Revert "Remove old node role label that is not used by kubeadm"

This reverts commit e25a5b1546.

cmd/kubeadm/app/apis/kubeadm/BUILD

@@ -13,6 +13,7 @@ go_library(
         "doc.go",
         "register.go",
         "types.go",
+        "well_known_labels.go",
         "zz_generated.deepcopy.go",
     ],
     tags = ["automanaged"],

cmd/kubeadm/app/apis/kubeadm/well_known_labels.go

@@ -0,0 +1,43 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kubeadm
+
+// Role labels are applied to Nodes to mark their purpose.  In particular, we
+// usually want to distinguish the master, so that we can isolate privileged
+// pods and operations.
+//
+// Originally we relied on not registering the master, on the fact that the
+// master was Unschedulable, and on static manifests for master components.
+// But we now do register masters in many environments, are generally moving
+// away from static manifests (for better manageability), and working towards
+// deprecating the unschedulable field (replacing it with taints & tolerations
+// instead).
+//
+// Even with tainting, a label remains the easiest way of making a positive
+// selection, so that pods can schedule only to master nodes for example, and
+// thus installations will likely define a label for their master nodes.
+//
+// So that we can recognize master nodes in consequent places though (such as
+// kubectl get nodes), we encourage installations to use the well-known labels.
+// We define NodeLabelRole, which is the preferred form, but we will also recognize
+// other forms that are known to be in widespread use (NodeLabelKubeadmAlphaRole).
+
+const (
+	// NodeLabelKubeadmAlphaRole is a label that kubeadm applies to a Node as a hint that it has a particular purpose.
+	// Use of NodeLabelRole is preferred.
+	NodeLabelKubeadmAlphaRole = "kubeadm.alpha.kubernetes.io/role"
+)

pkg/printers/internalversion/BUILD

@@ -59,6 +59,7 @@ go_library(
     ],
     tags = ["automanaged"],
     deps = [
+        "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
         "//federation/apis/federation:go_default_library",
         "//federation/apis/federation/v1beta1:go_default_library",
         "//federation/client/clientset_generated/federation_clientset:go_default_library",

pkg/printers/internalversion/describe.go

@@ -2421,6 +2421,7 @@ func describeNode(node *api.Node, nodeNonTerminatedPodsList *api.PodList, events
 	return tabbedString(func(out io.Writer) error {
 		w := NewPrefixWriter(out)
 		w.Write(LEVEL_0, "Name:\t%s\n", node.Name)
+		w.Write(LEVEL_0, "Role:\t%s\n", findNodeRole(node))
 		printLabelsMultiline(w, "Labels", node.Labels)
 		printAnnotationsMultiline(w, "Annotations", node.Annotations)
 		printNodeTaintsMultiline(w, "Taints", node.Spec.Taints)

pkg/printers/internalversion/printers.go

@@ -37,6 +37,7 @@ import (
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	"k8s.io/kubernetes/federation/apis/federation"
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/api/events"
@@ -1048,6 +1049,10 @@ func printNode(obj *api.Node, options printers.PrintOptions) ([]metav1alpha1.Tab
 	if obj.Spec.Unschedulable {
 		status = append(status, "SchedulingDisabled")
 	}
+	role := findNodeRole(obj)
+	if role != "" {
+		status = append(status, role)
+	}
 
 	row.Cells = append(row.Cells, obj.Name, strings.Join(status, ","), translateTimestamp(obj.CreationTimestamp), obj.Status.NodeInfo.KubeletVersion)
 	if options.Wide {
@@ -1078,6 +1083,19 @@ func getNodeExternalIP(node *api.Node) string {
 	return "<none>"
 }
 
+// findNodeRole returns the role of a given node, or "" if none found.
+// The role is determined by looking in order for:
+// * a kubernetes.io/role label
+// * a kubeadm.alpha.kubernetes.io/role label
+// If no role is found, ("", nil) is returned
+func findNodeRole(node *api.Node) string {
+	if role := node.Labels[kubeadm.NodeLabelKubeadmAlphaRole]; role != "" {
+		return role
+	}
+	// No role found
+	return ""
+}
+
 func printNodeList(list *api.NodeList, options printers.PrintOptions) ([]metav1alpha1.TableRow, error) {
 	rows := make([]metav1alpha1.TableRow, 0, len(list.Items))
 	for i := range list.Items {

pkg/printers/internalversion/printers_test.go

@@ -825,6 +825,16 @@ func TestPrintNodeStatus(t *testing.T) {
 			},
 			status: "Unknown,SchedulingDisabled",
 		},
+		{
+			node: api.Node{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:   "foo12",
+					Labels: map[string]string{"kubeadm.alpha.kubernetes.io/role": "node"},
+				},
+				Status: api.NodeStatus{Conditions: []api.NodeCondition{{Type: api.NodeReady, Status: api.ConditionTrue}}},
+			},
+			status: "Ready,node",
+		},
 	}
 
 	for _, test := range table {