fix(canal): Preserve binlog filename received in the fake rotate event (go-mysql-org#428)

* fix(canal): Preserve binlog filename received in the fake rotate event go-mysql-org#406

Author: mefcorvi

canal/sync.go

@@ -43,6 +43,11 @@ func (c *Canal) runSyncBinlog() error {
 
 	savePos := false
 	force := false
+
+	// The name of the binlog file received in the fake rotate event.
+	// It must be preserved until the new position is saved.
+	fakeRotateLogName := ""
+
 	for {
 		ev, err := s.GetEvent(c.ctx)
 		if err != nil {
@@ -51,11 +56,21 @@ func (c *Canal) runSyncBinlog() error {
 
 		// Update the delay between the Canal and the Master before the handler hooks are called
 		c.updateReplicationDelay(ev)
-		// if log pos equal zero ,it is a fake rotate event,ignore it.
-		// see https://github.com/mysql/mysql-server/blob/8cc757da3d87bf4a1f07dcfb2d3c96fed3806870/sql/rpl_binlog_sender.cc#L899
+
+		// If log pos equals zero then the received event is a fake rotate event and
+		// contains only a name of the next binlog file
+		// See https://github.com/mysql/mysql-server/blob/8e797a5d6eb3a87f16498edcb7261a75897babae/sql/rpl_binlog_sender.h#L235
+		// and https://github.com/mysql/mysql-server/blob/8cc757da3d87bf4a1f07dcfb2d3c96fed3806870/sql/rpl_binlog_sender.cc#L899
 		if ev.Header.LogPos == 0 {
+			switch e := ev.Event.(type) {
+			case *replication.RotateEvent:
+				fakeRotateLogName = string(e.NextLogName)
+				log.Infof("received fake rotate event, next log name is %s", e.NextLogName)
+			}
+
 			continue
 		}
+
 		savePos = false
 		force = false
 		pos := c.master.Position()
@@ -64,6 +79,11 @@ func (c *Canal) runSyncBinlog() error {
 		// next binlog pos
 		pos.Pos = ev.Header.LogPos
 
+		// new file name received in the fake rotate event
+		if fakeRotateLogName != "" {
+			pos.Name = fakeRotateLogName
+		}
+
 		// We only save position with RotateEvent and XIDEvent.
 		// For RowsEvent, we can't save the position until meeting XIDEvent
 		// which tells the whole transaction is over.
@@ -154,6 +174,8 @@ func (c *Canal) runSyncBinlog() error {
 		if savePos {
 			c.master.Update(pos)
 			c.master.UpdateTimestamp(ev.Header.Timestamp)
+			fakeRotateLogName = ""
+
 			if err := c.eventHandler.OnPosSynced(pos, c.master.GTIDSet(), force); err != nil {
 				return errors.Trace(err)
 			}