All Kubelet flags should be explicitly registered

This explicitly registers Kubelet flags from libraries that were
registering flags globally, and stops parsing the global flag set.
In general, we should always be explicit about flags we register
and parse, so that we maintain control over our command-line API.

cmd/kubelet/kubelet.go

@@ -24,6 +24,7 @@ import (
 	"fmt"
 	"os"
 
+	"github.com/golang/glog"
 	"github.com/spf13/pflag"
 
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
@@ -36,25 +37,43 @@ import (
 	"k8s.io/kubernetes/pkg/version/verflag"
 )
 
+func parseFlagSet(fs *pflag.FlagSet, args []string) error {
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+	fs.VisitAll(func(flag *pflag.Flag) {
+		glog.V(2).Infof("FLAG: --%s=%q", flag.Name, flag.Value)
+	})
+	return nil
+}
+
 func die(err error) {
 	fmt.Fprintf(os.Stderr, "error: %v\n", err)
 	os.Exit(1)
 }
 
 func main() {
-	// construct KubeletFlags object and register command line flags mapping
-	kubeletFlags := options.NewKubeletFlags()
-	kubeletFlags.AddFlags(pflag.CommandLine)
+	fs := pflag.NewFlagSet(os.Args[0], pflag.ExitOnError)
+	// set the normalize func, similar to k8s.io/apiserver/pkg/util/flag/flags.go:InitFlags
+	fs.SetNormalizeFunc(flag.WordSepNormalizeFunc)
+	// explicitly add flags from libs that register global flags
+	options.AddGlobalFlags(fs)
 
-	// construct KubeletConfiguration object and register command line flags mapping
+	// register kubelet flags
+	kubeletFlags := options.NewKubeletFlags()
+	kubeletFlags.AddFlags(fs)
+
+	// register kubelet config flags
 	defaultConfig, err := options.NewKubeletConfiguration()
 	if err != nil {
 		die(err)
 	}
-	options.AddKubeletConfigFlags(pflag.CommandLine, defaultConfig)
+	options.AddKubeletConfigFlags(fs, defaultConfig)
 
-	// parse the command line flags into the respective objects
-	flag.InitFlags()
+	// parse flags
+	if err := parseFlagSet(fs, os.Args[1:]); err != nil {
+		die(err)
+	}
 
 	// initialize logging and defer flush
 	logs.InitLogs()