/*
Copyright 2014 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package controlplane

import (
	"fmt"
	"net"
	"net/http"
	"os"
	"reflect"
	"strconv"
	"time"

	admissionregistrationv1 "k8s.io/api/admissionregistration/v1"
	admissionregistrationv1alpha1 "k8s.io/api/admissionregistration/v1alpha1"
	apiserverinternalv1alpha1 "k8s.io/api/apiserverinternal/v1alpha1"
	appsv1 "k8s.io/api/apps/v1"
	authenticationv1 "k8s.io/api/authentication/v1"
	authenticationv1alpha1 "k8s.io/api/authentication/v1alpha1"
	authenticationv1beta1 "k8s.io/api/authentication/v1beta1"
	authorizationapiv1 "k8s.io/api/authorization/v1"
	autoscalingapiv1 "k8s.io/api/autoscaling/v1"
	autoscalingapiv2 "k8s.io/api/autoscaling/v2"
	autoscalingapiv2beta1 "k8s.io/api/autoscaling/v2beta1"
	autoscalingapiv2beta2 "k8s.io/api/autoscaling/v2beta2"
	batchapiv1 "k8s.io/api/batch/v1"
	batchapiv1beta1 "k8s.io/api/batch/v1beta1"
	certificatesapiv1 "k8s.io/api/certificates/v1"
	certificatesv1alpha1 "k8s.io/api/certificates/v1alpha1"
	coordinationapiv1 "k8s.io/api/coordination/v1"
	apiv1 "k8s.io/api/core/v1"
	discoveryv1 "k8s.io/api/discovery/v1"
	discoveryv1beta1 "k8s.io/api/discovery/v1beta1"
	eventsv1 "k8s.io/api/events/v1"
	eventsv1beta1 "k8s.io/api/events/v1beta1"
	flowcontrolv1alpha1 "k8s.io/api/flowcontrol/v1alpha1"
	networkingapiv1 "k8s.io/api/networking/v1"
	networkingapiv1alpha1 "k8s.io/api/networking/v1alpha1"
	nodev1 "k8s.io/api/node/v1"
	nodev1beta1 "k8s.io/api/node/v1beta1"
	policyapiv1 "k8s.io/api/policy/v1"
	policyapiv1beta1 "k8s.io/api/policy/v1beta1"
	rbacv1 "k8s.io/api/rbac/v1"
	resourcev1alpha2 "k8s.io/api/resource/v1alpha2"
	schedulingapiv1 "k8s.io/api/scheduling/v1"
	storageapiv1 "k8s.io/api/storage/v1"
	storageapiv1alpha1 "k8s.io/api/storage/v1alpha1"
	storageapiv1beta1 "k8s.io/api/storage/v1beta1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime/schema"
	utilnet "k8s.io/apimachinery/pkg/util/net"
	"k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/uuid"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/apiserver/pkg/endpoints/discovery"
	apiserverfeatures "k8s.io/apiserver/pkg/features"
	"k8s.io/apiserver/pkg/registry/generic"
	genericapiserver "k8s.io/apiserver/pkg/server"
	"k8s.io/apiserver/pkg/server/dynamiccertificates"
	serverstorage "k8s.io/apiserver/pkg/server/storage"
	utilfeature "k8s.io/apiserver/pkg/util/feature"
	"k8s.io/client-go/informers"
	"k8s.io/client-go/kubernetes"
	corev1client "k8s.io/client-go/kubernetes/typed/core/v1"
	discoveryclient "k8s.io/client-go/kubernetes/typed/discovery/v1"
	"k8s.io/component-helpers/apimachinery/lease"
	"k8s.io/klog/v2"
	api "k8s.io/kubernetes/pkg/apis/core"
	flowcontrolv1beta1 "k8s.io/kubernetes/pkg/apis/flowcontrol/v1beta1"
	flowcontrolv1beta2 "k8s.io/kubernetes/pkg/apis/flowcontrol/v1beta2"
	flowcontrolv1beta3 "k8s.io/kubernetes/pkg/apis/flowcontrol/v1beta3"
	"k8s.io/kubernetes/pkg/controlplane/controller/apiserverleasegc"
	"k8s.io/kubernetes/pkg/controlplane/controller/clusterauthenticationtrust"
	"k8s.io/kubernetes/pkg/controlplane/controller/legacytokentracking"
	"k8s.io/kubernetes/pkg/controlplane/controller/systemnamespaces"
	"k8s.io/kubernetes/pkg/controlplane/reconcilers"
	kubeoptions "k8s.io/kubernetes/pkg/kubeapiserver/options"
	kubeletclient "k8s.io/kubernetes/pkg/kubelet/client"
	"k8s.io/kubernetes/pkg/routes"
	"k8s.io/kubernetes/pkg/serviceaccount"
	"k8s.io/utils/clock"

