Merge pull request #108447 from pacoxu/kubeadm-json-upgrade-plan

`Kubeadm upgrade plan` support json/yaml output

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

@@ -40,8 +40,12 @@ type Images struct {
 	Images []string
 }
 
+// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
+
 // ComponentUpgradePlan represents information about upgrade plan for one component
 type ComponentUpgradePlan struct {
+	metav1.TypeMeta
+
 	Name           string
 	CurrentVersion string
 	NewVersion     string

cmd/kubeadm/app/apis/output/v1alpha2/types.go

@@ -40,8 +40,12 @@ type Images struct {
 	Images []string `json:"images"`
 }
 
+// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
+
 // ComponentUpgradePlan represents information about upgrade plan for one component
 type ComponentUpgradePlan struct {
+	metav1.TypeMeta
+
 	Name           string `json:"name"`
 	CurrentVersion string `json:"currentVersion"`
 	NewVersion     string `json:"newVersion"`

cmd/kubeadm/app/apis/output/v1alpha2/zz_generated.deepcopy.go

@@ -70,6 +70,7 @@ func (in *ComponentConfigVersionState) DeepCopy() *ComponentConfigVersionState {
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *ComponentUpgradePlan) DeepCopyInto(out *ComponentUpgradePlan) {
 	*out = *in
+	out.TypeMeta = in.TypeMeta
 	return
 }
 
@@ -83,6 +84,14 @@ func (in *ComponentUpgradePlan) DeepCopy() *ComponentUpgradePlan {
 	return out
 }
 
+// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
+func (in *ComponentUpgradePlan) DeepCopyObject() runtime.Object {
+	if c := in.DeepCopy(); c != nil {
+		return c
+	}
+	return nil
+}
+
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *Images) DeepCopyInto(out *Images) {
 	*out = *in

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

@@ -70,6 +70,7 @@ func (in *ComponentConfigVersionState) DeepCopy() *ComponentConfigVersionState {
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *ComponentUpgradePlan) DeepCopyInto(out *ComponentUpgradePlan) {
 	*out = *in
+	out.TypeMeta = in.TypeMeta
 	return
 }
 
@@ -83,6 +84,14 @@ func (in *ComponentUpgradePlan) DeepCopy() *ComponentUpgradePlan {
 	return out
 }
 
+// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
+func (in *ComponentUpgradePlan) DeepCopyObject() runtime.Object {
+	if c := in.DeepCopy(); c != nil {
+		return c
+	}
+	return nil
+}
+
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *Images) DeepCopyInto(out *Images) {
 	*out = *in

cmd/kubeadm/app/cmd/certs.go

@@ -332,7 +332,7 @@ func getInternalCfg(cfgPath string, kubeconfigPath string, cfg kubeadmapiv1.Clus
 	if cfgPath == "" {
 		client, err := kubeconfigutil.ClientSetFromFile(kubeconfigPath)
 		if err == nil {
-			internalcfg, err := configutil.FetchInitConfigurationFromCluster(client, out, logPrefix, false, false)
+			internalcfg, err := configutil.FetchInitConfigurationFromCluster(client, nil, logPrefix, false, false)
 			if err == nil {
 				fmt.Println() // add empty line to separate the FetchInitConfigurationFromCluster output from the command output
 				return internalcfg, nil

cmd/kubeadm/app/cmd/config.go

@@ -371,7 +371,7 @@ func newCmdConfigImagesList(out io.Writer, mockK8sVersion *string) *cobra.Comman
 
 			printer, err := outputFlags.ToPrinter()
 			if err != nil {
-				return err
+				return errors.Wrap(err, "could not construct output printer")
 			}
 
 			imagesList, err := NewImagesList(cfgPath, externalcfg)
@@ -424,7 +424,7 @@ func (itp *imageTextPrinter) PrintObj(obj runtime.Object, writer io.Writer) erro
 // imageTextPrintFlags provides flags necessary for printing image in a text form.
 type imageTextPrintFlags struct{}
 
-// ToPrinter returns kubeadm printer for the text output format
+// ToPrinter returns a kubeadm printer for the text output format
 func (ipf *imageTextPrintFlags) ToPrinter(outputFormat string) (output.Printer, error) {
 	if outputFormat == output.TextOutput {
 		return &imageTextPrinter{}, nil

cmd/kubeadm/app/cmd/join.go

@@ -618,7 +618,7 @@ func fetchInitConfiguration(tlsBootstrapCfg *clientcmdapi.Config) (*kubeadmapi.I
 	}
 
 	// Fetches the init configuration
-	initConfiguration, err := configutil.FetchInitConfigurationFromCluster(tlsClient, os.Stdout, "preflight", true, false)
+	initConfiguration, err := configutil.FetchInitConfigurationFromCluster(tlsClient, nil, "preflight", true, false)
 	if err != nil {
 		return nil, errors.Wrap(err, "unable to fetch the kubeadm-config ConfigMap")
 	}

cmd/kubeadm/app/cmd/reset.go

@@ -98,7 +98,7 @@ func newResetData(cmd *cobra.Command, options *resetOptions, in io.Reader, out i
 	client, err := getClientset(options.kubeconfigPath, false)
 	if err == nil {
 		klog.V(1).Infof("[reset] Loaded client set from kubeconfig file: %s", options.kubeconfigPath)
-		cfg, err = configutil.FetchInitConfigurationFromCluster(client, out, "reset", false, false)
+		cfg, err = configutil.FetchInitConfigurationFromCluster(client, nil, "reset", false, false)
 		if err != nil {
 			klog.Warningf("[reset] Unable to fetch the kubeadm-config ConfigMap from cluster: %v", err)
 		}

cmd/kubeadm/app/cmd/token.go

@@ -169,7 +169,7 @@ func newCmdToken(out io.Writer, errW io.Writer) *cobra.Command {
 
 			printer, err := outputFlags.ToPrinter()
 			if err != nil {
-				return err
+				return errors.Wrap(err, "could not construct output printer")
 			}
 
 			return RunListTokens(out, errW, client, printer)
@@ -354,7 +354,7 @@ func (ttp *tokenTextPrinter) PrintObj(obj runtime.Object, writer io.Writer) erro
 // tokenTextPrintFlags provides flags necessary for printing bootstrap token in a text form.
 type tokenTextPrintFlags struct{}
 
-// ToPrinter returns kubeadm printer for the text output format
+// ToPrinter returns a kubeadm printer for the text output format
 func (tpf *tokenTextPrintFlags) ToPrinter(outputFormat string) (output.Printer, error) {
 	if outputFormat == output.TextOutput {
 		return &tokenTextPrinter{columns: []string{"TOKEN", "TTL", "EXPIRES", "USAGES", "DESCRIPTION", "EXTRA GROUPS"}}, nil

cmd/kubeadm/app/cmd/upgrade/apply.go

@@ -37,6 +37,7 @@ import (
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/apiclient"
 	configutil "k8s.io/kubernetes/cmd/kubeadm/app/util/config"
+	"k8s.io/kubernetes/cmd/kubeadm/app/util/output"
 )
 
 // applyFlags holds the information about the flags that can be passed to apply
@@ -103,7 +104,7 @@ func runApply(flags *applyFlags, args []string) error {
 	// Start with the basics, verify that the cluster is healthy and get the configuration from the cluster (using the ConfigMap)
 	klog.V(1).Infoln("[upgrade/apply] verifying health of cluster")
 	klog.V(1).Infoln("[upgrade/apply] retrieving configuration from cluster")
-	client, versionGetter, cfg, err := enforceRequirements(flags.applyPlanFlags, args, flags.dryRun, true)
+	client, versionGetter, cfg, err := enforceRequirements(flags.applyPlanFlags, args, flags.dryRun, true, &output.TextPrinter{})
 	if err != nil {
 		return err
 	}

cmd/kubeadm/app/cmd/upgrade/common.go

@@ -47,6 +47,7 @@ import (
 	configutil "k8s.io/kubernetes/cmd/kubeadm/app/util/config"
 	dryrunutil "k8s.io/kubernetes/cmd/kubeadm/app/util/dryrun"
 	kubeconfigutil "k8s.io/kubernetes/cmd/kubeadm/app/util/kubeconfig"
+	"k8s.io/kubernetes/cmd/kubeadm/app/util/output"
 )
 
