Hi Russell, Thanks for the research, and the patch! I've pushed it into our gerrit code review system here: https://reviews.mahara.org/#/c/5335
What you've described makes a lot of sense. We haven't experienced this issue with the large Mahara sites we host here at Catalyst IT, and those are all on Postgres. Doing a little checking, I see that we are using the default transaction level of READ COMMITTED on our hosted site databases. So, I think the best bet is probably to change the commit level to READ COMMITTED at the application level. I've amended your commit so that it sets that up along with the other basic database parameters when establishing the initial connection. Since this is what we're already doing on our many production Mahara sites, it's unlikely to cause problems (although race conditions are always a possibility). In answer to your item #3, we do not have any code in place to retry when a transaction fails. We have encountered so few cases of this so far, that we've just relied on "F5" in the web browser, as the retry mechanism. Anyway, please give the latest version of the patch a try and see if that helps: https://reviews.mahara.org/#/c/5335/ Cheers, Aaron -- 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/1492919 Title: Deadlock issues when 20-30 users copying collections & pages at the same time 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 Bug description: Multiple users on the forum have reported deadlock issues when there are many users (20-30) copying pages & collections at the same time. See https://mahara.org/interaction/forum/topic.php?id=7309&offset=0&limit=10 Note that 20 to 30 users is around the number you'd hit if you're running a whole class of users through a training session at the same time. The three reported cases of this are all in 15.04, so it may be a problem introduced in that version. The problem has been reported in both Postgres & MySQL. To manage notifications about this bug go to: https://bugs.launchpad.net/mahara/+bug/1492919/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~mahara-contributors Post to : mahara-contributors@lists.launchpad.net Unsubscribe : https://launchpad.net/~mahara-contributors More help : https://help.launchpad.net/ListHelp
