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Hi Mikhail,

Unfortunately I completely agree that using Glance with the XenServer plugin is painful.  As Keven pointed out, the current release of XenServer includes python 2.4 in dom0 (where the plugin runs) so having a dependency on nova.image or glanceclient is likely to introduce more pain than it might solve.

I would prefer approach 2; if we can reduce the amount of logic in the glance plugin and move it into the XenAPI driver in Nova then I think that would be a very good thing.

We would, of course, be interested in helping fix the plugin to support glance v2, so we should sync up on IRC in the new year (bobball)

Bob

________________________________
From: Mikhail Fedosin [mfedosin at mirantis.com]
Sent: 24 December 2015 13:51
To: OpenStack Development Mailing List (not for usage questions)
Subject: [openstack-dev] [Nova][Glance] Xenplugin + Glance_v2 = Hate

Hello! As you may know there is a big initiative to adopt glance v2 api in Nova and the important part is making related changes in xenglugin.
Unfortunately xenplugin doesn't use neither nova.image api nor glanceclient. Instead of this it has own http client implementation and bunch of hardcoded 'v1' urls (example, https://github.com/openstack/nova/blob/master/plugins/xenserver/xenapi/etc/xapi.d/plugins/glance#L130). It leads to the fact, that it will be really hard to switch it on v2 api right.

Personally I see 2 solutions:
1. Make xenplugin to adopt nova.image api, which will make it version-agnostic. Here it's not easy to implement and we won't be able to keep backward compatibility with the existing lowlevel code.
2. Also hardcode v2 urls on par with v1 and do the same thing as in nova.image - to determine current glance api version before request and then use appropriate urls in methods.

IMHO, the second solution is more preferable, because I understand how to do it and the v1/v2 compatibility will be 100%. It guarantees that we won't break any of existing deployments and it will allow to merge glance_v2 code in nova.image much quicker.

All opinions and advice will be very helpful. Thanks in advance!

--
Best regards,
Mikhail Fedosin
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