charts/kubernetes-stateless-chart/templates/horizontalpodautoscaler/manifest.yaml

{{/*
In Kubernetes, a HorizontalPodAutoscaler automatically updates a workload resource (such as a Deployment or
StatefulSet), with the aim of automatically scaling the workload to match demand.
Horizontal scaling means that the response to increased load is to deploy more Pods.
This is different from vertical scaling, which for Kubernetes would mean assigning
more resources (for example: memory or CPU) to the Pods that are already running for
the workload.
If the load decreases, and the number of Pods is above the configured minimum,
the HorizontalPodAutoscaler instructs the workload resource (the Deployment,
StatefulSet, or other similar resource) to scale back down.

Horizontal pod autoscaling does not apply to objects that can't be scaled (for example: a DaemonSet.)

When an HPA is enabled, it is recommended that the value of spec.replicas of the Deployment and / or
StatefulSet be removed from their manifest(s). If this isn't done, any time a change to that object
is applied, for example via kubectl apply -f deployment.yaml, this will instruct Kubernetes to scale
the current number of Pods to the value of the spec.replicas key. This may not be desired and could be
troublesome when an HPA is active.

Ref: https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/

Example walkthrough ref: https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale-walkthrough/
*/}}
{{- if .Values.include }}
{{- if .Values.autoscaling.enabled }}
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: {{ include "lib.appName" . }}
  namespace: {{ include "lib.namespace" . }}
  labels:
    app.kubernetes.io/component: {{ include "lib.componentName" . }}
    {{- include "lib.labels" . | nindent 4 }}
  annotations:
  {{- include "lib.annotations" . | nindent 4 }}
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: {{ include "lib.appName" . }}
  minReplicas: {{ .Values.autoscaling.minReplicas }}
  maxReplicas: {{ .Values.autoscaling.maxReplicas }}
  metrics:
    {{- if .Values.autoscaling.metrics.targetCPU }}
    - type: Resource
      resource:
        name: cpu
        target:
          type: Utilization
          averageUtilization: {{ .Values.autoscaling.metrics.targetCPU }}
    {{- end }}
    {{- if .Values.autoscaling.metrics.targetMemory }}
    - type: Resource
      resource:
        name: memory
        target:
          type: Utilization
          averageUtilization: {{ .Values.autoscaling.metrics.targetMemory }}
    {{- end }}
{{- end }}
{{- end }}