kubeadm: do not panic if etcd local alpha phase is called when an external etcd config is used

If etcd local alpha phase is called manually while the kubeadm configuration
points to an external etcd cluster kubeadm panics.

cmd/kubeadm/app/phases/etcd/local.go

@@ -37,6 +37,9 @@ const (
 
 // CreateLocalEtcdStaticPodManifestFile will write local etcd static pod manifest file.
 func CreateLocalEtcdStaticPodManifestFile(manifestDir string, cfg *kubeadmapi.InitConfiguration) error {
+	if cfg.ClusterConfiguration.Etcd.External != nil {
+		return fmt.Errorf("etcd static pod manifest cannot be generated for cluster using external etcd")
+	}
 	glog.V(1).Infoln("creating local etcd static pod manifest file")
 	// gets etcd StaticPodSpec, actualized for the current InitConfiguration
 	spec := GetEtcdPodSpec(cfg)

cmd/kubeadm/app/phases/etcd/local_test.go

@@ -54,34 +54,64 @@ func TestGetEtcdPodSpec(t *testing.T) {
 }
 
 func TestCreateLocalEtcdStaticPodManifestFile(t *testing.T) {
-
 	// Create temp folder for the test case
 	tmpdir := testutil.SetupTempDir(t)
 	defer os.RemoveAll(tmpdir)
 
-	// Creates a Master Configuration
-	cfg := &kubeadmapi.InitConfiguration{
-		ClusterConfiguration: kubeadmapi.ClusterConfiguration{
-			KubernetesVersion: "v1.7.0",
-			Etcd: kubeadmapi.Etcd{
-				Local: &kubeadmapi.LocalEtcd{
-					DataDir: "/var/lib/etcd",
-					Image:   "k8s.gcr.io/etcd",
+	var tests = []struct {
+		cfg           *kubeadmapi.InitConfiguration
+		expectedError bool
+	}{
+		{
+			cfg: &kubeadmapi.InitConfiguration{
+				ClusterConfiguration: kubeadmapi.ClusterConfiguration{
+					KubernetesVersion: "v1.7.0",
+					Etcd: kubeadmapi.Etcd{
+						Local: &kubeadmapi.LocalEtcd{
+							DataDir: "/var/lib/etcd",
+							Image:   "k8s.gcr.io/etcd",
+						},
+					},
 				},
 			},
+			expectedError: false,
+		},
+		{
+			cfg: &kubeadmapi.InitConfiguration{
+				ClusterConfiguration: kubeadmapi.ClusterConfiguration{
+					KubernetesVersion: "v1.7.0",
+					Etcd: kubeadmapi.Etcd{
+						External: &kubeadmapi.ExternalEtcd{
+							Endpoints: []string{
+								"https://etcd-instance:2379",
+							},
+							CAFile:   "/etc/kubernetes/pki/etcd/ca.crt",
+							CertFile: "/etc/kubernetes/pki/etcd/apiserver-etcd-client.crt",
+							KeyFile:  "/etc/kubernetes/pki/etcd/apiserver-etcd-client.key",
+						},
+					},
+				},
+			},
+			expectedError: true,
 		},
 	}
 
-	// Execute createStaticPodFunction
-	manifestPath := filepath.Join(tmpdir, kubeadmconstants.ManifestsSubDirName)
-	err := CreateLocalEtcdStaticPodManifestFile(manifestPath, cfg)
-	if err != nil {
-		t.Errorf("Error executing CreateEtcdStaticPodManifestFile: %v", err)
-	}
+	for _, test := range tests {
+		// Execute createStaticPodFunction
+		manifestPath := filepath.Join(tmpdir, kubeadmconstants.ManifestsSubDirName)
+		err := CreateLocalEtcdStaticPodManifestFile(manifestPath, test.cfg)
 
-	// Assert expected files are there
-	testutil.AssertFilesCount(t, manifestPath, 1)
-	testutil.AssertFileExists(t, manifestPath, kubeadmconstants.Etcd+".yaml")
+		if !test.expectedError {
+			if err != nil {
+				t.Errorf("CreateLocalEtcdStaticPodManifestFile failed when not expected: %v", err)
+			}
+			// Assert expected files are there
+			testutil.AssertFilesCount(t, manifestPath, 1)
+			testutil.AssertFileExists(t, manifestPath, kubeadmconstants.Etcd+".yaml")
+		} else {
+			testutil.AssertError(t, err, "etcd static pod manifest cannot be generated for cluster using external etcd")
+		}
+	}
 }
 
 func TestGetEtcdCommand(t *testing.T) {

cmd/kubeadm/test/util.go

@@ -143,6 +143,17 @@ func AssertFileExists(t *testing.T, dirName string, fileNames ...string) {
 	}
 }
 
+// AssertError checks that the provided error matches the expected output
+func AssertError(t *testing.T, err error, expected string) {
+	if err == nil {
+		t.Errorf("no error was found, but '%s' was expected", expected)
+		return
+	}
+	if err.Error() != expected {
+		t.Errorf("error '%s' does not match expected error: '%s'", err.Error(), expected)
+	}
+}
+
 // GetDefaultInternalConfig returns a defaulted kubeadmapi.InitConfiguration
 func GetDefaultInternalConfig(t *testing.T) *kubeadmapi.InitConfiguration {
 	internalcfg, err := configutil.ConfigFileAndDefaultsToInternalConfig("", &kubeadmapiv1alpha3.InitConfiguration{})