Open Stack

Hi,

On Tue, Feb 04, 2014 at 12:36:16PM -0500, Miguel Angel Ajo Pelayo wrote:
> 
> 
> Hi Ralf, I see we're on the same boat for this.
> 
>    It seems that a database migration introduces complications
> for future upgrades. It's not an easy path.
> 
>    My aim when I started this backport was trying to scale out
> neutron-server, starting several ones together. But I'm afraid
> we would find more bugs like this requiring db migrations.
> 
>    Have you actually tested running multiple servers in icehouse?,
> I just didn't have the time, but it's in my roadmap.
I actually ran into the bug in a single server setup. But that seems to happen
pretty rarely.

>    If that fixes the problem, may be some heavier approach (like
> table locking) could be used in the backport, without introducing 
> a new/conflicting migration.
Hm, there seems to be no clean way to do table locking in sqlalchemy. At least I
didn't find one.
 
> About the DB migration backport problem, the actual problem is:
[..]
> 1st step) fix E in icehouse to skip the real unique constraint insertion if it does already exist:
> 
> havana   | icehouse
>          |
> A<-B<-C<-|--D<-*E*<-F
>  
> 2nd step) insert E2 in the middle of B and C to keep the icehouse first reference happy:
> 
> havana      | icehouse
>             |
> A<-B<-E<-C<-|--D<-*E*<-F
> 
> What do you think?
I agree, that would likely be the right fix. But as it seems there are some
(more or less) strict rules about stable backports of migrations (which I
understand as it can get really tricky). So a solution that doesn't require
them would probabyl be preferable.
 
> ----- Original Message -----
> > From: "Ralf Haferkamp" <rhafer at suse.de>
> > To: openstack-dev at lists.openstack.org
> > Sent: Tuesday, February 4, 2014 4:02:36 PM
> > Subject: [openstack-dev] [Neutron] backporting database migrations to	stable/havana
> > 
> > Hi,
> > 
> > I am currently trying to backport the fix for
> > https://launchpad.net/bugs/1254246 to stable/havana. The current state of
> > that
> > is here: https://review.openstack.org/#/c/68929/
> > 
> > However, the fix requires a database migration to be applied (to add a unique
> > constraint to the agents table). And the current fix linked above will AFAIK
> > break havana->icehouse migrations. So I wonder what would be the correct way
> > to
> > do backport database migrations in neutron using alembic? Is there even a
> > correct way, or are backports of database migrations a no go?
> > 
> > --
> > regards,
> >     Ralf

-- 
Ralf