mahara-contributors team mailing list archive

[Russell Boyatt <russell.boyatt@xxxxxxxxxxxxx>]

Hmmm...."Error 1213: Deadlock found when trying to get lock" is from
MySQL rather than from mysqli.  So the error message has come from the
db at some point but that seems at odds with the lack of a latest
deadlock section in 'show engine innodb status'.  I'm not aware of an
option that if enabled would not report deadlocks in this way.

In your test cases, if you enable 'innodb_print_all_deadlocks' option do
you see a deadlock reported in the mysql error log?  (With isolation
level at read commited, I'm afraid I can't still trigger a deadlock for
copy pages/collections)

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

Title:
  MySQL deadlock issues with simultaneous users

Status in Mahara:
  In Progress
Status in Mahara 1.10 series:
  In Progress
Status in Mahara 15.04 series:
  In Progress
Status in Mahara 15.10 series:
  In Progress
Status in Mahara 16.04 series:
  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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