[openstack-dev] [heat] [glance] Heater Proposal
randall.burt at RACKSPACE.COM
Thu Dec 5 17:05:44 UTC 2013
On Dec 5, 2013, at 10:10 AM, Clint Byrum <clint at fewbar.com>
> Excerpts from Monty Taylor's message of 2013-12-04 17:54:45 -0800:
>> Why not just use glance?
> I've asked that question a few times, and I think I can collate the
> responses I've received below. I think enhancing glance to do these
> things is on the table:
> 1. Glance is for big blobs of data not tiny templates.
> 2. Versioning of a single resource is desired.
> 3. Tagging/classifying/listing/sorting
> 4. Glance is designed to expose the uploaded blobs to nova, not users
> My responses:
> 1: Irrelevant. Smaller things will fit in it just fine.
Fitting is one thing, optimizations around particular assumptions about the size of data and the frequency of reads/writes might be an issue, but I admit to ignorance about those details in Glance.
> 2: The swift API supports versions. We could also have git as a
> backend. This feels like something we can add as an optional feature
> without exploding Glance's scope and I imagine it would actually be a
> welcome feature for image authors as well. Think about Ubuntu maintaining
> official images. If they can keep the ID the same and just add a version
> (allowing users to lock down to a version if updated images cause issue)
> that seems like a really cool feature for images _and_ templates.
Agreed, though one could argue that using image names and looking up ID's or just using ID's as appropriate "sort of" handle this use case, but I agree that having image versioning seems a reasonable feature for Glance to have as well.
> 3: I'm sure glance image users would love to have those too.
And image metadata is already there so we don't have to go through those discussions all over again ;).
> 4: Irrelevant. Heat will need to download templates just like nova, and
> making images publicly downloadable is also a thing in glance.
Yeah, this was the kicker for me. I'd been thinking of adding the tenancy/public/private templates use case to the HeatR spec and realized that this was a good argument for Glance since it already has this feature.
> It strikes me that this might be a silo problem instead of an
> actual design problem. Folk should not be worried about jumping into
> Glance and adding features. Unless of course the Glance folk have
> reservations? (adding glance tag to the subject)
Perhaps, and if these use cases make sense for the Glance users in general, I wouldn't want to re-invent all those wheels either. I admit there's some appeal to being able to pass a template ID to stack-create or as the type of a provider resource and have an actual API to call that's already got a known, tested client that's already part of the OpenStack ecosystem
In the end, though, even if some and not all of our use cases make sense for the Glance folks, we still have the option of creating the HeatR service and having Glance as a possible back-end data store.
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