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I'd just like to echo Tim Bell's comments.

>From a rolling upgrade perspective where you have Glance nodes behind
a load balancer we'd probably need a way to manually 'hold back' on v1
until all nodes are upgraded to support v2 aswell.
(Otherwise your auto-discovery may hit an upgraded node but your
subsequent API request could hit a node which hasn't been upgraded yet.)


On 10/17/2013 03:12 PM, Eddie Sheffield wrote:
> I don't oppose having the version autodiscovered. But I do feel the option should be available to override if desired. I've had many problems with
over the years with autoconfiguring systems not doing what I need to be willing to depend on them 100% without a manual override available if at all
possible. I'm thinking particularly for testing or upgrade evaluation scenarios. For example, you want to turn on v2 in glance and evaluate it for a bit
before committing to using it for all of your nova nodes.
> 
> The current patch also had a couple of comments from Dan Prince and Chris Behrens early on when this was brought up there supporting the use of a
config value.
> 
> From the implementation side of things, to do this properly would require some changes to the glanceclient to allow querying of available versions.
Lacking that ability currently is one reason this is currently a config value. Once the client supports this, the nova side change would likely be quite
small.
> 
> Might I propose a compromise?
> 
> 1) For the VERY short term, keep the config value and get the change otherwise reviewed and hopefully accepted.
> 
> 2) Immediately file two blueprints:
>    - python-glanceclient - expose a way to discover available versions
>    - nova - depends on the glanceclient bp and allowing autodiscovery of glance version
>             and making the config value optional (tho not deprecated / removed)

Supporting both seems reasonable.  At least then *most* people don't
need to worry about it and it "just works", but the override is there if
necessary, since multiple people seem to be expressing a desire to have
it available.

Can we just do this all at once?  Adding this to glanceclient doesn't
seem like a huge task.

-- 
Russell Bryant