kubeadm: Use loadPodSpecFromFile instead of LoadPodFromFile

Implement and use loadPodSpecFromFile which loads and returns PodSpec object
from YAML or JSON file. Use this function in the places where LoadPodFromFile
is used to load Pod object and then return the PodSpec portion of it. This
also removes the dependency on //pkg/volume/util and its dependencies (thus,
making kubeadm more lean).

Signed-off-by: Rostislav M. Georgiev <rostislavg@vmware.com>

cmd/kubeadm/app/phases/selfhosting/BUILD

@@ -17,7 +17,6 @@ go_test(
     deps = [
         "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/util:go_default_library",
-        "//pkg/volume/util:go_default_library",
         "//vendor/k8s.io/api/apps/v1:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",
     ],
@@ -37,12 +36,13 @@ go_library(
         "//cmd/kubeadm/app/features:go_default_library",
         "//cmd/kubeadm/app/util:go_default_library",
         "//cmd/kubeadm/app/util/apiclient:go_default_library",
-        "//pkg/volume/util:go_default_library",
         "//vendor/github.com/golang/glog:go_default_library",
         "//vendor/k8s.io/api/apps/v1: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/runtime:go_default_library",
         "//vendor/k8s.io/client-go/kubernetes:go_default_library",
+        "//vendor/k8s.io/client-go/kubernetes/scheme:go_default_library",
     ],
 )
 

cmd/kubeadm/app/phases/selfhosting/selfhosting.go

@@ -18,6 +18,7 @@ package selfhosting
 
 import (
 	"fmt"
+	"io/ioutil"
 	"os"
 	"time"
 
@@ -26,12 +27,13 @@ import (
 	apps "k8s.io/api/apps/v1"
 	"k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
 	clientset "k8s.io/client-go/kubernetes"
+	clientscheme "k8s.io/client-go/kubernetes/scheme"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/features"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/apiclient"
-	volumeutil "k8s.io/kubernetes/pkg/volume/util"
 )
 
 const (
@@ -85,12 +87,11 @@ func CreateSelfHostedControlPlane(manifestsDir, kubeConfigDir string, cfg *kubea
 			continue
 		}
 
-		// Load the Static Pod file in order to be able to create a self-hosted variant of that file
+		// Load the Static Pod spec in order to be able to create a self-hosted variant of that file
-		pod, err := volumeutil.LoadPodFromFile(manifestPath)
+		podSpec, err := loadPodSpecFromFile(manifestPath)
 		if err != nil {
 			return err
 		}
-		podSpec := &pod.Spec
 
 		// Build a DaemonSet object from the loaded PodSpec
 		ds := BuildDaemonSet(componentName, podSpec, mutators)
@@ -174,3 +175,23 @@ func BuildSelfhostedComponentLabels(component string) map[string]string {
 func BuildSelfHostedComponentLabelQuery(componentName string) string {
 	return fmt.Sprintf("k8s-app=%s", kubeadmconstants.AddSelfHostedPrefix(componentName))
 }
+
+func loadPodSpecFromFile(filePath string) (*v1.PodSpec, error) {
+	podDef, err := ioutil.ReadFile(filePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read file path %s: %+v", filePath, err)
+	}
+
+	if len(podDef) == 0 {
+		return nil, fmt.Errorf("file was empty: %s", filePath)
+	}
+
+	codec := clientscheme.Codecs.UniversalDecoder()
+	pod := &v1.Pod{}
+
+	if err = runtime.DecodeInto(codec, podDef, pod); err != nil {
+		return nil, fmt.Errorf("failed decoding pod: %v", err)
+	}
+
+	return &pod.Spec, nil
+}

cmd/kubeadm/app/phases/selfhosting/selfhosting_test.go

@@ -26,7 +26,6 @@ import (
 	apps "k8s.io/api/apps/v1"
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util"
-	volumeutil "k8s.io/kubernetes/pkg/volume/util"
 )
 
 const (
@@ -494,11 +493,10 @@ func TestBuildDaemonSet(t *testing.T) {
 		}
 		defer os.Remove(tempFile)
 
-		pod, err := volumeutil.LoadPodFromFile(tempFile)
+		podSpec, err := loadPodSpecFromFile(tempFile)
 		if err != nil {
-			t.Fatalf("couldn't load the specified Pod")
+			t.Fatalf("couldn't load the specified Pod Spec")
 		}
-		podSpec := &pod.Spec
 
 		ds := BuildDaemonSet(rt.component, podSpec, GetDefaultMutators())
 		dsBytes, err := util.MarshalToYaml(ds, apps.SchemeGroupVersion)
@@ -517,6 +515,11 @@ func TestLoadPodSpecFromFile(t *testing.T) {
 		content     string
 		expectError bool
 	}{
+		{
+			// No content
+			content:     "",
+			expectError: true,
+		},
 		{
 			// Good YAML
 			content: `
@@ -570,11 +573,16 @@ spec:
 		}
 		defer os.Remove(tempFile)
 
-		_, err = volumeutil.LoadPodFromFile(tempFile)
+		_, err = loadPodSpecFromFile(tempFile)
 		if (err != nil) != rt.expectError {
 			t.Errorf("failed TestLoadPodSpecFromFile:\nexpected error:\n%t\nsaw:\n%v", rt.expectError, err)
 		}
 	}
+
+	_, err := loadPodSpecFromFile("")
+	if err == nil {
+		t.Error("unexpected success: loadPodSpecFromFile should return error when no file is given")
+	}
 }
 
 func createTempFileWithContent(content []byte) (string, error) {