I did a search through the Mahara code base for "db_start()", and found over 200 places where we use it. Some of these are reasonable, a few SQL queries together in the same function. Others are quite wide-ranging, like the collection copy. Or they do things like trigger events before calling db_commit(), which, depending on the registered event handlers, can lead to a lot of code getting executed.
That's interesting, those deadlock log files are definitely from the DB that I was running Mahara against (I made direct DB updates and saw them reflected in the web application). And the copy task did error out, with the errors coming from the mysqli driver saying "deadlock": [1213: Deadlock found when trying to get lock; try restarting transaction] But perhaps mysqli means something different by "deadlock" than the MySQL InnoDB engine does? Or maybe there's some kind of logging setting in this DB that's making it not show up? -- You received this bug notification because you are a member of Mahara Contributors, which is subscribed to Mahara. Matching subscriptions: Subscription for all Mahara Contributors -- please ask on #mahara-dev or mahara.org forum before editing or unsubscribing it! 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 To manage notifications about this bug go to: https://bugs.launchpad.net/mahara/+bug/1514608/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~mahara-contributors Post to : [email protected] Unsubscribe : https://launchpad.net/~mahara-contributors More help : https://help.launchpad.net/ListHelp
