Uploaded image for project: 'MariaDB Server'
  1. MariaDB Server
  2. MDEV-26031

unnessary xid logging in one phase commit case

    XMLWordPrintable

    Details

    • Type: Bug
    • Status: Closed (View Workflow)
    • Priority: Blocker
    • Resolution: Fixed
    • Affects Version/s: 10.2, 10.3, 10.4, 10.5, 10.6
    • Fix Version/s: 10.6.3
    • Component/s: Replication
    • Labels:
      None

      Description

      The bug was originally observed as hanging binlog background thread at shutdown similar to one of MDEV-21120:

      #14 MYSQL_BIN_LOG::stop_background_thread (this=0x55660e6b9ba0 <mysql_bin_log>) at /data/Server/10.6D/sql/log.cc:3411
      #15 0x000055660af0ff8e in close_connections () at /data/Server/10.6D/sql/mysqld.cc:1720
      #16 0x000055660af215bc in mysqld_main (argc=44, argv=<optimized out>) at /data/Server/10.6D/sql/mysqld.cc:5839
      
      

      The hang suggested a missed unlogging of a xid or signal notification to the thread loss.

      It turns out the former is the case.
      MDEV-21117 commit reveals an in-born two defects in MYSQL_BIN_LOG::write_transaction_to_binlog 's loop that marks event groups
      with the need of explicit xid unlogging:
      (1) the loop never expected to start from already
      reset ha_info (which is the one phase commit case that does not need the unlogging) as well as
      (2) had a logical flaw
      in its continuatio... condition to break after the first iteration snubbing any
      further ha_info in the list even if they might represent commit_checkpoint_request incapable engines - which would meant to mark the group which may not have happen on the first iteration.

      I set to fix starting from 10.2 though 10.6 is the most vulnerable due to (1) - the loop marks groups that should not be.

      Thanks to Elena Stepanova, Alice Sherepa and Marko Mäkelä who helped to identify it!

        Attachments

          Activity

            People

            Assignee:
            Elkin Andrei Elkin
            Reporter:
            Elkin Andrei Elkin
            Votes:
            0 Vote for this issue
            Watchers:
            4 Start watching this issue

              Dates

              Created:
              Updated:
              Resolved: