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  1. Percona Server
  2. PS-1827

LP #1736921: Inconsistent and unsafe FLUSH behavior in terms of replication

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      Description

      **Reported in Launchpad by Przemek last update 07-12-2017 13:25:26

      Description:
      Many of the FLUSH commands are bin-logged (but not all), and if GTID mode enabled, adding GTID sequence with local UUID.

      These commands also do not respect super_read_only=1.

      An example ones affected:
      FLUSH SLOW LOGS
      FLUSH HOSTS
      FLUSH STATUS
      FLUSH PRIVILEGES
      FLUSH USER_RESOURCES
      etc.

      Not affected:
      FLUSH LOGS
      FLUSH ENGINE LOGS
      FLUSH BINARY LOGS

      This may cause replication problems later as the cluster becomes inconsistent.

      Upstream report:
      https://bugs.mysql.com/bug.php?id=88720

      Somewhat related bugs:
      https://bugs.mysql.com/bug.php?id=83232
      https://bugs.launchpad.net/percona-server/+bug/1631816

      How to repeat:
      Test case seen in upstream report.

      Suggested fix:
      I don't see much sense in actually replicating these FLUSH commands at all, especially that most of them are related to local resources, which can be different on the slave side.

      If though any of these has to be replicated/bin-logged for some reason, it should respect at least the super_read_only setting.

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                • Assignee:
                  yura.sorokin Yura Sorokin
                  Reporter:
                  lpjirasync lpjirasync (Inactive)
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