Move GetHostname() from k/k/pkg/util/node to k/component-helpers/node/util

In fact, this actually uses pkg/util/node's GetHostname() but takes
the unit tests from cmd/kubeadm/app/util's private fork of that
function since they were more extensive. (Of course the fact that
kubeadm had a private fork of this function is a strong argument for
moving it to component-helpers.)

cmd/kube-proxy/app/server_others.go

@@ -46,6 +46,7 @@ import (
 	toolswatch "k8s.io/client-go/tools/watch"
 	"k8s.io/component-base/configz"
 	"k8s.io/component-base/metrics"
+	nodeutil "k8s.io/component-helpers/node/util"
 	utilsysctl "k8s.io/component-helpers/node/util/sysctl"
 	"k8s.io/kubernetes/pkg/proxy"
 	proxyconfigapi "k8s.io/kubernetes/pkg/proxy/apis/config"
@@ -59,7 +60,6 @@ import (
 	utilipset "k8s.io/kubernetes/pkg/util/ipset"
 	utiliptables "k8s.io/kubernetes/pkg/util/iptables"
 	utilipvs "k8s.io/kubernetes/pkg/util/ipvs"
-	utilnode "k8s.io/kubernetes/pkg/util/node"
 	"k8s.io/utils/exec"
 	netutils "k8s.io/utils/net"
 
@@ -96,7 +96,7 @@ func newProxyServer(
 		metrics.SetShowHidden()
 	}
 
-	hostname, err := utilnode.GetHostname(config.HostnameOverride)
+	hostname, err := nodeutil.GetHostname(config.HostnameOverride)
 	if err != nil {
 		return nil, err
 	}

cmd/kube-proxy/app/server_windows.go

@@ -36,13 +36,13 @@ import (
 	"k8s.io/client-go/tools/events"
 	"k8s.io/component-base/configz"
 	"k8s.io/component-base/metrics"
+	nodeutil "k8s.io/component-helpers/node/util"
 	"k8s.io/klog/v2"
 	"k8s.io/kubernetes/pkg/proxy"
 	proxyconfigapi "k8s.io/kubernetes/pkg/proxy/apis/config"
 	proxyconfigscheme "k8s.io/kubernetes/pkg/proxy/apis/config/scheme"
 	"k8s.io/kubernetes/pkg/proxy/healthcheck"
 	"k8s.io/kubernetes/pkg/proxy/winkernel"
-	utilnode "k8s.io/kubernetes/pkg/util/node"
 )
 
 // NewProxyServer returns a new ProxyServer.
@@ -71,7 +71,7 @@ func newProxyServer(config *proxyconfigapi.KubeProxyConfiguration, master string
 	}
 
 	// Create event recorder
-	hostname, err := utilnode.GetHostname(config.HostnameOverride)
+	hostname, err := nodeutil.GetHostname(config.HostnameOverride)
 	if err != nil {
 		return nil, err
 	}

cmd/kubeadm/app/phases/kubelet/flags.go

@@ -26,6 +26,7 @@ import (
 
 	"k8s.io/klog/v2"
 
+	nodeutil "k8s.io/component-helpers/node/util"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/images"
@@ -45,7 +46,7 @@ type kubeletFlagsOpts struct {
 // - "hostname-override" flag in NodeRegistrationOptions.KubeletExtraArgs
 // It also returns the hostname or an error if getting the hostname failed.
 func GetNodeNameAndHostname(cfg *kubeadmapi.NodeRegistrationOptions) (string, string, error) {
-	hostname, err := kubeadmutil.GetHostname("")
+	hostname, err := nodeutil.GetHostname("")
 	nodeName := hostname
 	if cfg.Name != "" {
 		nodeName = cfg.Name

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

@@ -30,6 +30,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	netutil "k8s.io/apimachinery/pkg/util/net"
 	bootstraputil "k8s.io/cluster-bootstrap/token/util"
+	nodeutil "k8s.io/component-helpers/node/util"
 	"k8s.io/klog/v2"
 	netutils "k8s.io/utils/net"
 
@@ -98,7 +99,7 @@ func SetBootstrapTokensDynamicDefaults(cfg *[]bootstraptokenv1.BootstrapToken) e
 // SetNodeRegistrationDynamicDefaults checks and sets configuration values for the NodeRegistration object
 func SetNodeRegistrationDynamicDefaults(cfg *kubeadmapi.NodeRegistrationOptions, controlPlaneTaint bool) error {
 	var err error
-	cfg.Name, err = kubeadmutil.GetHostname(cfg.Name)
+	cfg.Name, err = nodeutil.GetHostname(cfg.Name)
 	if err != nil {
 		return err
 	}

cmd/kubelet/app/server.go

@@ -75,6 +75,7 @@ import (
 	tracing "k8s.io/component-base/tracing"
 	"k8s.io/component-base/version"
 	"k8s.io/component-base/version/verflag"
+	nodeutil "k8s.io/component-helpers/node/util"
 	kubeletconfigv1beta1 "k8s.io/kubelet/config/v1beta1"
 	"k8s.io/kubernetes/cmd/kubelet/app/options"
 	"k8s.io/kubernetes/pkg/api/legacyscheme"
@@ -102,7 +103,6 @@ import (
 	kubeletutil "k8s.io/kubernetes/pkg/kubelet/util"
 	utilfs "k8s.io/kubernetes/pkg/util/filesystem"
 	"k8s.io/kubernetes/pkg/util/flock"
-	nodeutil "k8s.io/kubernetes/pkg/util/node"
 	"k8s.io/kubernetes/pkg/util/oom"
 	"k8s.io/kubernetes/pkg/util/rlimit"
 	"k8s.io/kubernetes/pkg/volume/util/hostutil"

pkg/util/node/node.go

@@ -20,8 +20,6 @@ import (
 	"context"
 	"fmt"
 	"net"
-	"os"
-	"strings"
 	"time"
 
