Use cobra for cli.

Signed-off-by: Lantao Liu <lantaol@google.com>

cmd/cri-containerd/cri_containerd.go

@@ -17,12 +17,13 @@ limitations under the License.
 package main
 
 import (
+	"flag"
 	"os"
 
 	"github.com/docker/docker/pkg/reexec"
 	"github.com/golang/glog"
 	"github.com/opencontainers/selinux/go-selinux"
-	"github.com/spf13/pflag"
+	"github.com/spf13/cobra"
 	"k8s.io/kubernetes/pkg/util/interrupt"
 
 	"github.com/kubernetes-incubator/cri-containerd/cmd/cri-containerd/options"
@@ -30,40 +31,69 @@ import (
 	"github.com/kubernetes-incubator/cri-containerd/pkg/version"
 )
 
+// Add \u200B to avoid the space trimming.
+const desc = "\u200B" + `             _                         __        _                      __
+  __________(_)      _________  ____  / /_____ _(_)____  ___  _________/ /
+ / ___/ ___/ /______/ ___/ __ \/ __ \/ __/ __ ` + "`" + `/ // __ \/ _ \/ ___/ __  /
+/ /__/ /  / //_____/ /__/ /_/ / / / / /_/ /_/ / // / / /  __/ /  / /_/ /
+\___/_/  /_/       \___/\____/_/ /_/\__/\__,_/_//_/ /_/\___/_/   \__,_/
+
+A containerd based Kubernetes CRI implementation.
+`
+
+var cmd = &cobra.Command{
+	Use:   "cri-containerd",
+	Short: "A containerd based Kubernetes CRI implementation.",
+	Long:  desc,
+}
+
+// Add golang flags as persistent flags.
+func init() {
+	cmd.PersistentFlags().AddGoFlagSet(flag.CommandLine)
+}
+
 func main() {
 	if reexec.Init() {
 		return
 	}
 	o := options.NewCRIContainerdOptions()
-	o.AddFlags(pflag.CommandLine)
-	if err := o.InitFlags(pflag.CommandLine); err != nil {
-		glog.Exitf("Failed to init CRI containerd flags: %v", err)
+
+	o.AddFlags(cmd.Flags())
+
+	cmd.Run = func(cmd *cobra.Command, args []string) {
+		if err := o.InitFlags(cmd.Flags()); err != nil {
+			glog.Exitf("Failed to init CRI containerd flags: %v", err)
+		}
+
+		// TODO(random-liu): Turn to subcommand.
+		glog.V(0).Infof("Run cri-containerd %+v", o)
+		if o.PrintVersion {
+			version.PrintVersion()
+			os.Exit(0)
+		}
+
+		if o.PrintDefaultConfig {
+			o.PrintDefaultTomlConfig()
+			os.Exit(0)
+		}
+		validateConfig(o)
+
+		glog.V(2).Infof("Run cri-containerd grpc server on socket %q", o.SocketPath)
+		s, err := server.NewCRIContainerdService(o.Config)
+		if err != nil {
+			glog.Exitf("Failed to create CRI containerd service: %v", err)
+		}
+		// Use interrupt handler to make sure the server is stopped properly.
+		// Pass in non-empty final function to avoid os.Exit(1). We expect `Run`
+		// to return itself.
+		h := interrupt.New(func(os.Signal) {}, s.Stop)
+		if err := h.Run(func() error { return s.Run() }); err != nil {
+			glog.Exitf("Failed to run cri-containerd grpc server: %v", err)
+		}
 	}
 
