Make the creation of namespace using POST and PATCH consistent

PATCH verb is used when creating a namespace using server-side apply,
while POST verb is used when creating a namespace using client-side
apply.

The difference in path between the two ways to create a namespace led to
an inconsistency when calling webhooks. When server-side apply is used,
the request sent to webhooks has the field "namespace" populated with
the name of namespace being created. On the other hand, when using
client-side apply the "namespace" field is omitted.

This commit aims to make the behaviour consistent and populates the
"namespace" field when creating a namespace using POST verb (i.e.
client-side apply).

staging/src/k8s.io/apiserver/pkg/admission/plugin/resourcequota/BUILD

@@ -60,7 +60,10 @@ go_test(
         "//staging/src/k8s.io/apimachinery/pkg/api/resource:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission:go_default_library",
         "//staging/src/k8s.io/apiserver/pkg/admission/plugin/resourcequota/apis/resourcequota:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission/plugin/resourcequota/apis/resourcequota/v1:go_default_library",
         "//staging/src/k8s.io/client-go/informers:go_default_library",
         "//staging/src/k8s.io/client-go/kubernetes/fake:go_default_library",
         "//vendor/github.com/hashicorp/golang-lru:go_default_library",

staging/src/k8s.io/apiserver/pkg/admission/plugin/resourcequota/admission.go

@@ -26,6 +26,7 @@ import (
 	"k8s.io/apiserver/pkg/admission"
 	genericadmissioninitializer "k8s.io/apiserver/pkg/admission/initializer"
 	resourcequotaapi "k8s.io/apiserver/pkg/admission/plugin/resourcequota/apis/resourcequota"
+	v1 "k8s.io/apiserver/pkg/admission/plugin/resourcequota/apis/resourcequota/v1"
 	"k8s.io/apiserver/pkg/admission/plugin/resourcequota/apis/resourcequota/validation"
 	quota "k8s.io/apiserver/pkg/quota/v1"
 	"k8s.io/apiserver/pkg/quota/v1/generic"
@@ -36,6 +37,8 @@ import (
 // PluginName is a string with the name of the plugin
 const PluginName = "ResourceQuota"
 
+var namespaceGVK = v1.SchemeGroupVersion.WithKind("Namespace").GroupKind()
+
 // Register registers a plugin
 func Register(plugins *admission.Plugins) {
 	plugins.Register(PluginName,
@@ -136,9 +139,13 @@ func (a *QuotaAdmission) Validate(ctx context.Context, attr admission.Attributes
 	if attr.GetSubresource() != "" {
 		return nil
 	}
-	// ignore all operations that are not namespaced
+	// ignore all operations that are not namespaced or creation of namespaces
-	if attr.GetNamespace() == "" {
+	if attr.GetNamespace() == "" || isNamespaceCreation(attr) {
 		return nil
 	}
 	return a.evaluator.Evaluate(attr)
 }
+
+func isNamespaceCreation(attr admission.Attributes) bool {
+	return attr.GetOperation() == admission.Create && attr.GetKind().GroupKind() == namespaceGVK
+}

staging/src/k8s.io/apiserver/pkg/admission/plugin/resourcequota/admission_test.go

@@ -17,10 +17,15 @@ limitations under the License.
 package resourcequota
 
 import (
+	"context"
+	"errors"
 	"testing"
 
 	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apiserver/pkg/admission"
+	v1 "k8s.io/apiserver/pkg/admission/plugin/resourcequota/apis/resourcequota/v1"
 )
 
