From 4d55c0687dbb6b6469bb17fd9e7e3b14ca6b4779 Mon Sep 17 00:00:00 2001
From: Ben Luddy <bluddy@redhat.com>
Date: Mon, 11 Sep 2023 13:59:21 -0400
Subject: [PATCH] Reuse SupportedMediaTypes for CR content-type negotiation.

In the course of calling NegotiateOutputMediaType, each CR endpoint handler invocation instantiates
six JSON serializers. Each instantiation marshals the serializer options to JSON to construct the
serializer identifier. Under heavy CR GET load, CPU profiling shows approximately 16% of the time
spent in WriteObjectNegotiated was in SupportedMediaTypes, most of that within json.identifier().
---
 .../pkg/apiserver/customresource_handler.go   | 81 ++++++++++---------
 1 file changed, 42 insertions(+), 39 deletions(-)

diff --git a/staging/src/k8s.io/apiextensions-apiserver/pkg/apiserver/customresource_handler.go b/staging/src/k8s.io/apiextensions-apiserver/pkg/apiserver/customresource_handler.go
index 2a6dcb80a7c..05b553ef864 100644
--- a/staging/src/k8s.io/apiextensions-apiserver/pkg/apiserver/customresource_handler.go
+++ b/staging/src/k8s.io/apiextensions-apiserver/pkg/apiserver/customresource_handler.go
@@ -833,6 +833,45 @@ func (r *crdHandler) getOrCreateServingInfoFor(uid types.UID, name string) (*crd
 			structuralSchemas:     structuralSchemas,
 			structuralSchemaGK:    kind.GroupKind(),
 			preserveUnknownFields: crd.Spec.PreserveUnknownFields,
+			supportedMediaTypes: []runtime.SerializerInfo{
+				{
+					MediaType:        "application/json",
+					MediaTypeType:    "application",
+					MediaTypeSubType: "json",
+					EncodesAsText:    true,
+					Serializer:       json.NewSerializer(json.DefaultMetaFactory, creator, typer, false),
+					PrettySerializer: json.NewSerializer(json.DefaultMetaFactory, creator, typer, true),
+					StrictSerializer: json.NewSerializerWithOptions(json.DefaultMetaFactory, creator, typer, json.SerializerOptions{
+						Strict: true,
+					}),
+					StreamSerializer: &runtime.StreamSerializerInfo{
+						EncodesAsText: true,
+						Serializer:    json.NewSerializer(json.DefaultMetaFactory, creator, typer, false),
+						Framer:        json.Framer,
+					},
+				},
+				{
+					MediaType:        "application/yaml",
+					MediaTypeType:    "application",
+					MediaTypeSubType: "yaml",
+					EncodesAsText:    true,
+					Serializer:       json.NewYAMLSerializer(json.DefaultMetaFactory, creator, typer),
+					StrictSerializer: json.NewSerializerWithOptions(json.DefaultMetaFactory, creator, typer, json.SerializerOptions{
+						Yaml:   true,
+						Strict: true,
+					}),
+				},
+				{
+					MediaType:        "application/vnd.kubernetes.protobuf",
+					MediaTypeType:    "application",
+					MediaTypeSubType: "vnd.kubernetes.protobuf",
+					Serializer:       protobuf.NewSerializer(creator, typer),
+					StreamSerializer: &runtime.StreamSerializerInfo{
+						Serializer: protobuf.NewRawSerializer(creator, typer),
+						Framer:     protobuf.LengthDelimitedFramer,
+					},
+				},
+			},
 		}
 		var standardSerializers []runtime.SerializerInfo
 		for _, s := range negotiatedSerializer.SupportedMediaTypes() {
@@ -1021,48 +1060,12 @@ type unstructuredNegotiatedSerializer struct {
 	structuralSchemas     map[string]*structuralschema.Structural // by version
 	structuralSchemaGK    schema.GroupKind
 	preserveUnknownFields bool
+
+	supportedMediaTypes []runtime.SerializerInfo
 }
 
 func (s unstructuredNegotiatedSerializer) SupportedMediaTypes() []runtime.SerializerInfo {
-	return []runtime.SerializerInfo{
-		{
-			MediaType:        "application/json",
-			MediaTypeType:    "application",
-			MediaTypeSubType: "json",
-			EncodesAsText:    true,
-			Serializer:       json.NewSerializer(json.DefaultMetaFactory, s.creator, s.typer, false),
-			PrettySerializer: json.NewSerializer(json.DefaultMetaFactory, s.creator, s.typer, true),
-			StrictSerializer: json.NewSerializerWithOptions(json.DefaultMetaFactory, s.creator, s.typer, json.SerializerOptions{
-				Strict: true,
-			}),
-			StreamSerializer: &runtime.StreamSerializerInfo{
-				EncodesAsText: true,
-				Serializer:    json.NewSerializer(json.DefaultMetaFactory, s.creator, s.typer, false),
-				Framer:        json.Framer,
-			},
-		},
-		{
-			MediaType:        "application/yaml",
-			MediaTypeType:    "application",
-			MediaTypeSubType: "yaml",
-			EncodesAsText:    true,
-			Serializer:       json.NewYAMLSerializer(json.DefaultMetaFactory, s.creator, s.typer),
-			StrictSerializer: json.NewSerializerWithOptions(json.DefaultMetaFactory, s.creator, s.typer, json.SerializerOptions{
-				Yaml:   true,
-				Strict: true,
-			}),
-		},
-		{
-			MediaType:        "application/vnd.kubernetes.protobuf",
-			MediaTypeType:    "application",
-			MediaTypeSubType: "vnd.kubernetes.protobuf",
-			Serializer:       protobuf.NewSerializer(s.creator, s.typer),
-			StreamSerializer: &runtime.StreamSerializerInfo{
-				Serializer: protobuf.NewRawSerializer(s.creator, s.typer),
-				Framer:     protobuf.LengthDelimitedFramer,
-			},
-		},
-	}
+	return s.supportedMediaTypes
 }
 
 func (s unstructuredNegotiatedSerializer) EncoderForVersion(encoder runtime.Encoder, gv runtime.GroupVersioner) runtime.Encoder {