mahara-contributors team mailing list archive

[Russell Boyatt <russell.boyatt@xxxxxxxxxxxxx>]

I've attached a copy of the JMeter test plan I've used to test copying
collections.  You'll need a file specifying some users to make use of it
(see 'Mahara users CSV' element in the test plan).

Adding a sleep to execute_sql() didn't make any difference from me
(either with jmeter or a 4 user browser test) but I probably have a much
smaller test db than you which might be making enough of a difference.

Did the deadlock messages from 'show engine innodb status' give anything
useful?

Looking at the page/collection page logic, one thing it does is delete
all rows in view_rows_columns before reinserting for a  given view.  If
nothing exists in view_rows_columns for that view, the deletes would
cause gap locks at the end of table.  Which could then cause the
following inserts to view_rows_columns to fail in the deadlock state
we've seen.

** Attachment added: "JMeter test plan for copy collection"
   https://bugs.launchpad.net/mahara/+bug/1514608/+attachment/4517293/+files/copy_collection_test.jmx

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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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