lock: add delay clean table lock when session close

config/config.go

@@ -94,7 +94,8 @@ type Config struct {
 	TreatOldVersionUTF8AsUTF8MB4 bool `toml:"treat-old-version-utf8-as-utf8mb4" json:"treat-old-version-utf8-as-utf8mb4"`
 	// EnableTableLock indicate whether enable table lock.
 	// TODO: remove this after table lock features stable.
-	EnableTableLock bool `toml:"enable-table-lock" json:"enable-table-lock"`
+	EnableTableLock     bool   `toml:"enable-table-lock" json:"enable-table-lock"`
+	DelayCleanTableLock uint64 `toml:"delay-clean-table-lock" json:"delay-clean-table-lock"`
 }
 
 // Log is the log section of config.
@@ -332,6 +333,7 @@ var defaultConf = Config{
 	CheckMb4ValueInUTF8:          true,
 	TreatOldVersionUTF8AsUTF8MB4: true,
 	EnableTableLock:              false,
+	DelayCleanTableLock:          0,
 	TxnLocalLatches: TxnLocalLatches{
 		Enabled:  true,
 		Capacity: 2048000,
@@ -599,6 +601,11 @@ var TableLockEnabled = func() bool {
 	return GetGlobalConfig().EnableTableLock
 }
 
+// TableLockDelayClean uses to get the time of delay clean table lock.
+var TableLockDelayClean = func() uint64 {
+	return GetGlobalConfig().DelayCleanTableLock
+}
+
 // ToLogConfig converts *Log to *logutil.LogConfig.
 func (l *Log) ToLogConfig() *logutil.LogConfig {
 	return logutil.NewLogConfig(l.Level, l.Format, l.SlowQueryFile, l.File, l.DisableTimestamp)

config/config.toml.example

@@ -57,6 +57,9 @@ treat-old-version-utf8-as-utf8mb4 = true
 # enable-table-lock is used to control table lock feature. Default is false, indicate the table lock feature is disabled.
 enable-table-lock = false
 
+# delay-clean-table-lock is used to control whether delayed-release the table lock in the abnormal situation. (Milliseconds)
+delay-clean-table-lock = 0
+
 [log]
 # Log level: debug, info, warn, error, fatal.
 level = "info"

config/config_test.go

@@ -63,6 +63,7 @@ unrecognized-option-test = true
 	_, err = f.WriteString(`
 token-limit = 0
 enable-table-lock = true
+delay-clean-table-lock = 5
 [performance]
 txn-entry-count-limit=2000
 txn-total-size-limit=2000
@@ -88,6 +89,7 @@ max-batch-size=128
 	c.Assert(conf.TiKVClient.MaxBatchSize, Equals, uint(128))
 	c.Assert(conf.TokenLimit, Equals, uint(1000))
 	c.Assert(conf.EnableTableLock, IsTrue)
+	c.Assert(conf.DelayCleanTableLock, Equals, uint64(5))
 	c.Assert(f.Close(), IsNil)
 	c.Assert(os.Remove(configFile), IsNil)
 

ddl/db_test.go

@@ -3181,6 +3181,39 @@ func (s *testDBSuite2) TestLockTables(c *C) {
 	tk2.MustExec("unlock tables")
 }
 
+func (s *testDBSuite2) TestTablesLockDelayClean(c *C) {
+	if israce.RaceEnabled {
+		c.Skip("skip race test")
+	}
+	s.tk = testkit.NewTestKit(c, s.store)
+	tk := s.tk
+	tk2 := testkit.NewTestKit(c, s.store)
+	tk2.MustExec("use test")
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t1,t2")
+	defer tk.MustExec("drop table if exists t1,t2")
+	tk.MustExec("create table t1 (a int)")
+	tk.MustExec("create table t2 (a int)")
+
+	tk.MustExec("lock tables t1 write")
+	checkTableLock(c, tk.Se, "test", "t1", model.TableLockWrite)
+	config.GetGlobalConfig().DelayCleanTableLock = 100
+	var wg sync.WaitGroup
+	wg.Add(1)
+	var startTime time.Time
+	go func() {
+		startTime = time.Now()
+		tk.Se.Close()
+		wg.Done()
+	}()
+	time.Sleep(50)
+	checkTableLock(c, tk.Se, "test", "t1", model.TableLockWrite)
+	wg.Wait()
+	c.Assert(time.Since(startTime).Seconds() > 0.1, IsTrue)
+	checkTableLock(c, tk.Se, "test", "t1", model.TableLockNone)
+	config.GetGlobalConfig().DelayCleanTableLock = 0
+}
+
 // TestConcurrentLockTables test concurrent lock/unlock tables.
 func (s *testDBSuite4) TestConcurrentLockTables(c *C) {
 	if israce.RaceEnabled {

session/session.go

@@ -1306,6 +1306,9 @@ func (s *session) Close() {
 	// TODO: do clean table locks when session exited without execute Close.
 	// TODO: do clean table locks when tidb-server was `kill -9`.
 	if s.HasLockedTables() && config.TableLockEnabled() {
+		if ds := config.TableLockDelayClean(); ds > 0 {
+			time.Sleep(time.Duration(ds) * time.Millisecond)
+		}
 		lockedTables := s.GetAllTableLocks()
 		err := domain.GetDomain(s).DDL().UnlockTables(s, lockedTables)
 		if err != nil {