File-position checkpoints can point inside a transaction, causing --resume to fail with a missing TABLE_MAP error

Using gh-ost v1.1.11 (2ed192cd39d8a5173b6ef7c4beaa746a2d3bf1aa) on Aurora MySQL 8.0 with binlog_format=ROW, without --gtid.

After running with --checkpoint --execute, stopping the process, and restarting with --resume, binlog streaming repeatedly fails with:

StreamEvents encountered unexpected error:
... invalid table id, no corresponding table map event

The streamer repeatedly reconnects at the same position. Row copying can reach 100%, but binlog processing remains stuck.

Evidence

The following is an actual checkpoint and surrounding binlog events, with database/table names anonymized and irrelevant columns omitted. Numeric positions are unchanged.

mysql> SELECT gh_ost_chk_id, gh_ost_chk_coords, gh_ost_is_cutover
       FROM app_db._table_a_ghk;

gh_ost_chk_id:     1
gh_ost_chk_coords: mysql-bin-changelog.001644:98771662
gh_ost_is_cutover: 0

mysql> SHOW BINLOG EVENTS
       IN 'mysql-bin-changelog.001644' FROM 98746801 LIMIT 10;

Pos       Event_type      End_log_pos  Info
98746801  Anonymous_Gtid   98746886     SET @@SESSION.GTID_NEXT='ANONYMOUS'
98746886  Query            98746991     BEGIN
98746991  Table_map        98747104     table_id: 5131 (app_db._other_table_gho; another concurrent migration)
98747104  Write_rows       98755290     table_id: 5131
98755290  Write_rows       98763476     table_id: 5131
98763476  Write_rows       98771662     table_id: 5131
98771662  Write_rows       98779848     table_id: 5131  <-- saved checkpoint
98779848  Write_rows       98786279     table_id: 5131 flags: STMT_END_F
98786279  Xid              98786310     COMMIT
98786310  Anonymous_Gtid   98786395     SET @@SESSION.GTID_NEXT='ANONYMOUS'

The checkpoint points to a Write_rows event after its required Table_map, rather than a transaction boundary.

Suspected cause

Checkpoint() saves GetCurrentBinlogCoordinates() as LastTrxCoords.

gh-ost/go/logic/migrator.go

Lines 1812 to 1838 in 2ed192c

    
           // Checkpoint attempts to write a checkpoint of the Migrator's current state. 
        
           // It gets the binlog coordinates of the last received trx and waits until the 
        
           // applier reaches that trx. At that point it's safe to resume from these coordinates. 
        
           func (mgtr *Migrator) Checkpoint(ctx context.Context) (*Checkpoint, error) { 
        
           	coords := mgtr.eventsStreamer.GetCurrentBinlogCoordinates() 
        
           	mgtr.applier.LastIterationRangeMutex.Lock() 
        
           	if mgtr.applier.LastIterationRangeMaxValues == nil || mgtr.applier.LastIterationRangeMinValues == nil { 
        
           		mgtr.applier.LastIterationRangeMutex.Unlock() 
        
           		return nil, errors.New("iteration range is empty, not checkpointing") 
        
           	} 
        
           	chk := &Checkpoint{ 
        
           		Iteration:         mgtr.migrationContext.GetIteration(), 
        
           		IterationRangeMin: mgtr.applier.LastIterationRangeMinValues.Clone(), 
        
           		IterationRangeMax: mgtr.applier.LastIterationRangeMaxValues.Clone(), 
        
           		LastTrxCoords:     coords, 
        
           		RowsCopied:        atomic.LoadInt64(&mgtr.migrationContext.TotalRowsCopied), 
        
           		DMLApplied:        atomic.LoadInt64(&mgtr.migrationContext.TotalDMLEventsApplied), 
        
           	} 
        
           	mgtr.applier.LastIterationRangeMutex.Unlock() 
        
           	for { 
        
           		if err := ctx.Err(); err != nil { 
        
           			return nil, err 
        
           		} 
        
           		mgtr.applier.CurrentCoordinatesMutex.Lock() 
        
           		if coords.SmallerThanOrEquals(mgtr.applier.CurrentCoordinates) { 
        
           			id, err := mgtr.applier.WriteCheckpoint(chk)

In file-position mode, currentCoordinates advances on every event, including intermediate row events.

gh-ost/go/binlog/gomysql_reader.go

Lines 163 to 176 in 2ed192c

    
           // Update binlog coords if using file-based coords. 
        
