test: Add emulated-version flag verification in flagz test

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

@@ -57,7 +57,7 @@ func (s *ServerRunOptions) Complete(ctx context.Context) (CompletedOptions, erro
 	if err != nil {
 		return CompletedOptions{}, err
 	}
-	controlplane, err := s.Options.Complete(ctx, *s.ParsedFlags, []string{"kubernetes.default.svc", "kubernetes.default", "kubernetes"}, []net.IP{apiServerServiceIP})
+	controlplane, err := s.Options.Complete(ctx, []string{"kubernetes.default.svc", "kubernetes.default", "kubernetes"}, []net.IP{apiServerServiceIP})
 	if err != nil {
 		return CompletedOptions{}, err
 	}

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

@@ -41,8 +41,6 @@ type ServerRunOptions struct {
 	CloudProvider                  *kubeoptions.CloudProviderOptions
 
 	Extra
-	// ParsedFlags hold the parsed CLI flags.
-	ParsedFlags *cliflag.NamedFlagSets
 }
 
 type Extra struct {
@@ -102,9 +100,6 @@ func NewServerRunOptions() *ServerRunOptions {
 
 // Flags returns flags for a specific APIServer by section name
 func (s *ServerRunOptions) Flags() (fss cliflag.NamedFlagSets) {
-	if s.ParsedFlags != nil {
-		return *s.ParsedFlags
-	}
 	s.Options.AddFlags(&fss)
 	s.CloudProvider.AddFlags(fss.FlagSet("cloud provider"))
 
@@ -161,6 +156,5 @@ func (s *ServerRunOptions) Flags() (fss cliflag.NamedFlagSets) {
 		"The number of apiservers running in the cluster, must be a positive number. (In use when --endpoint-reconciler-type=master-count is enabled.)")
 	fs.MarkDeprecated("apiserver-count", "apiserver-count is deprecated and will be removed in a future version.")
 
-	s.ParsedFlags = &fss
 	return fss
 }

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

@@ -334,7 +334,6 @@ func TestAddFlags(t *testing.T) {
 			CloudConfigFile: "/cloud-config",
 			CloudProvider:   "azure",
 		},
-		ParsedFlags: s.ParsedFlags,
 	}
 
 	expected.Authentication.OIDC.UsernameClaim = "sub"

cmd/kube-apiserver/app/server.go

@@ -48,6 +48,8 @@ import (
 	"k8s.io/component-base/term"
 	utilversion "k8s.io/component-base/version"
 	"k8s.io/component-base/version/verflag"
+	zpagesfeatures "k8s.io/component-base/zpages/features"
+	"k8s.io/component-base/zpages/flagz"
 	"k8s.io/klog/v2"
 	aggregatorapiserver "k8s.io/kube-aggregator/pkg/apiserver"
 	"k8s.io/kubernetes/cmd/kube-apiserver/app/options"
@@ -124,7 +126,11 @@ cluster's shared state through which all other components interact.`,
 
 	fs := cmd.Flags()
 	namedFlagSets := s.Flags()
-	s.ParsedFlags = &namedFlagSets
+	if utilfeature.DefaultFeatureGate.Enabled(zpagesfeatures.ComponentFlagz) {
+		s.Flagz = flagz.NamedFlagSetsReader{
+			FlagSets: namedFlagSets,
+		}
+	}
 	verflag.AddFlags(namedFlagSets.FlagSet("global"))
 	globalflag.AddGlobalFlags(namedFlagSets.FlagSet("global"), cmd.Name(), logs.SkipLoggingConfigurationFlags())
 	options.AddCustomGlobalFlags(namedFlagSets.FlagSet("generic"))

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

@@ -59,6 +59,8 @@ import (
 	featuregatetesting "k8s.io/component-base/featuregate/testing"
 	logsapi "k8s.io/component-base/logs/api/v1"
 	utilversion "k8s.io/component-base/version"
+	zpagesfeatures "k8s.io/component-base/zpages/features"
+	"k8s.io/component-base/zpages/flagz"
 	"k8s.io/klog/v2"
 	"k8s.io/kube-aggregator/pkg/apiserver"
 	"k8s.io/kubernetes/pkg/features"
@@ -213,7 +215,8 @@ func StartTestServer(t ktesting.TB, instanceOptions *TestServerInstanceOptions,
 		s.GenericServerRunOptions.RequestTimeout = instanceOptions.RequestTimeout
 	}
 
-	for _, f := range s.Flags().FlagSets {
+	namedFlagSets := s.Flags()
+	for _, f := range namedFlagSets.FlagSets {
 		fs.AddFlagSet(f)
 	}
 
@@ -356,6 +359,9 @@ func StartTestServer(t ktesting.TB, instanceOptions *TestServerInstanceOptions,
 	if err := fs.Parse(customFlags); err != nil {
 		return result, err
 	}
+	if utilfeature.DefaultFeatureGate.Enabled(zpagesfeatures.ComponentFlagz) {
+		s.Flagz = flagz.NamedFlagSetsReader{FlagSets: namedFlagSets}
+	}
 
 	// the RequestHeader options pointer gets replaced in the case of EnableCertAuth override
 	// and so flags are connected to a struct that no longer appears in the ServerOptions struct

pkg/controlplane/apiserver/config_test.go

@@ -25,7 +25,6 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	apiserveroptions "k8s.io/apiserver/pkg/server/options"
-	cliflag "k8s.io/component-base/cli/flag"
 	aggregatorscheme "k8s.io/kube-aggregator/pkg/apiserver/scheme"
 	"k8s.io/kubernetes/pkg/api/legacyscheme"
 	"k8s.io/kubernetes/pkg/controlplane/apiserver/options"
@@ -47,7 +46,7 @@ func TestBuildGenericConfig(t *testing.T) {
 	s.BindPort = ln.Addr().(*net.TCPAddr).Port
 	opts.SecureServing = s
 
-	completedOptions, err := opts.Complete(context.TODO(), cliflag.NamedFlagSets{}, nil, nil)
+	completedOptions, err := opts.Complete(context.TODO(), nil, nil)
 	if err != nil {
 		t.Fatalf("Failed to complete apiserver options: %v", err)
 	}

pkg/controlplane/apiserver/options/options.go

@@ -203,7 +203,7 @@ func (s *Options) AddFlags(fss *cliflag.NamedFlagSets) {
 		"Path to socket where a external JWT signer is listening. This flag is mutually exclusive with --service-account-signing-key-file and --service-account-key-file. Requires enabling feature gate (ExternalServiceAccountTokenSigner)")
 }
 
-func (o *Options) Complete(ctx context.Context, fss cliflag.NamedFlagSets, alternateDNS []string, alternateIPs []net.IP) (CompletedOptions, error) {
+func (o *Options) Complete(ctx context.Context, alternateDNS []string, alternateIPs []net.IP) (CompletedOptions, error) {
 	if o == nil {
 		return CompletedOptions{completedOptions: &completedOptions{}}, nil
 	}
@@ -259,8 +259,6 @@ func (o *Options) Complete(ctx context.Context, fss cliflag.NamedFlagSets, alter
 		}
 	}
 
-	completed.Flagz = flagz.NamedFlagSetsReader{FlagSets: fss}
-
 	return CompletedOptions{
 		completedOptions: &completed,
 	}, nil

pkg/controlplane/apiserver/samples/generic/server/server.go

@@ -24,7 +24,6 @@ import (
 	"path/filepath"
 
 	"github.com/spf13/cobra"
-	"github.com/spf13/pflag"
 	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
 	utilerrors "k8s.io/apimachinery/pkg/util/errors"
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
@@ -86,7 +85,7 @@ APIs.`,
 
 			ctx := genericapiserver.SetupSignalContext()
 
