Excerpts from Mike Bayer's message of 2015-06-12 09:42:42 -0700: > > On 6/12/15 11:37 AM, Mike Bayer wrote: > > > > > > On 6/11/15 9:32 PM, Eugene Nikanorov wrote: > >> Hi neutrons, > >> > >> I'd like to draw your attention to an issue discovered by rally gate job: > >> http://logs.openstack.org/96/190796/4/check/gate-rally-dsvm-neutron-rally/7a18e43/logs/screen-q-svc.txt.gz?level=TRACE > >> > >> I don't have bandwidth to take a deep look at it, but first > >> impression is that it is some issue with nested transaction support > >> either on sqlalchemy or pymysql side. > >> Also, besides errors with nested transactions, there are a lot of > >> Lock wait timeouts. > >> > >> I think it makes sense to start with reverting the patch that moves > >> to pymysql. > > My immediate reaction is that this is perhaps a concurrency-related > > issue; because PyMySQL is pure python and allows for full blown > > eventlet monkeypatching, I wonder if somehow the same PyMySQL > > connection is being used in multiple contexts. E.g. one greenlet > > starts up a savepoint, using identifier "_3" which is based on a > > counter that is local to the SQLAlchemy Connection, but then another > > greenlet shares that PyMySQL connection somehow with another > > SQLAlchemy Connection that uses the same identifier. > > reading more of the log, it seems the main issue is just that there's a > deadlock on inserting into the securitygroups table. The deadlock on > insert can be because of an index being locked. > > > I'd be curious to know how many greenlets are running concurrently here, > and what the overall transaction looks like within the operation that is > failing here (e.g. does each transaction insert multiple rows into > securitygroups? that would make a deadlock seem more likely).
This begs two questions: 1) Are we handling deadlocks with retries? It's important that we do that to be defensive. 2) Are we being careful to sort the table order in any multi-table transactions so that we minimize the chance of deadlocks happening because of any cross table deadlocks? __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