	// RESTStorage installers
	admissionregistrationrest "k8s.io/kubernetes/pkg/registry/admissionregistration/rest"
	apiserverinternalrest "k8s.io/kubernetes/pkg/registry/apiserverinternal/rest"
	appsrest "k8s.io/kubernetes/pkg/registry/apps/rest"
	authenticationrest "k8s.io/kubernetes/pkg/registry/authentication/rest"
	authorizationrest "k8s.io/kubernetes/pkg/registry/authorization/rest"
	autoscalingrest "k8s.io/kubernetes/pkg/registry/autoscaling/rest"
	batchrest "k8s.io/kubernetes/pkg/registry/batch/rest"
	certificatesrest "k8s.io/kubernetes/pkg/registry/certificates/rest"
	coordinationrest "k8s.io/kubernetes/pkg/registry/coordination/rest"
	corerest "k8s.io/kubernetes/pkg/registry/core/rest"
	discoveryrest "k8s.io/kubernetes/pkg/registry/discovery/rest"
	eventsrest "k8s.io/kubernetes/pkg/registry/events/rest"
	flowcontrolrest "k8s.io/kubernetes/pkg/registry/flowcontrol/rest"
	networkingrest "k8s.io/kubernetes/pkg/registry/networking/rest"
	noderest "k8s.io/kubernetes/pkg/registry/node/rest"
	policyrest "k8s.io/kubernetes/pkg/registry/policy/rest"
	rbacrest "k8s.io/kubernetes/pkg/registry/rbac/rest"
	resourcerest "k8s.io/kubernetes/pkg/registry/resource/rest"
	schedulingrest "k8s.io/kubernetes/pkg/registry/scheduling/rest"
	storagerest "k8s.io/kubernetes/pkg/registry/storage/rest"
)

const (
	// DefaultEndpointReconcilerInterval is the default amount of time for how often the endpoints for
	// the kubernetes Service are reconciled.
	DefaultEndpointReconcilerInterval = 10 * time.Second
	// DefaultEndpointReconcilerTTL is the default TTL timeout for the storage layer
	DefaultEndpointReconcilerTTL = 15 * time.Second
	// IdentityLeaseComponentLabelKey is used to apply a component label to identity lease objects, indicating:
	//   1. the lease is an identity lease (different from leader election leases)
	//   2. which component owns this lease
	IdentityLeaseComponentLabelKey = "apiserver.kubernetes.io/identity"
	// KubeAPIServer defines variable used internally when referring to kube-apiserver component
	KubeAPIServer = "kube-apiserver"
	// DeprecatedKubeAPIServerIdentityLeaseLabelSelector selects kube-apiserver identity leases
	DeprecatedKubeAPIServerIdentityLeaseLabelSelector = "k8s.io/component=kube-apiserver"
	// KubeAPIServerIdentityLeaseLabelSelector selects kube-apiserver identity leases
	KubeAPIServerIdentityLeaseLabelSelector = IdentityLeaseComponentLabelKey + "=" + KubeAPIServer
	// repairLoopInterval defines the interval used to run the Services ClusterIP and NodePort repair loops
	repairLoopInterval = 3 * time.Minute
)

var (
	// IdentityLeaseGCPeriod is the interval which the lease GC controller checks for expired leases
	// IdentityLeaseGCPeriod is exposed so integration tests can tune this value.
	IdentityLeaseGCPeriod = 3600 * time.Second
	// IdentityLeaseDurationSeconds is the duration of kube-apiserver lease in seconds
	// IdentityLeaseDurationSeconds is exposed so integration tests can tune this value.
	IdentityLeaseDurationSeconds = 3600
	// IdentityLeaseRenewIntervalSeconds is the interval of kube-apiserver renewing its lease in seconds
	// IdentityLeaseRenewIntervalSeconds is exposed so integration tests can tune this value.
	IdentityLeaseRenewIntervalPeriod = 10 * time.Second
)

// ExtraConfig defines extra configuration for the master
type ExtraConfig struct {
	ClusterAuthenticationInfo clusterauthenticationtrust.ClusterAuthenticationInfo

	APIResourceConfigSource  serverstorage.APIResourceConfigSource
	StorageFactory           serverstorage.StorageFactory
	EndpointReconcilerConfig EndpointReconcilerConfig
	EventTTL                 time.Duration
	KubeletClientConfig      kubeletclient.KubeletClientConfig

	EnableLogsSupport bool
	ProxyTransport    *http.Transport

	// Values to build the IP addresses used by discovery
	// The range of IPs to be assigned to services with type=ClusterIP or greater
	ServiceIPRange net.IPNet
	// The IP address for the GenericAPIServer service (must be inside ServiceIPRange)
	APIServerServiceIP net.IP

	// dual stack services, the range represents an alternative IP range for service IP
	// must be of different family than primary (ServiceIPRange)
	SecondaryServiceIPRange net.IPNet
	// the secondary IP address the GenericAPIServer service (must be inside SecondaryServiceIPRange)
	SecondaryAPIServerServiceIP net.IP

	// Port for the apiserver service.
	APIServerServicePort int

	// TODO, we can probably group service related items into a substruct to make it easier to configure
	// the API server items and `Extra*` fields likely fit nicely together.

