Instead of launching kubelet directly, exec

If the only component running on the node is the kubelet, exec with the
necessary args instead of running the code in the current process.

Author: smarterclayton

pkg/cmd/server/kubernetes/node/options/options.go

@@ -209,3 +209,7 @@ func buildKubeProxyConfig(options configapi.NodeConfig) (*componentconfig.KubePr
 
 	return proxyconfig, nil
 }
+
+func ToFlags(config *kubeletoptions.KubeletServer) []string {
+	return cmdflags.AsArgs(config.AddFlags, kubeletoptions.NewKubeletServer().AddFlags)
+}

pkg/cmd/server/start/start_node.go

@@ -5,14 +5,17 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"strings"
+	"syscall"
 
 	"github.com/coreos/go-systemd/daemon"
 	"github.com/golang/glog"
 	"github.com/spf13/cobra"
 
 	kerrors "k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/kubernetes/pkg/kubectl/cmd/templates"
 	kcmdutil "k8s.io/kubernetes/pkg/kubectl/cmd/util"
@@ -334,6 +337,15 @@ func StartNode(nodeConfig configapi.NodeConfig, components *utilflags.ComponentF
 		return err
 	}
 
+	if components.Calculated().Equal(sets.NewString(ComponentKubelet)) {
+		args := nodeoptions.ToFlags(server)
+		if path, err := exec.LookPath("kubelet"); err == nil {
+			glog.V(3).Infof("Exec %s %s", path, strings.Join(args, " "))
+			args = append([]string{path}, args...)
+			return syscall.Exec(path, args, os.Environ())
+		}
+	}
+
 	networkConfig, err := network.New(nodeConfig, server.ClusterDomain, proxyConfig, components.Enabled(ComponentProxy), components.Enabled(ComponentDNS) && len(nodeConfig.DNSBindAddress) > 0)
 	if err != nil {
 		return err

pkg/cmd/util/flags/flags.go

@@ -36,6 +36,33 @@ func Resolve(args map[string][]string, fn func(*pflag.FlagSet)) []error {
 	return Apply(args, fs)
 }
 
+func AsArgs(fn, defaultFn func(*pflag.FlagSet)) []string {
+	fs := pflag.NewFlagSet("extended", pflag.ContinueOnError)
+	fn(fs)
+	defaults := pflag.NewFlagSet("defaults", pflag.ContinueOnError)
+	defaultFn(defaults)
+	var args []string
+	fs.VisitAll(func(flag *pflag.Flag) {
+		defaultFlag := defaults.Lookup(flag.Name)
+		s := flag.Value.String()
+		defaultValue := defaultFlag.Value.String()
+		if s == defaultValue {
+			return
+		}
+		if values, err := fs.GetStringSlice(flag.Name); err == nil {
+			for _, s := range values {
+				args = append(args, fmt.Sprintf("--%s=%s", flag.Name, s))
+			}
+		} else {
+			if len(s) == 0 {
+				s = defaultValue
+			}
+			args = append(args, fmt.Sprintf("--%s=%s", flag.Name, s))
+		}
+	})
+	return args
+}
+
 // ComponentFlag represents a set of enabled components used in a command line.
 type ComponentFlag struct {
 	enabled    string