[Openstack-operators] [keystone] Request for Feedback: Online database migrations

Lance Bragstad lbragstad at gmail.com
Wed Dec 2 20:06:18 UTC 2015

Hey all,

I wanted to send out a follow up on this. Yesterday in the keystone meeting
we voted on Mitaka specs that we would like to commit to. The
online-migration spec was accepted as something we would definitely like to
see [0]. On the other hand, the development team doesn't really have enough
insight into the online-migration process to effectively move forward. We
want to shy away from over-architecting a migration solution that will
inevitably cause issues and confusion. The conversation started as we
compared using the expand/contract model versus stretching migrations over
several releases, all of which was had in IRC [1].

As a baby step, we came up with the following plan.

Merge a unit test into keystone that detects certain offline migration
operations. In order to pass the test, an exception has to be added to the
test case and formal release notes must be proposed with the schema change.
The release notes must explicitly detail the schema change, why it is
changing, how to migrate data if any, what variables downtime would depend
on, and any other useful bits an operator should know.

We're hoping that this type of process change makes it easier for operators
to plan migration changes, and schedule downtime if necessary. This
wouldn't guarantee online-migrations for keystone, but it's a step forward
as we gather more feedback from operators.



On Fri, Nov 27, 2015 at 3:52 AM, Jesse Pretorius <jesse.pretorius at gmail.com>

> Hi everyone,
> As we all know, upgrades are hard. Part of the problem relates to down
> time due to offline database migrations.
> The Keystone team has put together a spec [1] and is seeking feedback for
> implementing online schema migrations.
> Please weigh in, as operators, on the spec presented.
> [1] https://review.openstack.org/245186
> --
> Jesse Pretorius
> IRC: odyssey4me
> _______________________________________________
> OpenStack-operators mailing list
> OpenStack-operators at lists.openstack.org
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
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