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MDEV-5509: Seconds_behind_master incorrect in parallel replication

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The problem was a race between the SQL driver thread and the worker threads.
The SQL driver thread would set rli->last_master_timestamp to zero to
mark that it has caught up with the master, while the worker threads would
set it to the timestamp of the executed event. This can happen out-of-order
in parallel replication, causing the "caught up" status to be overwritten
and Seconds_Behind_Master to wrongly grow when the slave is idle.

To fix, introduce a separate flag rli->sql_thread_caught_up to mark that the
SQL driver thread is caught up. This avoids issues with worker threads
overwriting the SQL driver thread status. In parallel replication, we then
make SHOW SLAVE STATUS check in addition that all worker threads are idle
before showing Seconds_Behind_Master as 0 due to slave idle.
This commit is contained in:
unknown
2014-01-08 11:00:44 +01:00
parent bfdbb17990
commit 8cc6e90d74
7 changed files with 122 additions and 13 deletions
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18
mysql-test/suite/rpl/r/rpl_parallel2.result Normal file
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include/rpl_init.inc [topology=1->2]
*** MDEV-5509: Incorrect value for Seconds_Behind_Master if parallel replication ***
SET @old_parallel_threads=@@GLOBAL.slave_parallel_threads;
include/stop_slave.inc
SET GLOBAL slave_parallel_threads=5;
include/start_slave.inc
CREATE TABLE t1 (a INT PRIMARY KEY, b INT);
CALL mtr.add_suppression("Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT. Statement is unsafe because it uses a system function that may return a different value on the slave");
INSERT INTO t1 VALUES (1,sleep(2));
Warnings:
Note 1592 Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT. Statement is unsafe because it uses a system function that may return a different value on the slave.
Seconds_Behind_Master should be zero here because the slave is fully caught up and idle.
Seconds_Behind_Master = '0'
include/stop_slave.inc
SET GLOBAL slave_parallel_threads=@old_parallel_threads;
include/start_slave.inc
DROP TABLE t1;
include/rpl_end.inc