Merge pull request #52287 from yujuhong/rm-nsenter

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>..

kubelet: remove the --docker-exec-handler flag

Stop supporting the "nsenter" exec handler. Only the Docker native exec
handler is supported.

The flag was deprecated in Kubernetes 1.6 and is safe to remove
in Kubernetes 1.9 according to the deprecation policy.

**What this PR does / why we need it**:

**Which issue this PR fixes** : fixes #40229

**Special notes for your reviewer**:
N/A

**Release note**:

```release-note
Remove the --docker-exec-handler flag. Only native exec handler is supported.
```

cmd/kubelet/app/options/container_runtime.go

@@ -57,10 +57,6 @@ type ContainerRuntimeOptions struct {
 	PodSandboxImage string
 	// DockerEndpoint is the path to the docker endpoint to communicate with.
 	DockerEndpoint string
-	// DockerExecHandlerName is the handler to use when executing a command
-	// in a container. Valid values are 'native' and 'nsenter'. Defaults to
-	// 'native'.
-	DockerExecHandlerName string
 	// If no pulling progress is made before the deadline imagePullProgressDeadline,
 	// the image pulling will be cancelled. Defaults to 1m0s.
 	// +optional
@@ -107,7 +103,6 @@ func NewContainerRuntimeOptions() *ContainerRuntimeOptions {
 	return &ContainerRuntimeOptions{
 		DockerEndpoint:            dockerEndpoint,
 		DockershimRootDirectory:   "/var/lib/dockershim",
-		DockerExecHandlerName:     "native",
 		DockerDisableSharedPID:    true,
 		PodSandboxImage:           defaultPodSandboxImage,
 		ImagePullProgressDeadline: metav1.Duration{Duration: 1 * time.Minute},
@@ -125,9 +120,6 @@ func (s *ContainerRuntimeOptions) AddFlags(fs *pflag.FlagSet) {
 	fs.BoolVar(&s.DockerDisableSharedPID, "docker-disable-shared-pid", s.DockerDisableSharedPID, "The Container Runtime Interface (CRI) defaults to using a shared PID namespace for containers in a pod when running with Docker 1.13.1 or higher. Setting this flag reverts to the previous behavior of isolated PID namespaces. This ability will be removed in a future Kubernetes release.")
 	fs.StringVar(&s.PodSandboxImage, "pod-infra-container-image", s.PodSandboxImage, "The image whose network/ipc namespaces containers in each pod will use.")
 	fs.StringVar(&s.DockerEndpoint, "docker-endpoint", s.DockerEndpoint, "Use this for the docker endpoint to communicate with")
-	// TODO(#40229): Remove the docker-exec-handler flag.
-	fs.StringVar(&s.DockerExecHandlerName, "docker-exec-handler", s.DockerExecHandlerName, "Handler to use when executing a command in a container. Valid values are 'native' and 'nsenter'. Defaults to 'native'.")
-	fs.MarkDeprecated("docker-exec-handler", "this flag will be removed and only the 'native' handler will be supported in the future.")
 	fs.DurationVar(&s.ImagePullProgressDeadline.Duration, "image-pull-progress-deadline", s.ImagePullProgressDeadline.Duration, "If no pulling progress is made before this deadline, the image pulling will be cancelled.")
 
 	// Network plugin settings. Shared by both docker and rkt.

cmd/kubelet/app/server.go

@@ -855,7 +855,7 @@ func RunDockershim(c *kubeletconfiginternal.KubeletConfiguration, r *options.Con
 	}
 
 	ds, err := dockershim.NewDockerService(dockerClient, r.PodSandboxImage, streamingConfig, &pluginSettings,
-		c.RuntimeCgroups, c.CgroupDriver, r.DockerExecHandlerName, r.DockershimRootDirectory, r.DockerDisableSharedPID)
+		c.RuntimeCgroups, c.CgroupDriver, r.DockershimRootDirectory, r.DockerDisableSharedPID)
 	if err != nil {
 		return err
 	}