[openstack-dev] [keystone][nova][neutron][all] Rolling upgrades: database triggers and oslo.versionedobjects

David Stanek dstanek at dstanek.com
Thu Sep 1 13:45:44 UTC 2016


On Thu, Aug 25 at 13:13 -0400, Steve Martinelli wrote:
> The keystone team is pursuing a trigger-based approach to support rolling,
> zero-downtime upgrades. The proposed operator experience is documented here:
> 
>   http://docs.openstack.org/developer/keystone/upgrading.html
> 

I wanted to mention a few things. One of the reasons I suggested this
approach for keystone is that I've had success in the past using a
combination of triggers and code to do live, online migrations. Many
times using completely different schemas.

In keystone we are just talking about some simple data transformations
between columns and things like that. The triggers themselves shouldn't
get too complicated. If there are cases where triggers won't work, then
we won't force them. (A current example of this is encrypting
credentials.)

The online migrations are not required. Operators can still go the old
route and db_sync while others help test out the cutting edge features.

The triggers are not there during the entire lifecycle of the
application. The expand phase adds them and the contract removes them.

-- 
David Stanek
web: http://dstanek.com
blog: http://traceback.org



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