timeutil: fix unknown time zone 'posixrules' (#20560)

util/timeutil/time.go

@@ -60,6 +60,22 @@ type locCache struct {
 	locMap map[string]*time.Location
 }
 
+// inferOneStepLinkForPath only read one step link for the path, not like filepath.EvalSymlinks, which gets the
+// recursive final linked file of the path.
+func inferOneStepLinkForPath(path string) (string, error) {
+	fileInfo, err := os.Lstat(path)
+	if err != nil {
+		return path, err
+	}
+	if fileInfo.Mode()&os.ModeSymlink != 0 {
+		path, err = os.Readlink(path)
+		if err != nil {
+			return path, err
+		}
+	}
+	return path, nil
+}
+
 // InferSystemTZ reads system timezone from `TZ`, the path of the soft link of `/etc/localtime`. If both of them are failed, system timezone will be set to `UTC`.
 // It is exported because we need to use it during bootstap stage. And it should be only used at that stage.
 func InferSystemTZ() string {
@@ -72,6 +88,13 @@ func InferSystemTZ() string {
 	case !ok:
 		path, err1 := filepath.EvalSymlinks("/etc/localtime")
 		if err1 == nil {
+			if strings.Index(path, "posixrules") != -1 {
+				path, err1 = inferOneStepLinkForPath("/etc/localtime")
+				if err1 != nil {
+					logutil.BgLogger().Error("locate timezone files failed", zap.Error(err1))
+					return ""
+				}
+			}
 			name, err2 := inferTZNameFromFileName(path)
 			if err2 == nil {
 				return name

util/timeutil/time_test.go

@@ -19,6 +19,8 @@ package timeutil
 
 import (
 	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 
 	. "github.com/pingcap/check"
@@ -64,3 +66,24 @@ func (s *testTimeSuite) TestLocal(c *C) {
 	c.Assert(loc.String(), Equals, "UTC")
 	os.Unsetenv("TZ")
 }
+
+func (s *testTimeSuite) TestInferOneStepLinkForPath(c *C) {
+	os.Remove("/tmp/testlink1")
+	os.Remove("/tmp/testlink2")
+	os.Remove("/tmp/testlink3")
+	var link2, link3 string
+	var err error
+	var link1 *os.File
+	link1, err = os.Create("/tmp/testlink1")
+	c.Assert(err, IsNil)
+	err = os.Symlink(link1.Name(), "/tmp/testlink2")
+	c.Assert(err, IsNil)
+	err = os.Symlink("/tmp/testlink2", "/tmp/testlink3")
+	c.Assert(err, IsNil)
+	link2, err = inferOneStepLinkForPath("/tmp/testlink3")
+	c.Assert(err, IsNil)
+	c.Assert(link2, Equals, "/tmp/testlink2")
+	link3, err = filepath.EvalSymlinks("/tmp/testlink3")
+	c.Assert(err, IsNil)
+	c.Assert(strings.Index(link3, link1.Name()), Not(Equals), -1)
+}