Make it easier to reuse kubelet server code

cmd/kubelet/app/server.go

@@ -240,7 +240,7 @@ func (s *KubeletServer) Run(_ []string) error {
 
 	// TODO(vmarmol): Do this through container config.
 	if err := util.ApplyOomScoreAdj(0, s.OOMScoreAdj); err != nil {
-		glog.Info(err)
+		glog.Warning(err)
 	}
 
 	client, err := s.createAPIServerClient()
@@ -248,7 +248,7 @@ func (s *KubeletServer) Run(_ []string) error {
 		glog.Warningf("No API client: %v", err)
 	}
 
-	glog.Infof("Using root directory: %v", s.RootDirectory)
+	glog.V(2).Infof("Using root directory: %v", s.RootDirectory)
 
 	credentialprovider.SetPreferredDockercfgPath(s.RootDirectory)
 
@@ -267,7 +267,7 @@ func (s *KubeletServer) Run(_ []string) error {
 		RootFreeDiskMB:   s.LowDiskSpaceThresholdMB,
 	}
 	cloud := cloudprovider.InitCloudProvider(s.CloudProvider, s.CloudConfigFile)
-	glog.Infof("Successfully initialized cloud provider: %q from the config file: %q\n", s.CloudProvider, s.CloudConfigFile)
+	glog.V(2).Infof("Successfully initialized cloud provider: %q from the config file: %q\n", s.CloudProvider, s.CloudConfigFile)
 
 	hostNetworkSources, err := kubelet.GetValidatedSources(strings.Split(s.HostNetworkSources, ","))
 	if err != nil {
@@ -278,9 +278,9 @@ func (s *KubeletServer) Run(_ []string) error {
 		s.TLSCertFile = path.Join(s.CertDirectory, "kubelet.crt")
 		s.TLSPrivateKeyFile = path.Join(s.CertDirectory, "kubelet.key")
 		if err := util.GenerateSelfSignedCert(util.GetHostname(s.HostnameOverride), s.TLSCertFile, s.TLSPrivateKeyFile); err != nil {
-			glog.Fatalf("Unable to generate self signed cert: %v", err)
+			return fmt.Errorf("unable to generate self signed cert: %v", err)
 		}
-		glog.Infof("Using self-signed cert (%s, %s)", s.TLSCertFile, s.TLSPrivateKeyFile)
+		glog.V(4).Infof("Using self-signed cert (%s, %s)", s.TLSCertFile, s.TLSPrivateKeyFile)
 	}
 	tlsOptions := &kubelet.TLSOptions{
 		Config: &tls.Config{
@@ -295,7 +295,7 @@ func (s *KubeletServer) Run(_ []string) error {
 
 	mounter := mount.New()
 	if s.Containerized {
-		glog.Info("Running kubelet in containerized mode (experimental)")
+		glog.V(2).Info("Running kubelet in containerized mode (experimental)")
 		mounter = &mount.NsenterMounter{}
 	}
 
@@ -344,7 +344,9 @@ func (s *KubeletServer) Run(_ []string) error {
 		ConfigureCBR0:             s.ConfigureCBR0,
 	}
 
-	RunKubelet(&kcfg, nil)
+	if err := RunKubelet(&kcfg, nil); err != nil {
+		return err
+	}
 
 	if s.HealthzPort > 0 {
 		healthz.DefaultHealthz()
@@ -356,9 +358,12 @@ func (s *KubeletServer) Run(_ []string) error {
 		}, 5*time.Second)
 	}
 
-	// runs forever
-	select {}
+	if s.RunOnce {
+		return nil
+	}
 
+	// run forever
+	select {}
 }
 
 func (s *KubeletServer) authPathClientConfig(useDefaults bool) (*client.Config, error) {
@@ -509,16 +514,16 @@ func SimpleKubelet(client *client.Client,
 //   2 Kubelet binary
 //   3 Standalone 'kubernetes' binary
 // Eventually, #2 will be replaced with instances of #3
-func RunKubelet(kcfg *KubeletConfig, builder KubeletBuilder) {
+func RunKubelet(kcfg *KubeletConfig, builder KubeletBuilder) error {
 	kcfg.Hostname = util.GetHostname(kcfg.HostnameOverride)
 	eventBroadcaster := record.NewBroadcaster()
 	kcfg.Recorder = eventBroadcaster.NewRecorder(api.EventSource{Component: "kubelet", Host: kcfg.Hostname})
 	eventBroadcaster.StartLogging(glog.Infof)
 	if kcfg.KubeClient != nil {
-		glog.Infof("Sending events to api server.")
+		glog.V(4).Infof("Sending events to api server.")
 		eventBroadcaster.StartRecordingToSink(kcfg.KubeClient.Events(""))
 	} else {
-		glog.Infof("No api server defined - no events will be sent to API server.")
+		glog.Warning("No api server defined - no events will be sent to API server.")
 	}
 	capabilities.Setup(kcfg.AllowPrivileged, kcfg.HostNetworkSources)
 
@@ -532,18 +537,19 @@ func RunKubelet(kcfg *KubeletConfig, builder KubeletBuilder) {
 	}
 	k, podCfg, err := builder(kcfg)
 	if err != nil {
-		glog.Errorf("Failed to create kubelet: %s", err)
-		return
+		return fmt.Errorf("failed to create kubelet: %v", err)
 	}
 	// process pods and exit.
 	if kcfg.Runonce {
 		if _, err := k.RunOnce(podCfg.Updates()); err != nil {
-			glog.Errorf("--runonce failed: %v", err)
+			return fmt.Errorf("runonce failed: %v", err)
 		}
+		glog.Infof("Started kubelet as runonce")
 	} else {
 		startKubelet(k, podCfg, kcfg)
+		glog.Infof("Started kubelet")
 	}
-	glog.Infof("Started kubelet")
+	return nil
 }
 
 func startKubelet(k KubeletBootstrap, podCfg *config.PodConfig, kc *KubeletConfig) {