feat(oauth2-proxy): Support HPA spec.behavior for fine-grained scaling policy

* Reference (k8s docs): https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/\#configurable-scaling-behavior

Signed-off-by: younsl <[email protected]>

Author: younsl

helm/oauth2-proxy/templates/hpa.yaml

@@ -35,4 +35,15 @@ spec:
           type: Utilization
           averageUtilization: {{ .Values.autoscaling.targetCPUUtilizationPercentage }}
     {{- end }}
+  {{- if .Values.autoscaling.behavior }}
+  behavior:
+    {{- with .Values.autoscaling.behavior.scaleDown }}
+    scaleDown:
+      {{- toYaml . | nindent 6 }}
+    {{- end }}
+    {{- with .Values.autoscaling.behavior.scaleUp }}
+    scaleUp:
+      {{- toYaml . | nindent 6 }}
+    {{- end }}
+  {{- end }}
 {{- end }}

helm/oauth2-proxy/values.yaml

@@ -319,8 +319,28 @@ autoscaling:
   minReplicas: 1
   maxReplicas: 10
   targetCPUUtilizationPercentage: 80
-#  targetMemoryUtilizationPercentage: 80
+  # targetMemoryUtilizationPercentage: 80
   annotations: {}
+  # Configure HPA behavior policies for scaling if needed
+  # Ref: https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/#configuring-scaling-behavior
+  behavior: {}
+    # scaleDown:
+    #   stabilizationWindowSeconds: 300
+    #   policies:
+    #   - type: Percent
+    #     value: 100
+    #     periodSeconds: 15
+    #   selectPolicy: Min
+    # scaleUp:
+    #   stabilizationWindowSeconds: 0
+    #   policies:
+    #   - type: Percent
+    #     value: 100
+    #     periodSeconds: 15
+    #   - type: Pods
+    #     value: 4
+    #     periodSeconds: 15
+    #   selectPolicy: Max
 
 # Configure Kubernetes security context for pod
 # Ref: https://kubernetes.io/docs/tasks/configure-pod-container/security-context/