[openstack-dev] [Neutron] Issue with pymysql
bpavlovic at mirantis.com
Fri Jun 12 18:13:48 UTC 2015
Thanks for quick fix/revert https://review.openstack.org/#/c/191010/
This unblocked Rally gates...
On Fri, Jun 12, 2015 at 8:56 PM, Clint Byrum <clint at fewbar.com> wrote:
> 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
> > >>
> > >>
> > >> 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-request at lists.openstack.org?subject:unsubscribe
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the OpenStack-dev