	// The range of ports to be assigned to services with type=NodePort or greater
	ServiceNodePortRange utilnet.PortRange
	// If non-zero, the "kubernetes" services uses this port as NodePort.
	KubernetesServiceNodePort int

	// Number of masters running; all masters must be started with the
	// same value for this field. (Numbers > 1 currently untested.)
	MasterCount int

	// MasterEndpointReconcileTTL sets the time to live in seconds of an
	// endpoint record recorded by each master. The endpoints are checked at an
	// interval that is 2/3 of this value and this value defaults to 15s if
	// unset. In very large clusters, this value may be increased to reduce the
	// possibility that the master endpoint record expires (due to other load
	// on the etcd server) and causes masters to drop in and out of the
	// kubernetes service record. It is not recommended to set this value below
	// 15s.
	MasterEndpointReconcileTTL time.Duration

	// Selects which reconciler to use
	EndpointReconcilerType reconcilers.Type

	ServiceAccountIssuer        serviceaccount.TokenGenerator
	ServiceAccountMaxExpiration time.Duration
	ExtendExpiration            bool

	// ServiceAccountIssuerDiscovery
	ServiceAccountIssuerURL  string
	ServiceAccountJWKSURI    string
	ServiceAccountPublicKeys []interface{}

	VersionedInformers informers.SharedInformerFactory

	// RepairServicesInterval interval used by the repair loops for
	// the Services NodePort and ClusterIP resources
	RepairServicesInterval time.Duration
}

// Config defines configuration for the master
type Config struct {
	GenericConfig *genericapiserver.Config
	ExtraConfig   ExtraConfig
}

type completedConfig struct {
	GenericConfig genericapiserver.CompletedConfig
	ExtraConfig   *ExtraConfig
}

// CompletedConfig embeds a private pointer that cannot be instantiated outside of this package
type CompletedConfig struct {
	*completedConfig
}

// EndpointReconcilerConfig holds the endpoint reconciler and endpoint reconciliation interval to be
// used by the master.
type EndpointReconcilerConfig struct {
	Reconciler reconcilers.EndpointReconciler
	Interval   time.Duration
}

// Instance contains state for a Kubernetes cluster api server instance.
type Instance struct {
	GenericAPIServer *genericapiserver.GenericAPIServer

	ClusterAuthenticationInfo clusterauthenticationtrust.ClusterAuthenticationInfo
}

func (c *Config) createMasterCountReconciler() reconcilers.EndpointReconciler {
	endpointClient := corev1client.NewForConfigOrDie(c.GenericConfig.LoopbackClientConfig)
	endpointSliceClient := discoveryclient.NewForConfigOrDie(c.GenericConfig.LoopbackClientConfig)
	endpointsAdapter := reconcilers.NewEndpointsAdapter(endpointClient, endpointSliceClient)

	return reconcilers.NewMasterCountEndpointReconciler(c.ExtraConfig.MasterCount, endpointsAdapter)
}

func (c *Config) createNoneReconciler() reconcilers.EndpointReconciler {
	return reconcilers.NewNoneEndpointReconciler()
}

func (c *Config) createLeaseReconciler() reconcilers.EndpointReconciler {
	endpointClient := corev1client.NewForConfigOrDie(c.GenericConfig.LoopbackClientConfig)
	endpointSliceClient := discoveryclient.NewForConfigOrDie(c.GenericConfig.LoopbackClientConfig)
	endpointsAdapter := reconcilers.NewEndpointsAdapter(endpointClient, endpointSliceClient)

	ttl := c.ExtraConfig.MasterEndpointReconcileTTL
	config, err := c.ExtraConfig.StorageFactory.NewConfig(api.Resource("apiServerIPInfo"))
	if err != nil {
		klog.Fatalf("Error creating storage factory config: %v", err)
	}
	masterLeases, err := reconcilers.NewLeases(config, "/masterleases/", ttl)
	if err != nil {
		klog.Fatalf("Error creating leases: %v", err)
	}

	return reconcilers.NewLeaseEndpointReconciler(endpointsAdapter, masterLeases)
}

func (c *Config) createEndpointReconciler() reconcilers.EndpointReconciler {
	klog.Infof("Using reconciler: %v", c.ExtraConfig.EndpointReconcilerType)
	switch c.ExtraConfig.EndpointReconcilerType {
	// there are numerous test dependencies that depend on a default controller
	case reconcilers.MasterCountReconcilerType:
		return c.createMasterCountReconciler()
	case "", reconcilers.LeaseEndpointReconcilerType:
		return c.createLeaseReconciler()
	case reconcilers.NoneEndpointReconcilerType:
		return c.createNoneReconciler()
	default:
		klog.Fatalf("Reconciler not implemented: %v", c.ExtraConfig.EndpointReconcilerType)
	}
	return nil
}

