kubeadm: APIServerEndpoints -> APIServerEndpoint

cmd/kubeadm/app/apis/kubeadm/types.go

@@ -323,10 +323,8 @@ type BootstrapTokenDiscovery struct {
 	// fetched from the master.
 	Token string
 
-	// APIServerEndpoints is a set of IPs or domain names to API servers from which info
-	// will be fetched. Currently we only pay attention to one API server but
-	// hope to support >1 in the future.
-	APIServerEndpoints []string
+	// APIServerEndpoint is an IP or domain name to the API server from which info will be fetched.
+	APIServerEndpoint string
 
 	// CACertHashes specifies a set of public key pins to verify
 	// when token-based discovery is used. The root CA found during discovery

cmd/kubeadm/app/apis/kubeadm/v1alpha3/conversion.go

@@ -40,10 +40,12 @@ func Convert_v1alpha3_JoinConfiguration_To_kubeadm_JoinConfiguration(in *JoinCon
 		}
 	} else {
 		out.Discovery.BootstrapToken = &kubeadm.BootstrapTokenDiscovery{
-			APIServerEndpoints:       in.DiscoveryTokenAPIServers,
 			CACertHashes:             in.DiscoveryTokenCACertHashes,
 			UnsafeSkipCAVerification: in.DiscoveryTokenUnsafeSkipCAVerification,
 		}
+		if len(in.DiscoveryTokenAPIServers) != 0 {
+			out.Discovery.BootstrapToken.APIServerEndpoint = in.DiscoveryTokenAPIServers[0]
+		}
 		if len(in.DiscoveryToken) != 0 {
 			out.Discovery.BootstrapToken.Token = in.DiscoveryToken
 		} else {
@@ -64,7 +66,7 @@ func Convert_kubeadm_JoinConfiguration_To_v1alpha3_JoinConfiguration(in *kubeadm
 
 	if in.Discovery.BootstrapToken != nil {
 		out.DiscoveryToken = in.Discovery.BootstrapToken.Token
-		out.DiscoveryTokenAPIServers = in.Discovery.BootstrapToken.APIServerEndpoints
+		out.DiscoveryTokenAPIServers = []string{in.Discovery.BootstrapToken.APIServerEndpoint}
 		out.DiscoveryTokenCACertHashes = in.Discovery.BootstrapToken.CACertHashes
 		out.DiscoveryTokenUnsafeSkipCAVerification = in.Discovery.BootstrapToken.UnsafeSkipCAVerification
 

cmd/kubeadm/app/apis/kubeadm/v1beta1/types.go

@@ -301,10 +301,8 @@ type BootstrapTokenDiscovery struct {
 	// fetched from the master.
 	Token string `json:"token"`
 
-	// APIServerEndpoints is a set of IPs or domain names to API servers from which info
-	// will be fetched. Currently we only pay attention to one API server but
-	// hope to support >1 in the future.
-	APIServerEndpoints []string `json:"apiServerEndpoints,omitempty"`
+	// APIServerEndpoint is an IP or domain name to the API server from which info will be fetched.
+	APIServerEndpoint string `json:"apiServerEndpoint,omitempty"`
 
 	// CACertHashes specifies a set of public key pins to verify
 	// when token-based discovery is used. The root CA found during discovery

cmd/kubeadm/app/apis/kubeadm/v1beta1/zz_generated.conversion.go

@@ -288,7 +288,7 @@ func Convert_kubeadm_BootstrapToken_To_v1beta1_BootstrapToken(in *kubeadm.Bootst
 
 func autoConvert_v1beta1_BootstrapTokenDiscovery_To_kubeadm_BootstrapTokenDiscovery(in *BootstrapTokenDiscovery, out *kubeadm.BootstrapTokenDiscovery, s conversion.Scope) error {
 	out.Token = in.Token
-	out.APIServerEndpoints = *(*[]string)(unsafe.Pointer(&in.APIServerEndpoints))
+	out.APIServerEndpoint = in.APIServerEndpoint
 	out.CACertHashes = *(*[]string)(unsafe.Pointer(&in.CACertHashes))
 	out.UnsafeSkipCAVerification = in.UnsafeSkipCAVerification
 	return nil
@@ -301,7 +301,7 @@ func Convert_v1beta1_BootstrapTokenDiscovery_To_kubeadm_BootstrapTokenDiscovery(
 
