Adds a kubeadm config images pull command

cmd/kubeadm/app/cmd/config.go

 /*
-Copyright 2016 The Kubernetes Authors.
+Copyright 2018 The Kubernetes Authors.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -39,6 +39,7 @@ import (
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 	configutil "k8s.io/kubernetes/cmd/kubeadm/app/util/config"
 	kubeconfigutil "k8s.io/kubernetes/cmd/kubeadm/app/util/kubeconfig"
+	utilsexec "k8s.io/utils/exec"
 )
 
 // NewCmdConfig returns cobra.Command for "kubeadm config" command
@@ -214,13 +215,63 @@ func NewCmdConfigImages(out io.Writer) *cobra.Command {
 		RunE:  cmdutil.SubCmdRunE("images"),
 	}
 	cmd.AddCommand(NewCmdConfigImagesList(out))
+	cmd.AddCommand(NewCmdConfigImagesPull())
 	return cmd
 }
 
-// NewCmdConfigImagesList returns the "config images list" command
+// NewCmdConfigImagesPull returns the `config images pull` command
+func NewCmdConfigImagesPull() *cobra.Command {
+	cfg := &kubeadmapiv1alpha2.MasterConfiguration{}
+	kubeadmscheme.Scheme.Default(cfg)
+	var cfgPath, featureGatesString string
+	var err error
+	cmd := &cobra.Command{
+		Use:   "pull",
+		Short: "Pull images used by kubeadm.",
+		Run: func(_ *cobra.Command, _ []string) {
+			cfg.FeatureGates, err = features.NewFeatureGate(&features.InitFeatureGates, featureGatesString)
+			kubeadmutil.CheckErr(err)
+			internalcfg, err := configutil.ConfigFileAndDefaultsToInternalConfig(cfgPath, cfg)
+			kubeadmutil.CheckErr(err)
+			puller, err := images.NewImagePuller(utilsexec.New(), internalcfg.GetCRISocket())
+			kubeadmutil.CheckErr(err)
+			imagesPull := NewImagesPull(puller, images.GetAllImages(internalcfg))
+			kubeadmutil.CheckErr(imagesPull.PullAll())
+		},
+	}
+	AddImagesCommonConfigFlags(cmd.PersistentFlags(), cfg, &featureGatesString)
+	return cmd
+}
+
+// ImagesPull is the struct used to hold information relating to image pulling
+type ImagesPull struct {
+	puller images.Puller
+	images []string
+}
+
+// NewImagesPull initializes and returns the `config images pull` command
+func NewImagesPull(puller images.Puller, images []string) *ImagesPull {
+	return &ImagesPull{
+		puller: puller,
+		images: images,
+	}
+}
+
+// PullAll pulls all images that the ImagesPull knows about
+func (ip *ImagesPull) PullAll() error {
+	for _, image := range ip.images {
+		if err := ip.puller.Pull(image); err != nil {
+			return fmt.Errorf("failed to pull image %q: %v", image, err)
+		}
+		glog.Infof("[config/images] Pulled %s\n", image)
+	}
+	return nil
+}
+
+// NewCmdConfigImagesList returns the "kubeadm config images list" command
 func NewCmdConfigImagesList(out io.Writer) *cobra.Command {
 	cfg := &kubeadmapiv1alpha2.MasterConfiguration{}
-	kubeadmapiv1alpha2.SetDefaults_MasterConfiguration(cfg)
+	kubeadmscheme.Scheme.Default(cfg)
 	var cfgPath, featureGatesString string
 	var err error
 
@@ -228,15 +279,14 @@ func NewCmdConfigImagesList(out io.Writer) *cobra.Command {
 		Use:   "list",
 		Short: "Print a list of images kubeadm will use. The configuration file is used in case any images or image repositories are customized.",
 		Run: func(_ *cobra.Command, _ []string) {
-			if cfg.FeatureGates, err = features.NewFeatureGate(&features.InitFeatureGates, featureGatesString); err != nil {
-				kubeadmutil.CheckErr(err)
-			}
+			cfg.FeatureGates, err = features.NewFeatureGate(&features.InitFeatureGates, featureGatesString)
+			kubeadmutil.CheckErr(err)
 			imagesList, err := NewImagesList(cfgPath, cfg)
 			kubeadmutil.CheckErr(err)
 			kubeadmutil.CheckErr(imagesList.Run(out))
 		},
 	}
-	AddImagesListConfigFlags(cmd.PersistentFlags(), cfg, &featureGatesString)
+	AddImagesCommonConfigFlags(cmd.PersistentFlags(), cfg, &featureGatesString)
 	AddImagesListFlags(cmd.PersistentFlags(), &cfgPath)
 
 	return cmd
@@ -259,7 +309,7 @@ type ImagesList struct {
 	cfg *kubeadmapi.MasterConfiguration
 }
 
-// Run gets a list of images kubeadm expects to use and writes the result to the io.Writer passed in
+// Run runs the images command and writes the result to the io.Writer passed in
 func (i *ImagesList) Run(out io.Writer) error {
 	imgs := images.GetAllImages(i.cfg)
 	for _, img := range imgs {
@@ -269,8 +319,8 @@ func (i *ImagesList) Run(out io.Writer) error {
 	return nil
 }
 
