Add E2E test for CBOR client compatibility with older apiservers.

Clients must be able to use CBOR without a guarantee that all apiservers support it. The apiserver
aggregation layer avoids changing in any way that would require an aggregated apiservers to be
updated. This end-to-end test verifies that a client's content negotiation behaviors continue to
work over time when communicating with a 1.17 sample-apiserver.

test/e2e/apimachinery/protocol.go

@@ -26,12 +26,21 @@ import (
 	v1 "k8s.io/api/core/v1"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/fields"
+	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/watch"
+	"k8s.io/client-go/dynamic"
+	clientfeatures "k8s.io/client-go/features"
+	clientfeaturestesting "k8s.io/client-go/features/testing"
 	"k8s.io/client-go/kubernetes"
-	admissionapi "k8s.io/pod-security-admission/api"
+	aggregatorclientset "k8s.io/kube-aggregator/pkg/client/clientset_generated/clientset"
-
+	"k8s.io/kubernetes/test/e2e/feature"
 	"k8s.io/kubernetes/test/e2e/framework"
+	imageutils "k8s.io/kubernetes/test/utils/image"
+	admissionapi "k8s.io/pod-security-admission/api"
+	samplev1alpha1 "k8s.io/sample-apiserver/pkg/apis/wardle/v1alpha1"
+	samplev1alpha1client "k8s.io/sample-apiserver/pkg/generated/clientset/versioned/typed/wardle/v1alpha1"
 )
 
 var _ = SIGDescribe("client-go should negotiate", func() {
@@ -96,3 +105,67 @@ var _ = SIGDescribe("client-go should negotiate", func() {
 		})
 	}
 })
+
+var _ = SIGDescribe("CBOR", feature.CBOR, func() {
+	f := framework.NewDefaultFramework("cbor")
+	f.NamespacePodSecurityLevel = admissionapi.LevelBaseline
+
+	// Must be serial to avoid conflict with other tests that set up a sample apiserver.
+	f.It("clients remain compatible with the 1.17 sample-apiserver", f.WithSerial(), func(ctx context.Context) {
+		clientfeaturestesting.SetFeatureDuringTest(g.GinkgoTB(), clientfeatures.ClientsAllowCBOR, true)
+		clientfeaturestesting.SetFeatureDuringTest(g.GinkgoTB(), clientfeatures.ClientsPreferCBOR, true)
+
+		clientConfig, err := framework.LoadConfig()
+		framework.ExpectNoError(err)
+
+		aggregatorClient, err := aggregatorclientset.NewForConfig(clientConfig)
+		framework.ExpectNoError(err)
+
+		dynamicClient, err := dynamic.NewForConfig(clientConfig)
+		framework.ExpectNoError(err)
+
+		objectNames := generateSampleAPIServerObjectNames(f.Namespace.Name)
+		g.DeferCleanup(func(ctx context.Context) {
+			cleanupSampleAPIServer(ctx, f.ClientSet, aggregatorClient, objectNames, samplev1alpha1.SchemeGroupVersion.Version+"."+samplev1alpha1.SchemeGroupVersion.Group)
+		})
+		SetUpSampleAPIServer(ctx, f, aggregatorClient, imageutils.GetE2EImage(imageutils.APIServer), objectNames, samplev1alpha1.SchemeGroupVersion.Group, samplev1alpha1.SchemeGroupVersion.Version)
+
+		flunder := samplev1alpha1.Flunder{
+			ObjectMeta: metav1.ObjectMeta{
+				Name: "test-flunder",
+			},
+		}
+
+		g.By("making requests with a generated client", func() {
+			sampleClient, err := samplev1alpha1client.NewForConfig(clientConfig)
+			framework.ExpectNoError(err)
+
+			_, err = sampleClient.Flunders(f.Namespace.Name).List(ctx, metav1.ListOptions{LabelSelector: "a,!a"})
+			framework.ExpectNoError(err, "Failed to list with generated client")
+
+			_, err = sampleClient.Flunders(f.Namespace.Name).Create(ctx, &flunder, metav1.CreateOptions{DryRun: []string{metav1.DryRunAll}})
+			o.Expect(err).To(o.MatchError(apierrors.IsUnsupportedMediaType, "Expected 415 (Unsupported Media Type) response on first write with generated client"))
+
+			_, err = sampleClient.Flunders(f.Namespace.Name).Create(ctx, &flunder, metav1.CreateOptions{DryRun: []string{metav1.DryRunAll}})
+			framework.ExpectNoError(err, "Expected subsequent writes to succeed with generated client")
+		})
+
+		g.By("making requests with a dynamic client", func() {
+			unstructuredFlunderContent, err := runtime.DefaultUnstructuredConverter.ToUnstructured(&flunder)
+			framework.ExpectNoError(err)
+			unstructuredFlunder := &unstructured.Unstructured{Object: unstructuredFlunderContent}
+
+			flunderDynamicClient := dynamicClient.Resource(samplev1alpha1.SchemeGroupVersion.WithResource("flunders")).Namespace(f.Namespace.Name)
+
+			list, err := flunderDynamicClient.List(ctx, metav1.ListOptions{LabelSelector: "a,!a"})
+			framework.ExpectNoError(err, "Failed to list with dynamic client")
+			o.Expect(list.GetObjectKind().GroupVersionKind()).To(o.Equal(samplev1alpha1.SchemeGroupVersion.WithKind("FlunderList")))
+
+			_, err = flunderDynamicClient.Create(ctx, unstructuredFlunder, metav1.CreateOptions{DryRun: []string{metav1.DryRunAll}})
+			o.Expect(err).To(o.MatchError(apierrors.IsUnsupportedMediaType, "Expected 415 (Unsupported Media Type) response on first write with dynamic client"))
+
+			_, err = flunderDynamicClient.Create(ctx, unstructuredFlunder, metav1.CreateOptions{DryRun: []string{metav1.DryRunAll}})
+			framework.ExpectNoError(err, "Expected subsequent writes to succeed with dynamic client")
+		})
+	})
+})

test/e2e/feature/feature.go

@@ -34,6 +34,10 @@ var (
 	// TODO: document the feature (owning SIG, when to use this feature for a test)
 	BoundServiceAccountTokenVolume = framework.WithFeature(framework.ValidFeatures.Add("BoundServiceAccountTokenVolume"))
 
+	// Owner: sig-api-machinery
+	// Marks tests that exercise the CBOR data format for serving or storage.
+	CBOR = framework.WithFeature(framework.ValidFeatures.Add("CBOR"))
+
 	// TODO: document the feature (owning SIG, when to use this feature for a test)
 	CloudProvider = framework.WithFeature(framework.ValidFeatures.Add("CloudProvider"))