           // GTID coordinates are updated on receiving GTID events. 
        
           if !gmr.migrationContext.UseGTIDs { 
        
           	gmr.currentCoordinatesMutex.Lock() 
        
           	coords := gmr.currentCoordinates.(*mysql.FileBinlogCoordinates) 
        
           	prevCoords := coords.Clone().(*mysql.FileBinlogCoordinates) 
        
           	coords.LogPos = int64(ev.Header.LogPos) 
        
           	coords.EventSize = int64(ev.Header.EventSize) 
        
           	if coords.IsLogPosOverflowBeyond4Bytes(prevCoords) { 
        
           		gmr.currentCoordinatesMutex.Unlock() 
        
           		return fmt.Errorf("unexpected rows event at %+v, the binlog end_log_pos is overflow 4 bytes", coords) 
        
           	} 
        
           	gmr.currentCoordinatesMutex.Unlock() 
        
           }

Resume loads the saved coordinates and passes that position directly to StartSync(). The new reader therefore lacks the preceding table map.

gh-ost/go/logic/migrator.go

Lines 580 to 595 in 2ed192c

    
           if mgtr.migrationContext.Resume { 
        
           	lastCheckpoint, err := mgtr.applier.ReadLastCheckpoint() 
        
           	if err != nil { 
        
           		return mgtr.migrationContext.Log.Errorf("no checkpoint found, unable to resume: %+v", err) 
        
           	} 
        
           	mgtr.migrationContext.Log.Infof("Resuming from checkpoint coords=%+v range_min=%+v range_max=%+v iteration=%d", 
        
           		lastCheckpoint.LastTrxCoords, lastCheckpoint.IterationRangeMin.String(), lastCheckpoint.IterationRangeMax.String(), lastCheckpoint.Iteration) 
        
           	mgtr.migrationContext.MigrationIterationRangeMinValues = lastCheckpoint.IterationRangeMin 
        
           	mgtr.migrationContext.MigrationIterationRangeMaxValues = lastCheckpoint.IterationRangeMax 
        
           	mgtr.migrationContext.Iteration = lastCheckpoint.Iteration 
        
           	mgtr.migrationContext.TotalRowsCopied = lastCheckpoint.RowsCopied 
        
           	mgtr.migrationContext.TotalDMLEventsApplied = lastCheckpoint.DMLApplied 
        
           	mgtr.migrationContext.InitialStreamerCoords = lastCheckpoint.LastTrxCoords 
        
           	if err := mgtr.initiateStreaming(); err != nil { 
        
           		return err

gh-ost/go/binlog/gomysql_reader.go

Lines 92 to 102 in 2ed192c

    
           // Start sync with specified GTID set or binlog file and position 
        
           if gmr.migrationContext.UseGTIDs { 
        
           	coords := coordinates.(*mysql.GTIDBinlogCoordinates) 
        
           	gmr.binlogStreamer, err = gmr.binlogSyncer.StartSyncGTID(coords.GTIDSet.Clone()) 
        
           } else { 
        
           	coords := gmr.currentCoordinates.(*mysql.FileBinlogCoordinates) 
        
           	gmr.binlogStreamer, err = gmr.binlogSyncer.StartSync(gomysql.Position{ 
        
           		Name: coords.LogFile, 
        
           		Pos:  uint32(coords.LogPos)}, 
        
           	) 
        
           }

The reader separately tracks completed transactions in LastTrxCoords on XID events, but checkpoint creation does not use that value.

gh-ost/go/binlog/gomysql_reader.go

Lines 216 to 225 in 2ed192c

    
           case *replication.XIDEvent: 
        
           	if gmr.migrationContext.UseGTIDs { 
        
           		// event.GSet is the full executed GTID set maintained by the 
        
           		// syncer (MysqlGTIDSet or MariadbGTIDSet depending on flavor). 
        
           		if event.GSet != nil { 
        
           			gmr.LastTrxCoords = &mysql.GTIDBinlogCoordinates{GTIDSet: event.GSet} 
        
           		} 
        
           	} else { 
        
           		gmr.LastTrxCoords = gmr.currentCoordinates.Clone() 
        
           	}

Expected behavior

File-position checkpoints should store a restartable transaction boundary, while ensuring all preceding DML has been applied, so --resume can continue.

