// 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
}
// 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
}
}
}
}