Merge pull request #7652 from vmarmol/runtime-switch

Kubelet: Add container runtime option.

cmd/kubelet/app/server.go

@@ -100,6 +100,7 @@ type KubeletServer struct {
 	NodeStatusUpdateFrequency      time.Duration
 	ResourceContainer              string
 	CgroupRoot                     string
+	ContainerRuntime               string
 
 	// Flags intended for testing
 
@@ -153,6 +154,7 @@ func NewKubeletServer() *KubeletServer {
 		NodeStatusUpdateFrequency:   10 * time.Second,
 		ResourceContainer:           "/kubelet",
 		CgroupRoot:                  "",
+		ContainerRuntime:            "docker",
 	}
 }
 
@@ -205,6 +207,7 @@ func (s *KubeletServer) AddFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&s.CloudConfigFile, "cloud-config", s.CloudConfigFile, "The path to the cloud provider configuration file.  Empty string for no configuration file.")
 	fs.StringVar(&s.ResourceContainer, "resource-container", s.ResourceContainer, "Absolute name of the resource-only container to create and run the Kubelet in (Default: /kubelet).")
 	fs.StringVar(&s.CgroupRoot, "cgroup_root", s.CgroupRoot, "Optional root cgroup to use for pods. This is handled by the container runtime on a best effort basis. Default: '', which means use the container runtime default.")
+	fs.StringVar(&s.ContainerRuntime, "container_runtime", s.ContainerRuntime, "The container runtime to use. Possible values: 'docker'. Default: 'docker'.")
 
 	// Flags intended for testing, not recommended used in production environments.
 	fs.BoolVar(&s.ReallyCrashForTesting, "really-crash-for-testing", s.ReallyCrashForTesting, "If true, when panics occur crash. Intended for testing.")
@@ -305,6 +308,7 @@ func (s *KubeletServer) Run(_ []string) error {
 		NodeStatusUpdateFrequency: s.NodeStatusUpdateFrequency,
 		ResourceContainer:         s.ResourceContainer,
 		CgroupRoot:                s.CgroupRoot,
+		ContainerRuntime:          s.ContainerRuntime,
 	}
 
 	RunKubelet(&kcfg, nil)
@@ -414,6 +418,7 @@ func SimpleKubelet(client *client.Client,
 		ResourceContainer:         "/kubelet",
 		OSInterface:               osInterface,
 		CgroupRoot:                "",
+		ContainerRuntime:          "docker",
 	}
 	return &kcfg
 }
@@ -542,6 +547,7 @@ type KubeletConfig struct {
 	ResourceContainer              string
 	OSInterface                    kubecontainer.OSInterface
 	CgroupRoot                     string
+	ContainerRuntime               string
 }
 
 func createAndInitKubelet(kc *KubeletConfig) (k KubeletBootstrap, pc *config.PodConfig, err error) {
@@ -587,7 +593,8 @@ func createAndInitKubelet(kc *KubeletConfig) (k KubeletBootstrap, pc *config.Pod
 		kc.NodeStatusUpdateFrequency,
 		kc.ResourceContainer,
 		kc.OSInterface,
-		kc.CgroupRoot)
+		kc.CgroupRoot,
+		kc.ContainerRuntime)
 
 	if err != nil {
 		return nil, nil, err

pkg/kubelet/kubelet.go

@@ -120,7 +120,8 @@ func NewMainKubelet(
 	nodeStatusUpdateFrequency time.Duration,
 	resourceContainer string,
 	osInterface kubecontainer.OSInterface,
-	cgroupRoot string) (*Kubelet, error) {
+	cgroupRoot string,
+	containerRuntime string) (*Kubelet, error) {
 	if rootDirectory == "" {
 		return nil, fmt.Errorf("invalid root directory %q", rootDirectory)
 	}
@@ -240,6 +241,15 @@ func NewMainKubelet(
 	} else {
 		klet.networkPlugin = plug
 	}
+
+	// TODO(vmarmol,yjhong): Use container runtime.
+	// Initialize the runtime.
+	switch containerRuntime {
+	case "docker":
+		// Only supported one for now, continue.
+	default:
+		return nil, fmt.Errorf("unsupported container runtime %q specified", containerRuntime)
+	}
 	containerManager := dockertools.NewDockerManager(
 		dockerClient,
 		recorder,