Add version mapping in ComponentGlobalsRegistry.

Signed-off-by: Siyuan Zhang <sizhang@google.com>

cmd/kube-apiserver/app/options/options_test.go

@@ -53,7 +53,7 @@ func TestAddFlags(t *testing.T) {
 	featureGate := featuregate.NewFeatureGate()
 	componentRegistry := utilversion.NewComponentGlobalsRegistry()
 	effectiveVersion := utilversion.NewEffectiveVersion("1.32")
-	_ = componentRegistry.Register("test", effectiveVersion, featureGate, true)
+	utilruntime.Must(componentRegistry.Register("test", effectiveVersion, featureGate))
 	s := NewServerRunOptions(featureGate, effectiveVersion)
 	for _, f := range s.Flags().FlagSets {
 		fs.AddFlagSet(f)

cmd/kube-apiserver/app/testing/testserver.go

@@ -43,6 +43,7 @@ import (
 	"k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	utilerrors "k8s.io/apimachinery/pkg/util/errors"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/apimachinery/pkg/util/wait"
 	serveroptions "k8s.io/apiserver/pkg/server/options"
 	"k8s.io/apiserver/pkg/storage/storagebackend"
@@ -182,12 +183,12 @@ func StartTestServer(t ktesting.TB, instanceOptions *TestServerInstanceOptions,
 	fs := pflag.NewFlagSet("test", pflag.PanicOnError)
 
 	featureGate := utilfeature.DefaultMutableFeatureGate
-	binaryVersion := utilversion.DefaultKubeEffectiveVersion().BinaryVersion().String()
+	effectiveVersion := utilversion.DefaultKubeEffectiveVersion()
 	if instanceOptions.BinaryVersion != "" {
-		binaryVersion = instanceOptions.BinaryVersion
+		effectiveVersion = utilversion.NewEffectiveVersion(instanceOptions.BinaryVersion)
 	}
-	effectiveVersion := utilversion.NewEffectiveVersion(binaryVersion)
+	utilversion.DefaultComponentGlobalsRegistry.Reset()
-	_ = utilversion.DefaultComponentGlobalsRegistry.Register(utilversion.DefaultKubeComponent, effectiveVersion, featureGate, true)
+	utilruntime.Must(utilversion.DefaultComponentGlobalsRegistry.Register(utilversion.DefaultKubeComponent, effectiveVersion, featureGate))
 
 	s := options.NewServerRunOptions(featureGate, effectiveVersion)
 

pkg/controlplane/apiserver/config.go

@@ -46,7 +46,6 @@ import (
 	clientgoinformers "k8s.io/client-go/informers"
 	clientgoclientset "k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/util/keyutil"
-	"k8s.io/component-base/version"
 	aggregatorapiserver "k8s.io/kube-aggregator/pkg/apiserver"
 	openapicommon "k8s.io/kube-openapi/pkg/common"
 
@@ -172,9 +171,6 @@ func BuildGenericConfig(
 		sets.NewString("attach", "exec", "proxy", "log", "portforward"),
 	)
 
-	kubeVersion := version.Get()
-	genericConfig.Version = &kubeVersion
-
 	if genericConfig.EgressSelector != nil {
 		s.Etcd.StorageConfig.Transport.EgressLookup = genericConfig.EgressSelector.Lookup
 	}

pkg/controlplane/apiserver/options/options_test.go

@@ -48,7 +48,7 @@ func TestAddFlags(t *testing.T) {
 	featureGate := featuregate.NewFeatureGate()
 	effectiveVersion := utilversion.NewEffectiveVersion("1.32")
 	componentRegistry := utilversion.NewComponentGlobalsRegistry()
-	_ = componentRegistry.Register("test", effectiveVersion, featureGate, true)
+	utilruntime.Must(componentRegistry.Register("test", effectiveVersion, featureGate))
 	s := NewOptions(featureGate, effectiveVersion)
 	var fss cliflag.NamedFlagSets
 	s.AddFlags(&fss)

pkg/controlplane/instance_test.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	"crypto/tls"
 	"encoding/json"
+	"fmt"
 	"io"
 	"net"
 	"net/http"
@@ -118,9 +119,7 @@ func setUp(t *testing.T) (*etcd3testing.EtcdTestServer, Config, *assert.Assertio
 		t.Fatal(err)
 	}
 
-	kubeVersion := kubeversion.Get()
 	config.ControlPlane.Generic.Authorization.Authorizer = authorizerfactory.NewAlwaysAllowAuthorizer()
-	config.ControlPlane.Generic.Version = &kubeVersion
 	config.ControlPlane.StorageFactory = storageFactory
 	config.ControlPlane.Generic.LoopbackClientConfig = &restclient.Config{APIPath: "/api", ContentConfig: restclient.ContentConfig{NegotiatedSerializer: legacyscheme.Codecs}}
 	config.ControlPlane.Generic.PublicAddress = netutils.ParseIPSloppy("192.168.10.4")
@@ -243,9 +242,13 @@ func TestVersion(t *testing.T) {
 	if err != nil {
 		t.Errorf("unexpected error: %v", err)
 	}
+	expectedInfo := kubeversion.Get()
+	kubeVersion := utilversion.DefaultKubeEffectiveVersion().BinaryVersion()
+	expectedInfo.Major = fmt.Sprintf("%d", kubeVersion.Major())
+	expectedInfo.Minor = fmt.Sprintf("%d", kubeVersion.Minor())
 
-	if !reflect.DeepEqual(kubeversion.Get(), info) {
+	if !reflect.DeepEqual(expectedInfo, info) {
-		t.Errorf("Expected %#v, Got %#v", kubeversion.Get(), info)
+		t.Errorf("Expected %#v, Got %#v", expectedInfo, info)
 	}
 }
 

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

@@ -40,7 +40,6 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/runtime/serializer"
 	"k8s.io/apimachinery/pkg/util/wait"
-	"k8s.io/apimachinery/pkg/version"
 	"k8s.io/apiserver/pkg/endpoints/discovery"
 	"k8s.io/apiserver/pkg/endpoints/discovery/aggregated"
 	genericregistry "k8s.io/apiserver/pkg/registry/generic"
@@ -118,12 +117,6 @@ func (cfg *Config) Complete() CompletedConfig {
 	}
 
 	c.GenericConfig.EnableDiscovery = false
-	if c.GenericConfig.Version == nil {
-		c.GenericConfig.Version = &version.Info{
-			Major: "0",
-			Minor: "1",
-		}
-	}
 
 	return CompletedConfig{&c}
 }

staging/src/k8s.io/apiextensions-apiserver/pkg/cmd/server/testing/testserver.go

@@ -31,6 +31,7 @@ import (
 	extensionsapiserver "k8s.io/apiextensions-apiserver/pkg/apiserver"
 	"k8s.io/apiextensions-apiserver/pkg/cmd/server/options"
 	generatedopenapi "k8s.io/apiextensions-apiserver/pkg/generated/openapi"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/apimachinery/pkg/util/wait"
 	openapinamer "k8s.io/apiserver/pkg/endpoints/openapi"
 	genericapiserver "k8s.io/apiserver/pkg/server"
@@ -124,7 +125,8 @@ func StartTestServer(t Logger, _ *TestServerInstanceOptions, customFlags []strin
 
 	featureGate := utilfeature.DefaultMutableFeatureGate
 	effectiveVersion := utilversion.DefaultKubeEffectiveVersion()
-	_ = utilversion.DefaultComponentGlobalsRegistry.Register(utilversion.DefaultKubeComponent, effectiveVersion, featureGate, true)
+	utilversion.DefaultComponentGlobalsRegistry.Reset()
+	utilruntime.Must(utilversion.DefaultComponentGlobalsRegistry.Register(utilversion.DefaultKubeComponent, effectiveVersion, featureGate))
 	s := options.NewCustomResourceDefinitionsServerOptions(os.Stdout, os.Stderr, featureGate, effectiveVersion)
 
 	utilversion.DefaultComponentGlobalsRegistry.AddFlags(fs)

staging/src/k8s.io/apimachinery/pkg/util/version/version.go

@@ -23,6 +23,8 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+
+	apimachineryversion "k8s.io/apimachinery/pkg/version"
 )
 
 // Version is an opaque representation of a version number
@@ -31,6 +33,7 @@ type Version struct {
 	semver        bool
 	preRelease    string
 	buildMetadata string
+	info          apimachineryversion.Info
 }
 
 var (
@@ -252,19 +255,30 @@ func (v *Version) WithMinor(minor uint) *Version {
 	return &result
 }
 
-// SubtractMinor returns the version diff minor versions back, with the same major and no patch.
+// SubtractMinor returns the version with offset from the original minor, with the same major and no patch.
-// If diff >= current minor, the minor would be 0.
+// If -offset >= current minor, the minor would be 0.
-func (v *Version) SubtractMinor(diff uint) *Version {
+func (v *Version) OffsetMinor(offset int) *Version {
 	var minor uint
+	if offset >= 0 {
+		minor = v.Minor() + uint(offset)
+	} else {
+		diff := uint(-offset)
 		if diff < v.Minor() {
 			minor = v.Minor() - diff
 		}
+	}
 	return MajorMinor(v.Major(), minor)
 }
 
+// SubtractMinor returns the version diff minor versions back, with the same major and no patch.
+// If diff >= current minor, the minor would be 0.
+func (v *Version) SubtractMinor(diff uint) *Version {
+	return v.OffsetMinor(-int(diff))
+}
+
 // AddMinor returns the version diff minor versions forward, with the same major and no patch.
 func (v *Version) AddMinor(diff uint) *Version {
-	return MajorMinor(v.Major(), v.Minor()+diff)
+	return v.OffsetMinor(int(diff))
 }
 
 // WithPatch returns copy of the version object with requested patch number
@@ -441,3 +455,30 @@ func (v *Version) Compare(other string) (int, error) {
 	}
 	return v.compareInternal(ov), nil
 }
+
+// WithInfo returns copy of the version object with requested info
+func (v *Version) WithInfo(info apimachineryversion.Info) *Version {
+	result := *v
+	result.info = info
+	return &result
+}
+
+func (v *Version) Info() *apimachineryversion.Info {
+	if v == nil {
+		return nil
+	}
+	// in case info is empty, or the major and minor in info is different from the actual major and minor
+	v.info.Major = itoa(v.Major())
+	v.info.Minor = itoa(v.Minor())
+	if v.info.GitVersion == "" {
+		v.info.GitVersion = v.String()
+	}
+	return &v.info
+}
+
+func itoa(i uint) string {
+	if i == 0 {
+		return ""
+	}
+	return strconv.Itoa(int(i))
+}

staging/src/k8s.io/apimachinery/pkg/util/version/version_test.go

@@ -453,37 +453,42 @@ func TestHighestSupportedVersion(t *testing.T) {
 	}
 }
 
-func TestSubtractMinor(t *testing.T) {
+func TestOffsetMinor(t *testing.T) {
 	var tests = []struct {
 		version            string
-		diff               uint
+		diff               int
 		expectedComponents []uint
 	}{
 		{
 			version:            "1.0.2",
-			diff:               3,
+			diff:               -3,
 			expectedComponents: []uint{1, 0},
 		},
 		{
 			version:            "1.3.2-alpha+001",
-			diff:               2,
+			diff:               -2,
 			expectedComponents: []uint{1, 1},
 		},
 		{
 			version:            "1.3.2-alpha+001",
-			diff:               3,
+			diff:               -3,
 			expectedComponents: []uint{1, 0},
 		},
 		{
 			version:            "1.20",
-			diff:               5,
+			diff:               -5,
 			expectedComponents: []uint{1, 15},
 		},
+		{
+			version:            "1.20",
+			diff:               5,
+			expectedComponents: []uint{1, 25},
+		},
 	}
 
 	for _, test := range tests {
 		version, _ := ParseGeneric(test.version)
-		if !reflect.DeepEqual(test.expectedComponents, version.SubtractMinor(test.diff).Components()) {
+		if !reflect.DeepEqual(test.expectedComponents, version.OffsetMinor(test.diff).Components()) {
 			t.Error("parse returned un'expected components")
 		}
 	}

staging/src/k8s.io/apiserver/pkg/server/config.go

@@ -44,7 +44,6 @@ import (
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/version"
 	utilwaitgroup "k8s.io/apimachinery/pkg/util/waitgroup"
-	apimachineryversion "k8s.io/apimachinery/pkg/version"
 	"k8s.io/apiserver/pkg/admission"
 	"k8s.io/apiserver/pkg/audit"
 	"k8s.io/apiserver/pkg/authentication/authenticator"
@@ -150,8 +149,6 @@ type Config struct {
 	// done values in this values for this map are ignored.
 	PostStartHooks map[string]PostStartHookConfigEntry
 
-	// Version will enable the /version endpoint if non-nil
-	Version *apimachineryversion.Info
 	// EffectiveVersion determines which apis and features are available
 	// based on when the api/feature lifecyle.
 	EffectiveVersion utilversion.EffectiveVersion
@@ -702,12 +699,8 @@ func (c *Config) Complete(informers informers.SharedInformerFactory) CompletedCo
 		}
 		c.ExternalAddress = net.JoinHostPort(c.ExternalAddress, strconv.Itoa(port))
 	}
-	var ver *version.Version
+	completeOpenAPI(c.OpenAPIConfig, c.EffectiveVersion.EmulationVersion())
-	if c.EffectiveVersion != nil {
+	completeOpenAPIV3(c.OpenAPIV3Config, c.EffectiveVersion.EmulationVersion())
-		ver = c.EffectiveVersion.EmulationVersion()
-	}
-	completeOpenAPI(c.OpenAPIConfig, ver)
-	completeOpenAPIV3(c.OpenAPIV3Config, ver)
 
 	if c.DiscoveryAddresses == nil {
 		c.DiscoveryAddresses = discovery.DefaultAddresses{DefaultAddress: c.ExternalAddress}
@@ -834,7 +827,6 @@ func (c completedConfig) New(name string, delegationTarget DelegationTarget) (*G
 		StorageVersionManager: c.StorageVersionManager,
 
 		EffectiveVersion: c.EffectiveVersion,
-		Version:          c.Version,
 		FeatureGate:      c.FeatureGate,
 
 		muxAndDiscoveryCompleteSignals: map[string]<-chan struct{}{},
@@ -1103,7 +1095,7 @@ func installAPI(s *GenericAPIServer, c *Config) {
 		}
 	}
 