// Complete fills in any fields not set that are required to have valid data. It's mutating the receiver.
func (c *Config) Complete() CompletedConfig {
	cfg := completedConfig{
		c.GenericConfig.Complete(c.ExtraConfig.VersionedInformers),
		&c.ExtraConfig,
	}

	serviceIPRange, apiServerServiceIP, err := ServiceIPRange(cfg.ExtraConfig.ServiceIPRange)
	if err != nil {
		klog.Fatalf("Error determining service IP ranges: %v", err)
	}
	if cfg.ExtraConfig.ServiceIPRange.IP == nil {
		cfg.ExtraConfig.ServiceIPRange = serviceIPRange
	}
	if cfg.ExtraConfig.APIServerServiceIP == nil {
		cfg.ExtraConfig.APIServerServiceIP = apiServerServiceIP
	}

	discoveryAddresses := discovery.DefaultAddresses{DefaultAddress: cfg.GenericConfig.ExternalAddress}
	discoveryAddresses.CIDRRules = append(discoveryAddresses.CIDRRules,
		discovery.CIDRRule{IPRange: cfg.ExtraConfig.ServiceIPRange, Address: net.JoinHostPort(cfg.ExtraConfig.APIServerServiceIP.String(), strconv.Itoa(cfg.ExtraConfig.APIServerServicePort))})
	cfg.GenericConfig.DiscoveryAddresses = discoveryAddresses

	if cfg.ExtraConfig.ServiceNodePortRange.Size == 0 {
		// TODO: Currently no way to specify an empty range (do we need to allow this?)
		// We should probably allow this for clouds that don't require NodePort to do load-balancing (GCE)
		// but then that breaks the strict nestedness of ServiceType.
		// Review post-v1
		cfg.ExtraConfig.ServiceNodePortRange = kubeoptions.DefaultServiceNodePortRange
		klog.Infof("Node port range unspecified. Defaulting to %v.", cfg.ExtraConfig.ServiceNodePortRange)
	}

	if cfg.ExtraConfig.EndpointReconcilerConfig.Interval == 0 {
		cfg.ExtraConfig.EndpointReconcilerConfig.Interval = DefaultEndpointReconcilerInterval
	}

	if cfg.ExtraConfig.MasterEndpointReconcileTTL == 0 {
		cfg.ExtraConfig.MasterEndpointReconcileTTL = DefaultEndpointReconcilerTTL
	}

	if cfg.ExtraConfig.EndpointReconcilerConfig.Reconciler == nil {
		cfg.ExtraConfig.EndpointReconcilerConfig.Reconciler = c.createEndpointReconciler()
	}

	if cfg.ExtraConfig.RepairServicesInterval == 0 {
		cfg.ExtraConfig.RepairServicesInterval = repairLoopInterval
	}

	return CompletedConfig{&cfg}
}

// New returns a new instance of Master from the given config.
// Certain config fields will be set to a default value if unset.
// Certain config fields must be specified, including:
// KubeletClientConfig
func (c completedConfig) New(delegationTarget genericapiserver.DelegationTarget) (*Instance, error) {
	if reflect.DeepEqual(c.ExtraConfig.KubeletClientConfig, kubeletclient.KubeletClientConfig{}) {
		return nil, fmt.Errorf("Master.New() called with empty config.KubeletClientConfig")
	}

	s, err := c.GenericConfig.New("kube-apiserver", delegationTarget)
	if err != nil {
		return nil, err
	}

	if c.ExtraConfig.EnableLogsSupport {
		routes.Logs{}.Install(s.Handler.GoRestfulContainer)
	}

	// Metadata and keys are expected to only change across restarts at present,
	// so we just marshal immediately and serve the cached JSON bytes.
	md, err := serviceaccount.NewOpenIDMetadata(
		c.ExtraConfig.ServiceAccountIssuerURL,
		c.ExtraConfig.ServiceAccountJWKSURI,
		c.GenericConfig.ExternalAddress,
		c.ExtraConfig.ServiceAccountPublicKeys,
	)
	if err != nil {
		// If there was an error, skip installing the endpoints and log the
		// error, but continue on. We don't return the error because the
		// metadata responses require additional, backwards incompatible
		// validation of command-line options.
		msg := fmt.Sprintf("Could not construct pre-rendered responses for"+
			" ServiceAccountIssuerDiscovery endpoints. Endpoints will not be"+
			" enabled. Error: %v", err)
		if c.ExtraConfig.ServiceAccountIssuerURL != "" {
			// The user likely expects this feature to be enabled if issuer URL is
			// set and the feature gate is enabled. In the future, if there is no
			// longer a feature gate and issuer URL is not set, the user may not
			// expect this feature to be enabled. We log the former case as an Error
			// and the latter case as an Info.
			klog.Error(msg)
		} else {
			klog.Info(msg)
		}
	} else {
		routes.NewOpenIDMetadataServer(md.ConfigJSON, md.PublicKeysetJSON).
			Install(s.Handler.GoRestfulContainer)
	}

	m := &Instance{
		GenericAPIServer:          s,
		ClusterAuthenticationInfo: c.ExtraConfig.ClusterAuthenticationInfo,
	}