 func TestPrettyPrint(t *testing.T) {
@@ -122,3 +127,37 @@ func TestHasUsageStats(t *testing.T) {
 		}
 	}
 }
+
+type fakeEvaluator struct{}
+
+func (fakeEvaluator) Evaluate(a admission.Attributes) error {
+	return errors.New("should not be called")
+}
+
+func TestExcludedOperations(t *testing.T) {
+	a := &QuotaAdmission{
+		evaluator: fakeEvaluator{},
+	}
+	testCases := []struct {
+		desc string
+		attr admission.Attributes
+	}{
+		{
+			"subresource",
+			admission.NewAttributesRecord(nil, nil, schema.GroupVersionKind{}, "namespace", "name", schema.GroupVersionResource{}, "subresource", admission.Create, nil, false, nil),
+		},
+		{
+			"non-namespaced resource",
+			admission.NewAttributesRecord(nil, nil, schema.GroupVersionKind{}, "", "namespace", schema.GroupVersionResource{}, "", admission.Create, nil, false, nil),
+		},
+		{
+			"namespace creation",
+			admission.NewAttributesRecord(nil, nil, v1.SchemeGroupVersion.WithKind("Namespace"), "namespace", "namespace", schema.GroupVersionResource{}, "", admission.Create, nil, false, nil),
+		},
+	}
+	for _, test := range testCases {
+		if err := a.Validate(context.TODO(), test.attr, nil); err != nil {
+			t.Errorf("Test case: %q. Expected no error but got: %v", test.desc, err)
+		}
+	}
+}

staging/src/k8s.io/apiserver/pkg/endpoints/handlers/create.go

@@ -44,6 +44,8 @@ import (
 	utiltrace "k8s.io/utils/trace"
 )
 
+var namespaceGVK = schema.GroupVersionKind{Group: "", Version: "v1", Kind: "Namespace"}
+
 func createHandler(r rest.NamedCreater, scope *RequestScope, admit admission.Interface, includeName bool) http.HandlerFunc {
 	return func(w http.ResponseWriter, req *http.Request) {
 		// For performance tracking purposes.
@@ -76,7 +78,6 @@ func createHandler(r rest.NamedCreater, scope *RequestScope, admit admission.Int
 
 		ctx, cancel := context.WithTimeout(req.Context(), timeout)
 		defer cancel()
-		ctx = request.WithNamespace(ctx, namespace)
 		outputMediaType, _, err := negotiation.NegotiateOutputMediaType(req, scope.Serializer, scope)
 		if err != nil {
 			scope.err(err, w, req)
@@ -128,17 +129,21 @@ func createHandler(r rest.NamedCreater, scope *RequestScope, admit admission.Int
 		}
 		trace.Step("Conversion done")
 
+		// On create, get name from new object if unset
+		if len(name) == 0 {
+			_, name, _ = scope.Namer.ObjectName(obj)
+		}
+		if len(namespace) == 0 && *gvk == namespaceGVK {
+			namespace = name
+		}
+		ctx = request.WithNamespace(ctx, namespace)
+
 		ae := request.AuditEventFrom(ctx)
 		admit = admission.WithAudit(admit, ae)
 		audit.LogRequestObject(ae, obj, scope.Resource, scope.Subresource, scope.Serializer)
 
 		userInfo, _ := request.UserFrom(ctx)
 
-		// On create, get name from new object if unset
-		if len(name) == 0 {
-			_, name, _ = scope.Namer.ObjectName(obj)
-		}
-
 		trace.Step("About to store object in database")
 		admissionAttributes := admission.NewAttributesRecord(obj, nil, scope.Kind, namespace, name, scope.Resource, scope.Subresource, admission.Create, options, dryrun.IsDryRun(options.DryRun), userInfo)
 		requestFunc := func() (runtime.Object, error) {

test/integration/apiserver/admissionwebhook/admission_test.go

@@ -218,8 +218,8 @@ func (h *holder) reset(t *testing.T) {
 	}
 }
 func (h *holder) expect(gvr schema.GroupVersionResource, gvk, optionsGVK schema.GroupVersionKind, operation v1beta1.Operation, name, namespace string, object, oldObject, options bool) {
-	// Special-case namespaces, since the object name shows up in request attributes for update/delete requests
+	// Special-case namespaces, since the object name shows up in request attributes
-	if len(namespace) == 0 && gvk.Group == "" && gvk.Version == "v1" && gvk.Kind == "Namespace" && operation != v1beta1.Create {
+	if len(namespace) == 0 && gvk.Group == "" && gvk.Version == "v1" && gvk.Kind == "Namespace" {
 		namespace = name
 	}