[openstack-dev] [all][tc] SQL Schema Downgrades and Related Issues

Johannes Erdfelt johannes at erdfelt.com
Fri Jan 30 01:18:21 UTC 2015

On Thu, Jan 29, 2015, Morgan Fainberg <morgan.fainberg at gmail.com> wrote:
> The concept that there is a utility that can (and in many cases
> willfully) cause permanent, and in some cases irrevocable, data loss
> from a simple command line interface sounds crazy when I try and
> explain it to someone.
> The more I work with the data stored in SQL, and the more I think we
> should really recommend the tried-and-true best practices when trying
> to revert from a migration: Restore your DB to a known good state.

You mean like restoring from backup?

Unless your code deploy fails before it has any chance of running, then
you could have had new instances started or instances changed and then
restoring from backups would lose data.

If you meant another way of restoring your data, then there are
some strategies that downgrades could employ that doesn't lose data,
but there is nothing that can handle 100% of cases.

All of that said, for the Rackspace Public Cloud, we have never rolled
back our deploy. We have always rolled forward for any fixes we needed.

>From my perspective, I'd be fine with doing away with downgrades, but
I'm not sure how to document that deployers should roll forward if they
have any deploy problems.


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