 func autoConvert_kubeadm_BootstrapTokenDiscovery_To_v1beta1_BootstrapTokenDiscovery(in *kubeadm.BootstrapTokenDiscovery, out *BootstrapTokenDiscovery, s conversion.Scope) error {
 	out.Token = in.Token
-	out.APIServerEndpoints = *(*[]string)(unsafe.Pointer(&in.APIServerEndpoints))
+	out.APIServerEndpoint = in.APIServerEndpoint
 	out.CACertHashes = *(*[]string)(unsafe.Pointer(&in.CACertHashes))
 	out.UnsafeSkipCAVerification = in.UnsafeSkipCAVerification
 	return nil

cmd/kubeadm/app/apis/kubeadm/v1beta1/zz_generated.deepcopy.go

@@ -106,11 +106,6 @@ func (in *BootstrapToken) DeepCopy() *BootstrapToken {
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *BootstrapTokenDiscovery) DeepCopyInto(out *BootstrapTokenDiscovery) {
 	*out = *in
-	if in.APIServerEndpoints != nil {
-		in, out := &in.APIServerEndpoints, &out.APIServerEndpoints
-		*out = make([]string, len(*in))
-		copy(*out, *in)
-	}
 	if in.CACertHashes != nil {
 		in, out := &in.CACertHashes, &out.CACertHashes
 		*out = make([]string, len(*in))

cmd/kubeadm/app/apis/kubeadm/validation/validation.go

@@ -123,13 +123,8 @@ func ValidateDiscovery(d *kubeadm.Discovery, fldPath *field.Path) field.ErrorLis
 func ValidateDiscoveryBootstrapToken(b *kubeadm.BootstrapTokenDiscovery, fldPath *field.Path) field.ErrorList {
 	allErrs := field.ErrorList{}
 
-	if len(b.APIServerEndpoints) < 1 {
-		allErrs = append(allErrs, field.Required(fldPath, "APIServerEndpoints not set"))
-	}
-
-	// TODO remove once we support multiple api servers
-	if len(b.APIServerEndpoints) > 1 {
-		fmt.Println("[validation] WARNING: kubeadm doesn't fully support multiple API Servers yet")
+	if len(b.APIServerEndpoint) == 0 {
+		allErrs = append(allErrs, field.Required(fldPath, "APIServerEndpoint is not set"))
 	}
 
 	if len(b.CACertHashes) == 0 && !b.UnsafeSkipCAVerification {
@@ -137,7 +132,7 @@ func ValidateDiscoveryBootstrapToken(b *kubeadm.BootstrapTokenDiscovery, fldPath
 	}
 
 	allErrs = append(allErrs, ValidateToken(b.Token, fldPath.Child("token"))...)
-	allErrs = append(allErrs, ValidateDiscoveryTokenAPIServer(b.APIServerEndpoints, fldPath.Child("apiServerEndpoints"))...)
+	allErrs = append(allErrs, ValidateDiscoveryTokenAPIServer(b.APIServerEndpoint, fldPath.Child("apiServerEndpoints"))...)
 
 	return allErrs
 }
@@ -152,13 +147,11 @@ func ValidateDiscoveryFile(f *kubeadm.FileDiscovery, fldPath *field.Path) field.
 }
 
 // ValidateDiscoveryTokenAPIServer validates discovery token for API server
-func ValidateDiscoveryTokenAPIServer(apiServers []string, fldPath *field.Path) field.ErrorList {
+func ValidateDiscoveryTokenAPIServer(apiServer string, fldPath *field.Path) field.ErrorList {
 	allErrs := field.ErrorList{}
-	for _, m := range apiServers {
-		_, _, err := net.SplitHostPort(m)
-		if err != nil {
-			allErrs = append(allErrs, field.Invalid(fldPath, m, err.Error()))
-		}
+	_, _, err := net.SplitHostPort(apiServer)
+	if err != nil {
+		allErrs = append(allErrs, field.Invalid(fldPath, apiServer, err.Error()))
 	}
 	return allErrs
 }