-	routes.Version{Version: c.Version}.Install(s.Handler.GoRestfulContainer)
+	routes.Version{Version: c.EffectiveVersion.BinaryVersion().Info()}.Install(s.Handler.GoRestfulContainer)
 
 	if c.EnableDiscovery {
 		if utilfeature.DefaultFeatureGate.Enabled(genericfeatures.AggregatedDiscoveryEndpoint) {

staging/src/k8s.io/apiserver/pkg/server/config_test.go

@@ -40,6 +40,7 @@ import (
 	"k8s.io/apiserver/pkg/authentication/user"
 	"k8s.io/apiserver/pkg/endpoints/request"
 	"k8s.io/apiserver/pkg/server/healthz"
+	utilversion "k8s.io/apiserver/pkg/util/version"
 	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes/fake"
 	"k8s.io/client-go/rest"
@@ -90,6 +91,7 @@ func TestNewWithDelegate(t *testing.T) {
 	delegateConfig.PublicAddress = netutils.ParseIPSloppy("192.168.10.4")
 	delegateConfig.LegacyAPIGroupPrefixes = sets.NewString("/api")
 	delegateConfig.LoopbackClientConfig = &rest.Config{}
+	delegateConfig.EffectiveVersion = utilversion.NewEffectiveVersion("")
 	clientset := fake.NewSimpleClientset()
 	if clientset == nil {
 		t.Fatal("unable to create fake client set")
@@ -122,6 +124,7 @@ func TestNewWithDelegate(t *testing.T) {
 	wrappingConfig.PublicAddress = netutils.ParseIPSloppy("192.168.10.4")
 	wrappingConfig.LegacyAPIGroupPrefixes = sets.NewString("/api")
 	wrappingConfig.LoopbackClientConfig = &rest.Config{}
+	wrappingConfig.EffectiveVersion = utilversion.NewEffectiveVersion("")
 
 	wrappingConfig.HealthzChecks = append(wrappingConfig.HealthzChecks, healthz.NamedCheck("wrapping-health", func(r *http.Request) error {
 		return fmt.Errorf("wrapping failed healthcheck")

staging/src/k8s.io/apiserver/pkg/server/deleted_kinds.go

@@ -100,7 +100,7 @@ func (e *resourceExpirationEvaluator) shouldServe(gv schema.GroupVersion, versio
 	}
 
 	introduced, ok := versionedPtr.(introducedInterface)
-	// skip the introduced check for test where currentVersion is 0.0
+	// skip the introduced check for test when currentVersion is 0.0 to test all apis
 	if ok && (e.currentVersion.Major() > 0 || e.currentVersion.Minor() > 0) {
 		majorIntroduced, minorIntroduced := introduced.APILifecycleIntroduced()
 		verIntroduced := apimachineryversion.MajorMinor(uint(majorIntroduced), uint(minorIntroduced))

staging/src/k8s.io/apiserver/pkg/server/genericapiserver.go

@@ -40,7 +40,6 @@ import (
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/wait"
 	utilwaitgroup "k8s.io/apimachinery/pkg/util/waitgroup"
-	"k8s.io/apimachinery/pkg/version"
 	"k8s.io/apiserver/pkg/admission"
 	"k8s.io/apiserver/pkg/audit"
 	"k8s.io/apiserver/pkg/authorization/authorizer"
@@ -238,8 +237,6 @@ type GenericAPIServer struct {
 	// StorageVersionManager holds the storage versions of the API resources installed by this server.
 	StorageVersionManager storageversion.Manager
 
-	// Version will enable the /version endpoint if non-nil
-	Version *version.Info
 	// EffectiveVersion determines which apis and features are available
 	// based on when the api/feature lifecyle.
 	EffectiveVersion utilversion.EffectiveVersion

staging/src/k8s.io/apiserver/pkg/server/genericapiserver_test.go

@@ -138,7 +138,7 @@ func setUp(t *testing.T) (Config, *assert.Assertions) {
 	if clientset == nil {
 		t.Fatal("unable to create fake client set")
 	}
-
+	config.EffectiveVersion = utilversion.NewEffectiveVersion("")
 	config.OpenAPIConfig = DefaultOpenAPIConfig(testGetOpenAPIDefinitions, openapinamer.NewDefinitionNamer(runtime.NewScheme()))
 	config.OpenAPIConfig.Info.Version = "unversioned"
 	config.OpenAPIV3Config = DefaultOpenAPIV3Config(testGetOpenAPIDefinitions, openapinamer.NewDefinitionNamer(runtime.NewScheme()))
@@ -460,8 +460,9 @@ func TestNotRestRoutesHaveAuth(t *testing.T) {
 	config.EnableProfiling = true
 
 	kubeVersion := fakeVersion()
-	config.Version = &kubeVersion
+	effectiveVersion := utilversion.NewEffectiveVersion(kubeVersion.String())
-	config.EffectiveVersion = utilversion.NewEffectiveVersion(kubeVersion.String())
+	effectiveVersion.Set(effectiveVersion.BinaryVersion().WithInfo(kubeVersion), effectiveVersion.EmulationVersion(), effectiveVersion.MinCompatibilityVersion())
+	config.EffectiveVersion = effectiveVersion
 
 	s, err := config.Complete(nil).New("test", NewEmptyDelegate())
 	if err != nil {

staging/src/k8s.io/apiserver/pkg/server/options/serving_test.go

@@ -278,7 +278,6 @@ func TestServerRunWithSNI(t *testing.T) {
 			// launch server
 			config := setUp(t)
 			v := fakeVersion()
-			config.Version = &v
 			config.EffectiveVersion = utilversion.NewEffectiveVersion(v.String())
 
 			config.EnableIndex = true

staging/src/k8s.io/apiserver/pkg/server/storage/resource_encoding_config.go

@@ -157,6 +157,7 @@ func emulatedStorageVersion(binaryVersionOfResource schema.GroupVersion, example
 		}
 
 		// If it was introduced after current compatibility version, don't use it
+		// skip the introduced check for test when currentVersion is 0.0 to test all apis
 		if introduced, hasIntroduced := exampleOfGVK.(introducedInterface); hasIntroduced && (compatibilityVersion.Major() > 0 || compatibilityVersion.Minor() > 0) {
 			// API resource lifecycles should be relative to k8s api version
 			majorIntroduced, minorIntroduced := introduced.APILifecycleIntroduced()

staging/src/k8s.io/apiserver/pkg/util/version/registry.go

@@ -59,12 +59,29 @@ var DefaultComponentGlobalsRegistry ComponentGlobalsRegistry = NewComponentGloba
 
 const (
 	DefaultKubeComponent = "kube"
+
+	klogLevel = 2
 )
 
+type VersionMapping func(from *version.Version) *version.Version
+
 // ComponentGlobals stores the global variables for a component for easy access.
 type ComponentGlobals struct {
 	effectiveVersion MutableEffectiveVersion
 	featureGate      featuregate.MutableVersionedFeatureGate
+
+	// emulationVersionMapping contains the mapping from the emulation version of this component
+	// to the emulation version of another component.
+	emulationVersionMapping map[string]VersionMapping
+	// dependentEmulationVersion stores whether or not this component's EmulationVersion is dependent through mapping on another component.
+	// If true, the emulation version cannot be set from the flag, or version mapping from another component.
+	dependentEmulationVersion bool
+	// minCompatibilityVersionMapping contains the mapping from the min compatibility version of this component
+	// to the min compatibility version of another component.
+	minCompatibilityVersionMapping map[string]VersionMapping
+	// dependentMinCompatibilityVersion stores whether or not this component's MinCompatibilityVersion is dependent through mapping on another component
+	// If true, the min compatibility version cannot be set from the flag, or version mapping from another component.
+	dependentMinCompatibilityVersion bool
 }
 
 type ComponentGlobalsRegistry interface {
@@ -75,9 +92,8 @@ type ComponentGlobalsRegistry interface {
 	// Returns nil if the component is not registered.
 	FeatureGateFor(component string) featuregate.FeatureGate
 	// Register registers the EffectiveVersion and FeatureGate for a component.
-	// Overrides existing ComponentGlobals if it is already in the registry if override is true,
+	// returns error if the component is already registered.
-	// otherwise returns error if the component is already registered.
+	Register(component string, effectiveVersion MutableEffectiveVersion, featureGate featuregate.MutableVersionedFeatureGate) error
-	Register(component string, effectiveVersion MutableEffectiveVersion, featureGate featuregate.MutableVersionedFeatureGate, override bool) error
 	// ComponentGlobalsOrRegister would return the registered global variables for the component if it already exists in the registry.
 	// Otherwise, the provided variables would be registered under the component, and the same variables would be returned.
 	ComponentGlobalsOrRegister(component string, effectiveVersion MutableEffectiveVersion, featureGate featuregate.MutableVersionedFeatureGate) (MutableEffectiveVersion, featuregate.MutableVersionedFeatureGate)
@@ -85,25 +101,43 @@ type ComponentGlobalsRegistry interface {
 	AddFlags(fs *pflag.FlagSet)
 	// Set sets the flags for all global variables for all components registered.
 	Set() error
-	// SetAllComponents calls the Validate() function for all the global variables for all components registered.
+	// Validate calls the Validate() function for all the global variables for all components registered.
 	Validate() []error
+	// Reset removes all stored ComponentGlobals, configurations, and version mappings.
+	Reset()
+	// SetEmulationVersionMapping sets the mapping from the emulation version of one component
+	// to the emulation version of another component.
+	// Once set, the emulation version of the toComponent will be determined by the emulation version of the fromComponent,
+	// and cannot be set from cmd flags anymore.
+	// For a given component, its emulation version can only depend on one other component, no multiple dependency is allowed.
+	SetEmulationVersionMapping(fromComponent, toComponent string, f VersionMapping) error
 }
 
 type componentGlobalsRegistry struct {
-	componentGlobals map[string]ComponentGlobals
+	componentGlobals map[string]*ComponentGlobals
 	mutex            sync.RWMutex
-	// map of component name to emulation version set from the flag.
+	// list of component name to emulation version set from the flag.
-	emulationVersionConfig cliflag.ConfigurationMap
+	emulationVersionConfig []string
 	// map of component name to the list of feature gates set from the flag.
 	featureGatesConfig map[string][]string
 }
 
-func NewComponentGlobalsRegistry() ComponentGlobalsRegistry {
+func NewComponentGlobalsRegistry() *componentGlobalsRegistry {
 	return &componentGlobalsRegistry{
-		componentGlobals: make(map[string]ComponentGlobals),
+		componentGlobals:       make(map[string]*ComponentGlobals),
+		emulationVersionConfig: nil,
+		featureGatesConfig:     nil,
 	}
 }
 
+func (r *componentGlobalsRegistry) Reset() {
+	r.mutex.RLock()
+	defer r.mutex.RUnlock()
+	r.componentGlobals = make(map[string]*ComponentGlobals)
+	r.emulationVersionConfig = nil
+	r.featureGatesConfig = nil
+}
+
 func (r *componentGlobalsRegistry) EffectiveVersionFor(component string) EffectiveVersion {
 	r.mutex.RLock()
 	defer r.mutex.RUnlock()
@@ -124,8 +158,8 @@ func (r *componentGlobalsRegistry) FeatureGateFor(component string) featuregate.
 	return globals.featureGate
 }
 
-func (r *componentGlobalsRegistry) unsafeRegister(component string, effectiveVersion MutableEffectiveVersion, featureGate featuregate.MutableVersionedFeatureGate, override bool) error {
+func (r *componentGlobalsRegistry) unsafeRegister(component string, effectiveVersion MutableEffectiveVersion, featureGate featuregate.MutableVersionedFeatureGate) error {
-	if _, ok := r.componentGlobals[component]; ok && !override {
+	if _, ok := r.componentGlobals[component]; ok {
 		return fmt.Errorf("component globals of %s already registered", component)
 	}
 	if featureGate != nil {
@@ -133,18 +167,23 @@ func (r *componentGlobalsRegistry) unsafeRegister(component string, effectiveVer
 			return err
 		}
 	}
-	c := ComponentGlobals{effectiveVersion: effectiveVersion, featureGate: featureGate}
+	c := ComponentGlobals{
-	r.componentGlobals[component] = c
+		effectiveVersion:               effectiveVersion,
+		featureGate:                    featureGate,
+		emulationVersionMapping:        make(map[string]VersionMapping),
+		minCompatibilityVersionMapping: make(map[string]VersionMapping),
+	}
+	r.componentGlobals[component] = &c
 	return nil
 }
 
-func (r *componentGlobalsRegistry) Register(component string, effectiveVersion MutableEffectiveVersion, featureGate featuregate.MutableVersionedFeatureGate, override bool) error {
+func (r *componentGlobalsRegistry) Register(component string, effectiveVersion MutableEffectiveVersion, featureGate featuregate.MutableVersionedFeatureGate) error {
 	if effectiveVersion == nil {
 		return fmt.Errorf("cannot register nil effectiveVersion")
 	}
 	r.mutex.Lock()
 	defer r.mutex.Unlock()
-	return r.unsafeRegister(component, effectiveVersion, featureGate, override)
+	return r.unsafeRegister(component, effectiveVersion, featureGate)
 }
 
 func (r *componentGlobalsRegistry) ComponentGlobalsOrRegister(component string, effectiveVersion MutableEffectiveVersion, featureGate featuregate.MutableVersionedFeatureGate) (MutableEffectiveVersion, featuregate.MutableVersionedFeatureGate) {
@@ -154,13 +193,11 @@ func (r *componentGlobalsRegistry) ComponentGlobalsOrRegister(component string,
 	if ok {
 		return globals.effectiveVersion, globals.featureGate
 	}
-	utilruntime.Must(r.unsafeRegister(component, effectiveVersion, featureGate, false))
+	utilruntime.Must(r.unsafeRegister(component, effectiveVersion, featureGate))
 	return effectiveVersion, featureGate
 }
 
-func (r *componentGlobalsRegistry) knownFeatures() []string {
+func (r *componentGlobalsRegistry) unsafeKnownFeatures() []string {
-	r.mutex.Lock()
-	defer r.mutex.Unlock()
 	var known []string
 	for component, globals := range r.componentGlobals {
 		if globals.featureGate == nil {
@@ -174,18 +211,22 @@ func (r *componentGlobalsRegistry) knownFeatures() []string {
 	return known
 }
 