 // isKubeadmConfigPresent checks if a kubeadm config type is found in the provided document map
@@ -63,14 +64,14 @@ func isKubeadmConfigPresent(docmap kubeadmapi.DocumentMap) bool {
 // are loaded. This function allows the component configs to be loaded from a file that contains only them. If the file contains any kubeadm types
 // in it (API group "kubeadm.kubernetes.io" present), then the supplied file is treaded as a legacy reconfiguration style "--config" use and the
 // returned bool value is set to true (the only case to be done so).
-func loadConfig(cfgPath string, client clientset.Interface, skipComponentConfigs bool) (*kubeadmapi.InitConfiguration, bool, error) {
+func loadConfig(cfgPath string, client clientset.Interface, skipComponentConfigs bool, printer output.Printer) (*kubeadmapi.InitConfiguration, bool, error) {
 	// Used for info logs here
 	const logPrefix = "upgrade/config"
 
 	// The usual case here is to not have a config file, but rather load the config from the cluster.
 	// This is probably 90% of the time. So we handle it first.
 	if cfgPath == "" {
-		cfg, err := configutil.FetchInitConfigurationFromCluster(client, os.Stdout, logPrefix, false, skipComponentConfigs)
+		cfg, err := configutil.FetchInitConfigurationFromCluster(client, printer, logPrefix, false, skipComponentConfigs)
 		return cfg, false, err
 	}
 
@@ -98,7 +99,7 @@ func loadConfig(cfgPath string, client clientset.Interface, skipComponentConfigs
 
 	// If no kubeadm config types are present, we assume that there are manually upgraded component configs in the file.
 	// Hence, we load the kubeadm types from the cluster.
-	initCfg, err := configutil.FetchInitConfigurationFromCluster(client, os.Stdout, logPrefix, false, true)
+	initCfg, err := configutil.FetchInitConfigurationFromCluster(client, printer, logPrefix, false, true)
 	if err != nil {
 		return nil, false, err
 	}
@@ -121,27 +122,27 @@ func loadConfig(cfgPath string, client clientset.Interface, skipComponentConfigs
 }
 
 // enforceRequirements verifies that it's okay to upgrade and then returns the variables needed for the rest of the procedure
-func enforceRequirements(flags *applyPlanFlags, args []string, dryRun bool, upgradeApply bool) (clientset.Interface, upgrade.VersionGetter, *kubeadmapi.InitConfiguration, error) {
+func enforceRequirements(flags *applyPlanFlags, args []string, dryRun bool, upgradeApply bool, printer output.Printer) (clientset.Interface, upgrade.VersionGetter, *kubeadmapi.InitConfiguration, error) {
 	client, err := getClient(flags.kubeConfigPath, dryRun)
 	if err != nil {
 		return nil, nil, nil, errors.Wrapf(err, "couldn't create a Kubernetes client from file %q", flags.kubeConfigPath)
 	}
 
 	// Fetch the configuration from a file or ConfigMap and validate it
-	fmt.Println("[upgrade/config] Making sure the configuration is correct:")
+	printer.Printf("[upgrade/config] Making sure the configuration is correct:\n")
 
 	var newK8sVersion string
-	cfg, legacyReconfigure, err := loadConfig(flags.cfgPath, client, !upgradeApply)
+	cfg, legacyReconfigure, err := loadConfig(flags.cfgPath, client, !upgradeApply, printer)
 	if err != nil {
 		if apierrors.IsNotFound(err) {
-			fmt.Printf("[upgrade/config] In order to upgrade, a ConfigMap called %q in the %s namespace must exist.\n", constants.KubeadmConfigConfigMap, metav1.NamespaceSystem)
+			printer.Printf("[upgrade/config] In order to upgrade, a ConfigMap called %q in the %s namespace must exist.\n", constants.KubeadmConfigConfigMap, metav1.NamespaceSystem)
-			fmt.Println("[upgrade/config] Without this information, 'kubeadm upgrade' won't know how to configure your upgraded cluster.")
+			printer.Printf("[upgrade/config] Without this information, 'kubeadm upgrade' won't know how to configure your upgraded cluster.\n")
-			fmt.Println("")
+			printer.Println()
-			fmt.Println("[upgrade/config] Next steps:")
+			printer.Printf("[upgrade/config] Next steps:\n")
-			fmt.Printf("\t- OPTION 1: Run 'kubeadm config upload from-flags' and specify the same CLI arguments you passed to 'kubeadm init' when you created your control-plane.\n")
+			printer.Printf("\t- OPTION 1: Run 'kubeadm config upload from-flags' and specify the same CLI arguments you passed to 'kubeadm init' when you created your control-plane.\n")
-			fmt.Printf("\t- OPTION 2: Run 'kubeadm config upload from-file' and specify the same config file you passed to 'kubeadm init' when you created your control-plane.\n")
+			printer.Printf("\t- OPTION 2: Run 'kubeadm config upload from-file' and specify the same config file you passed to 'kubeadm init' when you created your control-plane.\n")
-			fmt.Printf("\t- OPTION 3: Pass a config file to 'kubeadm upgrade' using the --config flag.\n")
+			printer.Printf("\t- OPTION 3: Pass a config file to 'kubeadm upgrade' using the --config flag.\n")
-			fmt.Println("")
+			printer.Println()
 			err = errors.Errorf("the ConfigMap %q in the %s namespace used for getting configuration information was not found", constants.KubeadmConfigConfigMap, metav1.NamespaceSystem)
 		}
 		return nil, nil, nil, errors.Wrap(err, "[upgrade/config] FATAL")
@@ -161,7 +162,7 @@ func enforceRequirements(flags *applyPlanFlags, args []string, dryRun bool, upgr
 
 	// Ensure the user is root
 	klog.V(1).Info("running preflight checks")
-	if err := runPreflightChecks(client, ignorePreflightErrorsSet, &cfg.ClusterConfiguration); err != nil {
+	if err := runPreflightChecks(client, ignorePreflightErrorsSet, &cfg.ClusterConfiguration, printer); err != nil {
 		return nil, nil, nil, err
 	}
 
@@ -202,14 +203,14 @@ func enforceRequirements(flags *applyPlanFlags, args []string, dryRun bool, upgr
 	// Check if feature gate flags used in the cluster are consistent with the set of features currently supported by kubeadm
 	if msg := features.CheckDeprecatedFlags(&features.InitFeatureGates, cfg.FeatureGates); len(msg) > 0 {
 		for _, m := range msg {
-			fmt.Printf("[upgrade/config] %s\n", m)
+			printer.Printf("[upgrade/config] %s\n", m)
 		}
 		return nil, nil, nil, errors.New("[upgrade/config] FATAL. Unable to upgrade a cluster using deprecated feature-gate flags. Please see the release notes")
 	}
 
 	// If the user told us to print this information out; do it!
 	if flags.printConfig {
-		printConfiguration(&cfg.ClusterConfiguration, os.Stdout)
+		printConfiguration(&cfg.ClusterConfiguration, os.Stdout, printer)
 	}
 
 	// Use a real version getter interface that queries the API server, the kubeadm client and the Kubernetes CI system for latest versions
@@ -217,7 +218,7 @@ func enforceRequirements(flags *applyPlanFlags, args []string, dryRun bool, upgr
 }
 
 // printConfiguration prints the external version of the API to yaml
-func printConfiguration(clustercfg *kubeadmapi.ClusterConfiguration, w io.Writer) {
+func printConfiguration(clustercfg *kubeadmapi.ClusterConfiguration, w io.Writer, printer output.Printer) {
 	// Short-circuit if cfg is nil, so we can safely get the value of the pointer below
 	if clustercfg == nil {
 		return
@@ -225,18 +226,18 @@ func printConfiguration(clustercfg *kubeadmapi.ClusterConfiguration, w io.Writer
 
 	cfgYaml, err := configutil.MarshalKubeadmConfigObject(clustercfg)
 	if err == nil {
-		fmt.Fprintln(w, "[upgrade/config] Configuration used:")
+		printer.Fprintln(w, "[upgrade/config] Configuration used:")
 
 		scanner := bufio.NewScanner(bytes.NewReader(cfgYaml))
 		for scanner.Scan() {
-			fmt.Fprintf(w, "\t%s\n", scanner.Text())
+			printer.Fprintf(w, "\t%s\n", scanner.Text())
 		}
 	}
 }
 