cmd/kubeadm/app/apis/kubeadm/validation/validation_test.go

@@ -692,7 +692,7 @@ func TestValidateDiscoveryBootstrapToken(t *testing.T) {
 		expected bool
 	}{
 		{
-			"invalid: .APIServerEndpoints not set",
+			"invalid: .APIServerEndpoint not set",
 			&kubeadm.BootstrapTokenDiscovery{
 				Token: "abcdef.1234567890123456",
 			},
@@ -702,25 +702,16 @@ func TestValidateDiscoveryBootstrapToken(t *testing.T) {
 			"invalid: using token-based discovery without .BootstrapToken.CACertHashes and .BootstrapToken.UnsafeSkipCAVerification",
 			&kubeadm.BootstrapTokenDiscovery{
 				Token:                    "abcdef.1234567890123456",
-				APIServerEndpoints:       []string{"192.168.122.100:6443"},
+				APIServerEndpoint:        "192.168.122.100:6443",
 				UnsafeSkipCAVerification: false,
 			},
 			false,
 		},
 		{
-			"WARNING: kubeadm doesn't fully support multiple API Servers yet",
-			&kubeadm.BootstrapTokenDiscovery{
-				Token:                    "abcdef.1234567890123456",
-				APIServerEndpoints:       []string{"192.168.122.100:6443", "192.168.122.88:6443"},
-				UnsafeSkipCAVerification: true,
-			},
-			true,
-		},
-		{
 			"valid: using token-based discovery with .BootstrapToken.CACertHashes",
 			&kubeadm.BootstrapTokenDiscovery{
 				Token:                    "abcdef.1234567890123456",
-				APIServerEndpoints:       []string{"192.168.122.100:6443"},
+				APIServerEndpoint:        "192.168.122.100:6443",
 				CACertHashes:             []string{"sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc"},
 				UnsafeSkipCAVerification: false,
 			},
@@ -730,7 +721,7 @@ func TestValidateDiscoveryBootstrapToken(t *testing.T) {
 			"valid: using token-based discovery with .BootstrapToken.CACertHashe but skip ca verification",
 			&kubeadm.BootstrapTokenDiscovery{
 				Token:                    "abcdef.1234567890123456",
-				APIServerEndpoints:       []string{"192.168.122.100:6443"},
+				APIServerEndpoint:        "192.168.122.100:6443",
 				CACertHashes:             []string{"sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc"},
 				UnsafeSkipCAVerification: true,
 			},
@@ -753,20 +744,20 @@ func TestValidateDiscoveryBootstrapToken(t *testing.T) {
 
 func TestValidateDiscoveryTokenAPIServer(t *testing.T) {
 	var tests = []struct {
-		apiServerEndpoints []string
-		expected           bool
+		apiServerEndpoint string
+		expected          bool
 	}{
 		{
-			[]string{"192.168.122.100"},
+			"192.168.122.100",
 			false,
 		},
 		{
-			[]string{"192.168.122.100:6443"},
+			"192.168.122.100:6443",
 			true,
 		},
 	}
 	for _, rt := range tests {
-		actual := ValidateDiscoveryTokenAPIServer(rt.apiServerEndpoints, nil)
+		actual := ValidateDiscoveryTokenAPIServer(rt.apiServerEndpoint, nil)
 		if (len(actual) == 0) != rt.expected {
 			t.Errorf(
 				"failed ValidateDiscoveryTokenAPIServer:\n\texpected: %t\n\t  actual: %t",

cmd/kubeadm/app/apis/kubeadm/zz_generated.deepcopy.go

@@ -108,11 +108,6 @@ func (in *BootstrapToken) DeepCopy() *BootstrapToken {
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *BootstrapTokenDiscovery) DeepCopyInto(out *BootstrapTokenDiscovery) {
 	*out = *in
-	if in.APIServerEndpoints != nil {
-		in, out := &in.APIServerEndpoints, &out.APIServerEndpoints
-		*out = make([]string, len(*in))
-		copy(*out, *in)
-	}
 	if in.CACertHashes != nil {
 		in, out := &in.CACertHashes, &out.CACertHashes
 		*out = make([]string, len(*in))

cmd/kubeadm/app/cmd/config.go

@@ -277,7 +277,7 @@ func getDefaultNodeConfigBytes() ([]byte, error) {
 		Discovery: kubeadmapiv1beta1.Discovery{
 			BootstrapToken: &kubeadmapiv1beta1.BootstrapTokenDiscovery{
 				Token:                    placeholderToken.Token.String(),
-				APIServerEndpoints:       []string{"kube-apiserver:6443"},
+				APIServerEndpoint:        "kube-apiserver:6443",
 				UnsafeSkipCAVerification: true, // TODO: UnsafeSkipCAVerification: true needs to be set for validation to pass, but shouldn't be recommended as the default
 			},
 		},

