Describe sts on rollout history if the revision

Signed-off-by: Dinesh <dineshudt17@gmail.com>

staging/src/k8s.io/kubectl/pkg/polymorphichelpers/BUILD

@@ -95,6 +95,7 @@ go_test(
         "//staging/src/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/types:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/diff:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/util/json:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/watch:go_default_library",
         "//staging/src/k8s.io/client-go/kubernetes/fake:go_default_library",
         "//staging/src/k8s.io/client-go/testing:go_default_library",

staging/src/k8s.io/kubectl/pkg/polymorphichelpers/history.go

@@ -233,9 +233,8 @@ type StatefulSetHistoryViewer struct {
 
 // ViewHistory returns a list of the revision history of a statefulset
 // TODO: this should be a describer
-// TODO: needs to implement detailed revision view
 func (h *StatefulSetHistoryViewer) ViewHistory(namespace, name string, revision int64) (string, error) {
-	_, history, err := statefulSetHistory(h.c.AppsV1(), namespace, name)
+	sts, history, err := statefulSetHistory(h.c.AppsV1(), namespace, name)
 	if err != nil {
 		return "", err
 	}
@@ -243,9 +242,26 @@ func (h *StatefulSetHistoryViewer) ViewHistory(namespace, name string, revision
 	if len(history) <= 0 {
 		return "No rollout history found.", nil
 	}
-	revisions := make([]int64, 0, len(history))
+
-	for _, revision := range history {
+	historyInfo := make(map[int64]*appsv1.ControllerRevision)
-		revisions = append(revisions, revision.Revision)
+	for _, h := range history {
+		historyInfo[h.Revision] = h
+	}
+	if revision != 0 {
+		value, ok := historyInfo[revision]
+		if !ok {
+			return "", fmt.Errorf("unable to find the specified revision")
+		}
+		sts, err := applyStatefulSetHistory(sts, value)
+		if err != nil {
+			return "", fmt.Errorf("error unmarshelling sts: %w", err)
+		}
+		return printTemplate(&sts.Spec.Template)
+	}
+
+	revisions := make([]int64, 0, len(historyInfo))
+	for revision := range historyInfo {
+		revisions = append(revisions, revision)
 	}
 	sliceutil.SortInts64(revisions)
 
@@ -365,6 +381,24 @@ func applyDaemonSetHistory(ds *appsv1.DaemonSet, history *appsv1.ControllerRevis
 	return result, nil
 }
 
+// applyStatefulSetHistory returns a specific revision of StatefulSet by applying the given history to a copy of the given StatefulSet
+func applyStatefulSetHistory(sts *appsv1.StatefulSet, history *appsv1.ControllerRevision) (*appsv1.StatefulSet, error) {
+	stsBytes, err := json.Marshal(sts)
+	if err != nil {
+		return nil, err
+	}
+	patched, err := strategicpatch.StrategicMergePatch(stsBytes, history.Data.Raw, sts)
+	if err != nil {
+		return nil, err
+	}
+	result := &appsv1.StatefulSet{}
+	err = json.Unmarshal(patched, result)
+	if err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
 // TODO: copied here until this becomes a describer
 func tabbedString(f func(io.Writer) error) (string, error) {
 	out := new(tabwriter.Writer)

staging/src/k8s.io/kubectl/pkg/polymorphichelpers/history_test.go

@@ -27,6 +27,7 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apimachinery/pkg/util/json"
 	"k8s.io/client-go/kubernetes/fake"
 )
 
@@ -71,21 +72,25 @@ func TestViewHistory(t *testing.T) {
 			},
 			Spec: appsv1.StatefulSetSpec{Selector: &metav1.LabelSelector{MatchLabels: podStub.ObjectMeta.Labels}, Replicas: &replicas, Template: podStub},
 		}
-
+	)
-		ssStub1 = &appsv1.ControllerRevision{
+	stsRawData, err := json.Marshal(ssStub)
+	if err != nil {
+		t.Fatalf("error creating sts raw data: %v", err)
+	}
+	ssStub1 := &appsv1.ControllerRevision{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:            "moons",
 			Namespace:       "default",
 			Labels:          map[string]string{"foo": "bar"},
 			OwnerReferences: []metav1.OwnerReference{{"apps/v1", "StatefulSet", "moons", "1993", &trueVar, nil}},
 		},
+		Data:     runtime.RawExtension{Raw: stsRawData},
 		TypeMeta: metav1.TypeMeta{Kind: "StatefulSet", APIVersion: "apps/v1"},
 		Revision: 1,
 	}
-	)
 
 	fakeClientSet := fake.NewSimpleClientset(ssStub)
-	_, err := fakeClientSet.AppsV1().ControllerRevisions("default").Create(context.TODO(), ssStub1, metav1.CreateOptions{})
+	_, err = fakeClientSet.AppsV1().ControllerRevisions("default").Create(context.TODO(), ssStub1, metav1.CreateOptions{})
 	if err != nil {
 		t.Fatalf("create controllerRevisions error %v occurred ", err)
 	}
@@ -94,7 +99,8 @@ func TestViewHistory(t *testing.T) {
 		fakeClientSet,
 	}
 
-	result, err := sts.ViewHistory("default", "moons", 1)
+	t.Run("should show revisions list if the revision is not specified", func(t *testing.T) {
+		result, err := sts.ViewHistory("default", "moons", 0)
 		if err != nil {
 			t.Fatalf("error getting ViewHistory for a StatefulSets moons: %v", err)
 		}
@@ -106,7 +112,30 @@ func TestViewHistory(t *testing.T) {
 		if result != expected {
 			t.Fatalf("unexpected output  (%v was expected but got %v)", expected, result)
 		}
+	})
 
+	t.Run("should describe the revision if revision is specified", func(t *testing.T) {
+		result, err := sts.ViewHistory("default", "moons", 1)
+		if err != nil {
+			t.Fatalf("error getting ViewHistory for a StatefulSets moons: %v", err)
+		}
+
+		expected := `Pod Template:
+  Labels:	foo=bar
+  Containers:
+   test:
+    Image:	nginx
+    Port:	<none>
+    Host Port:	<none>
+    Environment:	<none>
+    Mounts:	<none>
+  Volumes:	<none>
+`
+
+		if result != expected {
+			t.Fatalf("unexpected output  (%v was expected but got %v)", expected, result)
+		}
+	})
 }
 
 func TestApplyDaemonSetHistory(t *testing.T) {