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MDEV-7818: Deadlock occurring with parallel replication and FTWRL

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Problem is that FLUSH TABLES WITH READ LOCK first blocks threads from
starting new commits, then waits for running commits to complete. But
in-order parallel replication needs commits to happen in a particular
order, so this can easily deadlock.

To fix this problem, this patch introduces a way to temporarily pause
the parallel replication worker threads. Before starting FTWRL, we let
all worker threads complete in-progress transactions, and then
wait. Then we proceed to take the global read lock. Once the lock is
obtained, we unpause the worker threads. Now commits are blocked from
starting by the global read lock, so the deadlock will no longer occur.
This commit is contained in:
Kristian Nielsen
2015-10-22 11:18:34 +02:00
parent 6d96fab7dd
commit ba02550166
8 changed files with 537 additions and 25 deletions
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92
mysql-test/suite/rpl/r/rpl_parallel2.result
View File

@@ -29,8 +29,98 @@ include/start_slave.inc
SELECT * FROM t1 WHERE a >= 10 ORDER BY a;
a b
10 0
*** MDEV-7818: Deadlock occurring with parallel replication and FTWRL ***
CREATE TABLE t2 (a INT PRIMARY KEY, b INT) ENGINE=InnoDB;
INSERT INTO t2 VALUES (1,0), (2,0), (3,0);
include/stop_slave.inc
SET @old_dbug= @@SESSION.debug_dbug;
SET @commit_id= 4242;
SET SESSION debug_dbug="+d,binlog_force_commit_id";
BEGIN;
UPDATE t2 SET b=b+1 WHERE a=2;
COMMIT;
BEGIN;
INSERT INTO t2 VALUES (4,10);
COMMIT;
SET SESSION debug_dbug= @old_dbug;
INSERT INTO t2 VALUES (5,0);
INSERT INTO t2 VALUES (6,0);
INSERT INTO t2 VALUES (7,0);
INSERT INTO t2 VALUES (8,0);
INSERT INTO t2 VALUES (9,0);
INSERT INTO t2 VALUES (10,0);
INSERT INTO t2 VALUES (11,0);
INSERT INTO t2 VALUES (12,0);
INSERT INTO t2 VALUES (13,0);
INSERT INTO t2 VALUES (14,0);
INSERT INTO t2 VALUES (15,0);
INSERT INTO t2 VALUES (16,0);
INSERT INTO t2 VALUES (17,0);
INSERT INTO t2 VALUES (18,0);
INSERT INTO t2 VALUES (19,0);
BEGIN;
SELECT * FROM t2 WHERE a=2 FOR UPDATE;
a b
2 0
include/start_slave.inc
FLUSH TABLES WITH READ LOCK;
COMMIT;
STOP SLAVE;
SELECT * FROM t2 ORDER BY a;
a b
1 0
2 1
3 0
4 10
5 0
6 0
7 0
8 0
9 0
10 0
11 0
12 0
13 0
14 0
15 0
16 0
17 0
18 0
19 0
UNLOCK TABLES;
include/wait_for_slave_to_stop.inc
include/start_slave.inc
SELECT * FROM t2 ORDER BY a;
a b
1 0
2 1
3 0
4 10
5 0
6 0
7 0
8 0
9 0
10 0
11 0
12 0
13 0
14 0
15 0
16 0
17 0
18 0
19 0
*** MDEV-8318: Assertion `!pool->busy' failed in pool_mark_busy(rpl_parallel_thread_pool*) on concurrent FTWRL ***
LOCK TABLE t2 WRITE;
FLUSH TABLES WITH READ LOCK;
FLUSH TABLES WITH READ LOCK;
KILL QUERY CID;
ERROR 70100: Query execution was interrupted
UNLOCK TABLES;
UNLOCK TABLES;
include/stop_slave.inc
SET GLOBAL slave_parallel_threads=@old_parallel_threads;
include/start_slave.inc
DROP TABLE t1;
DROP TABLE t1, t2;
include/rpl_end.inc