When in aggressive parallel mode MariaDB/MySQL replication could fail with:
Last_Errno: 1942 Last_Error: Error during XID COMMIT: failed to update GTID state in mysql.gtid_slave_pos: 1062: Duplicate entry '0-46158188501' for key 'PRIMARY'
This table is used for tracking the replication process and you might probably just do:
STOP/START SLAVE i.e. restart the replication and it would continue without errors.
MariaDB [(none)]> STOP SLAVE; Query OK, 0 rows affected (0.08 sec) MariaDB [(none)]> START SLAVE; Query OK, 0 rows affected (0.00 sec)
Optimistic or aggressive mode runs conflicting transactions in parallel and it sometimes happens to roll back. In our case probably something happened and the rollback failed and STOP/START saved the replication.
* Additional thoughts
If you try STOP/START and you get the same error, probably it worth trying truncating the table “mysql.gtid_slave_pos” if you do not use GTID Replication feature (the “show slave status” says “Using_Gtid: No”). And even if you use “Using_Gtid: No” you could probably always stop the replication, “change master” to use the old style and start again? Probably switching off the aggressive mode might help, too!
Keep on reading!