-func (r *componentGlobalsRegistry) versionFlagOptions(isEmulation bool) []string {
+func (r *componentGlobalsRegistry) unsafeVersionFlagOptions(isEmulation bool) []string {
-	r.mutex.Lock()
-	defer r.mutex.Unlock()
 	var vs []string
 	for component, globals := range r.componentGlobals {
 		binaryVer := globals.effectiveVersion.BinaryVersion()
 		if isEmulation {
+			if globals.dependentEmulationVersion {
+				continue
+			}
 			// emulated version could be between binaryMajor.{binaryMinor} and binaryMajor.{binaryMinor}
 			// TODO: change to binaryMajor.{binaryMinor-1} and binaryMajor.{binaryMinor} in 1.32
 			vs = append(vs, fmt.Sprintf("%s=%s..%s (default=%s)", component,
 				binaryVer.SubtractMinor(0).String(), binaryVer.String(), globals.effectiveVersion.EmulationVersion().String()))
 		} else {
+			if globals.dependentMinCompatibilityVersion {
+				continue
+			}
 			// min compatibility version could be between binaryMajor.{binaryMinor-1} and binaryMajor.{binaryMinor}
 			vs = append(vs, fmt.Sprintf("%s=%s..%s (default=%s)", component,
 				binaryVer.SubtractMinor(1).String(), binaryVer.String(), globals.effectiveVersion.MinCompatibilityVersion().String()))
@@ -200,51 +241,133 @@ func (r *componentGlobalsRegistry) AddFlags(fs *pflag.FlagSet) {
 		return
 	}
 	r.mutex.Lock()
+	defer r.mutex.Unlock()
 	for _, globals := range r.componentGlobals {
 		if globals.featureGate != nil {
 			globals.featureGate.Close()
 		}
 	}
-	r.emulationVersionConfig = make(cliflag.ConfigurationMap)
+	if r.emulationVersionConfig != nil || r.featureGatesConfig != nil {
+		klog.Warning("calling componentGlobalsRegistry.AddFlags more than once, the registry will be set by the latest flags")
+	}
+	r.emulationVersionConfig = []string{}
 	r.featureGatesConfig = make(map[string][]string)
-	r.mutex.Unlock()
 
-	fs.Var(&r.emulationVersionConfig, "emulated-version", ""+
+	fs.StringSliceVar(&r.emulationVersionConfig, "emulated-version", r.emulationVersionConfig, ""+
 		"The versions different components emulate their capabilities (APIs, features, ...) of.\n"+
 		"If set, the component will emulate the behavior of this version instead of the underlying binary version.\n"+
-		"Version format could only be major.minor, for example: '--emulated-version=wardle=1.2,kube=1.31'. Options are:\n"+strings.Join(r.versionFlagOptions(true), "\n"))
+		"Version format could only be major.minor, for example: '--emulated-version=wardle=1.2,kube=1.31'. Options are:\n"+strings.Join(r.unsafeVersionFlagOptions(true), "\n")+
+		"If the component is not specified, defaults to \"kube\"")
 
 	fs.Var(cliflag.NewColonSeparatedMultimapStringStringAllowDefaultEmptyKey(&r.featureGatesConfig), "feature-gates", "Comma-separated list of component:key=value pairs that describe feature gates for alpha/experimental features of different components.\n"+
 		"If the component is not specified, defaults to \"kube\". This flag can be repeatedly invoked. For example: --feature-gates 'wardle:featureA=true,wardle:featureB=false' --feature-gates 'kube:featureC=true'"+
-		"Options are:\n"+strings.Join(r.knownFeatures(), "\n"))
+		"Options are:\n"+strings.Join(r.unsafeKnownFeatures(), "\n"))
+}
+
+type componentVersion struct {
+	component string
+	ver       *version.Version
+}
+
+// getFullEmulationVersionConfig expands the given version config with version registered version mapping,
+// and returns the map of component to Version.
+func (r *componentGlobalsRegistry) getFullEmulationVersionConfig(
+	versionConfigMap map[string]*version.Version) (map[string]*version.Version, error) {
+	result := map[string]*version.Version{}
+	setQueue := []componentVersion{}
+	for comp, ver := range versionConfigMap {
+		if _, ok := r.componentGlobals[comp]; !ok {
+			return result, fmt.Errorf("component not registered: %s", comp)
+		}
+		klog.V(klogLevel).Infof("setting version %s=%s", comp, ver.String())
+		setQueue = append(setQueue, componentVersion{comp, ver})
+	}
+	for len(setQueue) > 0 {
+		cv := setQueue[0]
+		if _, visited := result[cv.component]; visited {
+			return result, fmt.Errorf("setting version of %s more than once, probably version mapping loop", cv.component)
+		}
+		setQueue = setQueue[1:]
+		result[cv.component] = cv.ver
+		for toComp, f := range r.componentGlobals[cv.component].emulationVersionMapping {
+			toVer := f(cv.ver)
+			if toVer == nil {
+				return result, fmt.Errorf("got nil version from mapping of %s=%s to component:%s", cv.component, cv.ver.String(), toComp)
+			}
+			klog.V(klogLevel).Infof("setting version %s=%s from version mapping of %s=%s", toComp, toVer.String(), cv.component, cv.ver.String())
+			setQueue = append(setQueue, componentVersion{toComp, toVer})
+		}
+	}
+	return result, nil
+}
+
+func toVersionMap(versionConfig []string) (map[string]*version.Version, error) {
+	m := map[string]*version.Version{}
+	for _, compVer := range versionConfig {
+		// default to "kube" of component is not specified
+		k := "kube"
+		v := compVer
+		if strings.Contains(compVer, "=") {
+			arr := strings.SplitN(compVer, "=", 2)
+			if len(arr) != 2 {
+				return m, fmt.Errorf("malformed pair, expect string=string")
+			}
+			k = strings.TrimSpace(arr[0])
+			v = strings.TrimSpace(arr[1])
+		}
+		ver, err := version.Parse(v)
+		if err != nil {
+			return m, err
+		}
+		if ver.Patch() != 0 {
+			return m, fmt.Errorf("patch version not allowed, got: %s=%s", k, ver.String())
+		}
+		if existingVer, ok := m[k]; ok {
+			return m, fmt.Errorf("duplicate version flag, %s=%s and %s=%s", k, existingVer.String(), k, ver.String())
+		}
+		m[k] = ver
+	}
+	return m, nil
 }
 
 func (r *componentGlobalsRegistry) Set() error {
 	r.mutex.Lock()
 	defer r.mutex.Unlock()
-	for comp, emuVer := range r.emulationVersionConfig {
+	emulationVersionConfigMap, err := toVersionMap(r.emulationVersionConfig)
-		if _, ok := r.componentGlobals[comp]; !ok {
-			return fmt.Errorf("component not registered: %s", comp)
-		}
-		klog.V(2).Infof("setting %s:emulation version to %s\n", comp, emuVer)
-		v, err := version.Parse(emuVer)
 	if err != nil {
 		return err
 	}
-		r.componentGlobals[comp].effectiveVersion.SetEmulationVersion(v)
+	for comp := range emulationVersionConfigMap {
+		if _, ok := r.componentGlobals[comp]; !ok {
+			return fmt.Errorf("component not registered: %s", comp)
+		}
+		// only components without any dependencies can be set from the flag.
+		if r.componentGlobals[comp].dependentEmulationVersion {
+			return fmt.Errorf("EmulationVersion of %s is set by mapping, cannot set it by flag", comp)
+		}
+	}
+	if emulationVersions, err := r.getFullEmulationVersionConfig(emulationVersionConfigMap); err != nil {
+		return err
+	} else {
+		for comp, ver := range emulationVersions {
+			r.componentGlobals[comp].effectiveVersion.SetEmulationVersion(ver)
+		}
 	}
 	// Set feature gate emulation version before setting feature gate flag values.
 	for comp, globals := range r.componentGlobals {
 		if globals.featureGate == nil {
 			continue
 		}
-		klog.V(2).Infof("setting %s:feature gate emulation version to %s\n", comp, globals.effectiveVersion.EmulationVersion().String())
+		klog.V(klogLevel).Infof("setting %s:feature gate emulation version to %s", comp, globals.effectiveVersion.EmulationVersion().String())
 		if err := globals.featureGate.SetEmulationVersion(globals.effectiveVersion.EmulationVersion()); err != nil {
 			return err
 		}
 	}
 	for comp, fg := range r.featureGatesConfig {
 		if comp == "" {
+			if _, ok := r.featureGatesConfig[DefaultKubeComponent]; ok {
+				return fmt.Errorf("set kube feature gates with default empty prefix or kube: prefix consistently, do not mix use")
+			}
 			comp = DefaultKubeComponent
 		}
 		if _, ok := r.componentGlobals[comp]; !ok {
@@ -255,7 +378,7 @@ func (r *componentGlobalsRegistry) Set() error {
 			return fmt.Errorf("component featureGate not registered: %s", comp)
 		}
 		flagVal := strings.Join(fg, ",")
-		klog.V(2).Infof("setting %s:feature-gates=%s\n", comp, flagVal)
+		klog.V(klogLevel).Infof("setting %s:feature-gates=%s", comp, flagVal)
 		if err := featureGate.Set(flagVal); err != nil {
 			return err
 		}
@@ -275,3 +398,39 @@ func (r *componentGlobalsRegistry) Validate() []error {
 	}
 	return errs
 }
+
+func (r *componentGlobalsRegistry) SetEmulationVersionMapping(fromComponent, toComponent string, f VersionMapping) error {
+	if f == nil {
+		return nil
+	}
+	klog.V(klogLevel).Infof("setting EmulationVersion mapping from %s to %s", fromComponent, toComponent)
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	if _, ok := r.componentGlobals[fromComponent]; !ok {
+		return fmt.Errorf("component not registered: %s", fromComponent)
+	}
+	if _, ok := r.componentGlobals[toComponent]; !ok {
+		return fmt.Errorf("component not registered: %s", toComponent)
+	}
+	// check multiple dependency
+	if r.componentGlobals[toComponent].dependentEmulationVersion {
+		return fmt.Errorf("mapping of %s already exists from another component", toComponent)
+	}
+	r.componentGlobals[toComponent].dependentEmulationVersion = true
+
+	versionMapping := r.componentGlobals[fromComponent].emulationVersionMapping
+	if _, ok := versionMapping[toComponent]; ok {
+		return fmt.Errorf("EmulationVersion from %s to %s already exists", fromComponent, toComponent)
+	}
+	versionMapping[toComponent] = f
+	klog.V(klogLevel).Infof("setting the default EmulationVersion of %s based on mapping from the default EmulationVersion of %s", fromComponent, toComponent)
+	defaultFromVersion := r.componentGlobals[fromComponent].effectiveVersion.EmulationVersion()
+	emulationVersions, err := r.getFullEmulationVersionConfig(map[string]*version.Version{fromComponent: defaultFromVersion})
+	if err != nil {
+		return err
+	}
+	for comp, ver := range emulationVersions {
+		r.componentGlobals[comp].effectiveVersion.SetEmulationVersion(ver)
+	}
+	return nil
+}

staging/src/k8s.io/apiserver/pkg/util/version/registry_test.go

@@ -22,8 +22,8 @@ import (
 	"testing"
 
 	"github.com/spf13/pflag"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/apimachinery/pkg/util/version"
-	cliflag "k8s.io/component-base/cli/flag"
 	"k8s.io/component-base/featuregate"
 )
 
@@ -39,30 +39,23 @@ func TestEffectiveVersionRegistry(t *testing.T) {
 	if r.EffectiveVersionFor(testComponent) != nil {
 		t.Fatalf("expected nil EffectiveVersion initially")
 	}
-	if err := r.Register(testComponent, ver1, nil, false); err != nil {
+	if err := r.Register(testComponent, ver1, nil); err != nil {
 		t.Fatalf("expected no error to register new component, but got err: %v", err)
 	}
 	if !r.EffectiveVersionFor(testComponent).EqualTo(ver1) {
 		t.Fatalf("expected EffectiveVersionFor to return the version registered")
 	}
 	// overwrite
-	if err := r.Register(testComponent, ver2, nil, false); err == nil {
+	if err := r.Register(testComponent, ver2, nil); err == nil {
 		t.Fatalf("expected error to register existing component when override is false")
 	}
-	if err := r.Register(testComponent, ver2, nil, true); err != nil {
+	if !r.EffectiveVersionFor(testComponent).EqualTo(ver1) {
-		t.Fatalf("expected no error to overriding existing component, but got err: %v", err)
-	}
-	if !r.EffectiveVersionFor(testComponent).EqualTo(ver2) {
 		t.Fatalf("expected EffectiveVersionFor to return the version overridden")
 	}
 }
 
 func testRegistry(t *testing.T) *componentGlobalsRegistry {
-	r := componentGlobalsRegistry{
+	r := NewComponentGlobalsRegistry()
-		componentGlobals:       map[string]ComponentGlobals{},
-		emulationVersionConfig: make(cliflag.ConfigurationMap),
-		featureGatesConfig:     make(map[string][]string),
-	}
 	verKube := NewEffectiveVersion("1.31")
 	fgKube := featuregate.NewVersionedFeatureGate(version.MustParse("0.0"))
 	err := fgKube.AddVersioned(map[featuregate.Feature]featuregate.VersionedSpecs{
@@ -102,19 +95,35 @@ func testRegistry(t *testing.T) *componentGlobalsRegistry {
 	if err != nil {
 		t.Fatal(err)
 	}
-	_ = r.Register(DefaultKubeComponent, verKube, fgKube, true)
+	utilruntime.Must(r.Register(DefaultKubeComponent, verKube, fgKube))
-	_ = r.Register(testComponent, verTest, fgTest, true)
+	utilruntime.Must(r.Register(testComponent, verTest, fgTest))
-	return &r
+	return r
 }
 
