[release-4.16] Backport StreamingCollectionEncoding for JSON and protobuf

pkg/features/kube_features.go

@@ -840,6 +840,14 @@ const (
 	// Enables a StatefulSet to start from an arbitrary non zero ordinal
 	StatefulSetStartOrdinal featuregate.Feature = "StatefulSetStartOrdinal"
 
+	// owner: @serathius
+	// Allow API server JSON encoder to encode collections item by item, instead of all at once.
+	StreamingCollectionEncodingToJSON featuregate.Feature = "StreamingCollectionEncodingToJSON"
+
+	// owner: serathius
+	// Allow API server Protobuf encoder to encode collections item by item, instead of all at once.
+	StreamingCollectionEncodingToProtobuf featuregate.Feature = "StreamingCollectionEncodingToProtobuf"
+
 	// owner: @robscott
 	// kep: https://kep.k8s.io/2433
 	// alpha: v1.21
@@ -1195,6 +1203,8 @@ var defaultKubernetesFeatureGates = map[featuregate.Feature]featuregate.FeatureS
 
 	StatefulSetStartOrdinal: {Default: true, PreRelease: featuregate.Beta},
 
+	StreamingCollectionEncodingToJSON: {Default: false, PreRelease: featuregate.Beta},
+
 	TopologyAwareHints: {Default: true, PreRelease: featuregate.Beta},
 
 	TopologyManagerPolicyAlphaOptions: {Default: false, PreRelease: featuregate.Alpha},

pkg/registry/core/rest/storage_core_generic.go

@@ -33,6 +33,9 @@ import (
 	"k8s.io/client-go/informers"
 	restclient "k8s.io/client-go/rest"
 
+	"k8s.io/apimachinery/pkg/runtime/serializer"
+	"k8s.io/apiserver/pkg/features"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/kubernetes/pkg/api/legacyscheme"
 	api "k8s.io/kubernetes/pkg/apis/core"
 	configmapstore "k8s.io/kubernetes/pkg/registry/core/configmap/storage"
@@ -68,6 +71,16 @@ func (c *GenericConfig) NewRESTStorage(apiResourceConfigSource serverstorage.API
 		ParameterCodec:               legacyscheme.ParameterCodec,
 		NegotiatedSerializer:         legacyscheme.Codecs,
 	}
+	opts := []serializer.CodecFactoryOptionsMutator{}
+	if utilfeature.DefaultFeatureGate.Enabled(features.StreamingCollectionEncodingToJSON) {
+		opts = append(opts, serializer.WithStreamingCollectionEncodingToJSON())
+	}
+	if utilfeature.DefaultFeatureGate.Enabled(features.StreamingCollectionEncodingToProtobuf) {
+		opts = append(opts, serializer.WithStreamingCollectionEncodingToProtobuf())
+	}
+	if len(opts) != 0 {
+		apiGroupInfo.NegotiatedSerializer = serializer.NewCodecFactory(legacyscheme.Scheme, opts...)
+	}
 
 	eventStorage, err := eventstore.NewREST(restOptionsGetter, uint64(c.EventTTL.Seconds()))
 	if err != nil {

staging/src/k8s.io/apiextensions-apiserver/pkg/apiserver/customresource_handler.go

@@ -69,8 +69,10 @@ import (
 	"k8s.io/apiserver/pkg/endpoints/handlers/responsewriters"
 	"k8s.io/apiserver/pkg/endpoints/metrics"
 	apirequest "k8s.io/apiserver/pkg/endpoints/request"
+	"k8s.io/apiserver/pkg/features"
 	"k8s.io/apiserver/pkg/registry/generic"
 	genericfilters "k8s.io/apiserver/pkg/server/filters"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/apiserver/pkg/util/webhook"
 	"k8s.io/apiserver/pkg/warning"
 	"k8s.io/client-go/scale"
@@ -826,6 +828,7 @@ func (r *crdHandler) getOrCreateServingInfoFor(uid types.UID, name string) (*crd
 		clusterScoped := crd.Spec.Scope == apiextensionsv1.ClusterScoped
 