cmd/kubeadm/app/cmd/join.go

@@ -177,10 +177,15 @@ func NewCmdJoin(out io.Writer) *cobra.Command {
 				cfg.Discovery.File = fd
 			} else {
 				cfg.Discovery.BootstrapToken = btd
-				cfg.Discovery.BootstrapToken.APIServerEndpoints = args
 				if len(cfg.Discovery.BootstrapToken.Token) == 0 {
 					cfg.Discovery.BootstrapToken.Token = token
 				}
+				if len(args) > 0 {
+					if len(cfgPath) == 0 && len(args) > 1 {
+						glog.Warningf("[join] WARNING: More than one API server endpoint supplied on command line %v. Using the first one.", args)
+					}
+					cfg.Discovery.BootstrapToken.APIServerEndpoint = args[0]
+				}
 			}
 
 			if len(cfg.Discovery.TLSBootstrapToken) == 0 {

cmd/kubeadm/app/discovery/token/BUILD

@@ -43,8 +43,5 @@ go_test(
     name = "go_default_test",
     srcs = ["token_test.go"],
     embed = [":go_default_library"],
-    deps = [
-        "//cmd/kubeadm/app/util/kubeconfig:go_default_library",
-        "//staging/src/k8s.io/client-go/tools/clientcmd/api:go_default_library",
-    ],
+    deps = ["//staging/src/k8s.io/client-go/tools/clientcmd/api:go_default_library"],
 )

cmd/kubeadm/app/discovery/token/token.go

@@ -60,7 +60,7 @@ func RetrieveValidatedConfigInfo(cfg *kubeadmapi.JoinConfiguration) (*clientcmda
 
 	// The function below runs for every endpoint, and all endpoints races with each other.
 	// The endpoint that wins the race and completes the task first gets its kubeconfig returned below
-	baseKubeConfig, err := runForEndpointsAndReturnFirst(cfg.Discovery.BootstrapToken.APIServerEndpoints, cfg.Discovery.Timeout.Duration, func(endpoint string) (*clientcmdapi.Config, error) {
+	baseKubeConfig, err := fetchKubeConfigWithTimeout(cfg.Discovery.BootstrapToken.APIServerEndpoint, cfg.Discovery.Timeout.Duration, func(endpoint string) (*clientcmdapi.Config, error) {
 
 		insecureBootstrapConfig := buildInsecureBootstrapKubeConfig(endpoint, cfg.ClusterName)
 		clusterName := insecureBootstrapConfig.Contexts[insecureBootstrapConfig.CurrentContext].Cluster
@@ -184,36 +184,36 @@ func buildSecureBootstrapKubeConfig(endpoint string, caCert []byte, clustername
 	return bootstrapConfig
 }
 
-// runForEndpointsAndReturnFirst loops the endpoints slice and let's the endpoints race for connecting to the master
-func runForEndpointsAndReturnFirst(endpoints []string, discoveryTimeout time.Duration, fetchKubeConfigFunc func(string) (*clientcmdapi.Config, error)) (*clientcmdapi.Config, error) {
+// fetchKubeConfigWithTimeout tries to run fetchKubeConfigFunc on every DiscoveryRetryInterval, but until discoveryTimeout is reached
+func fetchKubeConfigWithTimeout(apiEndpoint string, discoveryTimeout time.Duration, fetchKubeConfigFunc func(string) (*clientcmdapi.Config, error)) (*clientcmdapi.Config, error) {
 	stopChan := make(chan struct{})
 	var resultingKubeConfig *clientcmdapi.Config
 	var once sync.Once
 	var wg sync.WaitGroup
-	for _, endpoint := range endpoints {
-		wg.Add(1)
-		go func(apiEndpoint string) {
-			defer wg.Done()
-			wait.Until(func() {
-				fmt.Printf("[discovery] Trying to connect to API Server %q\n", apiEndpoint)
-				cfg, err := fetchKubeConfigFunc(apiEndpoint)
-				if err != nil {
-					fmt.Printf("[discovery] Failed to connect to API Server %q: %v\n", apiEndpoint, err)
-					return
-				}
-				fmt.Printf("[discovery] Successfully established connection with API Server %q\n", apiEndpoint)
-
-				// connection established, stop all wait threads
-				once.Do(func() {
-					close(stopChan)
-					resultingKubeConfig = cfg
-				})
-			}, constants.DiscoveryRetryInterval, stopChan)
-		}(endpoint)
-	}
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		wait.Until(func() {
+			fmt.Printf("[discovery] Trying to connect to API Server %q\n", apiEndpoint)
+			cfg, err := fetchKubeConfigFunc(apiEndpoint)
+			if err != nil {
+				fmt.Printf("[discovery] Failed to connect to API Server %q: %v\n", apiEndpoint, err)
+				return
+			}
+			fmt.Printf("[discovery] Successfully established connection with API Server %q\n", apiEndpoint)
+			once.Do(func() {
+				resultingKubeConfig = cfg
+				close(stopChan)
+			})
+		}, constants.DiscoveryRetryInterval, stopChan)
+	}()
+
 	select {
 	case <-time.After(discoveryTimeout):
-		close(stopChan)
+		once.Do(func() {
+			close(stopChan)
+		})
 		err := errors.Errorf("abort connecting to API servers after timeout of %v", discoveryTimeout)
 		fmt.Printf("[discovery] %v\n", err)
 		wg.Wait()

