Hey all, Mark, Yes, that's exactly what we were going to do! (and there is a similar class in eventlet itself, Victor is currently trying to run Nova with it applied, so we might end up with no module/class at all, but rather use the one from eventlet instead)
Thank you all for your feedback! Roman On Wed, Dec 4, 2013 at 1:45 AM, Mark McLoughlin <mar...@redhat.com> wrote: > On Mon, 2013-12-02 at 16:02 +0200, Victor Sergeyev wrote: >> Hi folks! >> >> At the moment I and Roman Podoliaka are working on splitting of >> openstack.common.db code into a separate library. And it would be nice to >> drop dependency on eventlet before oslo.db is released. >> >> Currently, there is only one place in oslo.db where we use eventlet - >> wrapping of DB API method calls to be executed by tpool threads. It wraps >> DB API calls to be executed by tpool threads. This is only needed when >> eventlet is used together with DB-API driver implemented as a Python C >> extension (eventlet can't monkey patch C code, so we end up with DB API >> calls blocking all green threads when using Python-MySQLdb). eventlet has a >> workaround known as 'tpool' which is basically a pool of real OS threads >> that can play nicely with eventlet event loop. tpool feature is >> experimental and known to have stability problems. There is a doubt that >> anyone is using it in production at all. Nova API (and probably other API >> services) has an option to prefork the process on start, so that they don't >> need to use tpool when using eventlet together Python-MySQLdb. >> >> We'd really like to drop tpool support from oslo.db, because as a library >> we should not be bound to any particular concurrency model. If a target >> project is using eventlet, we believe, it is its problem how to make it >> play nicely with Python-MySQLdb lib, but not the problem of oslo.db. >> Though, we could put tpool wrapper into another helper module within >> oslo-incubator. >> >> But we would really-really like not to have any eventlet related code in >> oslo.db. >> >> Are you using CONF.database.use_tpool in production? Does the approach with >> a separate tpool wrapper class seem reasonable? Or we can just drop tpool >> support at all, if no one is using it? > > Another approach is to put the tpool wrapper class in a separate module > which would be completely optional for users of the library. > > For example, you could imagine people who don't want this doing: > > from oslo import db > > dbapi = db.DBAPI() > > but if you want the tpool thing, you might do: > > from oslo import db > from oslo.db import eventlet as db_eventlet > > dbapi = db_eventlet.TpoolWrapper(db.DBAPI()) > > (I'm just making stuff up, but you get the idea) > > The key thing is that eventlet isn't a hard dependency of the library, > but the useful eventlet integration is still available in the library if > you want it. > > We did something similar in oslo.messaging, and the issues there were > probably more difficult to deal with. > > Mark. > > > _______________________________________________ > 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
