kubeadm: don't duplicate master taint if it already exists.

This helps enable a graceful upgrade/downgrade process between 1.6.x and
1.7.x kubeadm clusters (although no guarantees outside of that range) by
doing:

  $ kubeadm init --kubernetes-version <version> --skip-preflight-checks

Without this change, the command fails with an error that the node taint
is duplicated.

This is part of kubernetes/kubeadm#278

cmd/kubeadm/app/phases/apiconfig/BUILD

@@ -5,6 +5,7 @@ licenses(["notice"])
 load(
     "@io_bazel_rules_go//go:def.bzl",
     "go_library",
+    "go_test",
 )
 
 go_library(
@@ -42,3 +43,20 @@ filegroup(
     srcs = [":package-srcs"],
     tags = ["automanaged"],
 )
+
+go_test(
+    name = "go_default_test",
+    srcs = ["setupmaster_test.go"],
+    library = ":go_default_library",
+    tags = ["automanaged"],
+    deps = [
+        "//cmd/kubeadm/app/constants:go_default_library",
+        "//pkg/kubelet/apis:go_default_library",
+        "//pkg/util/node:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
+        "//vendor/k8s.io/client-go/kubernetes:go_default_library",
+        "//vendor/k8s.io/client-go/kubernetes/typed/core/v1:go_default_library",
+        "//vendor/k8s.io/client-go/pkg/api/v1:go_default_library",
+        "//vendor/k8s.io/client-go/rest:go_default_library",
+    ],
+)

cmd/kubeadm/app/phases/apiconfig/setupmaster.go

@@ -59,7 +59,7 @@ func attemptToUpdateMasterRoleLabelsAndTaints(client *clientset.Clientset) error
 
 	// The master node is tainted and labelled accordingly
 	n.ObjectMeta.Labels[kubeadmconstants.LabelNodeRoleMaster] = ""
-	n.Spec.Taints = append(n.Spec.Taints, v1.Taint{Key: kubeadmconstants.LabelNodeRoleMaster, Value: "", Effect: "NoSchedule"})
+	addTaintIfNotExists(n, v1.Taint{Key: kubeadmconstants.LabelNodeRoleMaster, Value: "", Effect: "NoSchedule"})
 
 	newData, err := json.Marshal(n)
 	if err != nil {
@@ -84,6 +84,16 @@ func attemptToUpdateMasterRoleLabelsAndTaints(client *clientset.Clientset) error
 	return nil
 }
 
+func addTaintIfNotExists(n *v1.Node, t v1.Taint) {
+	for _, taint := range n.Spec.Taints {
+		if taint == t {
+			return
+		}
+	}
+
+	n.Spec.Taints = append(n.Spec.Taints, t)
+}
+
 // UpdateMasterRoleLabelsAndTaints taints the master and sets the master label
 func UpdateMasterRoleLabelsAndTaints(client *clientset.Clientset) error {
 	// TODO: Use iterate instead of recursion

