Ejemplo n.º 1
0
// StartBinlogDumpFromTimestamp requests a replication binlog dump from
// the master mysqld at the given timestamp and then sends binlog
// events to the provided channel.
//
// The startup phase will list all the binary logs, and find the one
// that has events starting strictly before the provided timestamp. It
// will then start from there, and skip all events that are before the
// provided timestamp.
//
// The stream will continue in the background, waiting for new events if
// necessary, until the connection is closed, either by the master or
// by canceling the context.
//
// Note the context is valid and used until eventChan is closed.
func (sc *SlaveConnection) StartBinlogDumpFromTimestamp(ctx context.Context, timestamp int64) (<-chan replication.BinlogEvent, error) {
	ctx, sc.cancel = context.WithCancel(ctx)

	flavor, err := sc.mysqld.flavor()
	if err != nil {
		return nil, fmt.Errorf("StartBinlogDump needs flavor: %v", err)
	}

	// List the binlogs.
	binlogs, err := sc.Conn.ExecuteFetch("SHOW BINARY LOGS", 1000, false)
	if err != nil {
		return nil, fmt.Errorf("failed to SHOW BINARY LOGS: %v", err)
	}

	// Start with the most recent binlog file until we find the right event.
	var binlogIndex int
	var firstEvent replication.BinlogEvent
	for binlogIndex = len(binlogs.Rows) - 1; binlogIndex >= 0; binlogIndex-- {
		// Exit the loop early if context is canceled.
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		default:
		}

		// Start dumping the logs. The position is '4' to skip the
		// Binlog File Header. See this page for more info:
		// https://dev.mysql.com/doc/internals/en/binlog-file.html
		binlog := binlogs.Rows[binlogIndex][0].String()
		cmd := makeBinlogDumpCommand(4, 0, sc.slaveID, binlog)
		if err := sc.Conn.SendCommand(ComBinlogDump, cmd); err != nil {
			return nil, fmt.Errorf("failed to send the ComBinlogDump command: %v", err)
		}

		// Get the first event to get its timestamp. We skip ROTATE
		// events, as they don't have timestamps.
		for {
			buf, err := sc.Conn.ReadPacket()
			if err != nil {
				return nil, fmt.Errorf("couldn't start binlog dump of binlog %v: %v", binlog, err)
			}

			// Why would the master tell us to stop here?
			if buf[0] == 254 {
				return nil, fmt.Errorf("received EOF packet for first packet of binlog %v", binlog)
			}

			// Parse the full event.
			firstEvent = flavor.MakeBinlogEvent(buf[1:])
			if !firstEvent.IsValid() {
				return nil, fmt.Errorf("first event from binlog %v is not valid", binlog)
			}
			if !firstEvent.IsRotate() {
				break
			}
		}
		if int64(firstEvent.Timestamp()) < timestamp {
			// The first event in this binlog has a smaller
			// timestamp than what we need, we found a good
			// starting point.
			break
		}

		// The timestamp is higher, we need to try the older files.
		// Close and re-open our connection.
		sc.Conn.Close()
		conn, err := sc.mysqld.connectForReplication()
		if err != nil {
			return nil, err
		}
		sc.Conn = conn
	}
	if binlogIndex == -1 {
		// We haven't found a suitable binlog
		log.Errorf("couldn't find an old enough binlog to match timestamp >= %v (looked at %v files)", timestamp, len(binlogs.Rows))
		return nil, ErrBinlogUnavailable
	}

	// Now skip all events that have a smaller timestamp
	var event replication.BinlogEvent
	for {
		buf, err := sc.Conn.ReadPacket()
		if err != nil {
			return nil, fmt.Errorf("error reading packet while skipping binlog events: %v", err)
		}
		if buf[0] == 254 {
			// The master is telling us to stop.
			return nil, fmt.Errorf("received EOF packet in binlog dump while skipping packets: %#v", buf)
		}

		event = flavor.MakeBinlogEvent(buf[1:])
		if !event.IsValid() {
			return nil, fmt.Errorf("event from binlog is not valid (while skipping)")
		}
		if int64(event.Timestamp()) >= timestamp {
			// we found the first event to send
			break
		}

		// Exit the loop early if context is canceled.
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		default:
		}
	}

	// Now just loop sending and reading events.
	// FIXME(alainjobart) I think we can use a buffered channel for better performance.
	eventChan := make(chan replication.BinlogEvent)

	// Start reading events.
	sc.wg.Add(1)
	go func() {
		defer func() {
			close(eventChan)
			sc.wg.Done()
		}()