 func TestVersionFlagOptions(t *testing.T) {
 	r := testRegistry(t)
-	emuVers := strings.Join(r.versionFlagOptions(true), "\n")
+	emuVers := strings.Join(r.unsafeVersionFlagOptions(true), "\n")
 	expectedEmuVers := "kube=1.31..1.31 (default=1.31)\ntest=2.8..2.8 (default=2.8)"
 	if emuVers != expectedEmuVers {
 		t.Errorf("wanted emulation version flag options to be: %s, got %s", expectedEmuVers, emuVers)
 	}
-	minCompVers := strings.Join(r.versionFlagOptions(false), "\n")
+	minCompVers := strings.Join(r.unsafeVersionFlagOptions(false), "\n")
+	expectedMinCompVers := "kube=1.30..1.31 (default=1.30)\ntest=2.7..2.8 (default=2.7)"
+	if minCompVers != expectedMinCompVers {
+		t.Errorf("wanted min compatibility version flag options to be: %s, got %s", expectedMinCompVers, minCompVers)
+	}
+}
+
+func TestVersionFlagOptionsWithMapping(t *testing.T) {
+	r := testRegistry(t)
+	utilruntime.Must(r.SetEmulationVersionMapping(testComponent, DefaultKubeComponent,
+		func(from *version.Version) *version.Version { return from.OffsetMinor(3) }))
+	emuVers := strings.Join(r.unsafeVersionFlagOptions(true), "\n")
+	expectedEmuVers := "test=2.8..2.8 (default=2.8)"
+	if emuVers != expectedEmuVers {
+		t.Errorf("wanted emulation version flag options to be: %s, got %s", expectedEmuVers, emuVers)
+	}
+	minCompVers := strings.Join(r.unsafeVersionFlagOptions(false), "\n")
 	expectedMinCompVers := "kube=1.30..1.31 (default=1.30)\ntest=2.7..2.8 (default=2.7)"
 	if minCompVers != expectedMinCompVers {
 		t.Errorf("wanted min compatibility version flag options to be: %s, got %s", expectedMinCompVers, minCompVers)
@@ -123,7 +132,7 @@ func TestVersionFlagOptions(t *testing.T) {
 
 func TestVersionedFeatureGateFlag(t *testing.T) {
 	r := testRegistry(t)
-	known := strings.Join(r.knownFeatures(), "\n")
+	known := strings.Join(r.unsafeKnownFeatures(), "\n")
 	expectedKnown := "kube:AllAlpha=true|false (ALPHA - default=false)\n" +
 		"kube:AllBeta=true|false (BETA - default=false)\n" +
 		"kube:commonC=true|false (BETA - default=true)\n" +
@@ -140,85 +149,126 @@ func TestVersionedFeatureGateFlag(t *testing.T) {
 func TestFlags(t *testing.T) {
 	tests := []struct {
 		name                         string
-		emulationVersionFlag         string
+		flags                        []string
-		featureGatesFlag             string
 		parseError                   string
-		expectedKubeEmulationVersion *version.Version
+		expectedKubeEmulationVersion string
-		expectedTestEmulationVersion *version.Version
+		expectedTestEmulationVersion string
 		expectedKubeFeatureValues    map[featuregate.Feature]bool
 		expectedTestFeatureValues    map[featuregate.Feature]bool
 	}{
 		{
 			name:                         "setting kube emulation version",
-			emulationVersionFlag:         "kube=1.30",
+			flags:                        []string{"--emulated-version=kube=1.30"},
-			expectedKubeEmulationVersion: version.MajorMinor(1, 30),
+			expectedKubeEmulationVersion: "1.30",
 		},
 		{
-			name:                         "setting kube emulation version, prefix v ok",
+			name: "setting kube emulation version twice",
-			emulationVersionFlag:         "kube=v1.30",
+			flags: []string{
-			expectedKubeEmulationVersion: version.MajorMinor(1, 30),
+				"--emulated-version=kube=1.30",
+				"--emulated-version=kube=1.32",
+			},
+			parseError: "duplicate version flag, kube=1.30 and kube=1.32",
+		},
+		{
+			name:                         "prefix v ok",
+			flags:                        []string{"--emulated-version=kube=v1.30"},
+			expectedKubeEmulationVersion: "1.30",
+		},
+		{
+			name:       "patch version not ok",
+			flags:      []string{"--emulated-version=kube=1.30.2"},
+			parseError: "patch version not allowed, got: kube=1.30.2",
 		},
 		{
 			name:                         "setting test emulation version",
-			emulationVersionFlag:         "test=2.7",
+			flags:                        []string{"--emulated-version=test=2.7"},
-			expectedKubeEmulationVersion: version.MajorMinor(1, 31),
+			expectedKubeEmulationVersion: "1.31",
-			expectedTestEmulationVersion: version.MajorMinor(2, 7),
+			expectedTestEmulationVersion: "2.7",
 		},
 		{
-			name:                 "version missing component",
+			name:                         "version missing component default to kube",
-			emulationVersionFlag: "1.31",
+			flags:                        []string{"--emulated-version=1.30"},
-			parseError:           "component not registered: 1.31",
+			expectedKubeEmulationVersion: "1.30",
+		},
+		{
+			name:       "version missing component default to kube with duplicate",
+			flags:      []string{"--emulated-version=1.30", "--emulated-version=kube=1.30"},
+			parseError: "duplicate version flag, kube=1.30 and kube=1.30",
 		},
 		{
 			name:       "version unregistered component",
-			emulationVersionFlag: "test3=1.31",
+			flags:      []string{"--emulated-version=test3=1.31"},
 			parseError: "component not registered: test3",
 		},
 		{
 			name:       "invalid version",
-			emulationVersionFlag: "test=1.foo",
+			flags:      []string{"--emulated-version=test=1.foo"},
 			parseError: "illegal version string \"1.foo\"",
 		},
 		{
 			name: "setting test feature flag",
-			emulationVersionFlag:         "test=2.7",
+			flags: []string{
-			featureGatesFlag:             "test:testA=true",
+				"--emulated-version=test=2.7",
-			expectedKubeEmulationVersion: version.MajorMinor(1, 31),
+				"--feature-gates=test:testA=true",
-			expectedTestEmulationVersion: version.MajorMinor(2, 7),
+			},
+			expectedKubeEmulationVersion: "1.31",
+			expectedTestEmulationVersion: "2.7",
 			expectedKubeFeatureValues:    map[featuregate.Feature]bool{"kubeA": true, "kubeB": false, "commonC": true},
 			expectedTestFeatureValues:    map[featuregate.Feature]bool{"testA": true, "testB": false, "commonC": false},
 		},
 		{
 			name: "setting future test feature flag",
-			emulationVersionFlag: "test=2.7",
+			flags: []string{
-			featureGatesFlag:     "test:testA=true,test:testB=true",
+				"--emulated-version=test=2.7",
+				"--feature-gates=test:testA=true,test:testB=true",
+			},
 			parseError: "cannot set feature gate testB to true, feature is PreAlpha at emulated version 2.7",
 		},
 		{
 			name: "setting kube feature flag",
-			emulationVersionFlag:         "test=2.7,kube=1.30",
+			flags: []string{
-			featureGatesFlag:             "test:commonC=true,commonC=false,kube:kubeB=true",
+				"--emulated-version=test=2.7",
-			expectedKubeEmulationVersion: version.MajorMinor(1, 30),
+				"--emulated-version=kube=1.30",
-			expectedTestEmulationVersion: version.MajorMinor(2, 7),
+				"--feature-gates=kubeB=false,test:commonC=true",
+				"--feature-gates=commonC=false,kubeB=true",
+			},
+			expectedKubeEmulationVersion: "1.30",
+			expectedTestEmulationVersion: "2.7",
 			expectedKubeFeatureValues:    map[featuregate.Feature]bool{"kubeA": false, "kubeB": true, "commonC": false},
 			expectedTestFeatureValues:    map[featuregate.Feature]bool{"testA": false, "testB": false, "commonC": true},
 		},
+		{
+			name: "setting kube feature flag with different prefix",
+			flags: []string{
+				"--emulated-version=test=2.7",
+				"--emulated-version=kube=1.30",
+				"--feature-gates=kube:kubeB=false,test:commonC=true",
+				"--feature-gates=commonC=false,kubeB=true",
+			},
+			parseError: "set kube feature gates with default empty prefix or kube: prefix consistently, do not mix use",
+		},
 		{
 			name: "setting locked kube feature flag",
-			emulationVersionFlag: "test=2.7",
+			flags: []string{
-			featureGatesFlag:     "kubeA=false",
+				"--emulated-version=test=2.7",
+				"--feature-gates=kubeA=false",
+			},
 			parseError: "cannot set feature gate kubeA to false, feature is locked to true",
 		},
 		{
 			name: "setting unknown test feature flag",
-			emulationVersionFlag: "test=2.7",
+			flags: []string{
-			featureGatesFlag:     "test:testD=true",
+				"--emulated-version=test=2.7",
+				"--feature-gates=test:testD=true",
+			},
 			parseError: "unrecognized feature gate: testD",
 		},
 		{
 			name: "setting unknown component feature flag",
-			emulationVersionFlag: "test=2.7",
+			flags: []string{
-			featureGatesFlag:     "test3:commonC=true",
+				"--emulated-version=test=2.7",
+				"--feature-gates=test3:commonC=true",
+			},
 			parseError: "component not registered: test3",
 		},
 	}
@@ -227,9 +277,7 @@ func TestFlags(t *testing.T) {
 			fs := pflag.NewFlagSet("testflag", pflag.ContinueOnError)
 			r := testRegistry(t)
 			r.AddFlags(fs)
-
+			err := fs.Parse(test.flags)
-			err := fs.Parse([]string{fmt.Sprintf("--emulated-version=%s", test.emulationVersionFlag),
-				fmt.Sprintf("--feature-gates=%s", test.featureGatesFlag)})
 			if err == nil {
 				err = r.Set()
 			}
@@ -242,19 +290,11 @@ func TestFlags(t *testing.T) {
 			if err != nil {
 				t.Fatalf("%d: Parse() expected: nil, got: %v", i, err)
 			}
-			if test.expectedKubeEmulationVersion != nil {
+			if len(test.expectedKubeEmulationVersion) > 0 {
-				v := r.EffectiveVersionFor("kube").EmulationVersion()
+				assertVersionEqualTo(t, r.EffectiveVersionFor(DefaultKubeComponent).EmulationVersion(), test.expectedKubeEmulationVersion)
-				if !v.EqualTo(test.expectedKubeEmulationVersion) {
-					t.Fatalf("%d: EmulationVersion expected: %s, got: %s", i, test.expectedKubeEmulationVersion.String(), v.String())
-					return
-				}
-			}
-			if test.expectedTestEmulationVersion != nil {
-				v := r.EffectiveVersionFor("test").EmulationVersion()
-				if !v.EqualTo(test.expectedTestEmulationVersion) {
-					t.Fatalf("%d: EmulationVersion expected: %s, got: %s", i, test.expectedTestEmulationVersion.String(), v.String())
-					return
 			}
+			if len(test.expectedTestEmulationVersion) > 0 {
+				assertVersionEqualTo(t, r.EffectiveVersionFor(testComponent).EmulationVersion(), test.expectedTestEmulationVersion)
 			}
 			for f, v := range test.expectedKubeFeatureValues {
 				if r.FeatureGateFor(DefaultKubeComponent).Enabled(f) != v {
@@ -269,3 +309,110 @@ func TestFlags(t *testing.T) {
 		})
 	}
 }
+
+func TestVersionMapping(t *testing.T) {
+	r := NewComponentGlobalsRegistry()
+	ver1 := NewEffectiveVersion("0.58")
+	ver2 := NewEffectiveVersion("1.28")
+	ver3 := NewEffectiveVersion("2.10")
+
+	utilruntime.Must(r.Register("test1", ver1, nil))
+	utilruntime.Must(r.Register("test2", ver2, nil))
+	utilruntime.Must(r.Register("test3", ver3, nil))
+
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test1").EmulationVersion(), "0.58")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test2").EmulationVersion(), "1.28")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test3").EmulationVersion(), "2.10")
+
+	utilruntime.Must(r.SetEmulationVersionMapping("test2", "test3",
+		func(from *version.Version) *version.Version {
+			return version.MajorMinor(from.Major()+1, from.Minor()-19)
+		}))
+	utilruntime.Must(r.SetEmulationVersionMapping("test1", "test2",
+		func(from *version.Version) *version.Version {
+			return version.MajorMinor(from.Major()+1, from.Minor()-28)
+		}))
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test1").EmulationVersion(), "0.58")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test2").EmulationVersion(), "1.30")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test3").EmulationVersion(), "2.11")
+
+	fs := pflag.NewFlagSet("testflag", pflag.ContinueOnError)
+	r.AddFlags(fs)
+
+	if err := fs.Parse([]string{fmt.Sprintf("--emulated-version=%s", "test1=0.56")}); err != nil {
+		t.Fatal(err)
+		return
+	}
+	if err := r.Set(); err != nil {
+		t.Fatal(err)
+		return
+	}
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test1").EmulationVersion(), "0.56")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test2").EmulationVersion(), "1.28")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test3").EmulationVersion(), "2.09")
+}
+
+func TestVersionMappingWithMultipleDependency(t *testing.T) {
+	r := NewComponentGlobalsRegistry()
+	ver1 := NewEffectiveVersion("0.58")
+	ver2 := NewEffectiveVersion("1.28")
+	ver3 := NewEffectiveVersion("2.10")
+
+	utilruntime.Must(r.Register("test1", ver1, nil))
+	utilruntime.Must(r.Register("test2", ver2, nil))
+	utilruntime.Must(r.Register("test3", ver3, nil))
+
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test1").EmulationVersion(), "0.58")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test2").EmulationVersion(), "1.28")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test3").EmulationVersion(), "2.10")
+
+	utilruntime.Must(r.SetEmulationVersionMapping("test1", "test2",
+		func(from *version.Version) *version.Version {
+			return version.MajorMinor(from.Major()+1, from.Minor()-28)
+		}))
+	err := r.SetEmulationVersionMapping("test3", "test2",
+		func(from *version.Version) *version.Version {
+			return version.MajorMinor(from.Major()-1, from.Minor()+19)
+		})
+	if err == nil {
+		t.Errorf("expect error when setting 2nd mapping to test2")
+	}
+}
+
+func TestVersionMappingWithCyclicDependency(t *testing.T) {
+	r := NewComponentGlobalsRegistry()
+	ver1 := NewEffectiveVersion("0.58")
+	ver2 := NewEffectiveVersion("1.28")
+	ver3 := NewEffectiveVersion("2.10")
+
+	utilruntime.Must(r.Register("test1", ver1, nil))
+	utilruntime.Must(r.Register("test2", ver2, nil))
+	utilruntime.Must(r.Register("test3", ver3, nil))
+
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test1").EmulationVersion(), "0.58")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test2").EmulationVersion(), "1.28")
+	assertVersionEqualTo(t, r.EffectiveVersionFor("test3").EmulationVersion(), "2.10")
+
+	utilruntime.Must(r.SetEmulationVersionMapping("test1", "test2",
+		func(from *version.Version) *version.Version {
+			return version.MajorMinor(from.Major()+1, from.Minor()-28)
+		}))
+	utilruntime.Must(r.SetEmulationVersionMapping("test2", "test3",
+		func(from *version.Version) *version.Version {
+			return version.MajorMinor(from.Major()+1, from.Minor()-19)
+		}))
+	err := r.SetEmulationVersionMapping("test3", "test1",
+		func(from *version.Version) *version.Version {
+			return version.MajorMinor(from.Major()-2, from.Minor()+48)
+		})
+	if err == nil {
+		t.Errorf("expect cyclic version mapping error")
+	}
+}
+
+func assertVersionEqualTo(t *testing.T, ver *version.Version, expectedVer string) {
+	if ver.EqualTo(version.MustParse(expectedVer)) {
+		return
+	}
+	t.Errorf("expected: %s, got %s", expectedVer, ver.String())
+}

staging/src/k8s.io/apiserver/pkg/util/version/version.go

@@ -18,10 +18,8 @@ package version
 
 import (
 	"fmt"
-	"strings"
 	"sync/atomic"
 
