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MDEV-14014 Multi-Slave Replication Fail: bogus data in log event

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MDEV-7257 made a dump thread to read from binlog concurrently with
writers as long as the read bytes are below a water-mark
(MYSQL_BIN_LOG::binlog_end_pos). However it appeared to be possible a
dump thread reader reach out for bytes past the water mark through a
feature of IO_CACHE that fills in the internal buffer and while doing
so it could read what the reader is not supposed to see (the bytes
above MYSQL_BIN_LOG::binlog_end_pos).

The issue is fixed with constraining the IO_CACHE buffer fill to respect
the watermark.

An added unit test proves reading from file is bound to an external
parameter
passed to {IO_CACHE::end_of_file} cache member.
This commit is contained in:
Andrei Elkin
2018-03-18 21:01:41 +02:00
committed by Sergei Golubchik
parent 52a25d7b67
commit 00ccff48af
2 changed files with 37 additions and 1 deletions
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1
sql/sql_repl.cc
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@ -2538,6 +2538,7 @@ static int send_events(binlog_send_info *info, IO_CACHE* log, LOG_INFO* linfo,
linfo->pos= my_b_tell(log);
info->last_pos= my_b_tell(log);
log->end_of_file= end_pos;
while (linfo->pos < end_pos)
{
if (should_stop(info))