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  1. MariaDB Server
  2. MDEV-30619

Parallel Slave SQL Thread Can Update Seconds_Behind_Master with Active Workers

Details

    Description

      If the workers of a parallel replica are busy (potentially with long queues), but the SQL thread has no events left to distribute (so it goes idle). Then the next event that comes from the primary will update LMT with its timestamp, even if the workers may be quite far behind.

      Proposed fix is for the SQL thread to additionally check if there are uncommitted events. That is, we should add an atomic counter (displayable as a new system status variable), which the SQL thread increments on reads, and that the workers decrement on commits. last_master_timestamp should only be updated by the SQL thread with the MDEV-29639 logic if this counter is 0.

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          causes

          Bug - A problem which impairs or prevents the functions of the product. MDEV-31749 New test rpl.rpl_parallel_sbm in bb-10.4-MDEV-30619 sporadically fails in various locations (prepatch: lines 100, 177, 184) (postpatch_1: lines 180, 187)

          • Blocker - Blocks development and/or testing work, production could not run.
          • Closed
          includes

          Bug - A problem which impairs or prevents the functions of the product. MDEV-31749 New test rpl.rpl_parallel_sbm in bb-10.4-MDEV-30619 sporadically fails in various locations (prepatch: lines 100, 177, 184) (postpatch_1: lines 180, 187)

          • Blocker - Blocks development and/or testing work, production could not run.
          • Closed
          is caused by

          Bug - A problem which impairs or prevents the functions of the product. MDEV-29639 Seconds_Behind_Master is incorrect for Delayed, Parallel Replicas

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-23021 rpl.rpl_parallel_optimistic_until fails on BB with various pattern

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-30608 rpl.rpl_delayed_parallel_slave_sbm sometimes fails with Seconds_Behind_Master should not have used second transaction timestamp

          • Major - Major loss of function.
          • Closed

          New Feature - A new feature of the product, which has yet to be developed. MDEV-31895 Report a Replica's Time Difference with its Primary

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-32265 seconds_behind_master is inaccurate for Delayed replication

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-17516 Replication lag issue using parallel replication

          • Major - Major loss of function.
          • Stalled

          Activity

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            bnestere Brandon Nesterenko added a comment -

            Hi Andrei!

            This is ready for review as PR-2682

            bnestere Brandon Nesterenko added a comment - Hi Andrei! This is ready for review as PR-2682
            Roel Roel Van de Paar added a comment -

            Except for MDEV-31749 this is OK to push.

            Roel Roel Van de Paar added a comment - Except for MDEV-31749 this is OK to push.
            Roel Roel Van de Paar added a comment -

            Please note that rpl.rpl_parallel_optimistic_until test failures (ref MDEV-23021) may be more pronounced after the implementation of this patch.

            Roel Roel Van de Paar added a comment - Please note that rpl.rpl_parallel_optimistic_until test failures (ref MDEV-23021 ) may be more pronounced after the implementation of this patch.

            People

              Elkin Andrei Elkin
              bnestere Brandon Nesterenko
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              Dates

                Created:
                Updated:
                Resolved:

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