-// AddImagesListConfigFlags adds the flags that configure kubeadm (and affect the images kubeadm will use)
-func AddImagesListConfigFlags(flagSet *flag.FlagSet, cfg *kubeadmapiv1alpha2.MasterConfiguration, featureGatesString *string) {
+// AddImagesCommonConfigFlags adds the flags that configure kubeadm (and affect the images kubeadm will use)
+func AddImagesCommonConfigFlags(flagSet *flag.FlagSet, cfg *kubeadmapiv1alpha2.MasterConfiguration, featureGatesString *string) {
 	flagSet.StringVar(
 		&cfg.KubernetesVersion, "kubernetes-version", cfg.KubernetesVersion,
 		`Choose a specific Kubernetes version for the control plane.`,
@@ -283,3 +333,8 @@ func AddImagesListConfigFlags(flagSet *flag.FlagSet, cfg *kubeadmapiv1alpha2.Mas
 func AddImagesListFlags(flagSet *flag.FlagSet, cfgPath *string) {
 	flagSet.StringVar(cfgPath, "config", *cfgPath, "Path to kubeadm config file.")
 }
+
+// AddImagesPullFlags adds flags related to the `config images pull` command
+func AddImagesPullFlags(flagSet *flag.FlagSet, criSocketPath *string) {
+	flagSet.StringVar(criSocketPath, "cri-socket-path", *criSocketPath, "Path to the CRI socket.")
+}

cmd/kubeadm/app/cmd/config_test.go

@@ -35,7 +35,7 @@ const (
 	defaultNumberOfImages = 8
 )
 
-func TestNewCmdConfigListImages(t *testing.T) {
+func TestNewCmdConfigImagesList(t *testing.T) {
 	var output bytes.Buffer
 	images := cmd.NewCmdConfigImagesList(&output)
 	images.Run(nil, nil)
@@ -170,3 +170,27 @@ func TestConfigImagesListRunWithoutPath(t *testing.T) {
 		})
 	}
 }
+
+type fakePuller struct {
+	count map[string]int
+}
+
+func (f *fakePuller) Pull(image string) error {
+	f.count[image]++
+	return nil
+}
+
+func TestImagesPull(t *testing.T) {
+	puller := &fakePuller{
+		count: make(map[string]int),
+	}
+	images := []string{"a", "b", "c", "d", "a"}
+	ip := cmd.NewImagesPull(puller, images)
+	err := ip.PullAll()
+	if err != nil {
+		t.Fatalf("expected nil but found %v", err)
+	}
+	if puller.count["a"] != 2 {
+		t.Fatalf("expected 2 but found %v", puller.count["a"])
+	}
+}

cmd/kubeadm/app/images/BUILD

@@ -8,14 +8,19 @@ load(
 
 go_library(
     name = "go_default_library",
-    srcs = ["images.go"],
+    srcs = [
+        "images.go",
+        "puller.go",
+    ],
     importpath = "k8s.io/kubernetes/cmd/kubeadm/app/images",
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
+        "//cmd/kubeadm/app/apis/kubeadm/v1alpha1:go_default_library",
         "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/features:go_default_library",
         "//cmd/kubeadm/app/phases/addons/dns:go_default_library",
         "//cmd/kubeadm/app/util:go_default_library",
+        "//vendor/k8s.io/utils/exec:go_default_library",
     ],
 )
 
@@ -38,3 +43,13 @@ filegroup(
     srcs = [":package-srcs"],
     tags = ["automanaged"],
 )
+
+go_test(
+    name = "go_default_xtest",
+    srcs = ["puller_test.go"],
+    deps = [
+        ":go_default_library",
+        "//cmd/kubeadm/app/apis/kubeadm/v1alpha1:go_default_library",
+        "//vendor/k8s.io/utils/exec:go_default_library",
+    ],
+)

cmd/kubeadm/app/images/puller.go

+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package images
+
+import (
+	"fmt"
+
+	kubeadmapiv1alpha1 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha1"
+	utilsexec "k8s.io/utils/exec"
+)
+
+// Puller is an interface for pulling images
+type Puller interface {
+	Pull(string) error
+}
+
+// ImagePuller is a struct that can pull images and hides the implementation (crictl vs docker)
+type ImagePuller struct {
+	criSocket  string
+	exec       utilsexec.Interface
+	crictlPath string
+}
+
+// NewImagePuller returns a ready to go ImagePuller
+func NewImagePuller(execer utilsexec.Interface, criSocket string) (*ImagePuller, error) {
+	crictlPath, err := execer.LookPath("crictl")
+	if err != nil && criSocket != kubeadmapiv1alpha1.DefaultCRISocket {
+		return nil, fmt.Errorf("crictl is required for non docker container runtimes: %v", err)
+	}
+	return &ImagePuller{
+		exec:       execer,
+		criSocket:  criSocket,
+		crictlPath: crictlPath,
+	}, nil
+}
+
+// Pull pulls the actual image using either crictl or docker
+func (ip *ImagePuller) Pull(image string) error {
+	if ip.criSocket != kubeadmapiv1alpha1.DefaultCRISocket {
+		return ip.exec.Command(ip.crictlPath, "-r", ip.criSocket, "pull", image).Run()
+	}
+	return ip.exec.Command("sh", "-c", fmt.Sprintf("docker pull %v", image)).Run()
+}

