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  1. Percona Server for MySQL
  2. PS-7143

Suppress deadlock check for ACL Cache MDL lock to prevent server freeze

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    Details

    • Type: Bug
    • Status: Done
    • Priority: Medium
    • Resolution: Fixed
    • Affects Version/s: 8.0.18-9
    • Fix Version/s: 8.0.21-12
    • Component/s: None
    • Labels:
      None

      Description

      Having 2k connections per second the database becomes unresponsive if FLUSH PRIVILEGES or a GRANT/REVOKE command is executed.
      The FLUSH PRIVILEGES command success, however new connections pills up with Waiting for acl cache lock state eventually hitting max connections.
      Please find below an example of how processlist looks like:

      1186667687 unauthenticated user xx.xxx.xx.xxxx.:xxxx NULL Connect 25 login NULL 0 0
      1186667688 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 24 Waiting for acl cache lock NULL 0 0
      1186667689 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 24 login NULL 0 0
      1186667690 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 24 login NULL 0 0
      1186667691 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 24 login NULL 0 0
      1186667692 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 24 login NULL 0 0
      1186667693 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 23 login NULL 0 0
      1186667694 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 23 login NULL 0 0
      1186667695 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 23 login NULL 0 0
      1186667696 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 23 login NULL 0 0
      1186667697 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 23 login NULL 0 0
      1186667698 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 22 login NULL 0 0
      1186667699 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 22 Waiting for acl cache lock NULL 0 0
      1186667700 unauthenticated user xx.xxx.xxx.xxx:xxxxx NULL Connect 22 Waiting for acl cache lock NULL 0 0

      I've reproduced a similar behavior by limiting IO performance, however customer has shown there isn't IO pressure when having this behavior.

       

      Regards,

        Attachments

        1. acl_hang_v2.diff
          9 kB
        2. acl_hang.diff
          8 kB
        3. pthread_test.c
          0.7 kB

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            People

            Assignee:
            satya.bodapati Satya Bodapati
            Reporter:
            juan.arruti Juan Arruti
            Votes:
            1 Vote for this issue
            Watchers:
            6 Start watching this issue

              Dates

              Created:
              Updated:
              Resolved:

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