[openstack-dev] [Nova] FFE Request: Ephemeral RBD image support

Josh Durgin josh.durgin at inktank.com
Thu Mar 13 19:04:41 UTC 2014

On 03/12/2014 04:54 PM, Matt Riedemann wrote:
> On 3/12/2014 6:32 PM, Dan Smith wrote:
>>> I'm confused as to why we arrived at the decision to revert the commits
>>> since Jay's patch was accepted. I'd like some details about this
>>> decision, and what new steps we need to take to get this back in for
>>> Juno.
>> Jay's fix resolved the immediate problem that was reported by the user.
>> However, after realizing why the bug manifested itself and why it didn't
>> occur during our testing, all of the core members involved recommended a
>> revert as the least-risky course of action at this point. If it took
>> almost no time for that change to break a user that wasn't even using
>> the feature, we're fearful about what may crop up later.
>> We talked with the patch author (zhiyan) in IRC for a while after making
>> the decision to revert about what the path forward for Juno is. The
>> tl;dr as I recall is:
>>   1. Full Glance v2 API support merged
>>   2. Tests in tempest and nova that exercise Glance v2, and the new
>>      feature
>>   3. Push the feature patches back in
>> --Dan
>> _______________________________________________
>> OpenStack-dev mailing list
>> OpenStack-dev at lists.openstack.org
>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
> Those are essentially the steps as I remember them too.  Sean changed
> the dependencies in the blueprints so the nova glance v2 blueprint is
> the root dependency, then multiple images and then the other download
> handler blueprints at the top.  I haven't checked but the blueprints
> should be marked as not complete (not sure what that would be now) and
> marked for next, the v2 glance root blueprint should be marked as high
> priority too so we get the proper focus when Juno opens up.

These reverts are still confusing me. The use of glance's v2 api
is very limited and easy to protect from errors.

These patches use the v2 glance api for exactly one call - to get
image locations. This has been available and used by other
features in nova and cinder since 2012.

Jay's patch fixed the one issue that was found, and added tests for
several other cases. No other calls to glance v2 are used. The method
Jay fixed is the only one that accesses the response from glanceclient.
Furthermore, it's trivial to guard against more incompatibilities and
fall back to downloading normally if any errors occur. This already
happens if glance does not expose image locations.

Can we consider adding this safety valve and un-reverting these patches?


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