Merge pull request #59849 from yue9944882/forcibly-lower-staticpod-name

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lowercase node name in generated static pod name 

**What this PR does / why we need it**:
Cast appended node name to lowercase when generating static pod name on kubelet starting.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #59801 

**Special notes for your reviewer**:
Not sure about how to deal with other illegal node names e.g. containing invalid no-alphabetic characters. Maybe just let it fail-hard is not a bad idea.
But considering that containing uppercase letter in the hostname is somehow a usual case even in the production environment of some companies, tolerating uppercase and cast it implicitly should be good.

**Release note**:

```release-note
force node name lowercase on static pod name generating
```

pkg/kubelet/config/BUILD

@@ -107,6 +107,7 @@ go_test(
         "//pkg/apis/core/validation:go_default_library",
         "//pkg/kubelet/types:go_default_library",
         "//pkg/securitycontext:go_default_library",
+        "//vendor/github.com/stretchr/testify/assert:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/api/equality:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",

pkg/kubelet/config/common.go

@@ -21,6 +21,7 @@ import (
 	"crypto/md5"
 	"encoding/hex"
 	"fmt"
+	"strings"
 
 	"k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -44,7 +45,7 @@ import (
 
 // Generate a pod name that is unique among nodes by appending the nodeName.
 func generatePodName(name string, nodeName types.NodeName) string {
-	return fmt.Sprintf("%s-%s", name, nodeName)
+	return fmt.Sprintf("%s-%s", name, strings.ToLower(string(nodeName)))
 }
 
 func applyDefaults(pod *api.Pod, source string, isFile bool, nodeName types.NodeName) error {

pkg/kubelet/config/common_test.go

@@ -20,12 +20,17 @@ import (
 	"reflect"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+
 	"k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/kubernetes/pkg/api/legacyscheme"
 	"k8s.io/kubernetes/pkg/api/testapi"
+	"k8s.io/kubernetes/pkg/apis/core"
 	api "k8s.io/kubernetes/pkg/apis/core"
+	"k8s.io/kubernetes/pkg/apis/core/validation"
 	"k8s.io/kubernetes/pkg/securitycontext"
 )
 
@@ -189,3 +194,59 @@ func TestGetSelfLink(t *testing.T) {
 		}
 	}
 }
+
+func TestStaticPodNameGenerate(t *testing.T) {
+	testCases := []struct {
+		nodeName  types.NodeName
+		podName   string
+		expected  string
+		overwrite string
+		shouldErr bool
+	}{
+		{
+			"node1",
+			"static-pod1",
+			"static-pod1-node1",
+			"",
+			false,
+		},
+		{
+			"Node1",
+			"static-pod1",
+			"static-pod1-node1",
+			"",
+			false,
+		},
+		{
+			"NODE1",
+			"static-pod1",
+			"static-pod1-node1",
+			"static-pod1-NODE1",
+			true,
+		},
+	}
+	for _, c := range testCases {
+		assert.Equal(t, c.expected, generatePodName(c.podName, c.nodeName), "wrong pod name generated")
+		pod := &core.Pod{}
+		pod.Name = c.podName
+		if c.overwrite != "" {
+			pod.Name = c.overwrite
+		}
+		errs := validation.ValidatePod(pod)
+		if c.shouldErr {
+			specNameErrored := false
+			for _, err := range errs {
+				if err.Field == "metadata.name" {
+					specNameErrored = true
+				}
+			}
+			assert.NotEmpty(t, specNameErrored, "expecting error")
+		} else {
+			for _, err := range errs {
+				if err.Field == "metadata.name" {
+					t.Fail()
+				}
+			}
+		}
+	}
+}