-	glog.V(0).Infof("Run cri-containerd %+v", o)
-	if o.PrintVersion {
-		version.PrintVersion()
-		os.Exit(0)
-	}
-
-	if o.PrintDefaultConfig {
-		o.PrintDefaultTomlConfig()
-		os.Exit(0)
-	}
-
-	validateConfig(o)
-
-	glog.V(2).Infof("Run cri-containerd grpc server on socket %q", o.SocketPath)
-	s, err := server.NewCRIContainerdService(o.Config)
-	if err != nil {
-		glog.Exitf("Failed to create CRI containerd service: %v", err)
-	}
-	// Use interrupt handler to make sure the server to be stopped properly.
-	// Pass in non-empty final function to avoid os.Exit(1). We expect `Run`
-	// to return itself.
-	h := interrupt.New(func(os.Signal) {}, s.Stop)
-	if err := h.Run(func() error { return s.Run() }); err != nil {
-		glog.Exitf("Failed to run cri-containerd grpc server: %v", err)
+	if err := cmd.Execute(); err != nil {
+		glog.Exitf("Failed to execute cri-containerd: %v", err)
 	}
 }
 

cmd/cri-containerd/options/options.go

@@ -17,7 +17,6 @@ limitations under the License.
 package options
 
 import (
-	"flag"
 	"fmt"
 	"os"
 
@@ -26,8 +25,12 @@ import (
 	"github.com/spf13/pflag"
 )
 
-// configFilePathArgName is the path to the config file.
-const configFilePathArgName = "config"
+const (
+	// configFilePathArgName is the path to the config file.
+	configFilePathArgName = "config"
+	// defaultConfigFilePath is the default config file path.
+	defaultConfigFilePath = "/etc/cri-containerd/config.toml"
+)
 
 // ContainerdConfig contains config related to containerd
 type ContainerdConfig struct {
@@ -90,8 +93,8 @@ type Config struct {
 type CRIContainerdOptions struct {
 	// Config contains cri-containerd toml config
 	Config
-	// Path to the TOML config file
-	ConfigFilePath string
+	// Path to the TOML config file.
+	ConfigFilePath string `toml:"-"`
 	// PrintVersion indicates to print version information of cri-containerd.
 	PrintVersion bool
 	// PrintDefaultConfig indicates to print default toml config of cri-containerd.
@@ -106,7 +109,7 @@ func NewCRIContainerdOptions() *CRIContainerdOptions {
 // AddFlags adds cri-containerd command line options to pflag.
 func (c *CRIContainerdOptions) AddFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&c.ConfigFilePath, configFilePathArgName,
-		"/etc/cri-containerd/config.toml", "Path to the config file.")
+		defaultConfigFilePath, "Path to the config file.")
 	fs.StringVar(&c.SocketPath, "socket-path",
 		"/var/run/cri-containerd.sock", "Path to the socket which cri-containerd serves on.")
 	fs.StringVar(&c.RootDir, "root-dir",
@@ -149,19 +152,11 @@ func (c *CRIContainerdOptions) AddFlags(fs *pflag.FlagSet) {
 		-999, "Adjust the cri-containerd's oom score.")
 }
 
-// InitFlags must be called after adding all cli options flags are defined and
-// before flags are accessed by the program. Ths fuction adds flag.CommandLine
-// (the default set of command-line flags, parsed from os.Args) and then calls
-// pflag.Parse().
+// InitFlags load configurations from config file, and then overwrite with flags.
+// This function must be called inside `Run`, at that time flags should have been
+// parsed once.
 // precedence:  commandline > configfile > default
 func (c *CRIContainerdOptions) InitFlags(fs *pflag.FlagSet) error {
-	fs.AddGoFlagSet(flag.CommandLine)
-
-	commandline := os.Args[1:]
-	if err := fs.Parse(commandline); err != nil {
-		return err
-	}
-
 	// Load default config file if none provided
 	if _, err := toml.DecodeFile(c.ConfigFilePath, &c.Config); err != nil {
 		// the absence of default config file is normal case.
@@ -179,7 +174,7 @@ func (c *CRIContainerdOptions) InitFlags(fs *pflag.FlagSet) error {
 	// But the priority of the toml config value is higher than the default value,
 	// Without a way to insert the toml config value between the default value and the command line value.
 	// We parse twice one for default value, one for commandline value.
-	return fs.Parse(commandline)
+	return fs.Parse(os.Args[1:])
 }
 
 // PrintDefaultTomlConfig print default toml config of cri-containerd.