[openstack-dev] [Nova] Should we signal backwards incompatible changes in microversions?

Andrew Laski andrew at lascii.com
Fri Feb 12 20:55:32 UTC 2016

Starting a new thread to continue a thought that came up in
The Nova API microversion framework allows for backwards compatible and
backwards incompatible changes but there is no way to programmatically
distinguish the two. This means that as a user of the API I need to
understand every change between the version I'm using now and a new
version I would like to move to in case an intermediate version changes
default behaviors or removes something I'm currently using.

I would suggest that a more user friendly approach would be to
distinguish the two types of changes. Perhaps something like 2.x.y where
x is bumped for a backwards incompatible change and y is still
monotonically increasing regardless of bumps to x. So if the current
version is 2.2.7 a new backwards compatible change would bump to 2.2.8
or a new backwards incompatible change would bump to 2.3.8. As a user
this would allow me to fairly freely bump the version I'm consuming
until x changes at which point I need to take more care in moving to a
new version.

Just wanted to throw the idea out to get some feedback. Or perhaps this
was already discussed and dismissed when microversions were added and I
just missed it.

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