cmd/kubeadm/app/discovery/token/token_test.go

@@ -17,12 +17,11 @@ limitations under the License.
 package token
 
 import (
-	"strconv"
+	"fmt"
 	"testing"
 	"time"
 
 	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
-	kubeconfigutil "k8s.io/kubernetes/cmd/kubeadm/app/util/kubeconfig"
 )
 
 // testCertPEM is a simple self-signed test certificate issued with the openssl CLI:
@@ -49,41 +48,49 @@ c1vuFqTnJBPcb7W//R/GI2Paicm1cmns9NLnPR35exHxFTy+D1yxmGokpoPMdife
 aH+sfuxT8xeTPb3kjzF9eJTlnEquUDLM
 -----END CERTIFICATE-----`
 
-func TestRunForEndpointsAndReturnFirst(t *testing.T) {
+func TestFetchKubeConfigWithTimeout(t *testing.T) {
+	const testAPIEndpoint = "sample-endpoint:1234"
 	tests := []struct {
-		endpoints        []string
-		expectedEndpoint string
+		name             string
+		discoveryTimeout time.Duration
+		shouldFail       bool
 	}{
 		{
-			endpoints:        []string{"1", "2", "3"},
-			expectedEndpoint: "1",
+			name:             "Timeout if value is not returned on time",
+			discoveryTimeout: 1 * time.Second,
+			shouldFail:       true,
 		},
 		{
-			endpoints:        []string{"6", "5"},
-			expectedEndpoint: "5",
-		},
-		{
-			endpoints:        []string{"10", "4"},
-			expectedEndpoint: "4",
+			name:             "Don't timeout if value is returned on time",
+			discoveryTimeout: 5 * time.Second,
+			shouldFail:       false,
 		},
 	}
-	for _, rt := range tests {
-		returnKubeConfig, err := runForEndpointsAndReturnFirst(rt.endpoints, 5*time.Minute, func(endpoint string) (*clientcmdapi.Config, error) {
-			timeout, _ := strconv.Atoi(endpoint)
-			time.Sleep(time.Second * time.Duration(timeout))
-			return kubeconfigutil.CreateBasic(endpoint, "foo", "foo", []byte{}), nil
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			cfg, err := fetchKubeConfigWithTimeout(testAPIEndpoint, test.discoveryTimeout, func(apiEndpoint string) (*clientcmdapi.Config, error) {
+				if apiEndpoint != testAPIEndpoint {
+					return nil, fmt.Errorf("unexpected API server endpoint:\n\texpected: %q\n\tgot: %q", testAPIEndpoint, apiEndpoint)
+				}
+
+				time.Sleep(3 * time.Second)
+				return &clientcmdapi.Config{}, nil
+			})
+
+			if test.shouldFail {
+				if err == nil {
+					t.Fatal("unexpected success")
+				}
+			} else {
+				if err != nil {
+					t.Fatalf("unexpected failure: %v", err)
+				}
+				if cfg == nil {
+					t.Fatal("cfg is nil")
+				}
+			}
 		})
-		if err != nil {
-			t.Errorf("unexpected error: %v for endpoint %s", err, rt.expectedEndpoint)
-		}
-		endpoint := returnKubeConfig.Clusters[returnKubeConfig.Contexts[returnKubeConfig.CurrentContext].Cluster].Server
-		if endpoint != rt.expectedEndpoint {
-			t.Errorf(
-				"failed TestRunForEndpointsAndReturnFirst:\n\texpected: %s\n\t  actual: %s",
-				endpoint,
-				rt.expectedEndpoint,
-			)
-		}
 	}
 }
 

