Comment 8 for bug 1420606

I am able to produce the problem as described with slave_parallel_workers = 16

mysql> SHOW GLOBAL VARIABLES LIKE '%version%';
+-------------------------+--------------------------------------------------+
| Variable_name | Value |
+-------------------------+--------------------------------------------------+
| innodb_version | 5.6.22-rel72.0 |
| protocol_version | 10 |
| slave_type_conversions | |
| version | 5.6.22-72.0-log |
| version_comment | Percona Server (GPL), Release 72.0, Revision 738 |
| version_compile_machine | x86_64 |
| version_compile_os | Linux |
+-------------------------+--------------------------------------------------+

2015-03-18 00:07:42 6413 [Note] Slave: MTS Recovery has completed at relay log ./mysql_sandbox21088-relay-bin.000007, position 6124140 master log mysql-bin.000007, position 16222833.
2015-03-18 00:07:42 6413 [ERROR] Slave SQL: Cannot execute the current event group in the parallel mode. Encountered event Xid, relay-log name ./mysql_sandbox21088-relay-bin.000009, position 395 which prevents execution of this event group in parallel mode. Reason: the event is a part of a group that is unsupported in the parallel execution mode. Error_code: 1755
2015-03-18 00:07:42 6413 [Warning] Slave: Cannot execute the current event group in the parallel mode. Encountered event Xid, relay-log name ./mysql_sandbox21088-relay-bin.000009, position 395 which prevents execution of this event group in parallel mode. Reason: the event is a part of a group that is unsupported in the parallel execution mode. Error_code: 1755
2015-03-18 00:07:42 6413 [ERROR] Error running query, slave SQL thread aborted. Fix the problem, and restart the slave SQL thread with "SLAVE START". We stopped at log 'mysql-bin.000007' position 15873496

As soon as I enabled relay_log_recovery = 1 It turn's out to different error message as below:

2015-03-18 00:32:52 1731 [ERROR] --relay-log-recovery cannot be executed when the slave was stopped with an error or killed in MTS mode; consider using RESET SLAVE or restart the server with --relay-log-recovery = 0 followed by START SLAVE UNTIL SQL_AFTER_MTS_GAPS
2015-03-18 00:32:52 1731 [ERROR] Failed to initialize the master info structure
2015-03-18 00:32:52 1731 [Note] Check error log for additional messages. You will not be able to start replication until the issue is resolved and the server restarted.

mysql> > show slave status\G
*************************** 1. row ***************************
             Slave_IO_Running: No
            Slave_SQL_Running: No
                   Last_Errno: 1872
                   Last_Error: Slave failed to initialize relay log info structure from the repository
               Last_SQL_Errno: 1872
               Last_SQL_Error: Slave failed to initialize relay log info structure from the repository