feat(hpa): add customMetrics, selectPolicy, and configurable policies

[camjay]

Split from #172 per @sk-portkey's feedback — HPA enhancements only, redis.deployLocal removed.

• Support autoscaling.customMetrics for injecting arbitrary HPA metrics
• Add selectPolicy (Max/Min/Disabled) for scaleUp and scaleDown behavior
• Allow full policies override per direction; existing defaults preserved when not specified

Validated with helm lint and helm template (default values + custom overrides).

[Copilot]

Pull request overview

This PR enhances the portkey-gateway Helm chart’s HPA support by allowing users to inject arbitrary HPA metrics and more fully configure autoscaling behavior policies.

Changes:

• Add autoscaling.customMetrics to append arbitrary HPA metrics entries.
• Add selectPolicy support for both scaleUp and scaleDown behavior.
• Allow overriding behavior.scaleUp.policies / behavior.scaleDown.policies, while keeping existing defaults when not provided.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
charts/portkey-gateway/values.yaml	Adds commented examples for customMetrics, selectPolicy, and policies overrides.
charts/portkey-gateway/templates/gateway/hpa.yaml	Renders custom metrics and configurable selectPolicy / policies in the HPA spec.

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[Copilot]

policies override is gated by a truthy check. If a user explicitly sets autoscaling.behavior.scaleUp.policies: [] (or wants to intentionally render an empty list), Helm treats an empty list as false and this block will fall back to the chart defaults. Consider switching to a presence check (e.g., hasKey on the scaleUp map) so that explicitly-provided empty lists are honored, and defaults are only used when the key is absent.

[Copilot]

Same issue as scaleUp: if .Values.autoscaling.behavior.scaleDown.policies won’t distinguish between an absent key and an explicitly empty list, so policies: [] can’t be used to override/clear the defaults. Use a presence check (e.g., hasKey on the scaleDown map) to honor an explicit empty list and only apply defaults when the key is not set.

Suggested change

	scaleDown:
	stabilizationWindowSeconds: {{ .Values.autoscaling.behavior.scaleDown.stabilizationWindowSeconds | default 300 }}
	{{- if .Values.autoscaling.behavior.scaleDown.selectPolicy }}
	selectPolicy: {{ .Values.autoscaling.behavior.scaleDown.selectPolicy }}
	{{- end }}
	{{- if .Values.autoscaling.behavior.scaleDown.policies }}
	policies:
	{{- toYaml .Values.autoscaling.behavior.scaleDown.policies | nindent 8 }}
	{{- else }}
	policies:
	- type: Pods
	value: {{ .Values.autoscaling.behavior.scaleDown.podScaleDownValue | default 1 }}
	periodSeconds: {{ .Values.autoscaling.behavior.scaleDown.periodSeconds | default 60 }}
	{{- $scaleDown := .Values.autoscaling.behavior.scaleDown | default dict }}
	scaleDown:
	stabilizationWindowSeconds: {{ $scaleDown.stabilizationWindowSeconds | default 300 }}
	{{- if $scaleDown.selectPolicy }}
	selectPolicy: {{ $scaleDown.selectPolicy }}
	{{- end }}
	{{- if hasKey $scaleDown "policies" }}
	policies:
	{{- toYaml $scaleDown.policies | nindent 8 }}
	{{- else }}
	policies:
	- type: Pods
	value: {{ $scaleDown.podScaleDownValue | default 1 }}
	periodSeconds: {{ $scaleDown.periodSeconds | default 60 }}

[Copilot]

The template fallbacks for scaleUp don’t match the chart’s defaults in values.yaml (values.yaml sets podScaleUpValue: 2 and periodSeconds: 2, but the template defaults to 4 and 15). Align these defaults (or drop the | default here if you expect values.yaml to always define them) to avoid surprising behavior when users partially override autoscaling.behavior.scaleUp.

[Copilot]

selectPolicy examples here only show Max/Min, but the feature description mentions Disabled as well. Consider updating these commented examples to include/mention Disabled so users discover the full allowed set.