kubeadm: don't use the Docker SDK in util/system/docker_validator*

Instead of creating a Docker client and fetching an Info object
from the docker enpoint, call the "docker info" command
and populate a local dockerInfo struct from JSON output.

Also
- add unit tests.
- update import boss and bazel.

This change affects "test/e2e_node/e2e_node_suite_test.go"
as it consumes this Docker validator by calling
"system.ValidateSpec()".

cmd/kubeadm/.import-restrictions

@@ -112,15 +112,7 @@
 				"github.com/coreos/etcd/pkg/tlsutil",
 				"github.com/coreos/etcd/pkg/transport",
 				"github.com/davecgh/go-spew/spew",
-				"github.com/docker/distribution/digestset",
 				"github.com/docker/distribution/reference",
-				"github.com/docker/docker/api",
-				"github.com/docker/docker/client",
-				"github.com/docker/docker/pkg/term",
-				"github.com/docker/go-connections/nat",
-				"github.com/docker/go-connections/sockets",
-				"github.com/docker/go-connections/tlsconfig",
-				"github.com/docker/go-units",
 				"github.com/docker/libnetwork/ipvs",
 				"github.com/godbus/dbus",
 				"github.com/gogo/protobuf/proto",

cmd/kubeadm/app/util/system/BUILD

@@ -25,8 +25,6 @@ go_library(
     deps = [
         "//staging/src/k8s.io/apimachinery/pkg/util/errors:go_default_library",
         "//vendor/github.com/blang/semver:go_default_library",
-        "//vendor/github.com/docker/docker/api/types:go_default_library",
-        "//vendor/github.com/docker/docker/client:go_default_library",
         "//vendor/github.com/pkg/errors:go_default_library",
         "//vendor/k8s.io/klog:go_default_library",
     ],
@@ -44,7 +42,6 @@ go_test(
     embed = [":go_default_library"],
     tags = ["e2e"],
     deps = [
-        "//vendor/github.com/docker/docker/api/types:go_default_library",
         "//vendor/github.com/pkg/errors:go_default_library",
         "//vendor/github.com/stretchr/testify/assert:go_default_library",
     ],

cmd/kubeadm/app/util/system/docker_validator.go

@@ -17,11 +17,10 @@ limitations under the License.
 package system
 
 import (
-	"context"
+	"encoding/json"
+	"os/exec"
 	"regexp"
 
-	"github.com/docker/docker/api/types"
-	"github.com/docker/docker/client"
 	"github.com/pkg/errors"
 )
 
@@ -32,6 +31,14 @@ type DockerValidator struct {
 	Reporter Reporter
 }
 
+// dockerInfo holds a local subset of the Info struct from
+// github.com/docker/docker/api/types.
+// The JSON output from 'docker info' should map to this struct.
+type dockerInfo struct {
+	Driver        string `json:"Driver"`
+	ServerVersion string `json:"ServerVersion"`
+}
+
 // Name is part of the system.Validator interface.
 func (d *DockerValidator) Name() string {
 	return "docker"
@@ -51,18 +58,28 @@ func (d *DockerValidator) Validate(spec SysSpec) (error, error) {
 		return nil, nil
 	}
 
-	c, err := client.NewClient(dockerEndpoint, "", nil, nil)
+	// Run 'docker info' with a JSON output and unmarshal it into a dockerInfo object
+	info := dockerInfo{}
+	out, err := exec.Command("docker", "info", "--format", "{{json .}}").CombinedOutput()
 	if err != nil {
-		return nil, errors.Wrap(err, "failed to create docker client")
+		return nil, errors.Errorf(`failed executing "docker info --format '{{json .}}'"\noutput: %s\nerror: %v`, string(out), err)
 	}
-	info, err := c.Info(context.Background())
-	if err != nil {
-		return nil, errors.Wrap(err, "failed to get docker info")
+	if err := d.unmarshalDockerInfo(out, &info); err != nil {
+		return nil, err
 	}
+
+	// validate the resulted docker info object against the spec
 	return d.validateDockerInfo(spec.RuntimeSpec.DockerSpec, info)
 }
 
-func (d *DockerValidator) validateDockerInfo(spec *DockerSpec, info types.Info) (error, error) {
+func (d *DockerValidator) unmarshalDockerInfo(b []byte, info *dockerInfo) error {
+	if err := json.Unmarshal(b, &info); err != nil {
+		return errors.Wrap(err, "could not unmarshal the JSON output of 'docker info'")
+	}
+	return nil
+}
+
+func (d *DockerValidator) validateDockerInfo(spec *DockerSpec, info dockerInfo) (error, error) {
 	// Validate docker version.
 	matched := false
 	for _, v := range spec.Version {

cmd/kubeadm/app/util/system/docker_validator_test.go

@@ -17,9 +17,9 @@ limitations under the License.
 package system
 
 import (
+	"reflect"
 	"testing"
 