-	"github.com/spf13/pflag"
 	"k8s.io/apimachinery/pkg/util/version"
 	baseversion "k8s.io/component-base/version"
 )
@@ -40,37 +38,6 @@ type MutableEffectiveVersion interface {
 	Set(binaryVersion, emulationVersion, minCompatibilityVersion *version.Version)
 	SetEmulationVersion(emulationVersion *version.Version)
 	SetMinCompatibilityVersion(minCompatibilityVersion *version.Version)
-	// AddFlags adds the "{prefix}-emulated-version" to the flagset.
-	AddFlags(fs *pflag.FlagSet, prefix string)
-}
-
-type VersionVar struct {
-	val atomic.Pointer[version.Version]
-}
-
-// Set sets the flag value
-func (v *VersionVar) Set(s string) error {
-	components := strings.Split(s, ".")
-	if len(components) != 2 {
-		return fmt.Errorf("version %s is not in the format of major.minor", s)
-	}
-	ver, err := version.ParseGeneric(s)
-	if err != nil {
-		return err
-	}
-	v.val.Store(ver)
-	return nil
-}
-
-// String returns the flag value
-func (v *VersionVar) String() string {
-	ver := v.val.Load()
-	return ver.String()
-}
-
-// Type gets the flag type
-func (v *VersionVar) Type() string {
-	return "version"
 }
 
 type effectiveVersion struct {
@@ -78,9 +45,9 @@ type effectiveVersion struct {
 	// If the emulationVersion is set by the users, it could only contain major and minor versions.
 	// In tests, emulationVersion could be the same as the binary version, or set directly,
 	// which can have "alpha" as pre-release to continue serving expired apis while we clean up the test.
-	emulationVersion VersionVar
+	emulationVersion atomic.Pointer[version.Version]
 	// minCompatibilityVersion could only contain major and minor versions.
-	minCompatibilityVersion VersionVar
+	minCompatibilityVersion atomic.Pointer[version.Version]
 }
 
 func (m *effectiveVersion) BinaryVersion() *version.Version {
@@ -88,13 +55,17 @@ func (m *effectiveVersion) BinaryVersion() *version.Version {
 }
 
 func (m *effectiveVersion) EmulationVersion() *version.Version {
+	ver := m.emulationVersion.Load()
+	if ver != nil {
 		// Emulation version can have "alpha" as pre-release to continue serving expired apis while we clean up the test.
 		// The pre-release should not be accessible to the users.
-	return m.emulationVersion.val.Load().WithPreRelease(m.BinaryVersion().PreRelease())
+		return ver.WithPreRelease(m.BinaryVersion().PreRelease())
+	}
+	return ver
 }
 
 func (m *effectiveVersion) MinCompatibilityVersion() *version.Version {
-	return m.minCompatibilityVersion.val.Load()
+	return m.minCompatibilityVersion.Load()
 }
 
 func (m *effectiveVersion) EqualTo(other EffectiveVersion) bool {
@@ -109,26 +80,33 @@ func (m *effectiveVersion) String() string {
 		m.BinaryVersion().String(), m.EmulationVersion().String(), m.MinCompatibilityVersion().String())
 }
 
+func majorMinor(ver *version.Version) *version.Version {
+	if ver == nil {
+		return ver
+	}
+	return version.MajorMinor(ver.Major(), ver.Minor())
+}
+
 func (m *effectiveVersion) Set(binaryVersion, emulationVersion, minCompatibilityVersion *version.Version) {
 	m.binaryVersion.Store(binaryVersion)
-	m.emulationVersion.val.Store(version.MajorMinor(emulationVersion.Major(), emulationVersion.Minor()))
+	m.emulationVersion.Store(majorMinor(emulationVersion))
-	m.minCompatibilityVersion.val.Store(version.MajorMinor(minCompatibilityVersion.Major(), minCompatibilityVersion.Minor()))
+	m.minCompatibilityVersion.Store(majorMinor(minCompatibilityVersion))
 }
 
 func (m *effectiveVersion) SetEmulationVersion(emulationVersion *version.Version) {
-	m.emulationVersion.val.Store(version.MajorMinor(emulationVersion.Major(), emulationVersion.Minor()))
+	m.emulationVersion.Store(majorMinor(emulationVersion))
 }
 
 func (m *effectiveVersion) SetMinCompatibilityVersion(minCompatibilityVersion *version.Version) {
-	m.minCompatibilityVersion.val.Store(version.MajorMinor(minCompatibilityVersion.Major(), minCompatibilityVersion.Minor()))
+	m.minCompatibilityVersion.Store(majorMinor(minCompatibilityVersion))
 }
 
 func (m *effectiveVersion) Validate() []error {
 	var errs []error
 	// Validate only checks the major and minor versions.
 	binaryVersion := m.binaryVersion.Load().WithPatch(0)
-	emulationVersion := m.emulationVersion.val.Load()
+	emulationVersion := m.emulationVersion.Load()
-	minCompatibilityVersion := m.minCompatibilityVersion.val.Load()
+	minCompatibilityVersion := m.minCompatibilityVersion.Load()
 
 	// emulationVersion can only be 1.{binaryMinor-1}...1.{binaryMinor}.
 	maxEmuVer := binaryVersion
@@ -151,45 +129,36 @@ func (m *effectiveVersion) Validate() []error {
 	return errs
 }
 
-// AddFlags adds the "{prefix}-emulated-version" to the flagset.
+func newEffectiveVersion(binaryVersion *version.Version) MutableEffectiveVersion {
-func (m *effectiveVersion) AddFlags(fs *pflag.FlagSet, prefix string) {
-	if m == nil {
-		return
-	}
-	if len(prefix) > 0 && !strings.HasSuffix(prefix, "-") {
-		prefix += "-"
-	}
-	fs.Var(&m.emulationVersion, prefix+"emulated-version", ""+
-		"The version the K8s component emulates its capabilities (APIs, features, ...) of.\n"+
-		"If set, the component will emulate the behavior of this version instead of the underlying binary version.\n"+
-		"Any capabilities present in the binary version that were introduced after the emulated version will be unavailable and any capabilities removed after the emulated version will be available.\n"+
-		"This flag applies only to component capabilities, and does not disable bug fixes and performance improvements present in the binary version.\n"+
-		"Defaults to the binary version. The value should be between 1.{binaryMinorVersion-1} and 1.{binaryMinorVersion}.\n"+
-		"Format could only be major.minor")
-}
-
-func NewEffectiveVersion(binaryVer string) MutableEffectiveVersion {
 	effective := &effectiveVersion{}
-	binaryVersion := version.MustParse(binaryVer)
 	compatVersion := binaryVersion.SubtractMinor(1)
 	effective.Set(binaryVersion, binaryVersion, compatVersion)
 	return effective
 }
 
+func NewEffectiveVersion(binaryVer string) MutableEffectiveVersion {
+	if binaryVer == "" {
+		return &effectiveVersion{}
+	}
+	binaryVersion := version.MustParse(binaryVer)
+	return newEffectiveVersion(binaryVersion)
+}
+
 // DefaultBuildEffectiveVersion returns the MutableEffectiveVersion based on the
 // current build information.
 func DefaultBuildEffectiveVersion() MutableEffectiveVersion {
 	verInfo := baseversion.Get()
-	ver := NewEffectiveVersion(verInfo.String())
+	binaryVersion := version.MustParse(verInfo.String()).WithInfo(verInfo)
-	if ver.BinaryVersion().Major() == 0 && ver.BinaryVersion().Minor() == 0 {
+	if binaryVersion.Major() == 0 && binaryVersion.Minor() == 0 {
-		ver = DefaultKubeEffectiveVersion()
+		return DefaultKubeEffectiveVersion()
 	}
-	return ver
+	return newEffectiveVersion(binaryVersion)
 }
 
 // DefaultKubeEffectiveVersion returns the MutableEffectiveVersion based on the
 // latest K8s release.
 // Should update for each minor release!
 func DefaultKubeEffectiveVersion() MutableEffectiveVersion {
-	return NewEffectiveVersion("1.31")
+	binaryVersion := version.MustParse("1.31").WithInfo(baseversion.Get())
+	return newEffectiveVersion(binaryVersion)
 }

staging/src/k8s.io/apiserver/pkg/util/version/version_test.go

@@ -17,11 +17,8 @@ limitations under the License.
 package version
 
 import (
-	"fmt"
-	"strings"
 	"testing"
 
-	"github.com/spf13/pflag"
 	"k8s.io/apimachinery/pkg/util/version"
 )
 
@@ -127,54 +124,3 @@ func TestValidate(t *testing.T) {
 		})
 	}
 }
-
-func TestEffectiveVersionsFlag(t *testing.T) {
-	tests := []struct {
-		name                     string
-		emulationVersion         string
-		expectedEmulationVersion *version.Version
-		parseError               string
-	}{
-		{
-			name:                     "major.minor ok",
-			emulationVersion:         "1.30",
-			expectedEmulationVersion: version.MajorMinor(1, 30),
-		},
-		{
-			name:                     "v prefix ok",
-			emulationVersion:         "v1.30",
-			expectedEmulationVersion: version.MajorMinor(1, 30),
-		},
-		{
-			name:             "semantic version not ok",
-			emulationVersion: "1.30.1",
-			parseError:       "version 1.30.1 is not in the format of major.minor",
-		},
-		{
-			name:             "invalid version",
-			emulationVersion: "1.foo",
-			parseError:       "illegal version string",
-		},
-	}
-	for i, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			fs := pflag.NewFlagSet("testflag", pflag.ContinueOnError)
-			effective := NewEffectiveVersion("1.30")
-			effective.AddFlags(fs, "test")
-
-			err := fs.Parse([]string{fmt.Sprintf("--test-emulated-version=%s", test.emulationVersion)})
-			if test.parseError != "" {
-				if !strings.Contains(err.Error(), test.parseError) {
-					t.Fatalf("%d: Parse() Expected %v, Got %v", i, test.parseError, err)
-				}
-				return
-			}
-			if err != nil {
-				t.Fatalf("%d: Parse() Expected nil, Got %v", i, err)
-			}
-			if !effective.EmulationVersion().EqualTo(test.expectedEmulationVersion) {
-				t.Errorf("%d: EmulationVersion Expected %s, Got %s", i, test.expectedEmulationVersion.String(), effective.EmulationVersion().String())
-			}
-		})
-	}
-}

staging/src/k8s.io/component-base/featuregate/feature_gate.go

@@ -127,6 +127,9 @@ type MutableFeatureGate interface {
 	AddFlag(fs *pflag.FlagSet)
 	// Close sets closed to true, and prevents subsequent calls to Add
 	Close()
+	// OpenForModification sets closedForModification to false, and allows subsequent calls to SetEmulationVersion to change enabled features
+	// before the next Enabled is called.
+	OpenForModification()
 	// Set parses and stores flag gates for known features
 	// from a string like feature1=true,feature2=false,...
 	Set(value string) error
@@ -163,11 +166,25 @@ type MutableVersionedFeatureGate interface {
 	// SetEmulationVersion overrides the emulationVersion of the feature gate.
 	// Otherwise, the emulationVersion will be the same as the binary version.
 	// If set, the feature defaults and availability will be as if the binary is at the emulated version.
+	// Returns error if the new emulationVersion will change the enablement state of a feature that has already been queried.
+	// If you have to use featureGate.Enabled before parsing the flags, call featureGate.OpenForModification following featureGate.Enabled.
 	SetEmulationVersion(emulationVersion *version.Version) error
 	// GetAll returns a copy of the map of known feature names to versioned feature specs.
 	GetAllVersioned() map[Feature]VersionedSpecs
 	// AddVersioned adds versioned feature specs to the featureGate.
 	AddVersioned(features map[Feature]VersionedSpecs) error
+	// OverrideDefaultAtVersion sets a local override for the registered default value of a named
+	// feature for the prerelease lifecycle the given version is at.
+	// If the feature has not been previously registered (e.g. by a call to Add),
+	// has a locked default, or if the gate has already registered itself with a FlagSet, a non-nil
+	// error is returned.
+	//
+	// When two or more components consume a common feature, one component can override its
+	// default at runtime in order to adopt new defaults before or after the other
+	// components. For example, a new feature can be evaluated with a limited blast radius by
+	// overriding its default to true for a limited number of components without simultaneously
+	// changing its default for all consuming components.
+	OverrideDefaultAtVersion(name Feature, override bool, ver *version.Version) error
 }
 
