HPA Downscale Limiter

gistfile1.txt

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: hpa-downscale-limiter
  namespace: kube-system
spec:
  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: v1
kind: ServiceAccount
metadata:
  name: hpa-downscale-limiter
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: hpa-downscale-limiter-admin
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subjects:
  - name: hpa-downscale-limiter
    kind: ServiceAccount
    namespace: kube-system