 		// CRDs explicitly do not support protobuf, but some objects returned by the API server do
+		streamingCollections := utilfeature.DefaultFeatureGate.Enabled(features.StreamingCollectionEncodingToJSON)
 		negotiatedSerializer := unstructuredNegotiatedSerializer{
 			typer:                 typer,
 			creator:               creator,
@@ -839,10 +842,11 @@ func (r *crdHandler) getOrCreateServingInfoFor(uid types.UID, name string) (*crd
 					MediaTypeType:    "application",
 					MediaTypeSubType: "json",
 					EncodesAsText:    true,
-					Serializer:       json.NewSerializer(json.DefaultMetaFactory, creator, typer, false),
-					PrettySerializer: json.NewSerializer(json.DefaultMetaFactory, creator, typer, true),
+					Serializer:       json.NewSerializerWithOptions(json.DefaultMetaFactory, creator, typer, json.SerializerOptions{StreamingCollectionsEncoding: streamingCollections}),
+					PrettySerializer: json.NewSerializerWithOptions(json.DefaultMetaFactory, creator, typer, json.SerializerOptions{Pretty: true}),
 					StrictSerializer: json.NewSerializerWithOptions(json.DefaultMetaFactory, creator, typer, json.SerializerOptions{
-						Strict: true,
+						Strict:                       true,
+						StreamingCollectionsEncoding: streamingCollections,
 					}),
 					StreamSerializer: &runtime.StreamSerializerInfo{
 						EncodesAsText: true,
@@ -865,7 +869,9 @@ func (r *crdHandler) getOrCreateServingInfoFor(uid types.UID, name string) (*crd
 					MediaType:        "application/vnd.kubernetes.protobuf",
 					MediaTypeType:    "application",
 					MediaTypeSubType: "vnd.kubernetes.protobuf",
-					Serializer:       protobuf.NewSerializer(creator, typer),
+					Serializer: protobuf.NewSerializerWithOptions(creator, typer, protobuf.SerializerOptions{
+						StreamingCollectionsEncoding: utilfeature.DefaultFeatureGate.Enabled(features.StreamingCollectionEncodingToProtobuf),
+					}),
 					StreamSerializer: &runtime.StreamSerializerInfo{
 						Serializer: protobuf.NewRawSerializer(creator, typer),
 						Framer:     protobuf.LengthDelimitedFramer,
@@ -936,7 +942,15 @@ func (r *crdHandler) getOrCreateServingInfoFor(uid types.UID, name string) (*crd
 		scaleScope := *requestScopes[v.Name]
 		scaleConverter := scale.NewScaleConverter()
 		scaleScope.Subresource = "scale"
-		scaleScope.Serializer = serializer.NewCodecFactory(scaleConverter.Scheme())
+		var opts []serializer.CodecFactoryOptionsMutator
+		if utilfeature.DefaultFeatureGate.Enabled(features.StreamingCollectionEncodingToJSON) {
+			opts = append(opts, serializer.WithStreamingCollectionEncodingToJSON())
+		}
+		if utilfeature.DefaultFeatureGate.Enabled(features.StreamingCollectionEncodingToProtobuf) {
+			opts = append(opts, serializer.WithStreamingCollectionEncodingToProtobuf())
+		}
+		scaleScope.Serializer = serializer.NewCodecFactory(scaleConverter.Scheme(), opts...)
+
 		scaleScope.Kind = autoscalingv1.SchemeGroupVersion.WithKind("Scale")
 		scaleScope.Namer = handlers.ContextBasedNaming{
 			Namer:         meta.NewAccessor(),

staging/src/k8s.io/apimachinery/pkg/api/meta/help.go

@@ -221,6 +221,9 @@ func extractList(obj runtime.Object, allocNew bool) ([]runtime.Object, error) {
 	if err != nil {
 		return nil, err
 	}
+	if items.IsNil() {
+		return nil, nil
+	}
 	list := make([]runtime.Object, items.Len())
 	if len(list) == 0 {
 		return list, nil

staging/src/k8s.io/apimachinery/pkg/runtime/serializer/codec_factory.go

@@ -52,7 +52,7 @@ type serializerType struct {
 func newSerializersForScheme(scheme *runtime.Scheme, mf json.MetaFactory, options CodecFactoryOptions) []serializerType {
 	jsonSerializer := json.NewSerializerWithOptions(
 		mf, scheme, scheme,
-		json.SerializerOptions{Yaml: false, Pretty: false, Strict: options.Strict},
+		json.SerializerOptions{Yaml: false, Pretty: false, Strict: options.Strict, StreamingCollectionsEncoding: options.StreamingCollectionsEncodingToJSON},
 	)
 	jsonSerializerType := serializerType{
 		AcceptContentTypes: []string{runtime.ContentTypeJSON},
@@ -73,7 +73,7 @@ func newSerializersForScheme(scheme *runtime.Scheme, mf json.MetaFactory, option
 
 	strictJSONSerializer := json.NewSerializerWithOptions(
 		mf, scheme, scheme,
-		json.SerializerOptions{Yaml: false, Pretty: false, Strict: true},
+		json.SerializerOptions{Yaml: false, Pretty: false, Strict: true, StreamingCollectionsEncoding: options.StreamingCollectionsEncodingToJSON},
 	)
 	jsonSerializerType.StrictSerializer = strictJSONSerializer
 
@@ -85,7 +85,10 @@ func newSerializersForScheme(scheme *runtime.Scheme, mf json.MetaFactory, option
 		mf, scheme, scheme,
 		json.SerializerOptions{Yaml: true, Pretty: false, Strict: true},
 	)
-	protoSerializer := protobuf.NewSerializer(scheme, scheme)
+	protoSerializer := protobuf.NewSerializerWithOptions(scheme, scheme, protobuf.SerializerOptions{
+		StreamingCollectionsEncoding: options.StreamingCollectionsEncodingToProtobuf,
+	})
+
 	protoRawSerializer := protobuf.NewRawSerializer(scheme, scheme)
 
 	serializers := []serializerType{
@@ -136,6 +139,9 @@ type CodecFactoryOptions struct {
 	Strict bool
 	// Pretty includes a pretty serializer along with the non-pretty one
 	Pretty bool
+
+	StreamingCollectionsEncodingToJSON     bool
+	StreamingCollectionsEncodingToProtobuf bool
 }
 
 // CodecFactoryOptionsMutator takes a pointer to an options struct and then modifies it.
@@ -162,6 +168,18 @@ func DisableStrict(options *CodecFactoryOptions) {
 	options.Strict = false
 }
 
+func WithStreamingCollectionEncodingToJSON() CodecFactoryOptionsMutator {
+	return func(options *CodecFactoryOptions) {
+		options.StreamingCollectionsEncodingToJSON = true
+	}
+}
+
+func WithStreamingCollectionEncodingToProtobuf() CodecFactoryOptionsMutator {
+	return func(options *CodecFactoryOptions) {
+		options.StreamingCollectionsEncodingToProtobuf = true
+	}
+}
+
 // NewCodecFactory provides methods for retrieving serializers for the supported wire formats
 // and conversion wrappers to define preferred internal and external versions. In the future,
 // as the internal version is used less, callers may instead use a defaulting serializer and