kubeadm: Introduce config print init/join-defaults

In order to improve the UX of kubeadm, it was decided to introduce the
following subcommands:

- `kubeadm config print` - this is currently only a placeholder for subcommands
  that deal printing of some kind of configuration.
- `kubeadm config print init-defaults` - prints the default combination of
  InitConfiguration and ClusterConfiguration. Selected component configs can be
  printed too if the `--component-configs` command line switch is used.
- `kubeadm config print join-defaults` - prints the default JoinConfiguration.
  This command also supports the use of `--component-configs`.
- `kubeadm config print-defaults` is deprecated in favor of
  `kubeadm config print init/join-defaults`.

Signed-off-by: Rostislav M. Georgiev <rostislavg@vmware.com>

cmd/kubeadm/app/cmd/BUILD

@@ -95,9 +95,11 @@ go_test(
         "//cmd/kubeadm/app/apis/kubeadm/scheme:go_default_library",
         "//cmd/kubeadm/app/apis/kubeadm/v1beta1:go_default_library",
         "//cmd/kubeadm/app/apis/kubeadm/validation:go_default_library",
+        "//cmd/kubeadm/app/componentconfigs:go_default_library",
         "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/features:go_default_library",
         "//cmd/kubeadm/app/preflight:go_default_library",
+        "//cmd/kubeadm/app/util:go_default_library",
         "//cmd/kubeadm/app/util/config:go_default_library",
         "//cmd/kubeadm/app/util/runtime:go_default_library",
         "//staging/src/k8s.io/api/core/v1:go_default_library",

cmd/kubeadm/app/cmd/config.go

@@ -50,8 +50,8 @@ import (
 )
 
 var (
-	// sillyToken is only set statically to make kubeadm not randomize the token on every run
+	// placeholderToken is only set statically to make kubeadm not randomize the token on every run
-	sillyToken = kubeadmapiv1beta1.BootstrapToken{
+	placeholderToken = kubeadmapiv1beta1.BootstrapToken{
 		Token: &kubeadmapiv1beta1.BootstrapTokenString{
 			ID:     "abcdef",
 			Secret: "0123456789abcdef",
@@ -83,6 +83,7 @@ func NewCmdConfig(out io.Writer) *cobra.Command {
 	options.AddKubeConfigFlag(cmd.PersistentFlags(), &kubeConfigFile)
 
 	kubeConfigFile = cmdutil.FindExistingKubeConfig(kubeConfigFile)
+	cmd.AddCommand(NewCmdConfigPrint(out))
 	cmd.AddCommand(NewCmdConfigPrintDefault(out))
 	cmd.AddCommand(NewCmdConfigMigrate(out))
 	cmd.AddCommand(NewCmdConfigUpload(out, &kubeConfigFile))
@@ -91,6 +92,63 @@ func NewCmdConfig(out io.Writer) *cobra.Command {
 	return cmd
 }
 