	// install legacy rest storage

	if err := m.InstallLegacyAPI(&c, c.GenericConfig.RESTOptionsGetter); err != nil {
		return nil, err
	}

	clientset, err := kubernetes.NewForConfig(c.GenericConfig.LoopbackClientConfig)
	if err != nil {
		return nil, err
	}

	// TODO: update to a version that caches success but will recheck on failure, unlike memcache discovery
	discoveryClientForAdmissionRegistration := clientset.Discovery()

	// The order here is preserved in discovery.
	// If resources with identical names exist in more than one of these groups (e.g. "deployments.apps"" and "deployments.extensions"),
	// the order of this list determines which group an unqualified resource name (e.g. "deployments") should prefer.
	// This priority order is used for local discovery, but it ends up aggregated in `k8s.io/kubernetes/cmd/kube-apiserver/app/aggregator.go
	// with specific priorities.
	// TODO: describe the priority all the way down in the RESTStorageProviders and plumb it back through the various discovery
	// handlers that we have.
	restStorageProviders := []RESTStorageProvider{
		apiserverinternalrest.StorageProvider{},
		authenticationrest.RESTStorageProvider{Authenticator: c.GenericConfig.Authentication.Authenticator, APIAudiences: c.GenericConfig.Authentication.APIAudiences},
		authorizationrest.RESTStorageProvider{Authorizer: c.GenericConfig.Authorization.Authorizer, RuleResolver: c.GenericConfig.RuleResolver},
		autoscalingrest.RESTStorageProvider{},
		batchrest.RESTStorageProvider{},
		certificatesrest.RESTStorageProvider{},
		coordinationrest.RESTStorageProvider{},
		discoveryrest.StorageProvider{},
		networkingrest.RESTStorageProvider{},
		noderest.RESTStorageProvider{},
		policyrest.RESTStorageProvider{},
		rbacrest.RESTStorageProvider{Authorizer: c.GenericConfig.Authorization.Authorizer},
		schedulingrest.RESTStorageProvider{},
		storagerest.RESTStorageProvider{},
		flowcontrolrest.RESTStorageProvider{InformerFactory: c.GenericConfig.SharedInformerFactory},
		// keep apps after extensions so legacy clients resolve the extensions versions of shared resource names.
		// See https://github.com/kubernetes/kubernetes/issues/42392
		appsrest.StorageProvider{},
		admissionregistrationrest.RESTStorageProvider{Authorizer: c.GenericConfig.Authorization.Authorizer, DiscoveryClient: discoveryClientForAdmissionRegistration},
		eventsrest.RESTStorageProvider{TTL: c.ExtraConfig.EventTTL},
		resourcerest.RESTStorageProvider{},
	}
	if err := m.InstallAPIs(c.ExtraConfig.APIResourceConfigSource, c.GenericConfig.RESTOptionsGetter, restStorageProviders...); err != nil {
		return nil, err
	}

	m.GenericAPIServer.AddPostStartHookOrDie("start-cluster-authentication-info-controller", func(hookContext genericapiserver.PostStartHookContext) error {
		kubeClient, err := kubernetes.NewForConfig(hookContext.LoopbackClientConfig)
		if err != nil {
			return err
		}
		controller := clusterauthenticationtrust.NewClusterAuthenticationTrustController(m.ClusterAuthenticationInfo, kubeClient)

		// generate a context  from stopCh. This is to avoid modifying files which are relying on apiserver
		// TODO: See if we can pass ctx to the current method
		ctx := wait.ContextForChannel(hookContext.StopCh)

		// prime values and start listeners
		if m.ClusterAuthenticationInfo.ClientCA != nil {
			m.ClusterAuthenticationInfo.ClientCA.AddListener(controller)
			if controller, ok := m.ClusterAuthenticationInfo.ClientCA.(dynamiccertificates.ControllerRunner); ok {
				// runonce to be sure that we have a value.
				if err := controller.RunOnce(ctx); err != nil {
					runtime.HandleError(err)
				}
				go controller.Run(ctx, 1)
			}
		}
		if m.ClusterAuthenticationInfo.RequestHeaderCA != nil {
			m.ClusterAuthenticationInfo.RequestHeaderCA.AddListener(controller)
			if controller, ok := m.ClusterAuthenticationInfo.RequestHeaderCA.(dynamiccertificates.ControllerRunner); ok {
				// runonce to be sure that we have a value.
				if err := controller.RunOnce(ctx); err != nil {
					runtime.HandleError(err)
				}
				go controller.Run(ctx, 1)
			}
		}

		go controller.Run(ctx, 1)
		return nil
	})

	if utilfeature.DefaultFeatureGate.Enabled(apiserverfeatures.APIServerIdentity) {
		m.GenericAPIServer.AddPostStartHookOrDie("start-kube-apiserver-identity-lease-controller", func(hookContext genericapiserver.PostStartHookContext) error {
			kubeClient, err := kubernetes.NewForConfig(hookContext.LoopbackClientConfig)
			if err != nil {
				return err
			}