-			completedOptions, err := s.Complete(ctx, cliflag.NamedFlagSets{FlagSets: map[string]*pflag.FlagSet{"sample_generic_controlplane": fs}}, []string{}, []net.IP{})
+			completedOptions, err := s.Complete(ctx, []string{}, []net.IP{})
 			if err != nil {
 				return err
 			}

pkg/controlplane/apiserver/samples/generic/server/testing/testserver.go

@@ -37,10 +37,13 @@ import (
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/apiserver/pkg/storage/storagebackend"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/client-go/kubernetes"
 	restclient "k8s.io/client-go/rest"
 	cliflag "k8s.io/component-base/cli/flag"
 	logsapi "k8s.io/component-base/logs/api/v1"
+	zpagesfeatures "k8s.io/component-base/zpages/features"
+	"k8s.io/component-base/zpages/flagz"
 	"k8s.io/klog/v2"
 	controlplaneapiserver "k8s.io/kubernetes/pkg/controlplane/apiserver/options"
 	"k8s.io/kubernetes/test/utils/ktesting"
@@ -126,6 +129,9 @@ func StartTestServer(t ktesting.TB, instanceOptions *TestServerInstanceOptions,
 	o := server.NewOptions()
 	var fss cliflag.NamedFlagSets
 	o.AddFlags(&fss)
+	if utilfeature.DefaultFeatureGate.Enabled(zpagesfeatures.ComponentFlagz) {
+		o.Flagz = flagz.NamedFlagSetsReader{FlagSets: fss}
+	}
 
 	fs := pflag.NewFlagSet("test", pflag.PanicOnError)
 	for _, f := range fss.FlagSets {
@@ -164,7 +170,7 @@ func StartTestServer(t ktesting.TB, instanceOptions *TestServerInstanceOptions,
 	o.Authentication.ServiceAccounts.Issuers = []string{"https://foo.bar.example.com"}
 	o.Authentication.ServiceAccounts.KeyFiles = []string{saSigningKeyFile.Name()}
 
-	completedOptions, err := o.Complete(tCtx, fss, nil, nil)
+	completedOptions, err := o.Complete(tCtx, nil, nil)
 	if err != nil {
 		return result, fmt.Errorf("failed to set default ServerRunOptions: %w", err)
 	}

test/integration/controlplane/kube_apiserver_test.go

@@ -28,6 +28,9 @@ import (
 	"time"
 
 	"k8s.io/apiextensions-apiserver/test/integration/fixtures"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
+	featuregatetesting "k8s.io/component-base/featuregate/testing"
+	"k8s.io/component-base/zpages/features"
 
 	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
 
@@ -127,6 +130,47 @@ func TestLivezAndReadyz(t *testing.T) {
 	}
 }
 
+func TestFlagz(t *testing.T) {
+	featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.ComponentFlagz, true)
+	testServerFlags := append(framework.DefaultTestServerFlags(), "--emulated-version=1.32")
+	server := kubeapiservertesting.StartTestServerOrDie(t, nil, testServerFlags, framework.SharedEtcd())
+	defer server.TearDownFn()
+
+	client, err := kubernetes.NewForConfig(server.ClientConfig)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	res := client.CoreV1().RESTClient().Get().RequestURI("/flagz").Do(context.TODO())
+	var status int
+	res.StatusCode(&status)
+	if status != http.StatusOK {
+		t.Fatalf("flagz/ should be healthy, got %v", status)
+	}
+
+	expectedHeader := `
+kube-apiserver flags
+Warning: This endpoint is not meant to be machine parseable, has no formatting compatibility guarantees and is for debugging purposes only.`
+
+	raw, err := res.Raw()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.HasPrefix(raw, []byte(expectedHeader)) {
+		t.Fatalf("Header mismatch!\nExpected:\n%s\n\nGot:\n%s", expectedHeader, string(raw))
+	}
+	found := false
+	for _, line := range strings.Split(string(raw), "\n") {
+		if strings.Contains(line, "emulated-version") && strings.Contains(line, "1.32") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatalf("Expected flag --emulated-version=[1.32] to be reflected in /flagz output, got:\n%s", string(raw))
+	}
+}
+
 // TestOpenAPIDelegationChainPlumbing is a smoke test that checks for
 // the existence of some representative paths from the
 // apiextensions-server and the kube-aggregator server, both part of