handler,webhook:use variable to set min replicas (nmstate#812)

In order to set the number of minimum webhook replicas dynamically, the operator
yaml should accept a variable to set number of minimum replicas.

An example use-case for that would be to set the minimum number of webhook replicas to 0 when running
on a Single-Node-Openshift cluster, to no interfere with the upgrade process, where the
number of active webhook pods will be reduced from 1 to 0 to perform the upgrade.

This commit introduce this variable and sets it with a fixed value of 1. In a follow-up work
This could be enhanced to be completely dynamic.

Signed-off-by: alonsadan <asadan@redhat.com>

controllers/nmstate_controller.go

@@ -173,7 +173,10 @@ func (r *NMStateReconciler) applyHandler(instance *nmstatev1beta1.NMState) error
 		handlerTolerations = []corev1.Toleration{operatorExistsToleration}
 	}
 
-	const WEBHOOK_REPLICAS = int32(2)
+	const (
+		WEBHOOK_REPLICAS     = int32(2)
+		WEBHOOK_MIN_REPLICAS = int32(1)
+	)
 
 	data.Data["HandlerNamespace"] = os.Getenv("HANDLER_NAMESPACE")
 	data.Data["HandlerImage"] = os.Getenv("RELATED_IMAGE_HANDLER_IMAGE")
@@ -183,6 +186,7 @@ func (r *NMStateReconciler) applyHandler(instance *nmstatev1beta1.NMState) error
 	data.Data["WebhookTolerations"] = []corev1.Toleration{masterExistsNoScheduleToleration}
 	data.Data["WebhookAffinity"] = corev1.Affinity{}
 	data.Data["WebhookReplicas"] = WEBHOOK_REPLICAS
+	data.Data["WebhookMinReplicas"] = WEBHOOK_MIN_REPLICAS
 	data.Data["HandlerNodeSelector"] = amd64AndCRNodeSelector
 	data.Data["HandlerTolerations"] = handlerTolerations
 	data.Data["HandlerAffinity"] = corev1.Affinity{}

deploy/handler/operator.yaml

@@ -372,7 +372,7 @@ metadata:
   namespace: {{ .HandlerNamespace }}
   name: {{template "handlerPrefix" .}}nmstate-webhook
 spec:
-  minAvailable: 1
+  minAvailable: {{  .WebhookMinReplicas  }}
   selector:
     matchLabels:
       name: {{template "handlerPrefix" .}}nmstate-webhook