[openstack-dev] [nova][cinder] Nova is now using the Cinder volume attachments API - multiattach comes next

Jay S. Bryant jungleboyj at gmail.com
Sat Dec 9 20:28:27 UTC 2017

*happy dance*

A huge thanks to Ildiko Vansca (couldn't have made this happen without 
your leadership), Matt Riedemann, John Garbutt and John Griffith for 
making this happen.  You guys have worked so hard on this and it is 
greatly appreciated!


On 12/9/2017 1:15 PM, Matt Riedemann wrote:
> I just wanted to take a minute to recognize that the patch [1] to make 
> Nova use the new-style Cinder volume attach flow has merged.
> As one can tell from the patch set count alone, this has been in the 
> works for a long time now.
> We were talking about volume multi-attach support back in Mitaka at 
> the midcycle in Bristol. The early talks / patches would have piled 
> more technical debt onto Nova and further baked in Nova's need to 
> manage volume state, which is something we wanted to avoid, so at the 
> Newton summit in Austin we changed course and decided to prioritize 
> working on a new data model and API in Cinder, which eventually came 
> out as the 3.27 volume attachments API in Ocata.
> There was then serious work on both sides in Pike to start using the 
> new 3.27 API and we found out we needed some more changes to Cinder, 
> which became the 3.44 Cinder API in Queens. Now Nova has merged the 
> change at the end of a very long series of changes to enable the new 
> flow once 3.44 is available to Nova and computes are all upgraded to 
> understand the new flow. One can appreciate the complexity here if you 
> read through the Nova spec for the new attach flow [2].
> I was really happy to see [1] merge this week because I knew we needed 
> to get that in by the queens-2 milestone if we were going to have a 
> shot at (1) flushing out stability issues before Queens RC1 and (2) a 
> good chance to get multi-attach support into Nova in Queens.
> We have a plan for multi-attach support [3] which I think is doable 
> before feature freeze. The Cinder 3.48 API is now available too which 
> Nova needs to correctly detach a multi-attach volume.
> I want to thank everyone that's helped push this along for their 
> dedication and patience, especially John Griffith, Ildiko Vancsa, 
> Steve Noyes and John Garbutt. And thanks to Sean McGinnis, Jay Bryant, 
> Walter Boring and Balazs Gibizer for review support.
> We've had weekly meetings between the Nova and Cinder teams for at 
> least two years now and I can finally see the end so let's keep up the 
> momentum.
> [1] https://review.openstack.org/#/c/330285/
> [2] 
> https://specs.openstack.org/openstack/nova-specs/specs/queens/approved/cinder-new-attach-apis.html
> [3] 
> https://specs.openstack.org/openstack/nova-specs/specs/queens/approved/cinder-volume-multi-attach.html

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