Since forever [0], nova has gently recommended [1] that the placement service be upgraded first.
However, we've not made any serious effort to test scenarios where this isn't done. For example, we don't have grenade tests running placement at earlier levels. After a(nother) discussion [2] which touched on the impacts - real and imagined - of running new nova against old placement, we finally decided to turn the recommendation into a hard requirement [3]. This gives admins a crystal clear guideline, this lets us simplify our support statement, and also means we don't have to do 406 fallback code anymore. So we can do stuff like [4], and also avoid having to write (and subsequently remove) code like that in the future. Please direct any questions to #openstack-nova Your Faithful Scribe, efried [0] Like, since upgrading placement was a thing. [1] https://docs.openstack.org/nova/latest/user/upgrade.html#rolling-upgrade-process (#2, first bullet) [2] http://eavesdrop.openstack.org/irclogs/%23openstack-nova/%23openstack-nova.2018-03-26.log.html#t2018-03-26T17:35:11 [3] https://review.openstack.org/556631 [4] https://review.openstack.org/556633 __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev