Description:
1.configure semisync (make sure rpl_semi_sync_master_timeout is set to a very large value)
on master:
root@(none) 07:15:49>show variables like '%semi%';
+------------------------------------+-----------+
| Variable_name | Value |
+------------------------------------+-----------+
| rpl_semi_sync_master_enabled | ON |
| rpl_semi_sync_master_timeout | 100000000 |
| rpl_semi_sync_master_trace_level | 32 |
| rpl_semi_sync_master_wait_no_slave | ON |
| rpl_semi_sync_slave_enabled | OFF |
| rpl_semi_sync_slave_trace_level | 32 |
+------------------------------------+-----------+
6 rows in set (0.00 sec)
on slave:
root@(none) 07:16:52>show variables like '%semi%';
+---------------------------------+-------+
| Variable_name | Value |
+---------------------------------+-------+
| rpl_semi_sync_slave_enabled | ON |
| rpl_semi_sync_slave_trace_level | 32 |
+---------------------------------+-------+
2 rows in set (0.00 sec)
2. run workload on master, and then stop the io_thread on slave;
Because rpl_semi_sync_master_wait_no_slave is set to ON, then all user threads stall at:
ReplSemiSyncMaster::cond_timewait,ReplSemiSyncMaster::commitTrx
3.uninstall semisync plugin on master;
root@(none) 07:08:56>uninstall plugin rpl_semi_sync_master;
Query OK, 0 rows affected, 1 warning (0.00 sec)
root@(none) 07:09:01>
root@(none) 07:09:02>show warnings;
+---------+------+----------------------------------------------------+
| Level | Code | Message |
+---------+------+----------------------------------------------------+
| Warning | 1620 | Plugin is busy and will be uninstalled on shutdown |
+---------+------+----------------------------------------------------+
1 row in set (0.00 sec)
4.start io_thread on slave. Since the semisync_master_plugin was uninstalled (but not completely), it will be failed to connect to master, And the error message:
2013-12-19 19:22:29 21760 [ERROR] Error reading packet from server: Failed to run hook 'reserve_header' ( server_errno=1105)
5. I can't wake up the user threads by setting rpl_semi_sync_master_enabled
root@(none) 07:23:39>set global rpl_semi_sync_master_enabled = 0;
ERROR 1193 (HY000): Unknown system variable 'rpl_semi_sync_master_enabled'
Since the value of rpl_semi_sync_master_timeout is very large, I have to restart the server to kill these threads.
How to repeat:
described above.
Suggested fix:
wake up all user threads while uninstall the plugin.