+// NewCmdConfigPrint returns cobra.Command for "kubeadm config print" command
+func NewCmdConfigPrint(out io.Writer) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "print",
+		Short: "Print configuration",
+		Long:  "This command prints configurations for subcommands provided.",
+		RunE:  cmdutil.SubCmdRunE("print"),
+	}
+	cmd.AddCommand(NewCmdConfigPrintInitDefaults(out))
+	cmd.AddCommand(NewCmdConfigPrintJoinDefaults(out))
+	return cmd
+}
+
+// NewCmdConfigPrintInitDefaults returns cobra.Command for "kubeadm config print init-defaults" command
+func NewCmdConfigPrintInitDefaults(out io.Writer) *cobra.Command {
+	return newCmdConfigPrintActionDefaults(out, "init", getDefaultInitConfigBytes)
+}
+
+// NewCmdConfigPrintJoinDefaults returns cobra.Command for "kubeadm config print join-defaults" command
+func NewCmdConfigPrintJoinDefaults(out io.Writer) *cobra.Command {
+	return newCmdConfigPrintActionDefaults(out, "join", getDefaultNodeConfigBytes)
+}
+
+func newCmdConfigPrintActionDefaults(out io.Writer, action string, configBytesProc func() ([]byte, error)) *cobra.Command {
+	componentConfigs := []string{}
+	cmd := &cobra.Command{
+		Use:   fmt.Sprintf("%s-defaults", action),
+		Short: fmt.Sprintf("Print default %s configuration, that can be used for 'kubeadm %s'", action, action),
+		Long: fmt.Sprintf(dedent.Dedent(`
+			This command prints objects such as the default %s configuration that is used for 'kubeadm %s'.
+
+			Note that sensitive values like the Bootstrap Token fields are replaced with placeholder values like %q in order to pass validation but
+			not perform the real computation for creating a token.
+		`), action, action, placeholderToken),
+		Run: func(cmd *cobra.Command, args []string) {
+			runConfigPrintActionDefaults(out, componentConfigs, configBytesProc)
+		},
+	}
+	cmd.Flags().StringSliceVar(&componentConfigs, "component-configs", componentConfigs,
+		fmt.Sprintf("A comma-separated list for component config API objects to print the default values for. Available values: %v. If this flag is not set, no component configs will be printed.", getSupportedComponentConfigAPIObjects()))
+	return cmd
+}
+
+func runConfigPrintActionDefaults(out io.Writer, componentConfigs []string, configBytesProc func() ([]byte, error)) {
+	initialConfig, err := configBytesProc()
+	kubeadmutil.CheckErr(err)
+
+	allBytes := [][]byte{initialConfig}
+	for _, componentConfig := range componentConfigs {
+		cfgBytes, err := getDefaultComponentConfigAPIObjectBytes(componentConfig)
+		kubeadmutil.CheckErr(err)
+		allBytes = append(allBytes, cfgBytes)
+	}
+
+	fmt.Fprint(out, string(bytes.Join(allBytes, []byte(constants.YAMLDocumentSeparator))))
+}
+
 // NewCmdConfigPrintDefault returns cobra.Command for "kubeadm config print-default" command
 func NewCmdConfigPrintDefault(out io.Writer) *cobra.Command {
 	apiObjects := []string{}
@@ -104,9 +162,10 @@ func NewCmdConfigPrintDefault(out io.Writer) *cobra.Command {
 
 			For documentation visit: https://godoc.org/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha3
 
-			Note that sensitive values like the Bootstrap Token fields are replaced with silly values like %q in order to pass validation but
+			Note that sensitive values like the Bootstrap Token fields are replaced with placeholder values like %q in order to pass validation but
 			not perform the real computation for creating a token.
-		`), sillyToken),
+		`), placeholderToken),
+		Deprecated: "Please, use `kubeadm config print` instead.",
 		Run: func(cmd *cobra.Command, args []string) {
 			if len(apiObjects) == 0 {
 				apiObjects = getSupportedAPIObjects()
@@ -125,13 +184,21 @@ func NewCmdConfigPrintDefault(out io.Writer) *cobra.Command {
 	return cmd
 }
 
+func getDefaultComponentConfigAPIObjectBytes(apiObject string) ([]byte, error) {
+	registration, ok := componentconfigs.Known[componentconfigs.RegistrationKind(apiObject)]
+	if !ok {
+		return []byte{}, fmt.Errorf("--component-configs needs to contain some of %v", getSupportedComponentConfigAPIObjects())
+	}
+	return getDefaultComponentConfigBytes(registration)
+}
+
 func getDefaultAPIObjectBytes(apiObject string) ([]byte, error) {
 	switch apiObject {
 	case constants.InitConfigurationKind:
-		return getDefaultInitConfigBytes(constants.InitConfigurationKind)
+		return getDefaultInitConfigBytesByKind(constants.InitConfigurationKind)
 
 	case constants.ClusterConfigurationKind:
-		return getDefaultInitConfigBytes(constants.ClusterConfigurationKind)
+		return getDefaultInitConfigBytesByKind(constants.ClusterConfigurationKind)
 
 	case constants.JoinConfigurationKind:
 		return getDefaultNodeConfigBytes()
@@ -146,15 +213,23 @@ func getDefaultAPIObjectBytes(apiObject string) ([]byte, error) {
 	}
 }
 
-// getSupportedAPIObjects returns all currently supported API object names
+// getSupportedComponentConfigAPIObjects returns all currently supported component config API object names
-func getSupportedAPIObjects() []string {
+func getSupportedComponentConfigAPIObjects() []string {
-	objects := []string{constants.InitConfigurationKind, constants.ClusterConfigurationKind, constants.JoinConfigurationKind}
+	objects := []string{}
 	for componentType := range componentconfigs.Known {
 		objects = append(objects, string(componentType))
 	}
 	return objects
 }
 
