ignore minReplicas/maxReplicas in hpa webhook (#262)

api/autoscaling/v2/horizontalpodautoscaler_webhook.go

@@ -89,12 +89,15 @@ func (h *HPAWebhook) Default(ctx context.Context, obj runtime.Object) error {
 		return nil
 	}
 
-	hpa, _, err = h.hpaService.ChangeHPAFromTortoiseRecommendation(t, hpa, time.Now(), false) // we don't need to record metrics.
+	modifiedhpa, _, err := h.hpaService.ChangeHPAFromTortoiseRecommendation(t, hpa.DeepCopy(), time.Now(), false) // we don't need to record metrics.
 	if err != nil {
 		// Block updating HPA may be critical. Just ignore it with error logs.
 		log.FromContext(ctx).Error(err, "failed to get tortoise for mutating webhook of HPA", "hpa", klog.KObj(hpa), "tortoise", tortoiseName)
 		return nil
 	}
+	// Only overwrite metrics and ignore other fields like minReplicas and maxReplicas.
+	// If we want to overwrite minReplicas and maxReplicas, it'd be complicated because we have to consider the emergency mode.
+	hpa.Spec.Metrics = modifiedhpa.Spec.Metrics
 
 	return nil
 }

api/autoscaling/v2/testdata/mutating/mutate-by-recommendations/after.yaml

@@ -4,7 +4,7 @@ metadata:
   name: sample
   namespace: default
 spec:
-  maxReplicas: 12
+  maxReplicas: 10 # not overwritten
   metrics:
     - type: ContainerResource
       containerResource:
@@ -20,7 +20,7 @@ spec:
         target:
           type: Utilization
           averageUtilization: 30
-  minReplicas: 3
+  minReplicas: 1 # not overwritten
   scaleTargetRef:
     apiVersion: apps/v1
     kind: Deployment