 // runPreflightChecks runs the root preflight check
-func runPreflightChecks(client clientset.Interface, ignorePreflightErrors sets.String, cfg *kubeadmapi.ClusterConfiguration) error {
+func runPreflightChecks(client clientset.Interface, ignorePreflightErrors sets.String, cfg *kubeadmapi.ClusterConfiguration, printer output.Printer) error {
-	fmt.Println("[preflight] Running pre-flight checks.")
+	printer.Printf("[preflight] Running pre-flight checks.\n")
 	err := preflight.RunRootCheckOnly(ignorePreflightErrors)
 	if err != nil {
 		return err

cmd/kubeadm/app/cmd/upgrade/common_test.go

@@ -23,6 +23,7 @@ import (
 
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmapiv1 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta3"
+	"k8s.io/kubernetes/cmd/kubeadm/app/util/output"
 )
 
 func TestEnforceRequirements(t *testing.T) {
@@ -54,7 +55,7 @@ func TestEnforceRequirements(t *testing.T) {
 	}
 	for _, tt := range tcases {
 		t.Run(tt.name, func(t *testing.T) {
-			_, _, _, err := enforceRequirements(&tt.flags, nil, tt.dryRun, false)
+			_, _, _, err := enforceRequirements(&tt.flags, nil, tt.dryRun, false, &output.TextPrinter{})
 
 			if err == nil && tt.expectedErr {
 				t.Error("Expected error, but got success")
@@ -138,7 +139,7 @@ func TestPrintConfiguration(t *testing.T) {
 	for _, rt := range tests {
 		t.Run(rt.name, func(t *testing.T) {
 			rt.buf = bytes.NewBufferString("")
-			printConfiguration(rt.cfg, rt.buf)
+			printConfiguration(rt.cfg, rt.buf, &output.TextPrinter{})
 			actualBytes := rt.buf.Bytes()
 			if !bytes.Equal(actualBytes, rt.expectedBytes) {
 				t.Errorf(

cmd/kubeadm/app/cmd/upgrade/diff.go

@@ -118,7 +118,7 @@ func runDiff(flags *diffFlags, args []string) error {
 		if err != nil {
 			return errors.Wrapf(err, "couldn't create a Kubernetes client from file %q", flags.kubeConfigPath)
 		}
-		cfg, err = configutil.FetchInitConfigurationFromCluster(client, flags.out, "upgrade/diff", false, false)
+		cfg, err = configutil.FetchInitConfigurationFromCluster(client, nil, "upgrade/diff", false, false)
 	}
 	if err != nil {
 		return err

cmd/kubeadm/app/cmd/upgrade/node.go

@@ -139,7 +139,7 @@ func newNodeData(cmd *cobra.Command, args []string, options *nodeOptions) (*node
 	// Fetches the cluster configuration
 	// NB in case of control-plane node, we are reading all the info for the node; in case of NOT control-plane node
 	//    (worker node), we are not reading local API address and the CRI socket from the node object
-	cfg, err := configutil.FetchInitConfigurationFromCluster(client, os.Stdout, "upgrade", !isControlPlaneNode, false)
+	cfg, err := configutil.FetchInitConfigurationFromCluster(client, nil, "upgrade", !isControlPlaneNode, false)
 	if err != nil {
 		return nil, errors.Wrap(err, "unable to fetch the kubeadm-config ConfigMap")
 	}

cmd/kubeadm/app/cmd/upgrade/plan.go

@@ -28,16 +28,21 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/version"
+	"k8s.io/cli-runtime/pkg/genericclioptions"
+	"k8s.io/cli-runtime/pkg/printers"
 	clientset "k8s.io/client-go/kubernetes"
 	"k8s.io/klog/v2"
 
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
-	outputapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/output"
+	outputapischeme "k8s.io/kubernetes/cmd/kubeadm/app/apis/output/scheme"
+	outputapiv1alpha2 "k8s.io/kubernetes/cmd/kubeadm/app/apis/output/v1alpha2"
 	"k8s.io/kubernetes/cmd/kubeadm/app/componentconfigs"
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/phases/upgrade"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
+	"k8s.io/kubernetes/cmd/kubeadm/app/util/output"
 )
 
 type planFlags struct {
@@ -50,25 +55,202 @@ func newCmdPlan(apf *applyPlanFlags) *cobra.Command {
 		applyPlanFlags: apf,
 	}
 
+	outputFlags := newUpgradePlanPrintFlags(output.TextOutput)
+
 	cmd := &cobra.Command{
 		Use:   "plan [version] [flags]",
 		Short: "Check which versions are available to upgrade to and validate whether your current cluster is upgradeable. To skip the internet check, pass in the optional [version] parameter",
 		RunE: func(_ *cobra.Command, args []string) error {
-			return runPlan(flags, args)
+			printer, err := outputFlags.ToPrinter()
+			if err != nil {
+				return errors.Wrap(err, "could not construct output printer")
+			}
+
+			return runPlan(flags, args, printer)
 		},
 	}
 
+	outputFlags.AddFlags(cmd)
+
 	// Register the common flags for apply and plan
 	addApplyPlanFlags(cmd.Flags(), flags.applyPlanFlags)
 	return cmd
 }
 