			// generate a context  from stopCh. This is to avoid modifying files which are relying on apiserver
			// TODO: See if we can pass ctx to the current method
			ctx := wait.ContextForChannel(hookContext.StopCh)

			leaseName := m.GenericAPIServer.APIServerID
			holderIdentity := m.GenericAPIServer.APIServerID + "_" + string(uuid.NewUUID())

			controller := lease.NewController(
				clock.RealClock{},
				kubeClient,
				holderIdentity,
				int32(IdentityLeaseDurationSeconds),
				nil,
				IdentityLeaseRenewIntervalPeriod,
				leaseName,
				metav1.NamespaceSystem,
				// TODO: receive identity label value as a parameter when post start hook is moved to generic apiserver.
				labelAPIServerHeartbeatFunc(KubeAPIServer))
			go controller.Run(ctx)
			return nil
		})
		// Labels for apiserver idenitiy leases switched from k8s.io/component=kube-apiserver to apiserver.kubernetes.io/identity=kube-apiserver.
		// For compatibility, garbage collect leases with both labels for at least 1 release
		// TODO: remove in Kubernetes 1.28
		m.GenericAPIServer.AddPostStartHookOrDie("start-deprecated-kube-apiserver-identity-lease-garbage-collector", func(hookContext genericapiserver.PostStartHookContext) error {
			kubeClient, err := kubernetes.NewForConfig(hookContext.LoopbackClientConfig)
			if err != nil {
				return err
			}
			go apiserverleasegc.NewAPIServerLeaseGC(
				kubeClient,
				IdentityLeaseGCPeriod,
				metav1.NamespaceSystem,
				DeprecatedKubeAPIServerIdentityLeaseLabelSelector,
			).Run(hookContext.StopCh)
			return nil
		})
		// TODO: move this into generic apiserver and make the lease identity value configurable
		m.GenericAPIServer.AddPostStartHookOrDie("start-kube-apiserver-identity-lease-garbage-collector", func(hookContext genericapiserver.PostStartHookContext) error {
			kubeClient, err := kubernetes.NewForConfig(hookContext.LoopbackClientConfig)
			if err != nil {
				return err
			}
			go apiserverleasegc.NewAPIServerLeaseGC(
				kubeClient,
				IdentityLeaseGCPeriod,
				metav1.NamespaceSystem,
				KubeAPIServerIdentityLeaseLabelSelector,
			).Run(hookContext.StopCh)
			return nil
		})
	}

	m.GenericAPIServer.AddPostStartHookOrDie("start-legacy-token-tracking-controller", func(hookContext genericapiserver.PostStartHookContext) error {
		kubeClient, err := kubernetes.NewForConfig(hookContext.LoopbackClientConfig)
		if err != nil {
			return err
		}
		go legacytokentracking.NewController(kubeClient).Run(hookContext.StopCh)
		return nil
	})

	return m, nil
}

func labelAPIServerHeartbeatFunc(identity string) lease.ProcessLeaseFunc {
	return func(lease *coordinationapiv1.Lease) error {
		if lease.Labels == nil {
			lease.Labels = map[string]string{}
		}

		// This label indiciates the identity of the lease object.
		lease.Labels[IdentityLeaseComponentLabelKey] = identity

		hostname, err := os.Hostname()
		if err != nil {
			return err
		}

		// convenience label to easily map a lease object to a specific apiserver
		lease.Labels[apiv1.LabelHostname] = hostname
		return nil
	}
}

