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

@@ -54,13 +54,16 @@ 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
+	var tests = []struct {
-	cfg := &kubeadmapi.InitConfiguration{
+		cfg           *kubeadmapi.InitConfiguration
+		expectedError bool
+	}{
+		{
+			cfg: &kubeadmapi.InitConfiguration{
 				ClusterConfiguration: kubeadmapi.ClusterConfiguration{
 					KubernetesVersion: "v1.7.0",
 					Etcd: kubeadmapi.Etcd{
@@ -70,18 +73,45 @@ func TestCreateLocalEtcdStaticPodManifestFile(t *testing.T) {
 						},
 					},
 				},
+			},
+			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,
+		},
 	}
 
+	for _, test := range tests {
 		// Execute createStaticPodFunction
 		manifestPath := filepath.Join(tmpdir, kubeadmconstants.ManifestsSubDirName)
-	err := CreateLocalEtcdStaticPodManifestFile(manifestPath, cfg)
+		err := CreateLocalEtcdStaticPodManifestFile(manifestPath, test.cfg)
-	if err != nil {
-		t.Errorf("Error executing CreateEtcdStaticPodManifestFile: %v", err)
-	}
 
+		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{})