cmd/kubeadm/app/images/puller_test.go

+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package images_test
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+	"testing"
+
+	kubeadmdefaults "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha1"
+	"k8s.io/kubernetes/cmd/kubeadm/app/images"
+	"k8s.io/utils/exec"
+)
+
+type fakeCmd struct {
+	cmd  string
+	args []string
+	out  io.Writer
+}
+
+func (f *fakeCmd) Run() error {
+	fmt.Fprintf(f.out, "%v %v", f.cmd, strings.Join(f.args, " "))
+	return nil
+}
+func (f *fakeCmd) CombinedOutput() ([]byte, error) { return nil, nil }
+func (f *fakeCmd) Output() ([]byte, error)         { return nil, nil }
+func (f *fakeCmd) SetDir(dir string)               {}
+func (f *fakeCmd) SetStdin(in io.Reader)           {}
+func (f *fakeCmd) SetStdout(out io.Writer) {
+	f.out = out
+}
+func (f *fakeCmd) SetStderr(out io.Writer) {}
+func (f *fakeCmd) Stop()                   {}
+
+type fakeExecer struct {
+	cmd              exec.Cmd
+	lookPathSucceeds bool
+}
+
+func (f *fakeExecer) Command(cmd string, args ...string) exec.Cmd { return f.cmd }
+func (f *fakeExecer) CommandContext(ctx context.Context, cmd string, args ...string) exec.Cmd {
+	return f.cmd
+}
+func (f *fakeExecer) LookPath(file string) (string, error) {
+	if f.lookPathSucceeds {
+		return file, nil
+	}
+	return "", &os.PathError{Err: errors.New("does not exist")}
+}
+
+func TestImagePuller(t *testing.T) {
+	testcases := []struct {
+		name          string
+		criSocket     string
+		cmd           exec.Cmd
+		findCrictl    bool
+		expected      string
+		errorExpected bool
+	}{
+		{
+			name:      "New succeeds even if crictl is not in path",
+			criSocket: kubeadmdefaults.DefaultCRISocket,
+			cmd: &fakeCmd{
+				cmd:  "hello",
+				args: []string{"world", "and", "friends"},
+			},
+			findCrictl: false,
+			expected:   "hello world and friends",
+		},
+		{
+			name:      "New succeeds with crictl in path",
+			criSocket: "/not/default",
+			cmd: &fakeCmd{
+				cmd:  "crictl",
+				args: []string{"-r", "/some/socket", "imagename"},
+			},
+			findCrictl: true,
+			expected:   "crictl -r /some/socket imagename",
+		},
+		{
+			name:      "New fails with crictl not in path but is required",
+			criSocket: "/not/docker",
+			cmd: &fakeCmd{
+				cmd:  "crictl",
+				args: []string{"-r", "/not/docker", "an image"},
+			},
+			findCrictl:    false,
+			errorExpected: true,
+		},
+	}
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			var b bytes.Buffer
+			tc.cmd.SetStdout(&b)
+			fe := &fakeExecer{
+				cmd:              tc.cmd,
+				lookPathSucceeds: tc.findCrictl,
+			}
+			ip, err := images.NewImagePuller(fe, tc.criSocket)
+
+			if tc.errorExpected {
+				if err == nil {
+					t.Fatalf("expected an error but found nil: %v", fe)
+				}
+				return
+			}
+
+			if err != nil {
+				t.Fatalf("expected nil but found an error: %v", err)
+			}
+			if err = ip.Pull("imageName"); err != nil {
+				t.Fatalf("expected nil pulling an image but found: %v", err)
+			}
+			if b.String() != tc.expected {
+				t.Fatalf("expected %v but got: %v", tc.expected, b.String())
+			}
+		})
+	}
+}

docs/.generated_docs

@@ -60,6 +60,7 @@ docs/admin/kubeadm_completion.md
 docs/admin/kubeadm_config.md
 docs/admin/kubeadm_config_images.md
 docs/admin/kubeadm_config_images_list.md
+docs/admin/kubeadm_config_images_pull.md
 docs/admin/kubeadm_config_upload.md
 docs/admin/kubeadm_config_upload_from-file.md
 docs/admin/kubeadm_config_upload_from-flags.md
@@ -135,6 +136,7 @@ docs/man/man1/kubeadm-alpha-phase.1
 docs/man/man1/kubeadm-alpha.1
 docs/man/man1/kubeadm-completion.1
 docs/man/man1/kubeadm-config-images-list.1
+docs/man/man1/kubeadm-config-images-pull.1
 docs/man/man1/kubeadm-config-images.1
 docs/man/man1/kubeadm-config-upload-from-file.1
 docs/man/man1/kubeadm-config-upload-from-flags.1

docs/admin/kubeadm_config_images_pull.md

+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-images-list-images.1

+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-images-pull.1

+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.