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

gordon chung gord at live.ca
Thu Aug 25 19:51:39 UTC 2016

On 25/08/16 01:13 PM, 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:


This differs from Nova and Neutron's approaches to solve for rolling upgrades (which use oslo.versionedobjects), however Keystone is one of the few services that doesn't need to manage communication between multiple releases of multiple service components talking over the message bus (which is the original use case for oslo.versionedobjects, and for which it is aptly suited). Keystone simply scales horizontally and every node talks directly to the database.

just curious, but does Keystone have any IPC or is it still just a single service interacting with db? if the latter, you should be able to just apply migration with no downtime as long as you don't modify/delete existing columns. similar experience as others, haven't really used stored procedures in a while but it's a pain wrt to portability. considering OpenStack has a habit of supporting every driver under the sun, i'm guessing driver specific solutions will get more difficult over time.


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