Details
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Bug
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Status: Stalled (View Workflow)
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Major
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Resolution: Unresolved
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10.1.36
Description
Using parallel replication second behind master is wrongly reporting 0 when SQL thread is stopped and restarted long time after.
This happen by design
https://lists.launchpad.net/maria-developers/msg08958.html
but is really a show stopper for most proxy that send traffic to such slave thinking it's in sync with master.
My understanding is that slave_behind_master is computed after first commit so in this case the master is 2 days in advance and on a fresh restarted slave we get this
| 30 | system user | | tsce_unedic | Connect | 2211 | altering table | OPTIMIZE TABLE `requetes` | 0.000 |
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And we can see wrong second behind master
Seconds_Behind_Master: 0
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Using_Gtid: Slave_Pos
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Gtid_IO_Pos: 0-21-28557589
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Parallel_Mode: conservative
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but on his master
gtid_current_pos | 0-21-28570301
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A possible solution would be to update Seconds_Behind_Master by injecting a fake event in start slave with the max timestamp of all events read by the leader thread and send to to the worker threads .
To reproduce :
--source include/have_innodb.inc
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--source include/have_binlog_format_mixed.inc
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--let $rpl_topology=1->2
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--source include/rpl_init.inc
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# Test various aspects of parallel replication.
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--connection server_1
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ALTER TABLE mysql.gtid_slave_pos ENGINE=InnoDB;
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CREATE TABLE t1 (a INT PRIMARY KEY, b INT) ENGINE=InnoDB;
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--save_master_pos
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--connection server_2
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--sync_with_master
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--source include/stop_slave_sql_thread.inc
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SET GLOBAL slave_parallel_threads=4;
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--connection server_2
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--sync_with_master
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--source include/stop_slave.inc
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SET GLOBAL slave_parallel_threads=1;
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--connection server_1
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--disable_warnings
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INSERT INTO t1 VALUES (1, SLEEP(100));
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--wait 100s
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INSERT INTO t1 VALUES (1, SLEEP(1));
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--connection server_2
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--source include/start_slave.inc
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--let $status_items= Seconds_Behind_Master
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--source include/show_slave_status.inc
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--sync_with_master
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--let $status_items= Seconds_Behind_Master
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--source include/show_slave_status.inc
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Attachments
Issue Links
- is duplicated by
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- Closed
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- relates to
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MDEV-30458 Consolidate Serial Replica to Parallel Replica with 1 Worker Thread
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- Open
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- Stalled
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