1berry/MariaDB-server
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Fix incorrect reading of events from relaylog in parallel replication.

Browse Source 
The SQL thread keeps track of the position in the current relay log from
which to read the next event. This position is not normally used, but a
certain interaction with the IO thread can cause the SQL thread to re-open
the relay log and seek to the stored position.

In parallel replication, there were a couple of places where the position
was not updated. This created a race where a re-open of the relay log could
seek to the wrong position and start re-reading and processing events
already handled once, causing various kinds of problems.

Fix this by moving the position update into a single place in
apply_event_and_update_pos(), which should ensure that the position is
always updated in the parallel replication case.

This problem was found from the testcase of MDEV-10863, but it is logically
a separate problem.
This commit is contained in:
Kristian Nielsen 2016-11-16 11:00:38 +01:00
parent f1fcc1fc10
commit 390f2a013b
2 changed files with 7 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
sql/rpl_parallel.cc
View File

@ -2614,7 +2614,6 @@ rpl_parallel::do_event(rpl_group_info *serial_rgi, Log_event *ev,
/*
Queue the event for processing.
*/
rli->event_relay_log_pos= rli->future_event_relay_log_pos;
qev->ir= rli->last_inuse_relaylog;
++qev->ir->queued_count;
cur_thread->enqueue(qev);

7
sql/slave.cc
View File

@ -3569,6 +3569,13 @@ static int exec_relay_log_event(THD* thd, Relay_log_info* rli,
if (rli->mi->using_parallel())
{
int res= rli->parallel.do_event(serial_rgi, ev, event_size);
/*
In parallel replication, we need to update the relay log position
immediately so that it will be the correct position from which to
read the next event.
*/
if (res == 0)
rli->event_relay_log_pos= rli->future_event_relay_log_pos;
if (res >= 0)
DBUG_RETURN(res);
/*