+// newComponentUpgradePlan helper creates outputapiv1alpha2.ComponentUpgradePlan object
+func newComponentUpgradePlan(name, currentVersion, newVersion string) outputapiv1alpha2.ComponentUpgradePlan {
+	return outputapiv1alpha2.ComponentUpgradePlan{
+		Name:           name,
+		CurrentVersion: currentVersion,
+		NewVersion:     newVersion,
+	}
+}
+
+// upgradePlanPrintFlags defines a printer flag structure for the
+// upgrade plan kubeadm command and provides a method
+// of retrieving a known printer based on flag values provided.
+type upgradePlanPrintFlags struct {
+	// JSONYamlPrintFlags provides default flags necessary for json/yaml printing
+	JSONYamlPrintFlags *upgradePlanJSONYamlPrintFlags
+	// TextPrintFlags provides default flags necessary for text printing
+	TextPrintFlags *upgradePlanTextPrintFlags
+	// TypeSetterPrinter is an implementation of ResourcePrinter that wraps another printer with types set on the objects
+	TypeSetterPrinter *printers.TypeSetterPrinter
+	// OutputFormat contains currently set output format
+	OutputFormat string
+}
+
+func newUpgradePlanPrintFlags(outputFormat string) *upgradePlanPrintFlags {
+	return &upgradePlanPrintFlags{
+		JSONYamlPrintFlags: &upgradePlanJSONYamlPrintFlags{},
+		TextPrintFlags:     &upgradePlanTextPrintFlags{},
+		TypeSetterPrinter:  printers.NewTypeSetter(outputapischeme.Scheme),
+		OutputFormat:       strings.ToLower(outputFormat),
+	}
+}
+
+// AllowedFormats returns a list of allowed output formats
+func (pf *upgradePlanPrintFlags) AllowedFormats() []string {
+	ret := pf.TextPrintFlags.AllowedFormats()
+	return append(ret, pf.JSONYamlPrintFlags.AllowedFormats()...)
+}
+
+// AddFlags receives a *cobra.Command reference and binds
+// flags related to Kubeadm printing to it
+func (pf *upgradePlanPrintFlags) AddFlags(cmd *cobra.Command) {
+	pf.TextPrintFlags.AddFlags(cmd)
+	pf.JSONYamlPrintFlags.AddFlags(cmd)
+	// TODO: once we are confident the feature is graduated we should remove the EXPERIMENTAL text below:
+	// https://github.com/kubernetes/kubeadm/issues/494
+	cmd.Flags().StringVarP(&pf.OutputFormat, "output", "o", pf.OutputFormat, fmt.Sprintf("EXPERIMENTAL: Output format. One of: %s.", strings.Join(pf.AllowedFormats(), "|")))
+}
+
+// ToPrinter receives an outputFormat and returns a printer capable of
+// handling format printing.
+// Returns error if the specified outputFormat does not match supported formats.
+func (pf *upgradePlanPrintFlags) ToPrinter() (output.Printer, error) {
+	switch pf.OutputFormat {
+	case output.TextOutput:
+		return pf.TextPrintFlags.ToPrinter(pf.OutputFormat)
+	case output.JSONOutput:
+		return newUpgradePlanJSONYAMLPrinter(pf.TypeSetterPrinter.WrapToPrinter(pf.JSONYamlPrintFlags.ToPrinter(output.JSONOutput)))
+	case output.YAMLOutput:
+		return newUpgradePlanJSONYAMLPrinter(pf.TypeSetterPrinter.WrapToPrinter(pf.JSONYamlPrintFlags.ToPrinter(output.YAMLOutput)))
+	default:
+		return nil, genericclioptions.NoCompatiblePrinterError{OutputFormat: &pf.OutputFormat, AllowedFormats: pf.AllowedFormats()}
+	}
+}
+
+type upgradePlanJSONYamlPrintFlags struct {
+	genericclioptions.JSONYamlPrintFlags
+}
+
+// AllowedFormats returns a list of allowed output formats
+func (pf *upgradePlanJSONYamlPrintFlags) AllowedFormats() []string {
+	return []string{output.JSONOutput, output.YAMLOutput}
+}
+
+// upgradePlanJSONYAMLPrinter prints upgrade plan in a JSON or YAML format
+type upgradePlanJSONYAMLPrinter struct {
+	output.ResourcePrinterWrapper
+	Buffer []outputapiv1alpha2.ComponentUpgradePlan
+}
+
+// newUpgradePlanJSONYAMLPrinter creates a new upgradePlanJSONYAMLPrinter object
+func newUpgradePlanJSONYAMLPrinter(resourcePrinter printers.ResourcePrinter, err error) (output.Printer, error) {
+	if err != nil {
+		return nil, err
+	}
+	return &upgradePlanJSONYAMLPrinter{ResourcePrinterWrapper: output.ResourcePrinterWrapper{Printer: resourcePrinter}}, nil
+}
+
+// PrintObj is an implementation of ResourcePrinter.PrintObj that adds object to the buffer
+func (p *upgradePlanJSONYAMLPrinter) PrintObj(obj runtime.Object, writer io.Writer) error {
+	item, ok := obj.(*outputapiv1alpha2.ComponentUpgradePlan)
+	if !ok {
+		return errors.Errorf("expected ComponentUpgradePlan, but got %+v", obj)
+	}
+	p.Buffer = append(p.Buffer, *item)
+	return nil
+}
+
+// Flush writes any buffered data once last object is added
+func (p *upgradePlanJSONYAMLPrinter) Flush(writer io.Writer, last bool) {
+	if !last {
+		return
+	}
+	if len(p.Buffer) == 0 {
+		return
+	}
+	plan := &outputapiv1alpha2.UpgradePlan{Components: p.Buffer}
+	if err := p.Printer.PrintObj(plan, writer); err != nil {
+		fmt.Fprintf(os.Stderr, "could not flush output buffer: %v\n", err)
+	}
+}
+
+// Close empties the list of buffered components
+func (p *upgradePlanJSONYAMLPrinter) Close(writer io.Writer) {
+	p.Buffer = p.Buffer[:0]
+}
+
+// upgradePlanTextPrinter prints upgrade plan in a text form
+type upgradePlanTextPrinter struct {
+	output.TextPrinter
+	columns   []string
+	tabwriter *tabwriter.Writer
+}
+
+// Flush writes any buffered data
+func (p *upgradePlanTextPrinter) Flush(writer io.Writer, last bool) {
+	if p.tabwriter != nil {
+		p.tabwriter.Flush()
+		p.tabwriter = nil
+		p.Fprintln(writer, "")
+	}
+}
+
+// PrintObj is an implementation of ResourcePrinter.PrintObj for upgrade plan plain text output
+func (p *upgradePlanTextPrinter) PrintObj(obj runtime.Object, writer io.Writer) error {
+	if p.tabwriter == nil {
+		p.tabwriter = tabwriter.NewWriter(writer, 10, 4, 3, ' ', 0)
+		// Print header
+		fmt.Fprintln(p.tabwriter, strings.Join(p.columns, "\t"))
+	}
+
+	item, ok := obj.(*outputapiv1alpha2.ComponentUpgradePlan)
+	if !ok {
+		return errors.Errorf("expected ComponentUpgradePlan, but got %+v", obj)
+	}
+
+	// Print item
+	fmt.Fprintf(p.tabwriter, "%s\t%s\t%s\n", item.Name, item.CurrentVersion, item.NewVersion)
+	return nil
+}
+
+// upgradePlanTextPrintFlags provides flags necessary for printing upgrade plan in a text form
+type upgradePlanTextPrintFlags struct{}
+
+func (pf *upgradePlanTextPrintFlags) AddFlags(cmd *cobra.Command) {}
+
+// AllowedFormats returns a list of allowed output formats
+func (pf *upgradePlanTextPrintFlags) AllowedFormats() []string {
+	return []string{output.TextOutput}
+}
+
+// ToPrinter returns a kubeadm printer for the text output format
+func (pf *upgradePlanTextPrintFlags) ToPrinter(outputFormat string) (output.Printer, error) {
+	if outputFormat == output.TextOutput {
+		return &upgradePlanTextPrinter{columns: []string{"COMPONENT", "CURRENT", "TARGET"}}, nil
+	}
+	return nil, genericclioptions.NoCompatiblePrinterError{OutputFormat: &outputFormat, AllowedFormats: []string{output.JSONOutput, output.YAMLOutput, output.TextOutput}}
+}
+
 // runPlan takes care of outputting available versions to upgrade to for the user
-func runPlan(flags *planFlags, args []string) error {
+func runPlan(flags *planFlags, args []string, printer output.Printer) error {
 	// Start with the basics, verify that the cluster is healthy, build a client and a versionGetter. Never dry-run when planning.
 	klog.V(1).Infoln("[upgrade/plan] verifying health of cluster")
 	klog.V(1).Infoln("[upgrade/plan] retrieving configuration from cluster")
-	client, versionGetter, cfg, err := enforceRequirements(flags.applyPlanFlags, args, false, false)
+	client, versionGetter, cfg, err := enforceRequirements(flags.applyPlanFlags, args, false, false, printer)
 	if err != nil {
 		return err
 	}
@@ -79,7 +261,7 @@ func runPlan(flags *planFlags, args []string) error {
 
 	// Compute which upgrade possibilities there are
 	klog.V(1).Infoln("[upgrade/plan] computing upgrade possibilities")
-	availUpgrades, err := upgrade.GetAvailableUpgrades(versionGetter, flags.allowExperimentalUpgrades, flags.allowRCUpgrades, isExternalEtcd, client, constants.GetStaticPodDirectory())
+	availUpgrades, err := upgrade.GetAvailableUpgrades(versionGetter, flags.allowExperimentalUpgrades, flags.allowRCUpgrades, isExternalEtcd, client, constants.GetStaticPodDirectory(), printer)
 	if err != nil {
 		return errors.Wrap(err, "[upgrade/versions] FATAL")
 	}
@@ -109,27 +291,17 @@ func runPlan(flags *planFlags, args []string) error {
 		// in the human readable output if it did so
 		plan.ConfigVersions = configVersionStates
 
-		printUpgradePlan(&up, plan, unstableVersionFlag, isExternalEtcd, os.Stdout)
+		printUpgradePlan(&up, plan, unstableVersionFlag, isExternalEtcd, os.Stdout, printer)
 	}
 
 	// Finally, print the component config state table
-	printComponentConfigVersionStates(configVersionStates, os.Stdout)
+	printComponentConfigVersionStates(configVersionStates, os.Stdout, printer)
-
 	return nil
 }
 
-// newComponentUpgradePlan helper creates outputapi.ComponentUpgradePlan object
-func newComponentUpgradePlan(name, currentVersion, newVersion string) outputapi.ComponentUpgradePlan {
-	return outputapi.ComponentUpgradePlan{
-		Name:           name,
-		CurrentVersion: currentVersion,
-		NewVersion:     newVersion,
-	}
-}
-
 // TODO There is currently no way to cleanly output upgrades that involve adding, removing, or changing components
 // https://github.com/kubernetes/kubeadm/issues/810 was created to track addressing this.
-func appendDNSComponent(components []outputapi.ComponentUpgradePlan, up *upgrade.Upgrade, name string) []outputapi.ComponentUpgradePlan {
+func appendDNSComponent(components []outputapiv1alpha2.ComponentUpgradePlan, up *upgrade.Upgrade, name string) []outputapiv1alpha2.ComponentUpgradePlan {
 	beforeVersion := up.Before.DNSVersion
 	afterVersion := up.After.DNSVersion
 