// InstallLegacyAPI will install the legacy APIs for the restStorageProviders if they are enabled.
func (m *Instance) InstallLegacyAPI(c *completedConfig, restOptionsGetter generic.RESTOptionsGetter) error {
	legacyRESTStorageProvider := corerest.LegacyRESTStorageProvider{
		StorageFactory:              c.ExtraConfig.StorageFactory,
		ProxyTransport:              c.ExtraConfig.ProxyTransport,
		KubeletClientConfig:         c.ExtraConfig.KubeletClientConfig,
		EventTTL:                    c.ExtraConfig.EventTTL,
		ServiceIPRange:              c.ExtraConfig.ServiceIPRange,
		SecondaryServiceIPRange:     c.ExtraConfig.SecondaryServiceIPRange,
		ServiceNodePortRange:        c.ExtraConfig.ServiceNodePortRange,
		LoopbackClientConfig:        c.GenericConfig.LoopbackClientConfig,
		ServiceAccountIssuer:        c.ExtraConfig.ServiceAccountIssuer,
		ExtendExpiration:            c.ExtraConfig.ExtendExpiration,
		ServiceAccountMaxExpiration: c.ExtraConfig.ServiceAccountMaxExpiration,
		APIAudiences:                c.GenericConfig.Authentication.APIAudiences,
		Informers:                   c.ExtraConfig.VersionedInformers,
	}
	legacyRESTStorage, apiGroupInfo, err := legacyRESTStorageProvider.NewLegacyRESTStorage(c.ExtraConfig.APIResourceConfigSource, restOptionsGetter)
	if err != nil {
		return fmt.Errorf("error building core storage: %v", err)
	}
	if len(apiGroupInfo.VersionedResourcesStorageMap) == 0 { // if all core storage is disabled, return.
		return nil
	}

	controllerName := "bootstrap-controller"
	client := kubernetes.NewForConfigOrDie(c.GenericConfig.LoopbackClientConfig)
	// Kubernetes clusters contains the following system namespaces:
	// kube-system, kube-node-lease, kube-public, default
	m.GenericAPIServer.AddPostStartHookOrDie("start-system-namespaces-controller", func(hookContext genericapiserver.PostStartHookContext) error {
		go systemnamespaces.NewController(client, c.ExtraConfig.VersionedInformers.Core().V1().Namespaces()).Run(hookContext.StopCh)
		return nil
	})

	bootstrapController, err := c.NewBootstrapController(legacyRESTStorage, client)
	if err != nil {
		return fmt.Errorf("error creating bootstrap controller: %v", err)
	}
	m.GenericAPIServer.AddPostStartHookOrDie(controllerName, bootstrapController.PostStartHook)
	m.GenericAPIServer.AddPreShutdownHookOrDie(controllerName, bootstrapController.PreShutdownHook)

	if err := m.GenericAPIServer.InstallLegacyAPIGroup(genericapiserver.DefaultLegacyAPIPrefix, &apiGroupInfo); err != nil {
		return fmt.Errorf("error in registering group versions: %v", err)
	}
	return nil
}

// RESTStorageProvider is a factory type for REST storage.
type RESTStorageProvider interface {
	GroupName() string
	NewRESTStorage(apiResourceConfigSource serverstorage.APIResourceConfigSource, restOptionsGetter generic.RESTOptionsGetter) (genericapiserver.APIGroupInfo, error)
}

// InstallAPIs will install the APIs for the restStorageProviders if they are enabled.
func (m *Instance) InstallAPIs(apiResourceConfigSource serverstorage.APIResourceConfigSource, restOptionsGetter generic.RESTOptionsGetter, restStorageProviders ...RESTStorageProvider) error {
	apiGroupsInfo := []*genericapiserver.APIGroupInfo{}

	// used later in the loop to filter the served resource by those that have expired.
	resourceExpirationEvaluator, err := genericapiserver.NewResourceExpirationEvaluator(*m.GenericAPIServer.Version)
	if err != nil {
		return err
	}

	for _, restStorageBuilder := range restStorageProviders {
		groupName := restStorageBuilder.GroupName()
		apiGroupInfo, err := restStorageBuilder.NewRESTStorage(apiResourceConfigSource, restOptionsGetter)
		if err != nil {
			return fmt.Errorf("problem initializing API group %q : %v", groupName, err)
		}
		if len(apiGroupInfo.VersionedResourcesStorageMap) == 0 {
			// If we have no storage for any resource configured, this API group is effectively disabled.
			// This can happen when an entire API group, version, or development-stage (alpha, beta, GA) is disabled.
			klog.Infof("API group %q is not enabled, skipping.", groupName)
			continue
		}

		// Remove resources that serving kinds that are removed.
		// We do this here so that we don't accidentally serve versions without resources or openapi information that for kinds we don't serve.
		// This is a spot above the construction of individual storage handlers so that no sig accidentally forgets to check.
		resourceExpirationEvaluator.RemoveDeletedKinds(groupName, apiGroupInfo.Scheme, apiGroupInfo.VersionedResourcesStorageMap)
		if len(apiGroupInfo.VersionedResourcesStorageMap) == 0 {
			klog.V(1).Infof("Removing API group %v because it is time to stop serving it because it has no versions per APILifecycle.", groupName)
			continue
		}

		klog.V(1).Infof("Enabling API group %q.", groupName)

		if postHookProvider, ok := restStorageBuilder.(genericapiserver.PostStartHookProvider); ok {
			name, hook, err := postHookProvider.PostStartHook()
			if err != nil {
				klog.Fatalf("Error building PostStartHook: %v", err)
			}
			m.GenericAPIServer.AddPostStartHookOrDie(name, hook)
		}