 	"k8s.io/klog/v2"
@@ -42,26 +40,6 @@ const (
 	NodeUnreachablePodMessage = "Node %v which was running pod %v is unresponsive"
 )
 
-// GetHostname returns OS's hostname if 'hostnameOverride' is empty; otherwise, return 'hostnameOverride'.
-func GetHostname(hostnameOverride string) (string, error) {
-	hostName := hostnameOverride
-	if len(hostName) == 0 {
-		nodeName, err := os.Hostname()
-		if err != nil {
-			return "", fmt.Errorf("couldn't determine hostname: %v", err)
-		}
-		hostName = nodeName
-	}
-
-	// Trim whitespaces first to avoid getting an empty hostname
-	// For linux, the hostname is read from file /proc/sys/kernel/hostname directly
-	hostName = strings.TrimSpace(hostName)
-	if len(hostName) == 0 {
-		return "", fmt.Errorf("empty hostname is invalid")
-	}
-	return strings.ToLower(hostName), nil
-}
-
 // NoMatchError is a typed implementation of the error interface. It indicates a failure to get a matching Node.
 type NoMatchError struct {
 	addresses []v1.NodeAddress

pkg/util/node/node_test.go

@@ -198,38 +198,6 @@ func TestGetNodeHostIPs(t *testing.T) {
 	}
 }
 
-func TestGetHostname(t *testing.T) {
-	testCases := []struct {
-		hostName         string
-		expectedHostName string
-		expectError      bool
-	}{
-		{
-			hostName:    "   ",
-			expectError: true,
-		},
-		{
-			hostName:         " abc  ",
-			expectedHostName: "abc",
-			expectError:      false,
-		},
-	}
-
-	for idx, test := range testCases {
-		hostName, err := GetHostname(test.hostName)
-		if err != nil && !test.expectError {
-			t.Errorf("[%d]: unexpected error: %s", idx, err)
-		}
-		if err == nil && test.expectError {
-			t.Errorf("[%d]: expected error, got none", idx)
-		}
-		if test.expectedHostName != hostName {
-			t.Errorf("[%d]: expected output %q, got %q", idx, test.expectedHostName, hostName)
-		}
-
-	}
-}
-
 func TestIsNodeReady(t *testing.T) {
 	testCases := []struct {
 		name   string

pkg/volume/rbd/rbd_util.go

@@ -42,7 +42,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/errors"
 	"k8s.io/apimachinery/pkg/util/wait"
 	volumehelpers "k8s.io/cloud-provider/volume/helpers"
-	"k8s.io/kubernetes/pkg/util/node"
+	nodeutil "k8s.io/component-helpers/node/util"
 	"k8s.io/kubernetes/pkg/volume"
 	volutil "k8s.io/kubernetes/pkg/volume/util"
 )
@@ -327,7 +327,7 @@ func (util *rbdUtil) rbdUnlock(b rbdMounter) error {
 	}
 
 	// Construct lock id using host name and a magic prefix.
-	hostName, err := node.GetHostname("")
+	hostName, err := nodeutil.GetHostname("")
 	if err != nil {
 		return err
 	}

staging/src/k8s.io/component-helpers/node/util/hostname.go

@@ -17,20 +17,20 @@ limitations under the License.
 package util
 
 import (
+	"fmt"
 	"os"
 	"strings"
-
-	"github.com/pkg/errors"
 )
 
-// GetHostname returns OS's hostname if 'hostnameOverride' is empty; otherwise, return 'hostnameOverride'
+// GetHostname returns OS's hostname if 'hostnameOverride' is empty; otherwise, it returns
-// NOTE: This function copied from pkg/util/node package to avoid external kubeadm dependency
+// 'hostnameOverride'. In either case, the value is canonicalized (trimmed and
+// lowercased).
 func GetHostname(hostnameOverride string) (string, error) {
 	hostName := hostnameOverride
 	if len(hostName) == 0 {
 		nodeName, err := os.Hostname()
 		if err != nil {
-			return "", errors.Wrap(err, "couldn't determine hostname")
+			return "", fmt.Errorf("couldn't determine hostname: %w", err)
 		}
 		hostName = nodeName
 	}
@@ -39,7 +39,7 @@ func GetHostname(hostnameOverride string) (string, error) {
 	// For linux, the hostname is read from file /proc/sys/kernel/hostname directly
 	hostName = strings.TrimSpace(hostName)
 	if len(hostName) == 0 {
-		return "", errors.New("empty hostname is invalid")
+		return "", fmt.Errorf("empty hostname is invalid")
 	}
 
 	return strings.ToLower(hostName), nil

staging/src/k8s.io/component-helpers/node/util/hostname_test.go

@@ -17,11 +17,10 @@ limitations under the License.
 package util
 
 import (
+	"fmt"
 	"os"
 	"strings"
 	"testing"
-
-	"github.com/pkg/errors"
 )
 
 func TestGetHostname(t *testing.T) {
@@ -55,7 +54,7 @@ func TestGetHostname(t *testing.T) {
 			desc:        "hostname contains only spaces",
 			hostname:    " ",
 			result:      "",
-			expectedErr: errors.New("empty hostname is invalid"),
+			expectedErr: fmt.Errorf("empty hostname is invalid"),
 		},
 		{
 			desc:        "empty parameter",