@@ -140,7 +312,7 @@ func appendDNSComponent(components []outputapi.ComponentUpgradePlan, up *upgrade
 }
 
 // genUpgradePlan generates output-friendly upgrade plan out of upgrade.Upgrade structure
-func genUpgradePlan(up *upgrade.Upgrade, isExternalEtcd bool) (*outputapi.UpgradePlan, string, error) {
+func genUpgradePlan(up *upgrade.Upgrade, isExternalEtcd bool) (*outputapiv1alpha2.UpgradePlan, string, error) {
 	newK8sVersion, err := version.ParseSemantic(up.After.KubeVersion)
 	if err != nil {
 		return nil, "", errors.Wrapf(err, "Unable to parse normalized version %q as a semantic version", up.After.KubeVersion)
@@ -155,7 +327,7 @@ func genUpgradePlan(up *upgrade.Upgrade, isExternalEtcd bool) (*outputapi.Upgrad
 		}
 	}
 
-	components := []outputapi.ComponentUpgradePlan{}
+	components := []outputapiv1alpha2.ComponentUpgradePlan{}
 
 	if up.CanUpgradeKubelets() {
 		// The map is of the form <old-version>:<node-count>. Here all the keys are put into a slice and sorted
@@ -177,10 +349,10 @@ func genUpgradePlan(up *upgrade.Upgrade, isExternalEtcd bool) (*outputapi.Upgrad
 		components = append(components, newComponentUpgradePlan(constants.Etcd, up.Before.EtcdVersion, up.After.EtcdVersion))
 	}
 
-	return &outputapi.UpgradePlan{Components: components}, unstableVersionFlag, nil
+	return &outputapiv1alpha2.UpgradePlan{Components: components}, unstableVersionFlag, nil
 }
 
-func getComponentConfigVersionStates(cfg *kubeadmapi.ClusterConfiguration, client clientset.Interface, cfgPath string) ([]outputapi.ComponentConfigVersionState, error) {
+func getComponentConfigVersionStates(cfg *kubeadmapi.ClusterConfiguration, client clientset.Interface, cfgPath string) ([]outputapiv1alpha2.ComponentConfigVersionState, error) {
 	docmap := kubeadmapi.DocumentMap{}
 
 	if cfgPath != "" {
@@ -199,16 +371,7 @@ func getComponentConfigVersionStates(cfg *kubeadmapi.ClusterConfiguration, clien
 }
 
 // printUpgradePlan prints a UX-friendly overview of what versions are available to upgrade to
-func printUpgradePlan(up *upgrade.Upgrade, plan *outputapi.UpgradePlan, unstableVersionFlag string, isExternalEtcd bool, w io.Writer) {
+func printUpgradePlan(up *upgrade.Upgrade, plan *outputapiv1alpha2.UpgradePlan, unstableVersionFlag string, isExternalEtcd bool, writer io.Writer, printer output.Printer) {
-	// The tab writer writes to the "real" writer w
-	tabw := tabwriter.NewWriter(w, 10, 4, 3, ' ', 0)
-
-	// endOfTable helper function flashes table writer
-	endOfTable := func() {
-		tabw.Flush()
-		fmt.Fprintln(w, "")
-	}
-
 	printHeader := true
 	printManualUpgradeHeader := true
 	for _, component := range plan.Components {
@@ -217,41 +380,40 @@ func printUpgradePlan(up *upgrade.Upgrade, plan *outputapi.UpgradePlan, unstable
 			continue
 		} else if component.Name == constants.Kubelet {
 			if printManualUpgradeHeader {
-				fmt.Fprintln(w, "Components that must be upgraded manually after you have upgraded the control plane with 'kubeadm upgrade apply':")
+				printer.Fprintln(writer, "Components that must be upgraded manually after you have upgraded the control plane with 'kubeadm upgrade apply':")
-				fmt.Fprintln(tabw, "COMPONENT\tCURRENT\tTARGET")
+				plan := newComponentUpgradePlan(component.Name, component.CurrentVersion, component.NewVersion)
-				fmt.Fprintf(tabw, "%s\t%s\t%s\n", component.Name, component.CurrentVersion, component.NewVersion)
+				printer.PrintObj(&plan, writer)
 				printManualUpgradeHeader = false
 			} else {
-				fmt.Fprintf(tabw, "%s\t%s\t%s\n", "", component.CurrentVersion, component.NewVersion)
+				plan := newComponentUpgradePlan("", component.CurrentVersion, component.NewVersion)
+				printer.PrintObj(&plan, writer)
 			}
 		} else {
 			if printHeader {
 				// End of manual upgrades table
-				endOfTable()
+				printer.Flush(writer, false)
-
+				printer.Fprintf(writer, "Upgrade to the latest %s:\n", up.Description)
-				fmt.Fprintf(w, "Upgrade to the latest %s:\n", up.Description)
+				printer.Fprintln(writer, "")
-				fmt.Fprintln(w, "")
-				fmt.Fprintln(tabw, "COMPONENT\tCURRENT\tTARGET")
 				printHeader = false
 			}
-			fmt.Fprintf(tabw, "%s\t%s\t%s\n", component.Name, component.CurrentVersion, component.NewVersion)
+			plan := newComponentUpgradePlan(component.Name, component.CurrentVersion, component.NewVersion)
+			printer.PrintObj(&plan, writer)
 		}
 	}
-	// End of control plane table
+	printer.Flush(writer, true)
-	endOfTable()
 
-	//fmt.Fprintln(w, "")
+	printer.Fprintln(writer, "You can now apply the upgrade by executing the following command:")
-	fmt.Fprintln(w, "You can now apply the upgrade by executing the following command:")
+	printer.Fprintln(writer, "")
-	fmt.Fprintln(w, "")
+	printer.Fprintf(writer, "\tkubeadm upgrade apply %s%s\n", up.After.KubeVersion, unstableVersionFlag)
-	fmt.Fprintf(w, "\tkubeadm upgrade apply %s%s\n", up.After.KubeVersion, unstableVersionFlag)
+	printer.Fprintln(writer, "")
-	fmt.Fprintln(w, "")
 
 	if up.Before.KubeadmVersion != up.After.KubeadmVersion {
-		fmt.Fprintf(w, "Note: Before you can perform this upgrade, you have to update kubeadm to %s.\n", up.After.KubeadmVersion)
+		printer.Fprintf(writer, "Note: Before you can perform this upgrade, you have to update kubeadm to %s.\n", up.After.KubeadmVersion)
-		fmt.Fprintln(w, "")
+		printer.Fprintln(writer, "")
 	}
 
-	printLineSeparator(w)
+	printLineSeparator(writer, printer)
+	printer.Close(writer)
 }
 
 // sortedSliceFromStringIntMap returns a slice of the keys in the map sorted alphabetically
@@ -278,18 +440,17 @@ func yesOrNo(b bool) string {
 	return "no"
 }
 
-func printLineSeparator(w io.Writer) {
+func printLineSeparator(w io.Writer, printer output.Printer) {
-	fmt.Fprintln(w, "_____________________________________________________________________")
+	printer.Fprintf(w, "_____________________________________________________________________\n\n")
-	fmt.Fprintln(w, "")
 }
 
-func printComponentConfigVersionStates(versionStates []outputapi.ComponentConfigVersionState, w io.Writer) {
+func printComponentConfigVersionStates(versionStates []outputapiv1alpha2.ComponentConfigVersionState, w io.Writer, printer output.Printer) {
 	if len(versionStates) == 0 {
-		fmt.Fprintln(w, "No information available on component configs.")
+		printer.Fprintln(w, "No information available on component configs.")
 		return
 	}
 