		// Send the first binlog event, it has the format description.
		select {
		case eventChan <- firstEvent:
		case <-ctx.Done():
			return
		}

		// Then send the rest.
		for {
			select {
			case eventChan <- event:
			case <-ctx.Done():
				return
			}

			buf, err := sc.Conn.ReadPacket()
			if err != nil {
				if sqlErr, ok := err.(*sqldb.SQLError); ok && sqlErr.Number() == mysql.ErrServerLost {
					// ErrServerLost = Lost connection to MySQL server during query
					// This is not necessarily an error. It could just be that we closed
					// the connection from outside.
					log.Infof("connection closed during binlog stream (possibly intentional): %v", err)
					return
				}
				log.Errorf("read error while streaming binlog events: %v", err)
				return
			}

			if buf[0] == 254 {
				// The master is telling us to stop.
				log.Infof("received EOF packet in binlog dump: %#v", buf)
				return
			}

			// Skip the first byte because it's only used
			// for signaling EOF.
			event = flavor.MakeBinlogEvent(buf[1:])
		}
	}()

	return eventChan, nil
}
Ejemplo n.º 2
0
// parseEvents processes the raw binlog dump stream from the server, one event
// at a time, and groups them into transactions. It is called from within the
// service function launched by Stream().
//
// If the sendTransaction func returns io.EOF, parseEvents returns ErrClientEOF.
// If the events channel is closed, parseEvents returns ErrServerEOF.
// If the context is done, returns ctx.Err().
func (bls *Streamer) parseEvents(ctx context.Context, events <-chan replication.BinlogEvent) (replication.Position, error) {
	var statements []*binlogdatapb.BinlogTransaction_Statement
	var format replication.BinlogFormat
	var gtid replication.GTID
	var pos = bls.startPos
	var autocommit = true
	var err error

	// A begin can be triggered either by a BEGIN query, or by a GTID_EVENT.
	begin := func() {
		if statements != nil {
			// If this happened, it would be a legitimate error.
			log.Errorf("BEGIN in binlog stream while still in another transaction; dropping %d statements: %v", len(statements), statements)
			binlogStreamerErrors.Add("ParseEvents", 1)
		}
		statements = make([]*binlogdatapb.BinlogTransaction_Statement, 0, 10)
		autocommit = false
	}
	// A commit can be triggered either by a COMMIT query, or by an XID_EVENT.
	// Statements that aren't wrapped in BEGIN/COMMIT are committed immediately.
	commit := func(timestamp uint32) error {
		if int64(timestamp) >= bls.timestamp {
			trans := &binlogdatapb.BinlogTransaction{
				Statements: statements,
				EventToken: &querypb.EventToken{
					Timestamp: int64(timestamp),
					Position:  replication.EncodePosition(pos),
				},
			}
			if err = bls.sendTransaction(trans); err != nil {
				if err == io.EOF {
					return ErrClientEOF
				}
				return fmt.Errorf("send reply error: %v", err)
			}
		}
		statements = nil
		autocommit = true
		return nil
	}

	// Parse events.
	for {
		var ev replication.BinlogEvent
		var ok bool

		select {
		case ev, ok = <-events:
			if !ok {
				// events channel has been closed, which means the connection died.
				log.Infof("reached end of binlog event stream")
				return pos, ErrServerEOF
			}
		case <-ctx.Done():
			log.Infof("stopping early due to binlog Streamer service shutdown or client disconnect")
			return pos, ctx.Err()
		}

		// Validate the buffer before reading fields from it.
		if !ev.IsValid() {
			return pos, fmt.Errorf("can't parse binlog event, invalid data: %#v", ev)
		}

		// We need to keep checking for FORMAT_DESCRIPTION_EVENT even after we've
		// seen one, because another one might come along (e.g. on log rotate due to
		// binlog settings change) that changes the format.
		if ev.IsFormatDescription() {
			format, err = ev.Format()
			if err != nil {
				return pos, fmt.Errorf("can't parse FORMAT_DESCRIPTION_EVENT: %v, event data: %#v", err, ev)
			}
			continue
		}

		// We can't parse anything until we get a FORMAT_DESCRIPTION_EVENT that
		// tells us the size of the event header.
		if format.IsZero() {
			// The only thing that should come before the FORMAT_DESCRIPTION_EVENT
			// is a fake ROTATE_EVENT, which the master sends to tell us the name
			// of the current log file.
			if ev.IsRotate() {
				continue
			}
			return pos, fmt.Errorf("got a real event before FORMAT_DESCRIPTION_EVENT: %#v", ev)
		}

