+1 here too, Amazed with the performance gains, x2.4 seems a lot, and we'd get rid of deadlocks.
----- Original Message ----- > +1 > > I'm pretty excited about the possibilities here. I've had this > mysqldb/eventlet contention in the back of my mind for some time now. > I'm glad to see some work being done in this area. > > Carl > > On Fri, Jul 11, 2014 at 7:04 AM, Ihar Hrachyshka <ihrac...@redhat.com> wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > > Hash: SHA512 > > > > On 09/07/14 13:17, Ihar Hrachyshka wrote: > >> Hi all, > >> > >> Multiple projects are suffering from db lock timeouts due to > >> deadlocks deep in mysqldb library that we use to interact with > >> mysql servers. In essence, the problem is due to missing eventlet > >> support in mysqldb module, meaning when a db lock is encountered, > >> the library does not yield to the next green thread, allowing other > >> threads to eventually unlock the grabbed lock, and instead it just > >> blocks the main thread, that eventually raises timeout exception > >> (OperationalError). > >> > >> The failed operation is not retried, leaving failing request not > >> served. In Nova, there is a special retry mechanism for deadlocks, > >> though I think it's more a hack than a proper fix. > >> > >> Neutron is one of the projects that suffer from those timeout > >> errors a lot. Partly it's due to lack of discipline in how we do > >> nested calls in l3_db and ml2_plugin code, but that's not something > >> to change in foreseeable future, so we need to find another > >> solution that is applicable for Juno. Ideally, the solution should > >> be applicable for Icehouse too to allow distributors to resolve > >> existing deadlocks without waiting for Juno. > >> > >> We've had several discussions and attempts to introduce a solution > >> to the problem. Thanks to oslo.db guys, we now have more or less > >> clear view on the cause of the failures and how to easily fix them. > >> The solution is to switch mysqldb to something eventlet aware. The > >> best candidate is probably MySQL Connector module that is an > >> official MySQL client for Python and that shows some (preliminary) > >> good results in terms of performance. > > > > I've made additional testing, creating 2000 networks in parallel (10 > > thread workers) for both drivers and comparing results. > > > > With mysqldb: 215.81 sec > > With mysql-connector: 88.66 > > > > ~2.4 times performance boost, ok? ;) > > > > I think we should switch to that library *even* if we forget about all > > the nasty deadlocks we experience now. > > > >> > >> I've posted a Neutron spec for the switch to the new client in Juno > >> at [1]. Ideally, switch is just a matter of several fixes to > >> oslo.db that would enable full support for the new driver already > >> supported by SQLAlchemy, plus 'connection' string modified in > >> service configuration files, plus documentation updates to refer to > >> the new official way to configure services for MySQL. The database > >> code won't, ideally, require any major changes, though some > >> adaptation for the new client library may be needed. That said, > >> Neutron does not seem to require any changes, though it was > >> revealed that there are some alembic migration rules in Keystone or > >> Glance that need (trivial) modifications. > >> > >> You can see how trivial the switch can be achieved for a service > >> based on example for Neutron [2]. > >> > >> While this is a Neutron specific proposal, there is an obvious wish > >> to switch to the new library globally throughout all the projects, > >> to reduce devops burden, among other things. My vision is that, > >> ideally, we switch all projects to the new library in Juno, though > >> we still may leave several projects for K in case any issues arise, > >> similar to the way projects switched to oslo.messaging during two > >> cycles instead of one. Though looking at how easy Neutron can be > >> switched to the new library, I wouldn't expect any issues that > >> would postpone the switch till K. > >> > >> It was mentioned in comments to the spec proposal that there were > >> some discussions at the latest summit around possible switch in > >> context of Nova that revealed some concerns, though they do not > >> seem to be documented anywhere. So if you know anything about it, > >> please comment. > >> > >> So, we'd like to hear from other projects what's your take on that > >> move, whether you see any issues or have concerns about it. > >> > >> Thanks for your comments, /Ihar > >> > >> [1]: https://review.openstack.org/#/c/104905/ [2]: > >> https://review.openstack.org/#/c/105209/ > >> > >> _______________________________________________ OpenStack-dev > >> mailing list OpenStack-dev@lists.openstack.org > >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > >> > > -----BEGIN PGP SIGNATURE----- > > Version: GnuPG/MacGPG2 v2.0.22 (Darwin) > > Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ > > > > iQEcBAEBCgAGBQJTv9LHAAoJEC5aWaUY1u57d2cIAIAthLuM6qxN9fVjPwoICEae > > oSOLvaDNPpZ+xBBqKI+2l5aFiBXSkHzgCfWGHEZB4e+5odAzt8r3Dg5eG/hwckGt > > iZLPGLxcmvD5K0cRoSSPWkPC4KkOwKw0yQHl/JQarDcHQlLgO64jx3bzlB1LDxRu > > R/Bvqo1SBo8g/cupWyxJXNViu9z7zAlvcHLRg4j/AfNTsTDZRrSgbMF2/gLTMvN2 > > FPtkjBvZq++zOva5G5/TySr1b3QRBFCG0uetVbcVF//90XOw+O++rUiDW1v7vkA9 > > OS2sCIXmx1i8kt9yuvs0h11MS8qfX9rSXREJXyPq6NDmePdQdKFsozMdTmqaDfU= > > =JfiC > > -----END PGP SIGNATURE----- > > > > _______________________________________________ > > OpenStack-dev mailing list > > OpenStack-dev@lists.openstack.org > > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > > _______________________________________________ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > _______________________________________________ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