-	fmt.Fprintln(w, dedent.Dedent(`
+	printer.Fprintln(w, dedent.Dedent(`
 		The table below shows the current state of component configs as understood by this version of kubeadm.
 		Configs that have a "yes" mark in the "MANUAL UPGRADE REQUIRED" column require manual config upgrade or
 		resetting to kubeadm defaults before a successful upgrade can be performed. The version to manually
@@ -297,10 +458,10 @@ func printComponentConfigVersionStates(versionStates []outputapi.ComponentConfig
 	`))
 
 	tabw := tabwriter.NewWriter(w, 10, 4, 3, ' ', 0)
-	fmt.Fprintln(tabw, "API GROUP\tCURRENT VERSION\tPREFERRED VERSION\tMANUAL UPGRADE REQUIRED")
+	printer.Fprintln(tabw, "API GROUP\tCURRENT VERSION\tPREFERRED VERSION\tMANUAL UPGRADE REQUIRED")
 
 	for _, state := range versionStates {
-		fmt.Fprintf(tabw,
+		printer.Fprintf(tabw,
 			"%s\t%s\t%s\t%s\n",
 			state.Group,
 			strOrDash(state.CurrentVersion),
@@ -310,5 +471,5 @@ func printComponentConfigVersionStates(versionStates []outputapi.ComponentConfig
 	}
 
 	tabw.Flush()
-	printLineSeparator(w)
+	printLineSeparator(w, printer)
 }

cmd/kubeadm/app/cmd/upgrade/plan_test.go

@@ -22,6 +22,7 @@ import (
 	"testing"
 
 	"k8s.io/kubernetes/cmd/kubeadm/app/phases/upgrade"
+	"k8s.io/kubernetes/cmd/kubeadm/app/util/output"
 )
 
 func TestSortedSliceFromStringIntMap(t *testing.T) {
@@ -441,13 +442,19 @@ _____________________________________________________________________
 	for _, rt := range tests {
 		t.Run(rt.name, func(t *testing.T) {
 			rt.buf = bytes.NewBufferString("")
+			outputFlags := newUpgradePlanPrintFlags(output.TextOutput)
+			printer, err := outputFlags.ToPrinter()
+			if err != nil {
+				t.Errorf("failed ToPrinter, err: %+v", err)
+			}
+
 			// Generate and print upgrade plans
 			for _, up := range rt.upgrades {
 				plan, unstableVersionFlag, err := genUpgradePlan(&up, rt.externalEtcd)
 				if err != nil {
 					t.Errorf("failed genUpgradePlan, err: %+v", err)
 				}
-				printUpgradePlan(&up, plan, unstableVersionFlag, rt.externalEtcd, rt.buf)
+				printUpgradePlan(&up, plan, unstableVersionFlag, rt.externalEtcd, rt.buf, printer)
 			}
 			actualBytes := rt.buf.Bytes()
 			if !bytes.Equal(actualBytes, rt.expectedBytes) {
@@ -460,3 +467,164 @@ _____________________________________________________________________
 		})
 	}
 }
+
+func TestPrintAvailableUpgradesStructured(t *testing.T) {
+	upgrades := []upgrade.Upgrade{
+		{
+			Description: "version in the v1.8 series",
+			Before: upgrade.ClusterState{
+				KubeVersion: "v1.8.1",
+				KubeletVersions: map[string]uint16{
+					"v1.8.1": 1,
+				},
+				KubeadmVersion: "v1.8.2",
+				DNSVersion:     "1.14.5",
+				EtcdVersion:    "3.0.17",
+			},
+			After: upgrade.ClusterState{
+				KubeVersion:    "v1.8.3",
+				KubeadmVersion: "v1.8.3",
+				DNSVersion:     "1.14.5",
+				EtcdVersion:    "3.0.17",
+			},
+		},
+	}
+
+	var tests = []struct {
+		name         string
+		outputFormat string
+		buf          *bytes.Buffer
+		expected     string
+		externalEtcd bool
+	}{
+		{
+			name:         "JSON output",
+			outputFormat: "json",
+			expected: `{
+    "kind": "UpgradePlan",
+    "apiVersion": "output.kubeadm.k8s.io/v1alpha2",
+    "components": [
+        {
+            "name": "kubelet",
+            "currentVersion": "1 x v1.8.1",
+            "newVersion": "v1.8.3"
+        },
+        {
+            "name": "kube-apiserver",
+            "currentVersion": "v1.8.1",
+            "newVersion": "v1.8.3"
+        },
+        {
+            "name": "kube-controller-manager",
+            "currentVersion": "v1.8.1",
+            "newVersion": "v1.8.3"
+        },
+        {
+            "name": "kube-scheduler",
+            "currentVersion": "v1.8.1",
+            "newVersion": "v1.8.3"
+        },
+        {
+            "name": "kube-proxy",
+            "currentVersion": "v1.8.1",
+            "newVersion": "v1.8.3"
+        },
+        {
+            "name": "CoreDNS",
+            "currentVersion": "1.14.5",
+            "newVersion": "1.14.5"
+        },
+        {
+            "name": "etcd",
+            "currentVersion": "3.0.17",
+            "newVersion": "3.0.17"
+        }
+    ],
+    "configVersions": null
+}
+`,
+		},
+		{
+			name:         "YAML output",
+			outputFormat: "yaml",
+			expected: `apiVersion: output.kubeadm.k8s.io/v1alpha2
+components:
+- currentVersion: 1 x v1.8.1
+  name: kubelet
+  newVersion: v1.8.3
+- currentVersion: v1.8.1
+  name: kube-apiserver
+  newVersion: v1.8.3
+- currentVersion: v1.8.1
+  name: kube-controller-manager
+  newVersion: v1.8.3
+- currentVersion: v1.8.1
+  name: kube-scheduler
+  newVersion: v1.8.3
+- currentVersion: v1.8.1
+  name: kube-proxy
+  newVersion: v1.8.3
+- currentVersion: 1.14.5
+  name: CoreDNS
+  newVersion: 1.14.5
+- currentVersion: 3.0.17
+  name: etcd
+  newVersion: 3.0.17
+configVersions: null
+kind: UpgradePlan
+`,
+		},
+		{
+			name:         "Text output",
+			outputFormat: "Text",
+			expected: `Components that must be upgraded manually after you have upgraded the control plane with 'kubeadm upgrade apply':
+COMPONENT   CURRENT      TARGET
+kubelet     1 x v1.8.1   v1.8.3
+
+Upgrade to the latest version in the v1.8 series:
+
+COMPONENT                 CURRENT   TARGET
+kube-apiserver            v1.8.1    v1.8.3
+kube-controller-manager   v1.8.1    v1.8.3
+kube-scheduler            v1.8.1    v1.8.3
+kube-proxy                v1.8.1    v1.8.3
+CoreDNS                   1.14.5    1.14.5
+etcd                      3.0.17    3.0.17
+
+You can now apply the upgrade by executing the following command:
+
+	kubeadm upgrade apply v1.8.3
+
+Note: Before you can perform this upgrade, you have to update kubeadm to v1.8.3.
+
+_____________________________________________________________________
+
+`,
+		},
+	}
+
+	for _, rt := range tests {
+		t.Run(rt.name, func(t *testing.T) {
+			rt.buf = bytes.NewBufferString("")
+			outputFlags := newUpgradePlanPrintFlags(rt.outputFormat)
+			printer, err := outputFlags.ToPrinter()
+			if err != nil {
+				t.Errorf("failed ToPrinter, err: %+v", err)
+			}
+
+			// Generate and print upgrade plans
+			for _, up := range upgrades {
+				plan, unstableVersionFlag, err := genUpgradePlan(&up, rt.externalEtcd)
+				if err != nil {
+					t.Errorf("failed genUpgradePlan, err: %+v", err)
+				}
+				printUpgradePlan(&up, plan, unstableVersionFlag, rt.externalEtcd, rt.buf, printer)
+			}
+
+			actual := rt.buf.String()
+			if actual != rt.expected {
+				t.Errorf("failed PrintAvailableUpgrades:\n\nexpected:\n%s\n\nactual:\n%s", rt.expected, actual)
+			}
+		})
+	}
+}

cmd/kubeadm/app/componentconfigs/configset.go

@@ -28,7 +28,7 @@ import (
 	"k8s.io/klog/v2"
 
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
-	"k8s.io/kubernetes/cmd/kubeadm/app/apis/output"
+	outputapiv1alpha2 "k8s.io/kubernetes/cmd/kubeadm/app/apis/output/v1alpha2"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/apiclient"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/config/strict"
@@ -289,7 +289,7 @@ func FetchFromClusterWithLocalOverwrites(clusterCfg *kubeadmapi.ClusterConfigura
 
