Merge pull request #48487 from dixudx/validate_cadvisor_rootpath

Automatic merge from submit-queue (batch tested with PRs 48487, 49009, 49862, 49843, 49700)

validate cadvisor rootpath

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

When working on issue #48452, I found [KubeletConfiguration.RootDirectory](https://github.com/kubernetes/kubernetes/blob/master/cmd/kubelet/app/server.go#L525) was never been validated. The default value is set to ["/var/lib/kubelet"](https://github.com/kubernetes/kubernetes/blob/master/pkg/apis/componentconfig/v1alpha1/defaults.go#L342).

If this directory does not exist in the file system, the [cadvisor.manager](https://github.com/kubernetes/kubernetes/blob/master/vendor/github.com/google/cadvisor/manager/manager.go#L679) will fail to gather the information for metrics.

> error trying to get filesystem Device for dir /var/lib/kubelet: err: stat failed on /var/lib/kubelet with error: no such file or directory

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

/cc @feiskyer @k82cn

**Release note**:

```release-note
validate cadvisor rootpath
```

pkg/kubelet/cadvisor/cadvisor_linux.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"net"
 	"net/http"
+	"os"
 	"strconv"
 	"time"
 
@@ -105,6 +106,14 @@ func New(address string, port uint, runtime string, rootPath string) (Interface,
 		return nil, err
 	}
 
+	if _, err := os.Stat(rootPath); err != nil {
+		if os.IsNotExist(err) {
+			return nil, fmt.Errorf("rootDirectory %q does not exist", rootPath)
+		} else {
+			return nil, fmt.Errorf("failed to Stat %q: %v", rootPath, err)
+		}
+	}
+
 	cadvisorClient := &cadvisorClient{
 		runtime:  runtime,
 		rootPath: rootPath,

test/e2e_node/services/kubelet.go

@@ -83,6 +83,7 @@ const (
 	// Ports of different e2e services.
 	kubeletPort          = "10250"
 	kubeletReadOnlyPort  = "10255"
+	kubeletRootDirectory = "/var/lib/kubelet"
 	// Health check url of kubelet
 	kubeletHealthCheckURL = "http://127.0.0.1:" + kubeletReadOnlyPort + "/healthz"
 )
@@ -104,6 +105,10 @@ func (e *E2EServices) startKubelet() (*server, error) {
 		return nil, err
 	}
 	e.rmDirs = append(e.rmDirs, manifestPath)
+	err = createRootDirectory(kubeletRootDirectory)
+	if err != nil {
+		return nil, err
+	}
 	var killCommand, restartCommand *exec.Cmd
 	var isSystemd bool
 	// Apply default kubelet flags.
@@ -139,6 +144,7 @@ func (e *E2EServices) startKubelet() (*server, error) {
 		"--address", "0.0.0.0",
 		"--port", kubeletPort,
 		"--read-only-port", kubeletReadOnlyPort,
+		"--root-dir", kubeletRootDirectory,
 		"--volume-stats-agg-period", "10s", // Aggregate volumes frequently so tests don't need to wait as long
 		"--allow-privileged", "true",
 		"--serialize-image-pulls", "false",
@@ -237,6 +243,17 @@ current-context: local-context`)
 	return nil
 }
 
+func createRootDirectory(path string) error {
+	if _, err := os.Stat(path); err != nil {
+		if os.IsNotExist(err) {
+			return os.MkdirAll(path, os.FileMode(0755))
+		} else {
+			return err
+		}
+	}
+	return nil
+}
+
 func kubeconfigCWDPath() (string, error) {
 	cwd, err := os.Getwd()
 	if err != nil {