vars: add pd_enable_follower_handle_region to support get region from pd follower (#49231)

close #49747

Author: CabinfeverB

pkg/domain/domain_sysvars.go

@@ -69,6 +69,15 @@ func (do *Domain) setPDClientDynamicOption(name, sVal string) {
 			break
 		}
 		variable.EnableTSOFollowerProxy.Store(val)
+	case variable.PDEnableFollowerHandleRegion:
+		val := variable.TiDBOptOn(sVal)
+		// Note: EnableFollowerHandle is only used for region API now.
+		// If pd support more APIs in follower, the pd option may be changed.
+		err := do.updatePDClient(pd.EnableFollowerHandle, val)
+		if err != nil {
+			break
+		}
+		variable.EnablePDFollowerHandleRegion.Store(val)
 	}
 }
 

pkg/executor/set_test.go

@@ -652,6 +652,12 @@ func TestSetVar(t *testing.T) {
 	tk.MustExec("set global tidb_enable_tso_follower_proxy = 0")
 	tk.MustQuery("select @@tidb_enable_tso_follower_proxy").Check(testkit.Rows("0"))
 	require.Error(t, tk.ExecToErr("set tidb_enable_tso_follower_proxy = 1"))
+	tk.MustQuery("select @@pd_enable_follower_handle_region").Check(testkit.Rows("0"))
+	tk.MustExec("set global pd_enable_follower_handle_region = 1")
+	tk.MustQuery("select @@pd_enable_follower_handle_region").Check(testkit.Rows("1"))
+	tk.MustExec("set global pd_enable_follower_handle_region = 0")
+	tk.MustQuery("select @@pd_enable_follower_handle_region").Check(testkit.Rows("0"))
+	require.Error(t, tk.ExecToErr("set pd_enable_follower_handle_region = 1"))
 
 	tk.MustQuery("select @@tidb_enable_historical_stats").Check(testkit.Rows("1"))
 	tk.MustExec("set global tidb_enable_historical_stats = 1")

pkg/sessionctx/variable/sysvar.go

@@ -706,6 +706,12 @@ var defaultSysVars = []*SysVar{
 		(*SetPDClientDynamicOption.Load())(TiDBEnableTSOFollowerProxy, val)
 		return nil
 	}},
+	{Scope: ScopeGlobal, Name: PDEnableFollowerHandleRegion, Value: BoolToOnOff(DefPDEnableFollowerHandleRegion), Type: TypeBool, GetGlobal: func(_ context.Context, sv *SessionVars) (string, error) {
+		return BoolToOnOff(EnablePDFollowerHandleRegion.Load()), nil
+	}, SetGlobal: func(_ context.Context, s *SessionVars, val string) error {
+		(*SetPDClientDynamicOption.Load())(PDEnableFollowerHandleRegion, val)
+		return nil
+	}},
 	{Scope: ScopeGlobal, Name: TiDBEnableLocalTxn, Value: BoolToOnOff(DefTiDBEnableLocalTxn), Hidden: true, Type: TypeBool, Depended: true, GetGlobal: func(_ context.Context, sv *SessionVars) (string, error) {
 		return BoolToOnOff(EnableLocalTxn.Load()), nil
 	}, SetGlobal: func(_ context.Context, s *SessionVars, val string) error {

pkg/sessionctx/variable/tidb_vars.go

@@ -722,6 +722,9 @@ const (
 	// TiDBEnableTSOFollowerProxy indicates whether to enable the TSO Follower Proxy feature of PD client.
 	TiDBEnableTSOFollowerProxy = "tidb_enable_tso_follower_proxy"
 
+	// PDEnableFollowerHandleRegion indicates whether to enable the PD Follower handle region API.
+	PDEnableFollowerHandleRegion = "pd_enable_follower_handle_region"
+
 	// TiDBEnableOrderedResultMode indicates if stabilize query results.
 	TiDBEnableOrderedResultMode = "tidb_enable_ordered_result_mode"
 
@@ -1290,6 +1293,7 @@ const (
 	DefTiDBEnableLocalTxn                          = false
 	DefTiDBTSOClientBatchMaxWaitTime               = 0.0 // 0ms
 	DefTiDBEnableTSOFollowerProxy                  = false
+	DefPDEnableFollowerHandleRegion                = false
 	DefTiDBEnableOrderedResultMode                 = false
 	DefTiDBEnablePseudoForOutdatedStats            = false
 	DefTiDBRegardNULLAsPoint                       = true
@@ -1476,6 +1480,7 @@ var (
 	EnableLocalTxn                       = atomic.NewBool(DefTiDBEnableLocalTxn)
 	MaxTSOBatchWaitInterval              = atomic.NewFloat64(DefTiDBTSOClientBatchMaxWaitTime)
 	EnableTSOFollowerProxy               = atomic.NewBool(DefTiDBEnableTSOFollowerProxy)
+	EnablePDFollowerHandleRegion         = atomic.NewBool(DefPDEnableFollowerHandleRegion)
 	RestrictedReadOnly                   = atomic.NewBool(DefTiDBRestrictedReadOnly)
 	VarTiDBSuperReadOnly                 = atomic.NewBool(DefTiDBSuperReadOnly)
 	PersistAnalyzeOptions                = atomic.NewBool(DefTiDBPersistAnalyzeOptions)

tests/integrationtest/r/session/vars.result

@@ -62,6 +62,17 @@ set global tidb_enable_tso_follower_proxy = off;
 select @@tidb_enable_tso_follower_proxy;
 @@tidb_enable_tso_follower_proxy
 0
+select @@pd_enable_follower_handle_region;
+@@pd_enable_follower_handle_region
+0
+set global pd_enable_follower_handle_region = on;
+select @@pd_enable_follower_handle_region;
+@@pd_enable_follower_handle_region
+1
+set global pd_enable_follower_handle_region = off;
+select @@pd_enable_follower_handle_region;
+@@pd_enable_follower_handle_region
+0
 set tidb_tso_client_batch_max_wait_time = 0;
 Error 1229 (HY000): Variable 'tidb_tso_client_batch_max_wait_time' is a GLOBAL variable and should be set with SET GLOBAL
 set global tidb_enable_tso_follower_proxy = default;

tests/integrationtest/t/session/vars.test

@@ -35,6 +35,11 @@ set global tidb_enable_tso_follower_proxy = on;
 select @@tidb_enable_tso_follower_proxy;
 set global tidb_enable_tso_follower_proxy = off;
 select @@tidb_enable_tso_follower_proxy;
+select @@pd_enable_follower_handle_region;
+set global pd_enable_follower_handle_region = on;
+select @@pd_enable_follower_handle_region;
+set global pd_enable_follower_handle_region = off;
+select @@pd_enable_follower_handle_region;
 -- error 1229
 set tidb_tso_client_batch_max_wait_time = 0;
 set global tidb_enable_tso_follower_proxy = default;