 // GetVersionStates returns a slice of ComponentConfigVersionState structs
 // describing all supported component config groups that were identified on the cluster
-func GetVersionStates(clusterCfg *kubeadmapi.ClusterConfiguration, client clientset.Interface, docmap kubeadmapi.DocumentMap) ([]output.ComponentConfigVersionState, error) {
+func GetVersionStates(clusterCfg *kubeadmapi.ClusterConfiguration, client clientset.Interface, docmap kubeadmapi.DocumentMap) ([]outputapiv1alpha2.ComponentConfigVersionState, error) {
 	// We don't want to modify clusterCfg so we make a working deep copy of it.
 	// Also, we don't want the defaulted component configs so we get rid of them.
 	scratchClusterCfg := clusterCfg.DeepCopy()
@@ -308,13 +308,13 @@ func GetVersionStates(clusterCfg *kubeadmapi.ClusterConfiguration, client client
 		}
 	}
 
-	results := []output.ComponentConfigVersionState{}
+	results := []outputapiv1alpha2.ComponentConfigVersionState{}
 	for _, handler := range known {
 		group := handler.GroupVersion.Group
 		if vererr, ok := multipleVerErrs[group]; ok {
 			// If there is an UnsupportedConfigVersionError then we are dealing with a case where the config was user
 			// supplied and requires manual upgrade
-			results = append(results, output.ComponentConfigVersionState{
+			results = append(results, outputapiv1alpha2.ComponentConfigVersionState{
 				Group:                 group,
 				CurrentVersion:        vererr.OldVersion.Version,
 				PreferredVersion:      vererr.CurrentVersion.Version,
@@ -322,7 +322,7 @@ func GetVersionStates(clusterCfg *kubeadmapi.ClusterConfiguration, client client
 			})
 		} else if _, ok := scratchClusterCfg.ComponentConfigs[group]; ok {
 			// Normally loaded component config. No manual upgrade required on behalf of users.
-			results = append(results, output.ComponentConfigVersionState{
+			results = append(results, outputapiv1alpha2.ComponentConfigVersionState{
 				Group:            group,
 				CurrentVersion:   handler.GroupVersion.Version, // Currently kubeadm supports only one version per API
 				PreferredVersion: handler.GroupVersion.Version, // group so we can get away with these being the same
@@ -331,7 +331,7 @@ func GetVersionStates(clusterCfg *kubeadmapi.ClusterConfiguration, client client
 			// This config was either not present (user did not install an addon) or the config was unsupported kubeadm
 			// generated one and is therefore skipped so we can automatically re-generate it (no action required on
 			// behalf of the user).
-			results = append(results, output.ComponentConfigVersionState{
+			results = append(results, outputapiv1alpha2.ComponentConfigVersionState{
 				Group:            group,
 				PreferredVersion: handler.GroupVersion.Version,
 			})

cmd/kubeadm/app/componentconfigs/fakeconfig_test.go

@@ -35,7 +35,7 @@ import (
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmscheme "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/scheme"
 	kubeadmapiv1 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta3"
-	outputapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/output"
+	outputapiv1alpha2 "k8s.io/kubernetes/cmd/kubeadm/app/apis/output/v1alpha2"
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 )
@@ -615,12 +615,12 @@ func TestFetchFromClusterWithLocalOverwrites(t *testing.T) {
 
 func TestGetVersionStates(t *testing.T) {
 	fakeKnownContext(func() {
-		versionStateCurrent := outputapi.ComponentConfigVersionState{
+		versionStateCurrent := outputapiv1alpha2.ComponentConfigVersionState{
 			Group:            kubeadmapiv1.GroupName,
 			CurrentVersion:   currentClusterConfigVersion,
 			PreferredVersion: currentClusterConfigVersion,
 		}
-		versionStateOld := outputapi.ComponentConfigVersionState{
+		versionStateOld := outputapiv1alpha2.ComponentConfigVersionState{
 			Group:                 kubeadmapiv1.GroupName,
 			CurrentVersion:        oldClusterConfigVersion,
 			PreferredVersion:      currentClusterConfigVersion,
@@ -631,7 +631,7 @@ func TestGetVersionStates(t *testing.T) {
 			desc     string
 			obj      runtime.Object
 			config   string
-			expected outputapi.ComponentConfigVersionState
+			expected outputapiv1alpha2.ComponentConfigVersionState
 		}{
 			{
 				desc:     "appropriate cluster object without overwrite",
@@ -687,7 +687,7 @@ func TestGetVersionStates(t *testing.T) {
 			{
 				desc: "old signed config without an overwrite",
 				obj:  testClusterConfigMap(oldFooClusterConfig, true),
-				expected: outputapi.ComponentConfigVersionState{
+				expected: outputapiv1alpha2.ComponentConfigVersionState{
 					Group:            kubeadmapiv1.GroupName,
 					CurrentVersion:   "", // The config is treated as if it's missing
 					PreferredVersion: currentClusterConfigVersion,

cmd/kubeadm/app/phases/upgrade/compute.go

@@ -26,6 +26,7 @@ import (
 
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/phases/addons/dns"
+	"k8s.io/kubernetes/cmd/kubeadm/app/util/output"
 )
 
 // Upgrade defines an upgrade possibility to upgrade from a current version to a new one
@@ -72,8 +73,8 @@ type ClusterState struct {
 
 // GetAvailableUpgrades fetches all versions from the specified VersionGetter and computes which
 // kinds of upgrades can be performed
-func GetAvailableUpgrades(versionGetterImpl VersionGetter, experimentalUpgradesAllowed, rcUpgradesAllowed, externalEtcd bool, client clientset.Interface, manifestsDir string) ([]Upgrade, error) {
+func GetAvailableUpgrades(versionGetterImpl VersionGetter, experimentalUpgradesAllowed, rcUpgradesAllowed, externalEtcd bool, client clientset.Interface, manifestsDir string, printer output.Printer) ([]Upgrade, error) {
-	fmt.Println("[upgrade] Fetching available versions to upgrade to")
+	printer.Printf("[upgrade] Fetching available versions to upgrade to\n")
 
 	// Collect the upgrades kubeadm can do in this list
 	upgrades := []Upgrade{}
@@ -83,14 +84,14 @@ func GetAvailableUpgrades(versionGetterImpl VersionGetter, experimentalUpgradesA
 	if err != nil {
 		return upgrades, err
 	}
-	fmt.Printf("[upgrade/versions] Cluster version: %s\n", clusterVersionStr)
+	printer.Printf("[upgrade/versions] Cluster version: %s\n", clusterVersionStr)
 
 	// Get current kubeadm CLI version
 	kubeadmVersionStr, kubeadmVersion, err := versionGetterImpl.KubeadmVersion()
 	if err != nil {
 		return upgrades, err
 	}
-	fmt.Printf("[upgrade/versions] kubeadm version: %s\n", kubeadmVersionStr)
+	printer.Printf("[upgrade/versions] kubeadm version: %s\n", kubeadmVersionStr)
 
 	// Get and output the current latest stable version
 	stableVersionStr, stableVersion, err := versionGetterImpl.VersionFromCILabel("stable", "stable version")
@@ -99,7 +100,7 @@ func GetAvailableUpgrades(versionGetterImpl VersionGetter, experimentalUpgradesA
 		klog.Warningf("[upgrade/versions] WARNING: Falling back to current kubeadm version as latest stable version")
 		stableVersionStr, stableVersion = kubeadmVersionStr, kubeadmVersion
 	} else {
-		fmt.Printf("[upgrade/versions] Target version: %s\n", stableVersionStr)
+		printer.Printf("[upgrade/versions] Target version: %s\n", stableVersionStr)
 	}
 
 	// Get the kubelet versions in the cluster
@@ -148,7 +149,7 @@ func GetAvailableUpgrades(versionGetterImpl VersionGetter, experimentalUpgradesA
 		if err != nil {
 			klog.Warningf("[upgrade/versions] WARNING: %v\n", err)
 		} else {
-			fmt.Printf("[upgrade/versions] Latest %s: %s\n", description, patchVersionStr)
+			printer.Printf("[upgrade/versions] Latest %s: %s\n", description, patchVersionStr)
 
 			// Check if a minor version upgrade is possible when a patch release exists
 			// It's only possible if the latest patch version is higher than the current patch version
@@ -267,7 +268,7 @@ func GetAvailableUpgrades(versionGetterImpl VersionGetter, experimentalUpgradesA
 	}
 
