Adds a kubeadm config images pull command

This command will use crictl or docker to pull images locally.

The dockerfall back is needed because in some cases the kubelet is not
yet running so there is no CRI dockershim socket available.

Fixes kubernetes/kubeadm#812

Signed-off-by: Chuck Ha <ha.chuck@gmail.com>

cmd/kubeadm/app/cmd/config.go

@@ -1,5 +1,5 @@
 /*
-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

@@ -0,0 +1,57 @@
+/*
+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

@@ -0,0 +1,138 @@
+/*
+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

@@ -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-images-list-images.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-images-pull.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.