fix(kubernetes): sanitize non-UTF-8 host in metrics (#7998)

plugin/kubernetes/metrics_test.go

@@ -0,0 +1,27 @@
+package kubernetes
+
+import "testing"
+
+func TestSanitizeLabelValue(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{"valid ASCII", "example.com", "example.com"},
+		{"valid UTF-8", "例え.jp", "例え.jp"},
+		{"empty string", "", ""},
+		{"invalid single byte", "host\xff:443", "host\uFFFD:443"},
+		{"consecutive invalid bytes", "\xff\xfe\xfd", "\uFFFD"},
+		{"mixed valid and invalid", "ok\xffok\xfeok", "ok\uFFFDok\uFFFDok"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got := sanitizeLabelValue(tc.input)
+			if got != tc.expected {
+				t.Errorf("sanitizeLabelValue(%q) = %q, want %q", tc.input, got, tc.expected)
+			}
+		})
+	}
+}