[openstack-dev] Promoting healing script to scheme migration script?

Anna Kamyshnikova akamyshnikova at mirantis.com
Tue Jun 10 07:49:16 UTC 2014


Hi,

Here is a link to WIP healing script https://review.openstack.org/96438.
The idea on which it is based on is shown in this spec
https://review.openstack.org/95738.

Regards,
Ann


On Mon, Jun 9, 2014 at 7:07 PM, Johannes Erdfelt <johannes at erdfelt.com>
wrote:

> On Mon, Jun 09, 2014, Jakub Libosvar <libosvar at redhat.com> wrote:
> > I'd like to get some opinions on following idea:
> >
> > Because currently we have (thanks to Ann) WIP of healing script capable
> > of changing database scheme by comparing tables in the database to
> > models in current codebase, I started to think whether it could be used
> > generally to db upgrades instead of "generating" migration scripts.
>
> Do you have a link to these healing scripts?
>
> > If I understand correctly the purpose of migration scripts used to be to:
> > 1) separate changes according plugins
> > 2) upgrade database scheme
> > 3) migrate data according the changed scheme
> >
> > Since we dropped on conditional migrations, we can cross out no.1).
> > The healing script is capable of doing no.2) without any manual effort
> > and without adding migration script.
> >
> > That means if we will decide to go along with using script for updating
> > database scheme, migration scripts will be needed only for data
> > migration (no.3)) which are from my experience rare.
> >
> > Also other benefit would be that we won't need to store all database
> > models from Icehouse release which we probably will need in case we want
> > to "heal" database in order to achieve idempotent Icehouse database
> > scheme with Juno codebase.
> >
> > Please share your ideas and reveal potential glitches in the proposal.
>
> I'm actually working on a project to implement declarative schema
> migrations for Nova using the existing model we currently maintain.
>
> The main goals for our project are to reduce the amount of work
> maintaining the database schema but also to reduce the amount of
> downtime during software upgrades by doing schema changes online (where
> possible).
>
> I'd like to see what other haves done and are working on the future so
> we don't unnecessarily duplicate work :)
>
> JE
>
>
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