[kubeadm] Implement ReadStaticPodFromDisk

cmd/kubeadm/app/util/marshal.go

@@ -41,3 +41,20 @@ func MarshalToYamlForCodecs(obj runtime.Object, gv schema.GroupVersion, codecs s
 	encoder := codecs.EncoderForVersion(info.Serializer, gv)
 	return runtime.Encode(encoder, obj)
 }
+
+// UnmarshalFromYaml unmarshals yaml into an object.
+func UnmarshalFromYaml(buffer []byte, gv schema.GroupVersion) (runtime.Object, error) {
+	return UnmarshalFromYamlForCodecs(buffer, gv, clientsetscheme.Codecs)
+}
+
+// UnmarshalFromYamlForCodecs unmarshals yaml into an object using the specified codec
+func UnmarshalFromYamlForCodecs(buffer []byte, gv schema.GroupVersion, codecs serializer.CodecFactory) (runtime.Object, error) {
+	mediaType := "application/yaml"
+	info, ok := runtime.SerializerInfoForMediaType(codecs.SupportedMediaTypes(), mediaType)
+	if !ok {
+		return nil, fmt.Errorf("unsupported media type %q", mediaType)
+	}
+
+	decoder := codecs.DecoderToVersion(info.Serializer, gv)
+	return runtime.Decode(decoder, buffer)
+}

cmd/kubeadm/app/util/staticpod/BUILD

@@ -14,6 +14,7 @@ go_test(
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
         "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/features:go_default_library",
+        "//cmd/kubeadm/test:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/intstr:go_default_library",

cmd/kubeadm/app/util/staticpod/utils.go

@@ -198,6 +198,23 @@ func WriteStaticPodToDisk(componentName, manifestDir string, pod v1.Pod) error {
 	return nil
 }
 
+// ReadStaticPodFromDisk reads a static pod file from disk
+func ReadStaticPodFromDisk(manifestPath string) (*v1.Pod, error) {
+	buf, err := ioutil.ReadFile(manifestPath)
+	if err != nil {
+		return &v1.Pod{}, fmt.Errorf("failed to read manifest for %q: %v", manifestPath, err)
+	}
+
+	obj, err := util.UnmarshalFromYaml(buf, v1.SchemeGroupVersion)
+	if err != nil {
+		return &v1.Pod{}, fmt.Errorf("failed to unmarshal manifest for %q from YAML: %v", manifestPath, err)
+	}
+
+	pod := obj.(*v1.Pod)
+
+	return pod, nil
+}
+
 // GetProbeAddress returns an IP address or 127.0.0.1 to use for liveness probes
 // in static pod manifests.
 func GetProbeAddress(cfg *kubeadmapi.MasterConfiguration, componentName string) string {

cmd/kubeadm/app/util/staticpod/utils_test.go

@@ -17,6 +17,9 @@ limitations under the License.
 package staticpod
 
 import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
 	"reflect"
 	"sort"
 	"testing"
@@ -28,6 +31,7 @@ import (
 
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
+	testutil "k8s.io/kubernetes/cmd/kubeadm/test"
 )
 
 func TestComponentResources(t *testing.T) {
@@ -454,3 +458,73 @@ func TestGetExtraParameters(t *testing.T) {
 		}
 	}
 }
+
+const (
+	validPod = `
+apiVersion: v1
+kind: Pod
+metadata:
+  labels:
+    component: etcd
+    tier: control-plane
+  name: etcd
+  namespace: kube-system
+spec:
+  containers:
+  - image: gcr.io/google_containers/etcd-amd64:3.1.11
+status: {}
+`
+	invalidPod = `---{ broken yaml @@@`
+)
+
+func TestReadStaticPodFromDisk(t *testing.T) {
+	tests := []struct {
+		description   string
+		podYaml       string
+		expectErr     bool
+		writeManifest bool
+	}{
+		{
+			description:   "valid pod is marshaled",
+			podYaml:       validPod,
+			writeManifest: true,
+			expectErr:     false,
+		},
+		{
+			description:   "invalid pod fails to unmarshal",
+			podYaml:       invalidPod,
+			writeManifest: true,
+			expectErr:     true,
+		},
+		{
+			description:   "non-existent file returns error",
+			podYaml:       ``,
+			writeManifest: false,
+			expectErr:     true,
+		},
+	}
+
+	for _, rt := range tests {
+		tmpdir := testutil.SetupTempDir(t)
+		defer os.RemoveAll(tmpdir)
+
+		manifestPath := filepath.Join(tmpdir, "pod.yaml")
+		if rt.writeManifest {
+			err := ioutil.WriteFile(manifestPath, []byte(rt.podYaml), 0644)
+			if err != nil {
+				t.Fatalf("Failed to write pod manifest\n%s\n\tfatal error: %v", rt.description, err)
+			}
+		}
+
+		_, actualErr := ReadStaticPodFromDisk(manifestPath)
+		if (actualErr != nil) != rt.expectErr {
+			t.Errorf(
+				"ReadStaticPodFromDisk failed\n%s\n\texpected error: %t\n\tgot: %t\n\tactual error: %v",
+				rt.description,
+				rt.expectErr,
+				(actualErr != nil),
+				actualErr,
+			)
+		}
+	}
+}