cmd/kubeadm/app/phases/apiconfig/setupmaster_test.go

@@ -0,0 +1,157 @@
+/*
+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 apiconfig
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	clientset "k8s.io/client-go/kubernetes"
+	corev1 "k8s.io/client-go/kubernetes/typed/core/v1"
+	apiv1 "k8s.io/client-go/pkg/api/v1"
+	restclient "k8s.io/client-go/rest"
+	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
+	kubeletapis "k8s.io/kubernetes/pkg/kubelet/apis"
+	"k8s.io/kubernetes/pkg/util/node"
+)
+
+const masterLabel = kubeadmconstants.LabelNodeRoleMaster
+
+var masterTaint = &apiv1.Taint{Key: kubeadmconstants.LabelNodeRoleMaster, Value: "", Effect: "NoSchedule"}
+
+func TestUpdateMasterRoleLabelsAndTaints(t *testing.T) {
+	// Note: this test takes advantage of the deterministic marshalling of
+	// JSON provided by strategicpatch so that "expectedPatch" can use a
+	// string equality test instead of a logical JSON equality test. That
+	// will need to change if strategicpatch's behavior changes in the
+	// future.
+	tests := []struct {
+		name          string
+		existingLabel string
+		existingTaint *apiv1.Taint
+		expectedPatch string
+	}{
+		{
+			"master label and taint missing",
+			"",
+			nil,
+			"{\"metadata\":{\"labels\":{\"node-role.kubernetes.io/master\":\"\"}},\"spec\":{\"taints\":[{\"effect\":\"NoSchedule\",\"key\":\"node-role.kubernetes.io/master\",\"timeAdded\":null}]}}",
+		},
+		{
+			"master label missing",
+			"",
+			masterTaint,
+			"{\"metadata\":{\"labels\":{\"node-role.kubernetes.io/master\":\"\"}}}",
+		},
+		{
+			"master taint missing",
+			masterLabel,
+			nil,
+			"{\"spec\":{\"taints\":[{\"effect\":\"NoSchedule\",\"key\":\"node-role.kubernetes.io/master\",\"timeAdded\":null}]}}",
+		},
+		{
+			"nothing missing",
+			masterLabel,
+			masterTaint,
+			"{}",
+		},
+	}
+
+	for _, tc := range tests {
+		hostname := node.GetHostname("")
+		masterNode := &apiv1.Node{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: hostname,
+				Labels: map[string]string{
+					kubeletapis.LabelHostname: hostname,
+				},
+			},
+		}
+
+		if tc.existingLabel != "" {
+			masterNode.ObjectMeta.Labels[tc.existingLabel] = ""
+		}
+
+		if tc.existingTaint != nil {
+			masterNode.Spec.Taints = append(masterNode.Spec.Taints, *tc.existingTaint)
+		}
+
+		jsonNode, err := json.Marshal(masterNode)
+		if err != nil {
+			t.Fatalf("UpdateMasterRoleLabelsAndTaints(%s): unexpected encoding error: %v", tc.name, err)
+		}
+
+		var patchRequest string
+		s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+			w.Header().Set("Content-Type", "application/json")
+
+			if req.URL.Path != "/api/v1/nodes/"+hostname {
+				t.Errorf("UpdateMasterRoleLabelsAndTaints(%s): request for unexpected HTTP resource: %v", tc.name, req.URL.Path)
+				w.WriteHeader(http.StatusNotFound)
+				return
+			}
+
+			switch req.Method {
+			case "GET":
+			case "PATCH":
+				patchRequest = toString(req.Body)
+			default:
+				t.Errorf("UpdateMasterRoleLabelsAndTaints(%s): request for unexpected HTTP verb: %v", tc.name, req.Method)
+				w.WriteHeader(http.StatusNotFound)
+				return
+			}
+
+			w.WriteHeader(http.StatusOK)
+			w.Write(jsonNode)
+		}))
+		defer s.Close()
+
+		cs, err := clientsetFromTestServer(s)
+		if err != nil {
+			t.Fatalf("UpdateMasterRoleLabelsAndTaints(%s): unexpected error building clientset: %v", tc.name, err)
+		}
+
+		err = UpdateMasterRoleLabelsAndTaints(cs)
+		if err != nil {
+			t.Errorf("UpdateMasterRoleLabelsAndTaints(%s) returned unexpected error: %v", tc.name, err)
+		}
+
+		if tc.expectedPatch != patchRequest {
+			t.Errorf("UpdateMasterRoleLabelsAndTaints(%s) wanted patch %v, got %v", tc.name, tc.expectedPatch, patchRequest)
+		}
+	}
+}
+
+func clientsetFromTestServer(s *httptest.Server) (*clientset.Clientset, error) {
+	rc := &restclient.Config{Host: s.URL}
+	c, err := corev1.NewForConfig(rc)
+	if err != nil {
+		return nil, err
+	}
+	return &clientset.Clientset{CoreV1Client: c}, nil
+}
+
+func toString(r io.Reader) string {
+	buf := new(bytes.Buffer)
+	buf.ReadFrom(r)
+	return buf.String()
+}