Add control-plane label for master nodes on legacy clusters

blah

Author: rphillips

pkg/controller/node/node_controller.go

@@ -55,6 +55,8 @@ import (
 const (
 	// WorkerLabel defines the label associated with worker node.
 	WorkerLabel = "node-role.kubernetes.io/worker"
+	// ControlPlaneLabel defines the label associated with master/control-plane node.
+	ControlPlaneLabel = "node-role.kubernetes.io/control-plane"
 
 	// maxRetries is the number of times a machineconfig pool will be retried before it is dropped out of the queue.
 	// With the current rate-limiter in use (5ms*2^(maxRetries-1)) the following numbers represent the times
@@ -321,7 +323,6 @@ func (ctrl *Controller) makeMastersUnSchedulable(currentMasters []*corev1.Node)
 		}
 	}
 	return errs
-
 }
 
 // makeMasterNodeUnSchedulable makes master node unschedulable by removing worker label and adding `NoSchedule`
@@ -363,6 +364,12 @@ func (ctrl *Controller) makeMasterNodeSchedulable(node *corev1.Node) error {
 		if _, hasWorkerLabel := newLabels[WorkerLabel]; !hasWorkerLabel {
 			newLabels[WorkerLabel] = ""
 		}
+		// Legacy clusters do not have the node-role.kubernetes.io/control-plane
+		// label. When master nodes go schedulable again, let's add the
+		// control-plane label.
+		if _, hasControlPlaneLabel := newLabels[ControlPlaneLabel]; !hasControlPlaneLabel {
+			newLabels[ControlPlaneLabel] = ""
+		}
 		node.Labels = newLabels
 		// Remove master taint
 		newTaints := []corev1.Taint{}