kubeadm: delete the old "master" label during upgrade

- Rename the function in postupgrade.go to better reflect
what is being done.
- During "upgrade apply" find all nodes with the old label
and remove it by calling PatchNode.
- Update health check for CP nodes to not track "master"
labeled nodes. At this point all CP nodes should have
"control-plane" and we can use that selector only.

cmd/kubeadm/app/cmd/join.go

@@ -64,7 +64,7 @@ var (
 
 		* Certificate signing request was sent to apiserver and approval was received.
 		* The Kubelet was informed of the new secure connection details.
-		* Control plane (master) label and taint were applied to the new node.
+		* Control plane label and taint were applied to the new node.
 		* The Kubernetes control plane instances scaled up.
 		{{.etcdMessage}}
 

cmd/kubeadm/app/cmd/upgrade/apply.go

@@ -157,9 +157,10 @@ func runApply(flags *applyFlags, args []string) error {
 	}
 
 	// TODO: https://github.com/kubernetes/kubeadm/issues/2200
-	fmt.Printf("[upgrade/postupgrade] Applying label %s='' to Nodes with label %s='' (deprecated)\n",
-		kubeadmconstants.LabelNodeRoleControlPlane, kubeadmconstants.LabelNodeRoleOldControlPlane)
-	if err := upgrade.LabelOldControlPlaneNodes(client); err != nil {
+	fmt.Printf("[upgrade/postupgrade] Removing the deprecated label %s='' from all control plane Nodes. "+
+		"After this step only the label %s='' will be present on control plane Nodes.\n",
+		kubeadmconstants.LabelNodeRoleOldControlPlane, kubeadmconstants.LabelNodeRoleControlPlane)
+	if err := upgrade.RemoveOldControlPlaneLabel(client); err != nil {
 		return err
 	}
 

cmd/kubeadm/app/phases/upgrade/health.go

@@ -212,34 +212,17 @@ func deleteHealthCheckJob(client clientset.Interface, ns, jobName string) error
 
 // controlPlaneNodesReady checks whether all control-plane Nodes in the cluster are in the Running state
 func controlPlaneNodesReady(client clientset.Interface, _ *kubeadmapi.ClusterConfiguration) error {
-	// list nodes labeled with a "master" node-role
-	selectorOldControlPlane := labels.SelectorFromSet(labels.Set(map[string]string{
-		constants.LabelNodeRoleOldControlPlane: "",
-	}))
-	nodesWithOldLabel, err := client.CoreV1().Nodes().List(context.TODO(), metav1.ListOptions{
-		LabelSelector: selectorOldControlPlane.String(),
-	})
-	if err != nil {
-		return errors.Wrapf(err, "could not list nodes labeled with %q", constants.LabelNodeRoleOldControlPlane)
-	}
-
-	// list nodes labeled with a "control-plane" node-role
 	selectorControlPlane := labels.SelectorFromSet(labels.Set(map[string]string{
 		constants.LabelNodeRoleControlPlane: "",
 	}))
-	nodesControlPlane, err := client.CoreV1().Nodes().List(context.TODO(), metav1.ListOptions{
+	nodes, err := client.CoreV1().Nodes().List(context.TODO(), metav1.ListOptions{
 		LabelSelector: selectorControlPlane.String(),
 	})
 	if err != nil {
 		return errors.Wrapf(err, "could not list nodes labeled with %q", constants.LabelNodeRoleControlPlane)
 	}
 
-	nodes := append(nodesWithOldLabel.Items, nodesControlPlane.Items...)
-	if len(nodes) == 0 {
-		return errors.New("failed to find any nodes with a control-plane role")
-	}
-
-	notReadyControlPlanes := getNotReadyNodes(nodes)
+	notReadyControlPlanes := getNotReadyNodes(nodes.Items)
 	if len(notReadyControlPlanes) != 0 {
 		return errors.Errorf("there are NotReady control-planes in the cluster: %v", notReadyControlPlanes)
 	}

cmd/kubeadm/app/phases/upgrade/postupgrade.go

@@ -215,10 +215,9 @@ func rollbackFiles(files map[string]string, originalErr error) error {
 	return errors.Errorf("couldn't move these files: %v. Got errors: %v", files, errorsutil.NewAggregate(errs))
 }
 
-// LabelOldControlPlaneNodes finds all nodes with the legacy node-role label and also applies
-// the "control-plane" node-role label to them.
+// RemoveOldControlPlaneLabel finds all nodes with the legacy node-role label and removes it
 // TODO: https://github.com/kubernetes/kubeadm/issues/2200
-func LabelOldControlPlaneNodes(client clientset.Interface) error {
+func RemoveOldControlPlaneLabel(client clientset.Interface) error {
 	selectorOldControlPlane := labels.SelectorFromSet(labels.Set(map[string]string{
 		kubeadmconstants.LabelNodeRoleOldControlPlane: "",
 	}))
@@ -230,11 +229,8 @@ func LabelOldControlPlaneNodes(client clientset.Interface) error {
 	}
 
 	for _, n := range nodesWithOldLabel.Items {
-		if _, hasNewLabel := n.ObjectMeta.Labels[kubeadmconstants.LabelNodeRoleControlPlane]; hasNewLabel {
-			continue
-		}
 		err = apiclient.PatchNode(client, n.Name, func(n *v1.Node) {
-			n.ObjectMeta.Labels[kubeadmconstants.LabelNodeRoleControlPlane] = ""
+			delete(n.ObjectMeta.Labels, kubeadmconstants.LabelNodeRoleOldControlPlane)
 		})
 		if err != nil {
 			return err