 // MutableVersionedFeatureGateForTests is a feature gate interface that should only be used in tests.
@@ -197,6 +214,13 @@ type featureGate struct {
 	enabledRaw atomic.Value
 	// closed is set to true when AddFlag is called, and prevents subsequent calls to Add
 	closed bool
+	// closedForModification is set to true when Enabled is called, and prevents subsequent calls to SetEmulationVersion to change the enabled features.
+	// TODO: after all feature gates have migrated to versioned feature gates,
+	// closedForModification should also prevents subsequent calls to Set and SetFromMap to change the enabled features
+	closedForModification atomic.Bool
+	// queriedFeatures stores all the features that have been queried through the Enabled interface.
+	// It is reset when closedForModification is reset.
+	queriedFeatures  atomic.Value
 	emulationVersion atomic.Pointer[version.Version]
 }
 
@@ -205,8 +229,8 @@ func setUnsetAlphaGates(known map[Feature]VersionedSpecs, enabled map[Feature]bo
 		if k == "AllAlpha" || k == "AllBeta" {
 			continue
 		}
-		currentVersion := getCurrentVersion(v, cVer)
+		featureSpec := featureSpecAtEmulationVersion(v, cVer)
-		if currentVersion.PreRelease == Alpha {
+		if featureSpec.PreRelease == Alpha {
 			if _, found := enabled[k]; !found {
 				enabled[k] = val
 			}
@@ -219,8 +243,8 @@ func setUnsetBetaGates(known map[Feature]VersionedSpecs, enabled map[Feature]boo
 		if k == "AllAlpha" || k == "AllBeta" {
 			continue
 		}
-		currentVersion := getCurrentVersion(v, cVer)
+		featureSpec := featureSpecAtEmulationVersion(v, cVer)
-		if currentVersion.PreRelease == Beta {
+		if featureSpec.PreRelease == Beta {
 			if _, found := enabled[k]; !found {
 				enabled[k] = val
 			}
@@ -251,6 +275,7 @@ func NewVersionedFeatureGate(emulationVersion *version.Version) *featureGate {
 	f.enabled.Store(map[Feature]bool{})
 	f.enabledRaw.Store(map[string]bool{})
 	f.emulationVersion.Store(emulationVersion)
+	f.queriedFeatures.Store(map[Feature]struct{}{})
 	klog.V(1).Infof("new feature gate with emulationVersion=%s", f.emulationVersion.Load().String())
 	return f
 }
@@ -291,11 +316,11 @@ func (f *featureGate) Validate() []error {
 		return []error{fmt.Errorf("cannot cast enabledRaw to map[string]bool")}
 	}
 	enabled := map[Feature]bool{}
-	return f.unsafeSetFromMap(enabled, m)
+	return f.unsafeSetFromMap(enabled, m, f.EmulationVersion())
 }
 
 // unsafeSetFromMap stores flag gates for known features from a map[string]bool into an enabled map.
-func (f *featureGate) unsafeSetFromMap(enabled map[Feature]bool, m map[string]bool) []error {
+func (f *featureGate) unsafeSetFromMap(enabled map[Feature]bool, m map[string]bool, emulationVersion *version.Version) []error {
 	var errs []error
 	// Copy existing state
 	known := map[Feature]VersionedSpecs{}
@@ -312,26 +337,26 @@ func (f *featureGate) unsafeSetFromMap(enabled map[Feature]bool, m map[string]bo
 			errs = append(errs, fmt.Errorf("unrecognized feature gate: %s", k))
 			return errs
 		}
-		currentVersion := f.getCurrentVersion(versionedSpecs)
+		featureSpec := featureSpecAtEmulationVersion(versionedSpecs, emulationVersion)
-		if currentVersion.LockToDefault && currentVersion.Default != v {
+		if featureSpec.LockToDefault && featureSpec.Default != v {
-			errs = append(errs, fmt.Errorf("cannot set feature gate %v to %v, feature is locked to %v", k, v, currentVersion.Default))
+			errs = append(errs, fmt.Errorf("cannot set feature gate %v to %v, feature is locked to %v", k, v, featureSpec.Default))
 			continue
 		}
 		// Handle "special" features like "all alpha gates"
 		if fn, found := f.special[key]; found {
-			fn(known, enabled, v, f.emulationVersion.Load())
+			fn(known, enabled, v, emulationVersion)
 			enabled[key] = v
 			continue
 		}
-		if currentVersion.PreRelease == PreAlpha {
+		if featureSpec.PreRelease == PreAlpha {
-			errs = append(errs, fmt.Errorf("cannot set feature gate %v to %v, feature is PreAlpha at emulated version %s", k, v, f.EmulationVersion().String()))
+			errs = append(errs, fmt.Errorf("cannot set feature gate %v to %v, feature is PreAlpha at emulated version %s", k, v, emulationVersion.String()))
 			continue
 		}
 		enabled[key] = v
 
-		if currentVersion.PreRelease == Deprecated {
+		if featureSpec.PreRelease == Deprecated {
 			klog.Warningf("Setting deprecated feature gate %s=%t. It will be removed in a future release.", k, v)
-		} else if currentVersion.PreRelease == GA {
+		} else if featureSpec.PreRelease == GA {
 			klog.Warningf("Setting GA feature gate %s=%t. It will be removed in a future release.", k, v)
 		}
 	}
@@ -361,7 +386,7 @@ func (f *featureGate) SetFromMap(m map[string]bool) error {
 	}
 	f.enabledRaw.Store(enabledRaw)
 
-	errs := f.unsafeSetFromMap(enabled, enabledRaw)
+	errs := f.unsafeSetFromMap(enabled, enabledRaw, f.EmulationVersion())
 	if len(errs) == 0 {
 		// Persist changes
 		f.enabled.Store(enabled)
@@ -429,6 +454,10 @@ func (f *featureGate) AddVersioned(features map[Feature]VersionedSpecs) error {
 }
 
 func (f *featureGate) OverrideDefault(name Feature, override bool) error {
+	return f.OverrideDefaultAtVersion(name, override, f.EmulationVersion())
+}
+
+func (f *featureGate) OverrideDefaultAtVersion(name Feature, override bool, ver *version.Version) error {
 	f.lock.Lock()
 	defer f.lock.Unlock()
 
@@ -446,12 +475,12 @@ func (f *featureGate) OverrideDefault(name Feature, override bool) error {
 	if !ok {
 		return fmt.Errorf("cannot override default: feature %q is not registered", name)
 	}
-	spec := f.getCurrentVersion(specs)
+	spec := featureSpecAtEmulationVersion(specs, ver)
 	switch {
 	case spec.LockToDefault:
 		return fmt.Errorf("cannot override default: feature %q default is locked to %t", name, spec.Default)
 	case spec.PreRelease == PreAlpha:
-		return fmt.Errorf("cannot override default: feature %q is not available before emulation version %s", name, f.EmulationVersion().String())
+		return fmt.Errorf("cannot override default: feature %q is not available before version %s", name, ver.String())
 	case spec.PreRelease == Deprecated:
 		klog.Warningf("Overriding default of deprecated feature gate %s=%t. It will be removed in a future release.", name, override)
 	case spec.PreRelease == GA:
@@ -469,12 +498,12 @@ func (f *featureGate) OverrideDefault(name Feature, override bool) error {
 func (f *featureGate) GetAll() map[Feature]FeatureSpec {
 	retval := map[Feature]FeatureSpec{}
 	for k, v := range f.GetAllVersioned() {
-		spec := f.getCurrentVersion(v)
+		spec := f.featureSpecAtEmulationVersion(v)
 		if spec.PreRelease == PreAlpha {
 			// The feature is not available at the emulation version.
 			continue
 		}
-		retval[k] = *f.getCurrentVersion(v)
+		retval[k] = *f.featureSpecAtEmulationVersion(v)
 	}
 	return retval
 }
@@ -492,7 +521,6 @@ func (f *featureGate) SetEmulationVersion(emulationVersion *version.Version) err
 	f.lock.Lock()
 	defer f.lock.Unlock()
 	klog.V(1).Infof("set feature gate emulationVersion to %s", emulationVersion.String())
-	f.emulationVersion.Store(emulationVersion)
 
 	// Copy existing state
 	enabledRaw := map[string]bool{}
@@ -501,10 +529,24 @@ func (f *featureGate) SetEmulationVersion(emulationVersion *version.Version) err
 	}
 	// enabled map should be reset whenever emulationVersion is changed.
 	enabled := map[Feature]bool{}
-	errs := f.unsafeSetFromMap(enabled, enabledRaw)
+	errs := f.unsafeSetFromMap(enabled, enabledRaw, emulationVersion)
+
+	if f.closedForModification.Load() {
+		queriedFeatures := f.queriedFeatures.Load().(map[Feature]struct{})
+		known := f.known.Load().(map[Feature]VersionedSpecs)
+		for feature := range queriedFeatures {
+			newVal := featureEnabled(feature, enabled, known, emulationVersion)
+			oldVal := f.Enabled(feature)
+			// it is ok to modify emulation version if it does not result in feature enablemennt change for features that have already been queried.
+			if newVal != oldVal {
+				errs = append(errs, fmt.Errorf("SetEmulationVersion will change already queried feature:%s from %v to %v\ncall featureGate.OpenForModification() first to override", feature, oldVal, newVal))
+			}
+		}
+	}
 	if len(errs) == 0 {
 		// Persist changes
 		f.enabled.Store(enabled)
+		f.emulationVersion.Store(emulationVersion)
 	}
 	return utilerrors.NewAggregate(errs)
 }
@@ -514,32 +556,49 @@ func (f *featureGate) EmulationVersion() *version.Version {
 }
 
 // FeatureSpec returns the FeatureSpec at the EmulationVersion if the key exists, an error otherwise.
+// This is useful to keep multiple implementations of a feature based on the PreRelease or Version info.
 func (f *featureGate) FeatureSpec(key Feature) (FeatureSpec, error) {
 	if v, ok := f.known.Load().(map[Feature]VersionedSpecs)[key]; ok {
-		currentVersion := f.getCurrentVersion(v)
+		featureSpec := f.featureSpecAtEmulationVersion(v)
-		return *currentVersion, nil
+		return *featureSpec, nil
 	}
 	return FeatureSpec{}, fmt.Errorf("feature %q is not registered in FeatureGate %q", key, f.featureGateName)
 }
 
-// Enabled returns true if the key is enabled.  If the key is not known, this call will panic.
+func (f *featureGate) recordQueried(key Feature) {
-func (f *featureGate) Enabled(key Feature) bool {
+	queriedFeatures := map[Feature]struct{}{}
-	// fallback to default behavior, since we don't have emulation version set
+	for k := range f.queriedFeatures.Load().(map[Feature]struct{}) {
-	if v, ok := f.enabled.Load().(map[Feature]bool)[key]; ok {
+		queriedFeatures[k] = struct{}{}
+	}
+	queriedFeatures[key] = struct{}{}
+	f.queriedFeatures.Store(queriedFeatures)
+	f.closedForModification.Store(true)
+}
+
+func featureEnabled(key Feature, enabled map[Feature]bool, known map[Feature]VersionedSpecs, emulationVersion *version.Version) bool {
+	// check explicitly set enabled list
+	if v, ok := enabled[key]; ok {
 		return v
 	}
-	if v, ok := f.known.Load().(map[Feature]VersionedSpecs)[key]; ok {
+	if v, ok := known[key]; ok {
-		return f.getCurrentVersion(v).Default
+		return featureSpecAtEmulationVersion(v, emulationVersion).Default
 	}
 
-	panic(fmt.Errorf("feature %q is not registered in FeatureGate %q", key, f.featureGateName))
+	panic(fmt.Errorf("feature %q is not registered in FeatureGate", key))
 }
 
-func (f *featureGate) getCurrentVersion(v VersionedSpecs) *FeatureSpec {
+// Enabled returns true if the key is enabled.  If the key is not known, this call will panic.
-	return getCurrentVersion(v, f.EmulationVersion())
+func (f *featureGate) Enabled(key Feature) bool {
+	v := featureEnabled(key, f.enabled.Load().(map[Feature]bool), f.known.Load().(map[Feature]VersionedSpecs), f.EmulationVersion())
+	f.recordQueried(key)
+	return v
 }
 
-func getCurrentVersion(v VersionedSpecs, emulationVersion *version.Version) *FeatureSpec {
+func (f *featureGate) featureSpecAtEmulationVersion(v VersionedSpecs) *FeatureSpec {
+	return featureSpecAtEmulationVersion(v, f.EmulationVersion())
+}
+
+func featureSpecAtEmulationVersion(v VersionedSpecs, emulationVersion *version.Version) *FeatureSpec {
 	i := len(v) - 1
 	for ; i >= 0; i-- {
 		if v[i].Version.GreaterThan(emulationVersion) {
@@ -561,6 +620,18 @@ func (f *featureGate) Close() {
 	f.lock.Unlock()
 }
 
+// OpenForModification sets closedForModification to false, and allows subsequent calls to SetEmulationVersion to change enabled features
+// before the next Enabled is called.
+func (f *featureGate) OpenForModification() {
+	queriedFeatures := []Feature{}
+	for feature := range f.queriedFeatures.Load().(map[Feature]struct{}) {
+		queriedFeatures = append(queriedFeatures, feature)
+	}
+	klog.Warningf("open feature gate for modification after querying features: %v.", queriedFeatures)
+	f.closedForModification.Store(false)
+	f.queriedFeatures.Store(map[Feature]struct{}{})
+}
+
 // AddFlag adds a flag for setting global feature gates to the specified FlagSet.
 func (f *featureGate) AddFlag(fs *pflag.FlagSet) {
 	// TODO(mtaufen): Shouldn't we just close it on the first Set/SetFromMap instead?
@@ -590,11 +661,11 @@ func (f *featureGate) KnownFeatures() []string {
 			known = append(known, fmt.Sprintf("%s=true|false (%s - default=%t)", k, v[0].PreRelease, v[0].Default))
 			continue
 		}
-		currentV := f.getCurrentVersion(v)
+		featureSpec := f.featureSpecAtEmulationVersion(v)
-		if currentV.PreRelease == GA || currentV.PreRelease == Deprecated || currentV.PreRelease == PreAlpha {
+		if featureSpec.PreRelease == GA || featureSpec.PreRelease == Deprecated || featureSpec.PreRelease == PreAlpha {
 			continue
 		}
-		known = append(known, fmt.Sprintf("%s=true|false (%s - default=%t)", k, currentV.PreRelease, currentV.Default))
+		known = append(known, fmt.Sprintf("%s=true|false (%s - default=%t)", k, featureSpec.PreRelease, featureSpec.Default))
 	}
 	sort.Strings(known)
 	return known
@@ -620,7 +691,7 @@ func (f *featureGate) DeepCopy() MutableVersionedFeatureGate {
 
