session: make min start ts reporter aware of internal session from `g…

…et_lock()` (pingcap#38790)

close pingcap#38706

session/advisory_locks.go

@@ -50,7 +50,7 @@ func (a *advisoryLock) DecrReferences() {
 	a.referenceCount--
 }
 
-// References returns the current reference count for the advisory lock.
+// ReferenceCount returns the current reference count for the advisory lock.
 func (a *advisoryLock) ReferenceCount() int {
 	return a.referenceCount
 }

session/session.go

@@ -46,6 +46,7 @@ import (
 	"github.com/pingcap/tidb/ddl"
 	"github.com/pingcap/tidb/ddl/placement"
 	"github.com/pingcap/tidb/domain"
+	"github.com/pingcap/tidb/domain/infosync"
 	"github.com/pingcap/tidb/errno"
 	"github.com/pingcap/tidb/executor"
 	"github.com/pingcap/tidb/expression"
@@ -1815,10 +1816,11 @@ func (s *session) GetAdvisoryLock(lockName string, timeout int64) error {
 		lock.IncrReferences()
 		return nil
 	}
-	sess, err := createSession(s.GetStore())
+	sess, err := createSession(s.store)
 	if err != nil {
 		return err
 	}
+	infosync.StoreInternalSession(sess)
 	lock := &advisoryLock{session: sess, ctx: context.TODO()}
 	err = lock.GetLock(lockName, timeout)
 	if err != nil {
@@ -1840,6 +1842,7 @@ func (s *session) ReleaseAdvisoryLock(lockName string) (released bool) {
 		if lock.ReferenceCount() <= 0 {
 			lock.Close()
 			delete(s.advisoryLocks, lockName)
+			infosync.DeleteInternalSession(lock.session)
 		}
 		return true
 	}
@@ -1856,6 +1859,7 @@ func (s *session) ReleaseAllAdvisoryLocks() int {
 		lock.Close()
 		count += lock.ReferenceCount()
 		delete(s.advisoryLocks, lockName)
+		infosync.DeleteInternalSession(lock.session)
 	}
 	return count
 }
@@ -3024,6 +3028,10 @@ func createSessions(store kv.Storage, cnt int) ([]*session, error) {
 	return ses, nil
 }
 
+// createSession creates a new session.
+// Please note that such a session is not tracked by the internal session list.
+// This means the min ts reporter is not aware of it and may report a wrong min start ts.
+// In most cases you should use a session pool in domain instead.
 func createSession(store kv.Storage) (*session, error) {
 	return createSessionWithOpt(store, nil)
 }