"rpl.rpl_start_stop_slave" fail sporadically on 5.5

[Yura Sorokin]

Tested on CentOS 7 x64 with Percona Server 5.5.48

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rpl.rpl_start_stop_slave 'stmt' w2 [ fail ]
        Test ended at 2016-05-02 09:10:27

CURRENT_TEST: rpl.rpl_start_stop_slave
mysqltest: At line 30: query 'kill $connection_id' failed: 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1

The result from queries just before the failure was:
include/master-slave.inc
[connection master]
set @time_before_kill := (select CURRENT_TIMESTAMP);
[Time before the query]
[Connection ID of the slave I/O thread found]
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The probability of a failure is much higher when release binaries are used.
To reproduce, run the following
./mtr rpl.rpl_start_stop_slave rpl.rpl_start_stop_slave rpl.rpl_start_stop_slave rpl.rpl_start_stop_slave rpl.rpl_start_stop_slave rpl.rpl_start_stop_slave rpl.rpl_start_stop_slave rpl.rpl_start_stop_slave --repeat=32 --parallel=8

[Yura Sorokin (yura-sorokin)]

The problem seems to be in
--let $connection_id=`SELECT id FROM information_schema.processlist where state LIKE 'Waiting for master to send event'`

At this point slave connection may still be in 'Queueing master event to the relay log' state and therefore $connection_id can be empty.

To fix, we need to make sure that there is at least 1 connection with status 'Waiting for master to send event' before reading its id.
"wait_condition.inc" can be used for this.

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let $wait_condition= SELECT COUNT(*) = 1 FROM information_schema.processlist WHERE state LIKE 'Waiting for master to send event';
--source include/wait_condition.inc
--let $connection_id=`SELECT id FROM information_schema.processlist where state LIKE 'Waiting for master to send event'`
************************************************************************************************************************

[Yura Sorokin (yura-sorokin)]

https://github.com/percona/percona-server/pull/485

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-2145