MySQL Bugs: #72314: stop io_thread, start io_thread with GTID may cause data inconsistencies

Bug #72314	stop io_thread, start io_thread with GTID may cause data inconsistencies
Submitted:	11 Apr 2014 5:04	Modified:	25 Feb 2015 5:01
Reporter:	Santosh Praneeth Banda	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Replication	Severity:	S1 (Critical)
Version:		OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	replication

Description:
This is similar to http://bugs.mysql.com/bug.php?id=69943 but doesn't cause entire transaction to miss.

steps leading to this scenario. Note that sql_thread is not stopped at all during these steps

slave IO_thread writes a partial transaction in the relay log before it restarts

end of relay_log_1

set @@global.gtid_next='master_uid:100';
begin;
insert into t1 values(1);

ROTATE EVENT to relay_log_2

relay_log_2

set @@global.gtid_next='master_uid:100';
begin;
insert into t1 values(1);
insert into t1 values(2);
commit;

The fix for http://bugs.mysql.com/bug.php?id=69943 causes master to resend the gtid master_uuid:100.

But slave sql_thread executes the partial transaction before completely executing the full transaction which may cause data inconsistencies between master and slave

** Rows on master

select * from t1;
1
2

** Rows on slave

select * from t1;
1
1
2

How to repeat:
Explained in description. You may use the script mentioned in bug #69943

Suggested fix:
when using GTID protocol sql_thread must rollback a transaction on seeing a format description event from master.

Hello Santosh,

Thank you for the bug report.
I cannot repeat described behavior with the old test case provided in Bug #69943.
Do you have simplified test to reproduce this issue?
Also, Is this similar to Bug #72392?

Thanks,
Umesh

No feedback was provided for this bug for over a month, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

This issue has been fixed as part of internal Bug #18472603 and with
change log entry as in 5.6.21
http://dev.mysql.com/doc/relnotes/mysql/5.6/en/news-5-6-21.html:

"When using GTIDs with MASTER_AUTO_POSITION enabled, if an I/O thread was restarted it failed with an ER_GTID_NEXT_TYPE_UNDEFINED_GROUP error due to a partial transaction not being correctly rolled back before resuming the I/O thread. This fix ensures that the partial transaction is correctly rolled back. (Bug #18472603)".