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  1. MariaDB Server
  2. MDEV-8405

slave_transaction_retries < slave-parallel-threads quite risky

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      I encountered 11 instances of the following in a binlog group commit along with one other transaction on a different table.

      UPDATE variable SET value='a:0:{}'
      WHERE ( (name = 'rules_event_whitelist') )

      the slave settings where:

      (replication not in gtid mode)
      slave_transaction_retries=10 (default)
      slave-parallel-threads=20

      master had binlog_commit_wait_count=20

      as such the replication was stopped and the error was in the log:

      150701  2:01:33 [ERROR] Slave worker thread retried transaction 10 time(s) in vain, giving up. Consider raising the value of the slave_transaction_retries variable.
      150701  2:01:33 [ERROR] Slave SQL: Deadlock found when trying to get lock; try restarting transaction, Gtid 0-8-1270304033, Internal MariaDB error code: 1213
      150701  2:01:33 [Warning] Slave: Connection was killed Error_code: 1927
      150701  2:01:33 [Warning] Slave: Connection was killed Error_code: 1927
      150701  2:01:33 [Warning] Slave: Deadlock found when trying to get lock; try restarting transaction Error_code: 1213
      150701  2:01:33 [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.010502' position 38545619

      a) Stopping replication after slave_transaction_retries has been achieved puts me in a much worse state than continuing to try, so is there any case where slave_transaction_retries is useful (apart from catching a coding error)?

      b) is slave_transaction_retries = slave-parallel-threads sufficient to resolve this in the mean time? or do i need to set this to factorial(slave-parallel-threads) ?

      I read though MDEV-7882 and it looked different. Does anything else post 10.0.17 release change the handling of this situation?

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            Assignee:
            knielsen Kristian Nielsen
            Reporter:
            danblack Daniel Black
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