[CASCL-506] Allow minReplicas=0 on DatadogPodAutoscaler#3048
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Relax the kubebuilder validation on DatadogPodAutoscalerConstraints.MinReplicas from Minimum=1 to Minimum=0 to admit scale-to-zero configurations. The horizontal controller already honors any non-nil MinReplicas value (default of 1 only applies when unset), so this is purely an admission relaxation. Scale-from-zero remains gated on the recommendation source being able to emit signals at 0 replicas (e.g. queue-based metrics); CPU-based recommendations are unusable at 0 pods. Regenerated CRDs (DatadogPodAutoscaler v1alpha1 + v1alpha2 and DatadogPodAutoscalerClusterProfile) via 'make manifests'. Refs: https://datadoghq.atlassian.net/browse/CASCL-506
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What does this PR do?
Relaxes the kubebuilder validation on
DatadogPodAutoscalerConstraints.MinReplicasfromMinimum=1toMinimum=0, so aDatadogPodAutoscaler(andDatadogPodAutoscalerClusterProfile) withspec.constraints.minReplicas: 0is admitted by the API server. CRDs were regenerated viamake manifests.Motivation
Refs https://datadoghq.atlassian.net/browse/CASCL-506 (feature request: support horizontal scale from/to 0).
We hit this in dd-analytics while experimenting with DPA on Airflow Celery worker groups. Workers are queue-driven and idle between DAG runs, so scaling to 0 between bursts is a clear cost win. The CRD currently rejects this configuration outright:
```
DatadogPodAutoscaler.datadoghq.com "airflow-wg-adp-integrations" is invalid:
spec.constraints.minReplicas: Invalid value: 0:
spec.constraints.minReplicas in body should be greater than or equal to 1
```
This PR removes the admission-level block. It is intentionally a minimal change to unblock experimentation/design work on CASCL-506; it does not by itself make scale-from-0 work end-to-end -- see Additional Notes.
Additional Notes
pkg/clusteragent/autoscaling/workload/controller_horizontal.go) already honors any non-nilMinReplicas. The hardcodeddefaultMinReplicas = 1only applies when the field is unset, so this is purely an admission relaxation -- no controller code change is required.(running + queued) / replicasis undefined at 0 replicas. Queue-length-style external metrics work because the source is external to the workload.MinReplicasgodoc to call this out explicitly so users don't expect magic scale-up behavior just from settingminReplicas: 0.Minimum Agent Versions
No agent-side changes are required for this PR (controller already accepts the value). Mentioning for completeness:
Describe your test plan
Manual verification (suggested for reviewer): apply the regenerated CRD to a kind cluster, then `kubectl apply` a DPA with `spec.constraints.minReplicas: 0` and confirm admission succeeds; apply one with `-1` and confirm it is still rejected.
Checklist