		// Strip the checksum, if any. We don't actually verify the checksum, so discard it.
		ev, _, err = ev.StripChecksum(format)
		if err != nil {
			return pos, fmt.Errorf("can't strip checksum from binlog event: %v, event data: %#v", err, ev)
		}

		// Update the GTID if the event has one. The actual event type could be
		// something special like GTID_EVENT (MariaDB, MySQL 5.6), or it could be
		// an arbitrary event with a GTID in the header (Google MySQL).
		if ev.HasGTID(format) {
			gtid, err = ev.GTID(format)
			if err != nil {
				return pos, fmt.Errorf("can't get GTID from binlog event: %v, event data: %#v", err, ev)
			}
			pos = replication.AppendGTID(pos, gtid)
		}

		switch {
		case ev.IsGTID(): // GTID_EVENT
			if ev.IsBeginGTID(format) {
				begin()
			}
		case ev.IsXID(): // XID_EVENT (equivalent to COMMIT)
			if err = commit(ev.Timestamp()); err != nil {
				return pos, err
			}
		case ev.IsIntVar(): // INTVAR_EVENT
			name, value, err := ev.IntVar(format)
			if err != nil {
				return pos, fmt.Errorf("can't parse INTVAR_EVENT: %v, event data: %#v", err, ev)
			}
			statements = append(statements, &binlogdatapb.BinlogTransaction_Statement{
				Category: binlogdatapb.BinlogTransaction_Statement_BL_SET,
				Sql:      []byte(fmt.Sprintf("SET %s=%d", name, value)),
			})
		case ev.IsRand(): // RAND_EVENT
			seed1, seed2, err := ev.Rand(format)
			if err != nil {
				return pos, fmt.Errorf("can't parse RAND_EVENT: %v, event data: %#v", err, ev)
			}
			statements = append(statements, &binlogdatapb.BinlogTransaction_Statement{
				Category: binlogdatapb.BinlogTransaction_Statement_BL_SET,
				Sql:      []byte(fmt.Sprintf("SET @@RAND_SEED1=%d, @@RAND_SEED2=%d", seed1, seed2)),
			})
		case ev.IsQuery(): // QUERY_EVENT
			// Extract the query string and group into transactions.
			q, err := ev.Query(format)
			if err != nil {
				return pos, fmt.Errorf("can't get query from binlog event: %v, event data: %#v", err, ev)
			}
			switch cat := getStatementCategory(q.SQL); cat {
			case binlogdatapb.BinlogTransaction_Statement_BL_BEGIN:
				begin()
			case binlogdatapb.BinlogTransaction_Statement_BL_ROLLBACK:
				// Rollbacks are possible under some circumstances. Since the stream
				// client keeps track of its replication position by updating the set
				// of GTIDs it's seen, we must commit an empty transaction so the client
				// can update its position.
				statements = nil
				fallthrough
			case binlogdatapb.BinlogTransaction_Statement_BL_COMMIT:
				if err = commit(ev.Timestamp()); err != nil {
					return pos, err
				}
			default: // BL_DDL, BL_DML, BL_SET, BL_UNRECOGNIZED
				if q.Database != "" && q.Database != bls.dbname {
					// Skip cross-db statements.
					continue
				}
				setTimestamp := &binlogdatapb.BinlogTransaction_Statement{
					Category: binlogdatapb.BinlogTransaction_Statement_BL_SET,
					Sql:      []byte(fmt.Sprintf("SET TIMESTAMP=%d", ev.Timestamp())),
				}
				statement := &binlogdatapb.BinlogTransaction_Statement{
					Category: cat,
					Sql:      []byte(q.SQL),
				}
				// If the statement has a charset and it's different than our client's
				// default charset, send it along with the statement.
				// If our client hasn't told us its charset, always send it.
				if bls.clientCharset == nil || (q.Charset != nil && *q.Charset != *bls.clientCharset) {
					setTimestamp.Charset = q.Charset
					statement.Charset = q.Charset
				}
				statements = append(statements, setTimestamp, statement)
				if autocommit {
					if err = commit(ev.Timestamp()); err != nil {
						return pos, err
					}
				}
			}
		case ev.IsPreviousGTIDs(): // PREVIOUS_GTIDS_EVENT
			// MySQL 5.6 only: The Binlogs contain an
			// event that gives us all the previously
			// applied commits. It is *not* an
			// authoritative value, unless we started from
			// the beginning of a binlog file.
			if !bls.usePreviousGTIDs {
				continue
			}
			newPos, err := ev.PreviousGTIDs(format)
			if err != nil {
				return pos, err
			}
			pos = newPos
			if err = commit(ev.Timestamp()); err != nil {
				return pos, err
			}
		}
	}
}