" ]; then kubectl patch hpa --namespace=$namespace $hpa --patch="{\"spec\": {\"minReplicas\": "$target"}}" fi done done restartPolicy: OnFailure---apiVersion: v1kind: ServiceAccountmetadata: name: hpa-downscale-limiter namespace: kube-system---apiVersion: rbac.authorization.k8s.io/v1beta1kind: ClusterRoleBindingmetadata: name: hpa-downscale-limiter-adminroleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: cluster-adminsubjects: - name: hpa-downscale-limiter kind: ServiceAccount namespace: kube-system
Horizontal Pod Autoscaler automatically scales the number of pods in a replication controller, deployment, replica set or stateful set based on observed CPU utilization (or, with beta support you also can use application-provided metrics). From the most basic perspective, the Horizontal Pod Autoscaler controller operates on the ratio between desired metric value and current metric value:
desiredReplicas = ceil[currentReplicas * ( currentMetricValue / desiredMetricValue )]If multiple metrics are specified in a HorizontalPodAutoscaler, this calculation is done for each metric, and then the largest of the desired replica counts is chosen. However, before the scale recommendation is recorded. The controller considers all recommendations within a configurable window choosing the highest recommendation from within that window. This value can be configured using the --horizontal-pod-autoscaler-downscale-stabilization flag, which defaults to 5 minutes. This means that scaledowns will occur gradually, smoothing out the impact of rapidly fluctuating metric values.
Based on what I've explained, it means that no you can't. However for spiky traffic you can still use: --horizontal-pod-autoscaler-downscale-stabilization flag.