cmd/kubeadm/app/preflight/checks.go

@@ -950,17 +950,15 @@ func RunJoinNodeChecks(execer utilsexec.Interface, cfg *kubeadmapi.JoinConfigura
 
 	addIPv6Checks := false
 	if cfg.Discovery.BootstrapToken != nil {
-		for _, server := range cfg.Discovery.BootstrapToken.APIServerEndpoints {
-			ipstr, _, err := net.SplitHostPort(server)
-			if err == nil {
-				checks = append(checks,
-					HTTPProxyCheck{Proto: "https", Host: ipstr},
-				)
-				if !addIPv6Checks {
-					if ip := net.ParseIP(ipstr); ip != nil {
-						if ip.To4() == nil && ip.To16() != nil {
-							addIPv6Checks = true
-						}
+		ipstr, _, err := net.SplitHostPort(cfg.Discovery.BootstrapToken.APIServerEndpoint)
+		if err == nil {
+			checks = append(checks,
+				HTTPProxyCheck{Proto: "https", Host: ipstr},
+			)
+			if !addIPv6Checks {
+				if ip := net.ParseIP(ipstr); ip != nil {
+					if ip.To4() == nil && ip.To16() != nil {
+						addIPv6Checks = true
 					}
 				}
 			}

cmd/kubeadm/app/preflight/checks_test.go

@@ -256,7 +256,7 @@ func TestRunJoinNodeChecks(t *testing.T) {
 			cfg: &kubeadmapi.JoinConfiguration{
 				Discovery: kubeadmapi.Discovery{
 					BootstrapToken: &kubeadmapi.BootstrapTokenDiscovery{
-						APIServerEndpoints: []string{"192.168.1.15"},
+						APIServerEndpoint: "192.168.1.15",
 					},
 				},
 			},
@@ -266,7 +266,7 @@ func TestRunJoinNodeChecks(t *testing.T) {
 			cfg: &kubeadmapi.JoinConfiguration{
 				Discovery: kubeadmapi.Discovery{
 					BootstrapToken: &kubeadmapi.BootstrapTokenDiscovery{
-						APIServerEndpoints: []string{"2001:1234::1:15"},
+						APIServerEndpoint: "2001:1234::1:15",
 					},
 				},
 			},

cmd/kubeadm/app/util/config/testdata/conversion/node/internal.yaml

@@ -6,8 +6,7 @@ ClusterName: kubernetes
 ControlPlane: false
 Discovery:
   BootstrapToken:
-    APIServerEndpoints:
-    - kube-apiserver:6443
+    APIServerEndpoint: kube-apiserver:6443
     CACertHashes: null
     Token: abcdef.0123456789abcdef
     UnsafeSkipCAVerification: true

cmd/kubeadm/app/util/config/testdata/conversion/node/v1beta1.yaml

@@ -6,8 +6,7 @@ caCertPath: /etc/kubernetes/pki/ca.crt
 clusterName: kubernetes
 discovery:
   bootstrapToken:
-    apiServerEndpoints:
-    - kube-apiserver:6443
+    apiServerEndpoint: kube-apiserver:6443
     token: abcdef.0123456789abcdef
     unsafeSkipCAVerification: true
   timeout: 5m0s

cmd/kubeadm/app/util/config/testdata/defaulting/node/defaulted.yaml

@@ -6,8 +6,7 @@ caCertPath: /etc/kubernetes/pki/ca.crt
 clusterName: kubernetes
 discovery:
   bootstrapToken:
-    apiServerEndpoints:
-    - kube-apiserver:6443
+    apiServerEndpoint: kube-apiserver:6443
     token: abcdef.0123456789abcdef
     unsafeSkipCAVerification: true
   timeout: 5m0s