[nova][cinder] Why can't nova in stein work with cinder from queens?
mriedemos at gmail.com
Wed Nov 21 21:11:57 UTC 2018
A change in nova  was approved which makes an assertion that we
(nova? openstack?) do not support running nova from stein with cinder
from queens, and I guess I'd like to know where that support statement
is written down? Granted, I know we don't gate that way but I'm not
aware of anything preventing it from working given we use microversions
and nova, as the client, should be able to work with cinder from v1, v2
or v3 assuming it's doing version discovery correctly (which we've been
doing in nova since queens when we needed to start using the cinder
v3.44 volume attachments API for multiattach - but it's not required).
In fact, nova-api still has compatibility code for older versions of
cinder to determine what it should do about working with volume
attachments . I've been thinking lately about how to drop that code
which would at the very least require a release note saying nova
requires cinder >= queens, but nothing like that was requested in the
change that drops support for cinder v1 from nova and asserts that nova
in stein requires cinder >= queens.
Maybe I'm just yelling at kids to get off my lawn, but I don't really
want this to be precedent without some discussion because I know at
various times operators have complained about upgrades being hard
because they assume all of the services must be upgraded to the same
release at the same time, and I don't think that is true, or should be
true, because if it is, we're doing a really bad job of defining
versioned interfaces between the services.
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