+// getSupportedAPIObjects returns all currently supported API object names
+func getSupportedAPIObjects() []string {
+	baseObjects := []string{constants.InitConfigurationKind, constants.ClusterConfigurationKind, constants.JoinConfigurationKind}
+	objects := getSupportedComponentConfigAPIObjects()
+	objects = append(objects, baseObjects...)
+	return objects
+}
+
 // getAllAPIObjectNames returns currently supported API object names and their historical aliases
 // NB. currently there is no historical supported API objects, but we keep this function for future changes
 func getAllAPIObjectNames() []string {
@@ -171,18 +246,21 @@ func getDefaultedInitConfig() (*kubeadmapi.InitConfiguration, error) {
 		ClusterConfiguration: kubeadmapiv1beta1.ClusterConfiguration{
 			KubernetesVersion: fmt.Sprintf("v1.%d.0", constants.MinimumControlPlaneVersion.Minor()+1),
 		},
-		BootstrapTokens: []kubeadmapiv1beta1.BootstrapToken{sillyToken},
+		BootstrapTokens: []kubeadmapiv1beta1.BootstrapToken{placeholderToken},
 	})
 }
 
-// TODO: This is now invoked for both InitConfiguration and ClusterConfiguration, we should make separate versions of it
+func getDefaultInitConfigBytes() ([]byte, error) {
-func getDefaultInitConfigBytes(kind string) ([]byte, error) {
 	internalcfg, err := getDefaultedInitConfig()
 	if err != nil {
 		return []byte{}, err
 	}
 
-	b, err := configutil.MarshalKubeadmConfigObject(internalcfg)
+	return configutil.MarshalKubeadmConfigObject(internalcfg)
+}
+
+func getDefaultInitConfigBytesByKind(kind string) ([]byte, error) {
+	b, err := getDefaultInitConfigBytes()
 	if err != nil {
 		return []byte{}, err
 	}
@@ -197,7 +275,7 @@ func getDefaultNodeConfigBytes() ([]byte, error) {
 	internalcfg, err := configutil.JoinConfigFileAndDefaultsToInternalConfig("", &kubeadmapiv1beta1.JoinConfiguration{
 		Discovery: kubeadmapiv1beta1.Discovery{
 			BootstrapToken: &kubeadmapiv1beta1.BootstrapTokenDiscovery{
-				Token:                    sillyToken.Token.String(),
+				Token:                    placeholderToken.Token.String(),
 				APIServerEndpoints:       []string{"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/config_test.go

@@ -18,17 +18,24 @@ package cmd_test
 
 import (
 	"bytes"
+	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"reflect"
+	"sort"
 	"strings"
 	"testing"
 
 	"github.com/renstrom/dedent"
+	"github.com/spf13/cobra"
 
 	kubeadmapiv1beta1 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta1"
 	"k8s.io/kubernetes/cmd/kubeadm/app/cmd"
+	"k8s.io/kubernetes/cmd/kubeadm/app/componentconfigs"
+	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/features"
+	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 	configutil "k8s.io/kubernetes/cmd/kubeadm/app/util/config"
 	utilruntime "k8s.io/kubernetes/cmd/kubeadm/app/util/runtime"
 	"k8s.io/utils/exec"
@@ -272,3 +279,96 @@ func tempConfig(t *testing.T, config []byte) (string, func()) {
 		os.RemoveAll(tmpDir)
 	}
 }
+
+func TestNewCmdConfigPrintActionDefaults(t *testing.T) {
+	tests := []struct {
+		name             string
+		expectedKinds    []string // need to be sorted
+		componentConfigs string
+		cmdProc          func(out io.Writer) *cobra.Command
+	}{
+		{
+			name: "InitConfiguration: No component configs",
+			expectedKinds: []string{
+				constants.ClusterConfigurationKind,
+				constants.InitConfigurationKind,
+			},
+			cmdProc: cmd.NewCmdConfigPrintInitDefaults,
+		},
+		{
+			name: "InitConfiguration: KubeProxyConfiguration",
+			expectedKinds: []string{
+				constants.ClusterConfigurationKind,
+				constants.InitConfigurationKind,
+				string(componentconfigs.KubeProxyConfigurationKind),
+			},
+			componentConfigs: "KubeProxyConfiguration",
+			cmdProc:          cmd.NewCmdConfigPrintInitDefaults,
+		},
+		{
+			name: "InitConfiguration: KubeProxyConfiguration and KubeletConfiguration",
+			expectedKinds: []string{
+				constants.ClusterConfigurationKind,
+				constants.InitConfigurationKind,
+				string(componentconfigs.KubeProxyConfigurationKind),
+				string(componentconfigs.KubeletConfigurationKind),
+			},
+			componentConfigs: "KubeProxyConfiguration,KubeletConfiguration",
+			cmdProc:          cmd.NewCmdConfigPrintInitDefaults,
+		},
+		{
+			name: "JoinConfiguration: No component configs",
+			expectedKinds: []string{
+				constants.JoinConfigurationKind,
+			},
+			cmdProc: cmd.NewCmdConfigPrintJoinDefaults,
+		},
+		{
+			name: "JoinConfiguration: KubeProxyConfiguration",
+			expectedKinds: []string{
+				constants.JoinConfigurationKind,
+				string(componentconfigs.KubeProxyConfigurationKind),
+			},
+			componentConfigs: "KubeProxyConfiguration",
+			cmdProc:          cmd.NewCmdConfigPrintJoinDefaults,
+		},
+		{
+			name: "JoinConfiguration: KubeProxyConfiguration and KubeletConfiguration",
+			expectedKinds: []string{
+				constants.JoinConfigurationKind,
+				string(componentconfigs.KubeProxyConfigurationKind),
+				string(componentconfigs.KubeletConfigurationKind),
+			},
+			componentConfigs: "KubeProxyConfiguration,KubeletConfiguration",
+			cmdProc:          cmd.NewCmdConfigPrintJoinDefaults,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			var output bytes.Buffer
+
+			command := test.cmdProc(&output)
+			if err := command.Flags().Set("component-configs", test.componentConfigs); err != nil {
+				t.Fatalf("failed to set component-configs flag")
+			}
+			command.Run(nil, nil)
+
+			gvkmap, err := kubeadmutil.SplitYAMLDocuments(output.Bytes())
+			if err != nil {
+				t.Fatalf("unexpected failure of SplitYAMLDocuments: %v", err)
+			}
+
+			gotKinds := []string{}
+			for gvk := range gvkmap {
+				gotKinds = append(gotKinds, gvk.Kind)
+			}
+
+			sort.Strings(gotKinds)
+
+			if !reflect.DeepEqual(gotKinds, test.expectedKinds) {
+				t.Fatalf("kinds not matching:\n\texpectedKinds: %v\n\tgotKinds: %v\n", test.expectedKinds, gotKinds)
+			}
+		})
+	}
+}