 	// Add a newline in the end of this output to leave some space to the next output section
-	fmt.Println("")
+	printer.Println()
 
 	return upgrades, nil
 }

cmd/kubeadm/app/phases/upgrade/compute_test.go

@@ -31,6 +31,7 @@ import (
 	clientsetfake "k8s.io/client-go/kubernetes/fake"
 
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
+	"k8s.io/kubernetes/cmd/kubeadm/app/util/output"
 )
 
 type fakeVersionGetter struct {
@@ -652,7 +653,7 @@ func TestGetAvailableUpgrades(t *testing.T) {
 				t.Fatalf("Unable to create test static pod manifest: %v", err)
 			}
 
-			actualUpgrades, actualErr := GetAvailableUpgrades(rt.vg, rt.allowExperimental, rt.allowRCs, rt.externalEtcd, client, manifestsDir)
+			actualUpgrades, actualErr := GetAvailableUpgrades(rt.vg, rt.allowExperimental, rt.allowRCs, rt.externalEtcd, client, manifestsDir, &output.TextPrinter{})
 			if !reflect.DeepEqual(actualUpgrades, rt.expectedUpgrades) {
 				t.Errorf("failed TestGetAvailableUpgrades\n\texpected upgrades: %v\n\tgot: %v", rt.expectedUpgrades, actualUpgrades)
 			}

cmd/kubeadm/app/util/config/cluster.go

@@ -20,7 +20,6 @@ import (
 	"context"
 	"crypto/x509"
 	"fmt"
-	"io"
 	"path/filepath"
 	"strings"
 
@@ -42,12 +41,16 @@ import (
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/apiclient"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/config/strict"
+	"k8s.io/kubernetes/cmd/kubeadm/app/util/output"
 )
 
 // FetchInitConfigurationFromCluster fetches configuration from a ConfigMap in the cluster
-func FetchInitConfigurationFromCluster(client clientset.Interface, w io.Writer, logPrefix string, newControlPlane, skipComponentConfigs bool) (*kubeadmapi.InitConfiguration, error) {
+func FetchInitConfigurationFromCluster(client clientset.Interface, printer output.Printer, logPrefix string, newControlPlane, skipComponentConfigs bool) (*kubeadmapi.InitConfiguration, error) {
-	fmt.Fprintf(w, "[%s] Reading configuration from the cluster...\n", logPrefix)
+	if printer == nil {
-	fmt.Fprintf(w, "[%s] FYI: You can look at this config file with 'kubectl -n %s get cm %s -o yaml'\n", logPrefix, metav1.NamespaceSystem, constants.KubeadmConfigConfigMap)
+		printer = &output.TextPrinter{}
+	}
+	printer.Printf("[%s] Reading configuration from the cluster...\n", logPrefix)
+	printer.Printf("[%s] FYI: You can look at this config file with 'kubectl -n %s get cm %s -o yaml'\n", logPrefix, metav1.NamespaceSystem, constants.KubeadmConfigConfigMap)
 
 	// Fetch the actual config from cluster
 	cfg, err := getInitConfigurationFromCluster(constants.KubernetesDir, client, newControlPlane, skipComponentConfigs)

cmd/kubeadm/app/util/output/output.go

@@ -28,8 +28,16 @@ import (
 	"k8s.io/cli-runtime/pkg/printers"
 )
 
-// TextOutput describes the plain text output
+const (
-const TextOutput = "text"
+	// TextOutput describes the plain text output
+	TextOutput = "text"
+
+	// JSONOutput describes the JSON output
+	JSONOutput = "json"
+
+	// YAMLOutput describes the YAML output
+	YAMLOutput = "yaml"
+)
 
 // TextPrintFlags is an interface to handle custom text output
 type TextPrintFlags interface {
@@ -44,7 +52,7 @@ type PrintFlags struct {
 	JSONYamlPrintFlags *genericclioptions.JSONYamlPrintFlags
 	// KubeTemplatePrintFlags composes print flags that provide both a JSONPath and a go-template printer.
 	KubeTemplatePrintFlags *genericclioptions.KubeTemplatePrintFlags
-	// JSONYamlPrintFlags provides default flags necessary for kubeadm text printing.
+	// TextPrintFlags provides default flags necessary for kubeadm text printing.
 	TextPrintFlags TextPrintFlags
 	// TypeSetterPrinter is an implementation of ResourcePrinter that wraps another printer with types set on the objects
 	TypeSetterPrinter *printers.TypeSetterPrinter
@@ -52,7 +60,7 @@ type PrintFlags struct {
 	OutputFormat *string
 }
 
-// AllowedFormats returns list of allowed output formats
+// AllowedFormats returns a list of allowed output formats
 func (pf *PrintFlags) AllowedFormats() []string {
 	ret := []string{TextOutput}
 	ret = append(ret, pf.JSONYamlPrintFlags.AllowedFormats()...)
@@ -133,7 +141,12 @@ func NewOutputFlags(textPrintFlags TextPrintFlags) *PrintFlags {
 type Printer interface {
 	PrintObj(obj runtime.Object, writer io.Writer) error
 	Fprintf(writer io.Writer, format string, args ...interface{}) (n int, err error)
+	Fprintln(writer io.Writer, args ...interface{}) (n int, err error)
 	Printf(format string, args ...interface{}) (n int, err error)
+	Println(args ...interface{}) (n int, err error)
+
+	Flush(writer io.Writer, last bool)
+	Close(writer io.Writer)
 }
 
 // TextPrinter implements Printer interface for generic text output
@@ -151,11 +164,29 @@ func (tp *TextPrinter) Fprintf(writer io.Writer, format string, args ...interfac
 	return fmt.Fprintf(writer, format, args...)
 }
 
+// Fprintln is a wrapper around fmt.Fprintln
+func (tp *TextPrinter) Fprintln(writer io.Writer, args ...interface{}) (n int, err error) {
+	return fmt.Fprintln(writer, args...)
+}
+
 // Printf is a wrapper around fmt.Printf
 func (tp *TextPrinter) Printf(format string, args ...interface{}) (n int, err error) {
 	return fmt.Printf(format, args...)
 }
 
+// Println is a wrapper around fmt.Printf
+func (tp *TextPrinter) Println(args ...interface{}) (n int, err error) {
+	return fmt.Println(args...)
+}
+
+// Flush writes any buffered data
+func (tp *TextPrinter) Flush(writer io.Writer, last bool) {
+}
+
+// Close flushes any buffered data and closes the printer
+func (tp *TextPrinter) Close(writer io.Writer) {
+}
+
 // ResourcePrinterWrapper wraps ResourcePrinter and implements Printer interface
 type ResourcePrinterWrapper struct {
 	Printer printers.ResourcePrinter
@@ -169,6 +200,14 @@ func NewResourcePrinterWrapper(resourcePrinter printers.ResourcePrinter, err err
 	return &ResourcePrinterWrapper{Printer: resourcePrinter}, nil
 }
 
+// Flush writes any buffered data
+func (rpw *ResourcePrinterWrapper) Flush(writer io.Writer, last bool) {
+}
+
+// Close flushes any buffered data and closes the printer
+func (rpw *ResourcePrinterWrapper) Close(writer io.Writer) {
+}
+
 // PrintObj is an implementation of ResourcePrinter.PrintObj that calls underlying printer API
 func (rpw *ResourcePrinterWrapper) PrintObj(obj runtime.Object, writer io.Writer) error {
 	return rpw.Printer.PrintObj(obj, writer)
@@ -181,9 +220,23 @@ func (rpw *ResourcePrinterWrapper) Fprintf(writer io.Writer, format string, args
 	return 0, nil
 }
 
+// Fprintln is an empty method to satisfy the Printer interface
+// and silent info printing for structured output
+// This method is usually redefined for the text output
+func (rpw *ResourcePrinterWrapper) Fprintln(writer io.Writer, args ...interface{}) (n int, err error) {
+	return 0, nil
+}
+
 // Printf is an empty method to satisfy Printer interface
 // and silent info printing for structured output
 // This method is usually redefined for the text output
 func (rpw *ResourcePrinterWrapper) Printf(format string, args ...interface{}) (n int, err error) {
 	return 0, nil
 }
+
+// Println is an empty method to satisfy Printer interface
+// and silent info printing for structured output
+// This method is usually redefined for the text output
+func (rpw *ResourcePrinterWrapper) Println(args ...interface{}) (n int, err error) {
+	return 0, nil
+}