 	// Construct a new featureGate around the copied state.
 	// Note that specialFeatures is treated as immutable by convention,
-	// and we maintain the value of f.closed across the copy.
+	// and we maintain the value of f.closed across the copy, but resets closedForModification.
 	fg := &featureGate{
 		special: specialFeatures,
 		closed:  f.closed,
@@ -629,6 +700,7 @@ func (f *featureGate) DeepCopy() MutableVersionedFeatureGate {
 	fg.known.Store(known)
 	fg.enabled.Store(enabled)
 	fg.enabledRaw.Store(enabledRaw)
+	fg.queriedFeatures.Store(map[Feature]struct{}{})
 	return fg
 }
 
@@ -636,9 +708,15 @@ func (f *featureGate) DeepCopy() MutableVersionedFeatureGate {
 func (f *featureGate) Reset(m map[string]bool) {
 	enabled := map[Feature]bool{}
 	enabledRaw := map[string]bool{}
+	queriedFeatures := map[Feature]struct{}{}
 	f.enabled.Store(enabled)
 	f.enabledRaw.Store(enabledRaw)
 	_ = f.SetFromMap(m)
+	f.closedForModification.Store(false)
+	f.queriedFeatures.Store(queriedFeatures)
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	f.closed = false
 }
 
 func (f *featureGate) EnabledRawMap() map[string]bool {

staging/src/k8s.io/component-base/featuregate/feature_gate_test.go

@@ -1280,6 +1280,48 @@ func TestVersionedFeatureGateOverrideDefault(t *testing.T) {
 		}
 	})
 
+	t.Run("overrides at specific version take effect", func(t *testing.T) {
+		f := NewVersionedFeatureGate(version.MustParse("1.29"))
+		require.NoError(t, f.SetEmulationVersion(version.MustParse("1.28")))
+		if err := f.AddVersioned(map[Feature]VersionedSpecs{
+			"TestFeature1": {
+				{Version: version.MustParse("1.28"), Default: true},
+			},
+			"TestFeature2": {
+				{Version: version.MustParse("1.26"), Default: false},
+				{Version: version.MustParse("1.29"), Default: false},
+			},
+		}); err != nil {
+			t.Fatal(err)
+		}
+		if f.OverrideDefaultAtVersion("TestFeature1", false, version.MustParse("1.27")) == nil {
+			t.Error("expected error when attempting to override the default for a feature not available at given version")
+		}
+		require.NoError(t, f.OverrideDefaultAtVersion("TestFeature2", true, version.MustParse("1.27")))
+		if !f.Enabled("TestFeature1") {
+			t.Error("expected TestFeature1 to have effective default of true")
+		}
+		if !f.Enabled("TestFeature2") {
+			t.Error("expected TestFeature2 to have effective default of true")
+		}
+		f.OpenForModification()
+		require.NoError(t, f.SetEmulationVersion(version.MustParse("1.29")))
+		if !f.Enabled("TestFeature1") {
+			t.Error("expected TestFeature1 to have effective default of true")
+		}
+		if f.Enabled("TestFeature2") {
+			t.Error("expected TestFeature2 to have effective default of false")
+		}
+		f.OpenForModification()
+		require.NoError(t, f.SetEmulationVersion(version.MustParse("1.26")))
+		if f.Enabled("TestFeature1") {
+			t.Error("expected TestFeature1 to have effective default of false")
+		}
+		if !f.Enabled("TestFeature2") {
+			t.Error("expected TestFeature2 to have effective default of true")
+		}
+	})
+
 	t.Run("overrides are preserved across deep copies", func(t *testing.T) {
 		f := NewVersionedFeatureGate(version.MustParse("1.29"))
 		require.NoError(t, f.SetEmulationVersion(version.MustParse("1.28")))
@@ -1433,7 +1475,7 @@ func TestVersionedFeatureGateOverrideDefault(t *testing.T) {
 	})
 }
 
-func TestGetCurrentVersion(t *testing.T) {
+func TestFeatureSpecAtEmulationVersion(t *testing.T) {
 	specs := VersionedSpecs{{Version: version.MustParse("1.29"), Default: true, PreRelease: GA},
 		{Version: version.MustParse("1.28"), Default: false, PreRelease: Beta},
 		{Version: version.MustParse("1.25"), Default: false, PreRelease: Alpha},
@@ -1469,11 +1511,41 @@ func TestGetCurrentVersion(t *testing.T) {
 		},
 	}
 	for i, test := range tests {
-		t.Run(fmt.Sprintf("getCurrentVersion for emulationVersion %s", test.cVersion), func(t *testing.T) {
+		t.Run(fmt.Sprintf("featureSpecAtEmulationVersion for emulationVersion %s", test.cVersion), func(t *testing.T) {
-			result := getCurrentVersion(specs, version.MustParse(test.cVersion))
+			result := featureSpecAtEmulationVersion(specs, version.MustParse(test.cVersion))
 			if !reflect.DeepEqual(*result, test.expect) {
-				t.Errorf("%d: getCurrentVersion(, %s) Expected %v, Got %v", i, test.cVersion, test.expect, result)
+				t.Errorf("%d: featureSpecAtEmulationVersion(, %s) Expected %v, Got %v", i, test.cVersion, test.expect, result)
 			}
 		})
 	}
 }
+
+func TestOpenForModification(t *testing.T) {
+	const testBetaGate Feature = "testBetaGate"
+	f := NewVersionedFeatureGate(version.MustParse("1.29"))
+
+	err := f.AddVersioned(map[Feature]VersionedSpecs{
+		testBetaGate: {
+			{Version: version.MustParse("1.29"), Default: true, PreRelease: Beta},
+			{Version: version.MustParse("1.28"), Default: false, PreRelease: Beta},
+			{Version: version.MustParse("1.26"), Default: false, PreRelease: Alpha},
+		},
+	})
+	require.NoError(t, err)
+
+	if f.Enabled(testBetaGate) != true {
+		t.Errorf("Expected true")
+	}
+	err = f.SetEmulationVersion(version.MustParse("1.28"))
+	if err == nil {
+		t.Fatalf("Expected error when SetEmulationVersion after querying features")
+	}
+	if f.Enabled(testBetaGate) != true {
+		t.Errorf("Expected true")
+	}
+	f.OpenForModification()
+	require.NoError(t, f.SetEmulationVersion(version.MustParse("1.28")))
+	if f.Enabled(testBetaGate) != false {
+		t.Errorf("Expected false at 1.28")
+	}
+}

staging/src/k8s.io/kube-aggregator/pkg/apiserver/apiserver.go

@@ -38,7 +38,6 @@ import (
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/transport"
 	"k8s.io/component-base/tracing"
-	"k8s.io/component-base/version"
 	v1 "k8s.io/kube-aggregator/pkg/apis/apiregistration/v1"
 	v1helper "k8s.io/kube-aggregator/pkg/apis/apiregistration/v1/helper"
 	"k8s.io/kube-aggregator/pkg/apis/apiregistration/v1beta1"
@@ -185,8 +184,6 @@ func (cfg *Config) Complete() CompletedConfig {
 	// the kube aggregator wires its own discovery mechanism
 	// TODO eventually collapse this by extracting all of the discovery out
 	c.GenericConfig.EnableDiscovery = false
-	version := version.Get()
-	c.GenericConfig.Version = &version
 
 	return CompletedConfig{&c}
 }

staging/src/k8s.io/sample-apiserver/pkg/apiserver/apiserver.go

@@ -17,17 +17,13 @@ limitations under the License.
 package apiserver
 
 import (
-	"strconv"
-
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/runtime/serializer"
-	"k8s.io/apimachinery/pkg/version"
 	"k8s.io/apiserver/pkg/registry/rest"
 	genericapiserver "k8s.io/apiserver/pkg/server"
 
-	utilversion "k8s.io/apiserver/pkg/util/version"
 	"k8s.io/sample-apiserver/pkg/apis/wardle"
 	"k8s.io/sample-apiserver/pkg/apis/wardle/install"
 	wardleregistry "k8s.io/sample-apiserver/pkg/registry"
@@ -94,11 +90,6 @@ func (cfg *Config) Complete() CompletedConfig {
 		cfg.GenericConfig.Complete(),
 		&cfg.ExtraConfig,
 	}
-	wardleEffectiveVersion := utilversion.DefaultComponentGlobalsRegistry.EffectiveVersionFor(WardleComponentName)
-	c.GenericConfig.Version = &version.Info{
-		Major: strconv.Itoa(int(wardleEffectiveVersion.BinaryVersion().Major())),
-		Minor: strconv.Itoa(int(wardleEffectiveVersion.BinaryVersion().Minor())),
-	}
 
 	return CompletedConfig{&c}
 }

staging/src/k8s.io/sample-apiserver/pkg/cmd/server/start.go

@@ -59,23 +59,15 @@ type WardleServerOptions struct {
 	AlternateDNS []string
 }
 
-func mapWardleEffectiveVersionToKubeEffectiveVersion(registry utilversion.ComponentGlobalsRegistry) error {
+func wardleEmulationVersionToKubeEmulationVersion(ver *version.Version) *version.Version {
-	wardleVer := registry.EffectiveVersionFor(apiserver.WardleComponentName)
+	if ver.Major() != 1 {
-	kubeVer := registry.EffectiveVersionFor(utilversion.DefaultKubeComponent).(utilversion.MutableEffectiveVersion)
-	// map from wardle emulation version to kube emulation version.
-	emulationVersionMap := map[string]string{
-		"1.2": kubeVer.BinaryVersion().AddMinor(1).String(),
-		"1.1": kubeVer.BinaryVersion().String(),
-		"1.0": kubeVer.BinaryVersion().SubtractMinor(1).String(),
-	}
-	wardleEmulationVer := wardleVer.EmulationVersion()
-	if kubeEmulationVer, ok := emulationVersionMap[wardleEmulationVer.String()]; ok {
-		kubeVer.SetEmulationVersion(version.MustParse(kubeEmulationVer))
-	} else {
-		return fmt.Errorf("cannot find mapping from wardle emulation version: %s to kube version", wardleVer.EmulationVersion().String())
-	}
 		return nil
 	}
+	kubeVer := utilversion.DefaultKubeEffectiveVersion().BinaryVersion()
+	// "1.1" maps to kubeVer
+	offset := int(ver.Minor()) - 1
+	return kubeVer.OffsetMinor(offset)
+}
 
 // NewWardleServerOptions returns a new WardleServerOptions
 func NewWardleServerOptions(out, errOut io.Writer) *WardleServerOptions {
@@ -100,11 +92,7 @@ func NewCommandStartWardleServer(ctx context.Context, defaults *WardleServerOpti
 		Short: "Launch a wardle API server",
 		Long:  "Launch a wardle API server",
 		PersistentPreRunE: func(*cobra.Command, []string) error {
-			if err := utilversion.DefaultComponentGlobalsRegistry.Set(); err != nil {
+			return utilversion.DefaultComponentGlobalsRegistry.Set()
-				return err
-			}
-			// convert wardle effective version to kube effective version to be used in generic api server, and set the generic api server feature gate.
-			return mapWardleEffectiveVersionToKubeEffectiveVersion(utilversion.DefaultComponentGlobalsRegistry)
 		},
 		RunE: func(c *cobra.Command, args []string) error {
 			if err := o.Complete(); err != nil {
@@ -133,10 +121,10 @@ func NewCommandStartWardleServer(ctx context.Context, defaults *WardleServerOpti
 			{Version: version.MustParse("1.0"), Default: false, PreRelease: featuregate.Alpha},
 		},
 	}))
-	utilruntime.Must(utilversion.DefaultComponentGlobalsRegistry.Register(apiserver.WardleComponentName, wardleEffectiveVersion, wardleFeatureGate, false))
+	utilruntime.Must(utilversion.DefaultComponentGlobalsRegistry.Register(apiserver.WardleComponentName, wardleEffectiveVersion, wardleFeatureGate))
 	_, _ = utilversion.DefaultComponentGlobalsRegistry.ComponentGlobalsOrRegister(
 		utilversion.DefaultKubeComponent, utilversion.DefaultKubeEffectiveVersion(), utilfeature.DefaultMutableFeatureGate)
-
+	utilruntime.Must(utilversion.DefaultComponentGlobalsRegistry.SetEmulationVersionMapping(apiserver.WardleComponentName, utilversion.DefaultKubeComponent, wardleEmulationVersionToKubeEmulationVersion))
 	utilversion.DefaultComponentGlobalsRegistry.AddFlags(flags)
 
 	return cmd
@@ -189,8 +177,8 @@ func (o *WardleServerOptions) Config() (*apiserver.Config, error) {
 	serverConfig.OpenAPIV3Config.Info.Title = "Wardle"
 	serverConfig.OpenAPIV3Config.Info.Version = "0.1"
 
-	serverConfig.FeatureGate = utilversion.DefaultComponentGlobalsRegistry.FeatureGateFor(utilversion.DefaultKubeComponent)
+	serverConfig.FeatureGate = utilversion.DefaultComponentGlobalsRegistry.FeatureGateFor(apiserver.WardleComponentName)
-	serverConfig.EffectiveVersion = utilversion.DefaultComponentGlobalsRegistry.EffectiveVersionFor(utilversion.DefaultKubeComponent)
+	serverConfig.EffectiveVersion = utilversion.DefaultComponentGlobalsRegistry.EffectiveVersionFor(apiserver.WardleComponentName)
 
 	if err := o.RecommendedOptions.ApplyTo(serverConfig); err != nil {
 		return nil, err

staging/src/k8s.io/sample-apiserver/pkg/cmd/server/start_test.go

@@ -21,13 +21,11 @@ import (
 
 	"k8s.io/apimachinery/pkg/util/version"
 	utilversion "k8s.io/apiserver/pkg/util/version"
-	"k8s.io/sample-apiserver/pkg/apiserver"
 
 	"github.com/stretchr/testify/assert"
 )
 