docs/.generated_docs

@@ -75,7 +75,9 @@ docs/admin/kubeadm_config_images.md
 docs/admin/kubeadm_config_images_list.md
 docs/admin/kubeadm_config_images_pull.md
 docs/admin/kubeadm_config_migrate.md
-docs/admin/kubeadm_config_print-default.md
+docs/admin/kubeadm_config_print.md
+docs/admin/kubeadm_config_print_init-defaults.md
+docs/admin/kubeadm_config_print_join-defaults.md
 docs/admin/kubeadm_config_upload.md
 docs/admin/kubeadm_config_upload_from-file.md
 docs/admin/kubeadm_config_upload_from-flags.md
@@ -172,6 +174,9 @@ docs/man/man1/kubeadm-config-images-pull.1
 docs/man/man1/kubeadm-config-images.1
 docs/man/man1/kubeadm-config-migrate.1
 docs/man/man1/kubeadm-config-print-default.1
+docs/man/man1/kubeadm-config-print-init-defaults.1
+docs/man/man1/kubeadm-config-print-join-defaults.1
+docs/man/man1/kubeadm-config-print.1
 docs/man/man1/kubeadm-config-upload-from-file.1
 docs/man/man1/kubeadm-config-upload-from-flags.1
 docs/man/man1/kubeadm-config-upload.1

docs/admin/kubeadm_config_print_init-defaults.md

@@ -0,0 +1,3 @@
+This file is autogenerated, but we've stopped checking such files into the
+repository to reduce the need for rebases. Please run hack/generate-docs.sh to
+populate this file.

docs/admin/kubeadm_config_print_join-defaults.md

@@ -0,0 +1,3 @@
+This file is autogenerated, but we've stopped checking such files into the
+repository to reduce the need for rebases. Please run hack/generate-docs.sh to
+populate this file.

docs/man/man1/kubeadm-config-print-init-defaults.1

@@ -0,0 +1,3 @@
+This file is autogenerated, but we've stopped checking such files into the
+repository to reduce the need for rebases. Please run hack/generate-docs.sh to
+populate this file.

docs/man/man1/kubeadm-config-print-join-defaults.1

@@ -0,0 +1,3 @@
+This file is autogenerated, but we've stopped checking such files into the
+repository to reduce the need for rebases. Please run hack/generate-docs.sh to
+populate this file.

docs/man/man1/kubeadm-config-print.1

@@ -0,0 +1,3 @@
+This file is autogenerated, but we've stopped checking such files into the
+repository to reduce the need for rebases. Please run hack/generate-docs.sh to
+populate this file.