-	"github.com/docker/docker/api/types"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -33,61 +33,61 @@ func TestValidateDockerInfo(t *testing.T) {
 	}
 	for _, test := range []struct {
 		name string
-		info types.Info
+		info dockerInfo
 		err  bool
 		warn bool
 	}{
 		{
 			name: "unsupported Docker version 1.12.1",
-			info: types.Info{Driver: "driver_2", ServerVersion: "1.12.1"},
+			info: dockerInfo{Driver: "driver_2", ServerVersion: "1.12.1"},
 			err:  true,
 			warn: false,
 		},
 		{
 			name: "unsupported driver",
-			info: types.Info{Driver: "bad_driver", ServerVersion: "1.13.1"},
+			info: dockerInfo{Driver: "bad_driver", ServerVersion: "1.13.1"},
 			err:  true,
 			warn: false,
 		},
 		{
 			name: "valid Docker version 1.13.1",
-			info: types.Info{Driver: "driver_1", ServerVersion: "1.13.1"},
+			info: dockerInfo{Driver: "driver_1", ServerVersion: "1.13.1"},
 			err:  false,
 			warn: false,
 		},
 		{
 			name: "valid Docker version 17.03.0-ce",
-			info: types.Info{Driver: "driver_2", ServerVersion: "17.03.0-ce"},
+			info: dockerInfo{Driver: "driver_2", ServerVersion: "17.03.0-ce"},
 			err:  false,
 			warn: false,
 		},
 		{
 			name: "valid Docker version 17.06.0-ce",
-			info: types.Info{Driver: "driver_2", ServerVersion: "17.06.0-ce"},
+			info: dockerInfo{Driver: "driver_2", ServerVersion: "17.06.0-ce"},
 			err:  false,
 			warn: false,
 		},
 		{
 			name: "valid Docker version 17.09.0-ce",
-			info: types.Info{Driver: "driver_2", ServerVersion: "17.09.0-ce"},
+			info: dockerInfo{Driver: "driver_2", ServerVersion: "17.09.0-ce"},
 			err:  false,
 			warn: false,
 		},
 		{
 			name: "valid Docker version 18.06.0-ce",
-			info: types.Info{Driver: "driver_2", ServerVersion: "18.06.0-ce"},
+			info: dockerInfo{Driver: "driver_2", ServerVersion: "18.06.0-ce"},
 			err:  false,
 			warn: false,
 		},
 		{
 			name: "valid Docker version 18.09.1-ce",
-			info: types.Info{Driver: "driver_2", ServerVersion: "18.09.1-ce"},
+			info: dockerInfo{Driver: "driver_2", ServerVersion: "18.09.1-ce"},
 			err:  false,
 			warn: false,
 		},
 		{
 			name: "Docker version 19.01.0 is not in the list of validated versions",
-			info: types.Info{Driver: "driver_2", ServerVersion: "19.01.0"},
+			info: dockerInfo{Driver: "driver_2", ServerVersion: "19.01.0"},
 			err:  false,
 			warn: true,
 		},
@@ -107,3 +107,41 @@ func TestValidateDockerInfo(t *testing.T) {
 		})
 	}
 }
+
+func TestUnmarshalDockerInfo(t *testing.T) {
+	v := &DockerValidator{}
+
+	testCases := []struct {
+		name          string
+		input         string
+		expectedInfo  dockerInfo
+		expectedError bool
+	}{
+		{
+			name:         "valid: expected dockerInfo is valid",
+			input:        `{ "Driver":"foo", "ServerVersion":"bar" }`,
+			expectedInfo: dockerInfo{Driver: "foo", ServerVersion: "bar"},
+		},
+		{
+			name:          "invalid: the JSON input is not valid",
+			input:         `{ "Driver":"foo"`,
+			expectedError: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			var err error
+			info := dockerInfo{}
+			if err = v.unmarshalDockerInfo([]byte(tc.input), &info); (err != nil) != tc.expectedError {
+				t.Fatalf("failed unmarshaling; expected error: %v, got: %v, error: %v", tc.expectedError, (err != nil), err)
+			}
+			if err != nil {
+				return
+			}
+			if !reflect.DeepEqual(tc.expectedInfo, info) {
+				t.Fatalf("dockerInfo do not match, expected: %#v, got: %#v", tc.expectedInfo, info)
+			}
+		})
+	}
+}