-func TestMapBinaryEffectiveVersionToKubeEffectiveVersion(t *testing.T) {
+func TestWardleEmulationVersionToKubeEmulationVersion(t *testing.T) {
-	wardleEffectiveVersion := utilversion.NewEffectiveVersion("1.2")
 	defaultKubeEffectiveVersion := utilversion.DefaultKubeEffectiveVersion()
 
 	testCases := []struct {
@@ -35,32 +33,26 @@ func TestMapBinaryEffectiveVersionToKubeEffectiveVersion(t *testing.T) {
 		wardleEmulationVer       *version.Version
 		expectedKubeEmulationVer *version.Version
 	}{
+		{
+			desc:                     "same version as than kube binary",
+			wardleEmulationVer:       version.MajorMinor(1, 1),
+			expectedKubeEmulationVer: defaultKubeEffectiveVersion.BinaryVersion(),
+		},
 		{
 			desc:                     "1 version higher than kube binary",
 			wardleEmulationVer:       version.MajorMinor(1, 2),
-			expectedKubeEmulationVer: defaultKubeEffectiveVersion.BinaryVersion().AddMinor(1),
+			expectedKubeEmulationVer: defaultKubeEffectiveVersion.BinaryVersion().OffsetMinor(1),
 		},
 		{
 			desc:               "no mapping",
-			wardleEmulationVer: version.MajorMinor(1, 10),
+			wardleEmulationVer: version.MajorMinor(2, 10),
 		},
 	}
 
 	for _, tc := range testCases {
 		t.Run(tc.desc, func(t *testing.T) {
-			registry := utilversion.NewComponentGlobalsRegistry()
+			mappedKubeEmulationVer := wardleEmulationVersionToKubeEmulationVersion(tc.wardleEmulationVer)
-			_ = registry.Register(apiserver.WardleComponentName, wardleEffectiveVersion, nil, true)
+			assert.True(t, mappedKubeEmulationVer.EqualTo(tc.expectedKubeEmulationVer))
-			_ = registry.Register(utilversion.DefaultKubeComponent, defaultKubeEffectiveVersion, nil, true)
-
-			wardleEffectiveVersion.SetEmulationVersion(tc.wardleEmulationVer)
-			err := mapWardleEffectiveVersionToKubeEffectiveVersion(registry)
-			if tc.expectedKubeEmulationVer == nil {
-				if err == nil {
-					t.Fatal("expected error, no error found")
-				}
-			} else {
-				assert.True(t, registry.EffectiveVersionFor(utilversion.DefaultKubeComponent).EmulationVersion().EqualTo(tc.expectedKubeEmulationVer))
-			}
 		})
 	}
 }

test/integration/apiserver/apiserver_test.go

@@ -56,6 +56,7 @@ import (
 	"k8s.io/apimachinery/pkg/watch"
 	"k8s.io/apiserver/pkg/endpoints/handlers"
 	"k8s.io/apiserver/pkg/storage/storagebackend"
+	utilversion "k8s.io/apiserver/pkg/util/version"
 	"k8s.io/client-go/discovery/cached/memory"
 	"k8s.io/client-go/dynamic"
 	clientset "k8s.io/client-go/kubernetes"
@@ -3103,6 +3104,48 @@ func TestEmulatedStorageVersion(t *testing.T) {
 	}
 }
 
+// TestAllowedEmulationVersions tests the TestServer can start without problem for all allowed emulation versions.
+func TestAllowedEmulationVersions(t *testing.T) {
+	tcs := []struct {
+		name             string
+		emulationVersion string
+	}{
+		{
+			name:             "default",
+			emulationVersion: utilversion.DefaultKubeEffectiveVersion().EmulationVersion().String(),
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.emulationVersion, func(t *testing.T) {
+			server := kubeapiservertesting.StartTestServerOrDie(t, nil,
+				[]string{fmt.Sprintf("--emulated-version=kube=%s", tc.emulationVersion)}, framework.SharedEtcd())
+			defer server.TearDownFn()
+
+			rt, err := restclient.TransportFor(server.ClientConfig)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			req, err := http.NewRequest("GET", server.ClientConfig.Host+"/", nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			resp, err := rt.RoundTrip(req)
+			if err != nil {
+				t.Fatal(err)
+			}
+			expectedStatusCode := 200
+			if resp.StatusCode != expectedStatusCode {
+				t.Errorf("expect status code: %d, got : %d\n", expectedStatusCode, resp.StatusCode)
+			}
+			defer func() {
+				_ = resp.Body.Close()
+			}()
+		})
+	}
+}
+
 func TestEnableEmulationVersion(t *testing.T) {
 	server := kubeapiservertesting.StartTestServerOrDie(t,
 		&kubeapiservertesting.TestServerInstanceOptions{BinaryVersion: "1.32"},

test/integration/client/client_test.go

@@ -48,6 +48,7 @@ import (
 	clientset "k8s.io/client-go/kubernetes"
 	"k8s.io/utils/pointer"
 
+	utilversion "k8s.io/apiserver/pkg/util/version"
 	"k8s.io/component-base/version"
 	kubeapiservertesting "k8s.io/kubernetes/cmd/kube-apiserver/app/testing"
 	"k8s.io/kubernetes/pkg/api/legacyscheme"
@@ -65,7 +66,12 @@ func TestClient(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	if e, a := version.Get(), *info; !reflect.DeepEqual(e, a) {
+	expectedInfo := version.Get()
+	kubeVersion := utilversion.DefaultKubeEffectiveVersion().BinaryVersion()
+	expectedInfo.Major = fmt.Sprintf("%d", kubeVersion.Major())
+	expectedInfo.Minor = fmt.Sprintf("%d", kubeVersion.Minor())
+
+	if e, a := expectedInfo, *info; !reflect.DeepEqual(e, a) {
 		t.Errorf("expected %#v, got %#v", e, a)
 	}
 

test/integration/etcd/crd_overlap_storage_test.go

@@ -32,11 +32,9 @@ import (
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/wait"
-	utilversion "k8s.io/apiserver/pkg/util/version"
 	"k8s.io/client-go/dynamic"
 	apiregistrationv1 "k8s.io/kube-aggregator/pkg/apis/apiregistration/v1"
 	apiregistrationclient "k8s.io/kube-aggregator/pkg/client/clientset_generated/clientset/typed/apiregistration/v1"
-	"k8s.io/kubernetes/cmd/kube-apiserver/app/options"
 )
 
 // TestOverlappingBuiltInResources ensures the list of group-resources the custom resource finalizer should skip is up to date
@@ -71,9 +69,7 @@ func TestOverlappingBuiltInResources(t *testing.T) {
 
 // TestOverlappingCustomResourceAPIService ensures creating and deleting a custom resource overlapping with APIServices does not destroy APIService data
 func TestOverlappingCustomResourceAPIService(t *testing.T) {
-	apiServer := StartRealAPIServerOrDie(t, func(opts *options.ServerRunOptions) {
+	apiServer := StartRealAPIServerOrDie(t)
-		opts.GenericServerRunOptions.EffectiveVersion = utilversion.NewEffectiveVersion("1.30")
-	})
 	defer apiServer.Cleanup()
 
 	apiServiceClient, err := apiregistrationclient.NewForConfig(apiServer.Config)
@@ -235,9 +231,7 @@ func TestOverlappingCustomResourceAPIService(t *testing.T) {
 
 // TestOverlappingCustomResourceCustomResourceDefinition ensures creating and deleting a custom resource overlapping with CustomResourceDefinition does not destroy CustomResourceDefinition data
 func TestOverlappingCustomResourceCustomResourceDefinition(t *testing.T) {
-	apiServer := StartRealAPIServerOrDie(t, func(opts *options.ServerRunOptions) {
+	apiServer := StartRealAPIServerOrDie(t)
-		opts.GenericServerRunOptions.EffectiveVersion = utilversion.NewEffectiveVersion("1.30")
-	})
 	defer apiServer.Cleanup()
 
 	crdClient, err := crdclient.NewForConfig(apiServer.Config)

test/integration/etcd/etcd_cross_group_test.go

@@ -39,7 +39,7 @@ import (
 func TestCrossGroupStorage(t *testing.T) {
 	apiServer := StartRealAPIServerOrDie(t, func(opts *options.ServerRunOptions) {
 		// force enable all resources so we can check storage.
-		opts.GenericServerRunOptions.EffectiveVersion = utilversion.NewEffectiveVersion("1.30")
+		opts.GenericServerRunOptions.EffectiveVersion = utilversion.NewEffectiveVersion("0.0")
 	})
 	defer apiServer.Cleanup()
 

test/integration/examples/apiserver_test.go

@@ -226,6 +226,18 @@ func TestAPIServiceWaitOnStart(t *testing.T) {
 }
 
 func TestAggregatedAPIServer(t *testing.T) {
+	t.Run("WithoutWardleFeatureGateAtV1.2", func(t *testing.T) {
+		testAggregatedAPIServer(t, false, "1.2")
+	})
+	t.Run("WithoutWardleFeatureGateAtV1.1", func(t *testing.T) {
+		testAggregatedAPIServer(t, false, "1.1")
+	})
+	t.Run("WithWardleFeatureGateAtV1.1", func(t *testing.T) {
+		testAggregatedAPIServer(t, true, "1.1")
+	})
+}
+
+func testAggregatedAPIServer(t *testing.T, enableWardleFeatureGate bool, emulationVersion string) {
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Minute)
 	t.Cleanup(cancel)
 
@@ -240,7 +252,7 @@ func TestAggregatedAPIServer(t *testing.T) {
 	// endpoints cannot have loopback IPs so we need to override the resolver itself
 	t.Cleanup(app.SetServiceResolverForTests(staticURLServiceResolver(fmt.Sprintf("https://127.0.0.1:%d", wardlePort))))
 
-	testServer := kastesting.StartTestServerOrDie(t, &kastesting.TestServerInstanceOptions{EnableCertAuth: true}, nil, framework.SharedEtcd())
+	testServer := kastesting.StartTestServerOrDie(t, &kastesting.TestServerInstanceOptions{EnableCertAuth: true, BinaryVersion: "1.32"}, nil, framework.SharedEtcd())
 	defer testServer.TearDownFn()
 	kubeClientConfig := rest.CopyConfig(testServer.ClientConfig)
 	// force json because everything speaks it
@@ -286,15 +298,18 @@ func TestAggregatedAPIServer(t *testing.T) {
 		o.RecommendedOptions.SecureServing.Listener = listener
 		o.RecommendedOptions.SecureServing.BindAddress = netutils.ParseIPSloppy("127.0.0.1")
 		wardleCmd := sampleserver.NewCommandStartWardleServer(ctx, o)
-		wardleCmd.SetArgs([]string{
+		args := []string{
 			"--authentication-kubeconfig", wardleToKASKubeConfigFile,
 			"--authorization-kubeconfig", wardleToKASKubeConfigFile,
 			"--etcd-servers", framework.GetEtcdURL(),
 			"--cert-dir", wardleCertDir,
 			"--kubeconfig", wardleToKASKubeConfigFile,
-			"--emulated-version", "wardle=1.1",
+			"--emulated-version", fmt.Sprintf("wardle=%s", emulationVersion),
-			"--feature-gates", "wardle:BanFlunder=true",
+		}
-		})
+		if enableWardleFeatureGate {
+			args = append(args, "--feature-gates", "wardle:BanFlunder=true")
+		}
+		wardleCmd.SetArgs(args)
 		if err := wardleCmd.Execute(); err != nil {
 			t.Error(err)
 		}
@@ -393,6 +408,8 @@ func TestAggregatedAPIServer(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	// clean up data after test is done
+	defer wardleClient.Fischers().Delete(ctx, "panda", metav1.DeleteOptions{})
 	fischersList, err := wardleClient.Fischers().List(ctx, metav1.ListOptions{})
 	if err != nil {
 		t.Fatal(err)
@@ -409,8 +426,16 @@ func TestAggregatedAPIServer(t *testing.T) {
 			Name: "badname",
 		},
 	}, metav1.CreateOptions{})
-	if err == nil {
+	banFlunder := enableWardleFeatureGate || emulationVersion == "1.2"
-		t.Fatal("expect flunder:badname not admitted")
+	if banFlunder && err == nil {
+		t.Fatal("expect flunder:badname not admitted when wardle feature gates are specified")
+	}
+	if !banFlunder {
+		if err != nil {
+			t.Fatal("expect flunder:badname admitted when wardle feature gates are not specified")
+		} else {
+			defer wardleClient.Flunders(metav1.NamespaceSystem).Delete(ctx, "badname", metav1.DeleteOptions{})
+		}
 	}
 	_, err = wardleClient.Flunders(metav1.NamespaceSystem).Create(ctx, &wardlev1alpha1.Flunder{
 		ObjectMeta: metav1.ObjectMeta{
@@ -420,12 +445,17 @@ func TestAggregatedAPIServer(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	defer wardleClient.Flunders(metav1.NamespaceSystem).Delete(ctx, "panda", metav1.DeleteOptions{})
 	flunderList, err := wardleClient.Flunders(metav1.NamespaceSystem).List(ctx, metav1.ListOptions{})
 	if err != nil {
 		t.Fatal(err)
 	}
-	if len(flunderList.Items) != 1 {
+	expectedFlunderCount := 2
-		t.Errorf("expected one flunder: %#v", flunderList.Items)
+	if banFlunder {
+		expectedFlunderCount = 1
+	}
+	if len(flunderList.Items) != expectedFlunderCount {
+		t.Errorf("expected %d flunder: %#v", expectedFlunderCount, flunderList.Items)
 	}
 	if len(flunderList.ResourceVersion) == 0 {
 		t.Error("expected non-empty resource version for flunder list")

test/integration/servicecidr/allocator_test.go

@@ -29,7 +29,6 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/wait"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
-	utilversion "k8s.io/apiserver/pkg/util/version"
 	"k8s.io/client-go/kubernetes"
 	featuregatetesting "k8s.io/component-base/featuregate/testing"
 	"k8s.io/kubernetes/cmd/kube-apiserver/app/options"
@@ -123,7 +122,6 @@ func TestServiceAllocIPAddress(t *testing.T) {
 		ModifyServerRunOptions: func(opts *options.ServerRunOptions) {
 			opts.ServiceClusterIPRanges = serviceCIDR
 			opts.GenericServerRunOptions.AdvertiseAddress = netutils.ParseIPSloppy("2001:db8::10")
-			opts.GenericServerRunOptions.EffectiveVersion = utilversion.NewEffectiveVersion("1.31")
 			opts.APIEnablement.RuntimeConfig.Set("networking.k8s.io/v1alpha1=true")
 		},
 	})