[openstack-dev] Work around DB in OpenStack (Oslo, Nova, Cinder, Glance)

Johannes Erdfelt johannes at erdfelt.com
Wed Jul 3 14:26:25 UTC 2013

On Wed, Jul 03, 2013, Michael Still <mikal at stillhq.com> wrote:
> On Wed, Jul 3, 2013 at 3:50 AM, Boris Pavlovic <boris at pavlovic.me> wrote:
> > Question:
> >   Why we should put in oslo slqlalchemy-migrate monkey patches, when we are
> > planing to switch to alembic?
> >
> > Answer:
> >    If we don’t put in oslo sqlalchemy-migrate monkey patches. We won't be
> > able to work on 7 point at all until 8 and 10 points will be implemented in
> > every project. Also work around 8 point is not finished, so we are not able
> > to implement 10 points in any of project. So this blocks almost all work in
> > all projects. I think that these 100-200 lines of code are not so big price
> > for saving few cycles of time.
> We've talked in the past (Folsom summit?) about alembic, but I'm not
> aware of anyone who is actually working on it. Is someone working on
> moving us to alembic? If not, it seems unfair to block database work
> on something no one is actually working on.

I've started working on a non-alembic migration path that was discussed
at the Grizzly summit.

While alembic is better than sqlalchemy-migrate, it still requires long
downtimes when some migrations are run. We discussed moving to an
expand/contract cycle where migrations add new columns, allow migrations
to slowly (relatively speaking) migrate data over, then (possibly) remove
any old columns.


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