		apiGroupsInfo = append(apiGroupsInfo, &apiGroupInfo)
	}

	if err := m.GenericAPIServer.InstallAPIGroups(apiGroupsInfo...); err != nil {
		return fmt.Errorf("error in registering group versions: %v", err)
	}
	return nil
}

var (
	// stableAPIGroupVersionsEnabledByDefault is a list of our stable versions.
	stableAPIGroupVersionsEnabledByDefault = []schema.GroupVersion{
		admissionregistrationv1.SchemeGroupVersion,
		apiv1.SchemeGroupVersion,
		appsv1.SchemeGroupVersion,
		authenticationv1.SchemeGroupVersion,
		authorizationapiv1.SchemeGroupVersion,
		autoscalingapiv1.SchemeGroupVersion,
		autoscalingapiv2.SchemeGroupVersion,
		batchapiv1.SchemeGroupVersion,
		certificatesapiv1.SchemeGroupVersion,
		coordinationapiv1.SchemeGroupVersion,
		discoveryv1.SchemeGroupVersion,
		eventsv1.SchemeGroupVersion,
		networkingapiv1.SchemeGroupVersion,
		nodev1.SchemeGroupVersion,
		policyapiv1.SchemeGroupVersion,
		rbacv1.SchemeGroupVersion,
		storageapiv1.SchemeGroupVersion,
		schedulingapiv1.SchemeGroupVersion,
	}

	// legacyBetaEnabledByDefaultResources is the list of beta resources we enable.  You may only add to this list
	// if your resource is already enabled by default in a beta level we still serve AND there is no stable API for it.
	// see https://github.com/kubernetes/enhancements/tree/master/keps/sig-architecture/3136-beta-apis-off-by-default
	// for more details.
	legacyBetaEnabledByDefaultResources = []schema.GroupVersionResource{
		flowcontrolv1beta2.SchemeGroupVersion.WithResource("flowschemas"),                 // remove in 1.29
		flowcontrolv1beta2.SchemeGroupVersion.WithResource("prioritylevelconfigurations"), // remove in 1.29
		flowcontrolv1beta3.SchemeGroupVersion.WithResource("flowschemas"),                 // deprecate in 1.29, remove in 1.32
		flowcontrolv1beta3.SchemeGroupVersion.WithResource("prioritylevelconfigurations"), // deprecate in 1.29, remove in 1.32
	}
	// betaAPIGroupVersionsDisabledByDefault is for all future beta groupVersions.
	betaAPIGroupVersionsDisabledByDefault = []schema.GroupVersion{
		authenticationv1beta1.SchemeGroupVersion,
		autoscalingapiv2beta1.SchemeGroupVersion,
		autoscalingapiv2beta2.SchemeGroupVersion,
		batchapiv1beta1.SchemeGroupVersion,
		discoveryv1beta1.SchemeGroupVersion,
		eventsv1beta1.SchemeGroupVersion,
		nodev1beta1.SchemeGroupVersion, // remove in 1.26
		policyapiv1beta1.SchemeGroupVersion,
		storageapiv1beta1.SchemeGroupVersion,
		flowcontrolv1beta1.SchemeGroupVersion,
		flowcontrolv1beta2.SchemeGroupVersion,
		flowcontrolv1beta3.SchemeGroupVersion,
	}

	// alphaAPIGroupVersionsDisabledByDefault holds the alpha APIs we have.  They are always disabled by default.
	alphaAPIGroupVersionsDisabledByDefault = []schema.GroupVersion{
		admissionregistrationv1alpha1.SchemeGroupVersion,
		apiserverinternalv1alpha1.SchemeGroupVersion,
		authenticationv1alpha1.SchemeGroupVersion,
		resourcev1alpha2.SchemeGroupVersion,
		certificatesv1alpha1.SchemeGroupVersion,
		networkingapiv1alpha1.SchemeGroupVersion,
		storageapiv1alpha1.SchemeGroupVersion,
		flowcontrolv1alpha1.SchemeGroupVersion,
	}
)

// DefaultAPIResourceConfigSource returns default configuration for an APIResource.
func DefaultAPIResourceConfigSource() *serverstorage.ResourceConfig {
	ret := serverstorage.NewResourceConfig()
	// NOTE: GroupVersions listed here will be enabled by default. Don't put alpha or beta versions in the list.
	ret.EnableVersions(stableAPIGroupVersionsEnabledByDefault...)

	// disable alpha and beta versions explicitly so we have a full list of what's possible to serve
	ret.DisableVersions(betaAPIGroupVersionsDisabledByDefault...)
	ret.DisableVersions(alphaAPIGroupVersionsDisabledByDefault...)

	// enable the legacy beta resources that were present before stopped serving new beta APIs by default.
	ret.EnableResources(legacyBetaEnabledByDefaultResources...)

	return ret
}