Sunbelt Computer Software

PL/B Language Development and Support

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File-position checkpoints can point inside a transaction, causing --resume to fail with a missing TABLE_MAP error #1776

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	// Checkpoint attempts to write a checkpoint of the Migrator's current state.
	// It gets the binlog coordinates of the last received trx and waits until the
	// applier reaches that trx. At that point it's safe to resume from these coordinates.
	func (mgtr Migrator) Checkpoint(ctx context.Context) (Checkpoint, error) {
	coords := mgtr.eventsStreamer.GetCurrentBinlogCoordinates()
	mgtr.applier.LastIterationRangeMutex.Lock()
	if mgtr.applier.LastIterationRangeMaxValues == nil \|\| mgtr.applier.LastIterationRangeMinValues == nil {
	mgtr.applier.LastIterationRangeMutex.Unlock()
	return nil, errors.New("iteration range is empty, not checkpointing")
	}
	chk := &Checkpoint{
	Iteration: mgtr.migrationContext.GetIteration(),
	IterationRangeMin: mgtr.applier.LastIterationRangeMinValues.Clone(),
	IterationRangeMax: mgtr.applier.LastIterationRangeMaxValues.Clone(),
	LastTrxCoords: coords,
	RowsCopied: atomic.LoadInt64(&mgtr.migrationContext.TotalRowsCopied),
	DMLApplied: atomic.LoadInt64(&mgtr.migrationContext.TotalDMLEventsApplied),
	}
	mgtr.applier.LastIterationRangeMutex.Unlock()

	for {
	if err := ctx.Err(); err != nil {
	return nil, err
	}
	mgtr.applier.CurrentCoordinatesMutex.Lock()
	if coords.SmallerThanOrEquals(mgtr.applier.CurrentCoordinates) {
	id, err := mgtr.applier.WriteCheckpoint(chk)

	// Update binlog coords if using file-based coords.
	// GTID coordinates are updated on receiving GTID events.
	if !gmr.migrationContext.UseGTIDs {
	gmr.currentCoordinatesMutex.Lock()
	coords := gmr.currentCoordinates.(*mysql.FileBinlogCoordinates)
	prevCoords := coords.Clone().(*mysql.FileBinlogCoordinates)
	coords.LogPos = int64(ev.Header.LogPos)
	coords.EventSize = int64(ev.Header.EventSize)
	if coords.IsLogPosOverflowBeyond4Bytes(prevCoords) {
	gmr.currentCoordinatesMutex.Unlock()
	return fmt.Errorf("unexpected rows event at %+v, the binlog end_log_pos is overflow 4 bytes", coords)
	}
	gmr.currentCoordinatesMutex.Unlock()
	}

	if mgtr.migrationContext.Resume {
	lastCheckpoint, err := mgtr.applier.ReadLastCheckpoint()
	if err != nil {
	return mgtr.migrationContext.Log.Errorf("no checkpoint found, unable to resume: %+v", err)
	}
	mgtr.migrationContext.Log.Infof("Resuming from checkpoint coords=%+v range_min=%+v range_max=%+v iteration=%d",
	lastCheckpoint.LastTrxCoords, lastCheckpoint.IterationRangeMin.String(), lastCheckpoint.IterationRangeMax.String(), lastCheckpoint.Iteration)

	mgtr.migrationContext.MigrationIterationRangeMinValues = lastCheckpoint.IterationRangeMin
	mgtr.migrationContext.MigrationIterationRangeMaxValues = lastCheckpoint.IterationRangeMax
	mgtr.migrationContext.Iteration = lastCheckpoint.Iteration
	mgtr.migrationContext.TotalRowsCopied = lastCheckpoint.RowsCopied
	mgtr.migrationContext.TotalDMLEventsApplied = lastCheckpoint.DMLApplied
	mgtr.migrationContext.InitialStreamerCoords = lastCheckpoint.LastTrxCoords
	if err := mgtr.initiateStreaming(); err != nil {
	return err

	// Start sync with specified GTID set or binlog file and position
	if gmr.migrationContext.UseGTIDs {
	coords := coordinates.(*mysql.GTIDBinlogCoordinates)
	gmr.binlogStreamer, err = gmr.binlogSyncer.StartSyncGTID(coords.GTIDSet.Clone())
	} else {
	coords := gmr.currentCoordinates.(*mysql.FileBinlogCoordinates)
	gmr.binlogStreamer, err = gmr.binlogSyncer.StartSync(gomysql.Position{
	Name: coords.LogFile,
	Pos: uint32(coords.LogPos)},
	)
	}

	case *replication.XIDEvent:
	if gmr.migrationContext.UseGTIDs {
	// event.GSet is the full executed GTID set maintained by the
	// syncer (MysqlGTIDSet or MariadbGTIDSet depending on flavor).
	if event.GSet != nil {
	gmr.LastTrxCoords = &mysql.GTIDBinlogCoordinates{GTIDSet: event.GSet}
	}
	} else {
	gmr.LastTrxCoords = gmr.currentCoordinates.Clone()
	}

Sunbelt Computer Software

PL/B Language Development and Support

File-position checkpoints can point inside a transaction, causing --resume to fail with a missing TABLE_MAP error #1776

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