mahara-contributors team mailing list archive

[Russell Boyatt <russell.boyatt@xxxxxxxxxxxxx>]

Yes, maybe disabling transactions for MySQL is the way to go for the
moment.  At least until the longer operations currently in one
transactions can be looked at in more detail.  Other than copy
page/collection, what other operations might be long running?  I'd be
happy to build some JMeter test plans as it's likely they'll be useful.

Are those innodb engine status messages from the system where you
encountered the deadlock?  Neither actually show a deadlock error in the
database, just the list of currently running transactions.  I'd expect a
section in there called 'LATEST DETECTED DEADLOCK' (it will also give a
timestamp as the first line).

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https://bugs.launchpad.net/bugs/1514608

Title:
  MySQL deadlock issues with simultaneous users

Status in Mahara:
  In Progress

Bug description:
  The patch in Bug 1492919 resolved the deadlock issues for some users,
  but others are still reporting that they are getting deadlocks. This
  seems to be an issue unique to MySQL, and it can happen with as few as
  2 or 3 concurrent users.

  It has been reported across all stable versions. Strangely, it seems
  to be a relatively recent issue (i.e. we never heard this with Mahara
  1.8 or 1.7, etc), so this suggests it was triggered by something that
  changed fairly recently. One possible candidate is our switch to the
  mysqli driver (before that Mahara wasn't doing transactions at all, in
  mysql).

  See also:
  * https://mahara.org/interaction/forum/topic.php?id=7309
  * https://mahara.org/interaction/forum/topic.php?id=7432

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