[openstack-dev] [Glance][Nova][Cinder] glance_store and glance

Jesse Cook jesse.cook at RACKSPACE.COM
Fri Aug 7 14:40:50 UTC 2015


On 8/7/15, 8:46 AM, "Matt Riedemann" <mriedem at linux.vnet.ibm.com> wrote:

>
>
>On 8/7/2015 3:56 AM, Kuvaja, Erno wrote:
>> Hi,
>>
>> Flagged Nova and Cinder into this discussion as they were the first
>>intended adopters iirc.
>>
>> I don't have big religious view about this topic. I wasn't huge fan of
>>the idea separating it in the first place and I'm not huge fan of
>>keeping it separate either.
>>
>> After couple of cycles we have so far witnessed only the downside of
>>glance_store being on it's own. We break even our own gate with our own
>>lib releases, we have one extra bug tracker to look after and even not
>>huge but it just increases the load on the release and stable teams as
>>well.
>>
>> In my understanding the interest within Nova to consume glance_store
>>directly has pretty much died off since we separated it, please do
>>correct me if I'm wrong.
>> I haven't heard anyone expressing any interest to consume glance_store
>>directly within Cinder either.
>> So far I have failed to see use-case for glance_store alone apart from
>>Glance API Server and the original intended use-cases/consumers have
>>either not expressed interest what so ever or directly expressed being
>>not interested.
>>
>> Do we have any reason what so ever keeping doing the extra work to keep
>>these two components separate? I'm more than happy to do so or at least
>>extend this discussion for a cycle if there is projects out there
>>planning to utilize it. I don't want to be in middle of separating it
>>again next cycle because someone wanted to consume and forked out the
>>old tree because we decided to kill it but I'm not keen to take the
>>overhead of it either without reason.
>>
>> - Erno
>>
>>> -----Original Message-----
>>> From: Nikhil Komawar [mailto:nik.komawar at gmail.com]
>>> Sent: Friday, August 07, 2015 6:21 AM
>>> To: openstack-dev at lists.openstack.org
>>> Subject: [openstack-dev] [Glance] glance_store and glance
>>>
>>> Hi,
>>>
>>> During the mid-cycle we had another proposal that wanted to put back
>>>the
>>> glance_store library back into the Glance repo and not leave it is as a
>>> separate repo/project.
>>>
>>> The questions outstanding are: what are the use cases that want it as a
>>> separate library?
>>>
>>> The original use cases that supported a separate lib have not had much
>>> progress or adoption yet. There have been complaints about overhead of
>>> maintaining it as a separate lib and version tracking without much
>>>gain.
>>> The proposals for the re-factor of the library is also a worrysome
>>>topic in
>>> terms of the stability of the codebase.
>>>
>>> The original use cases from my memory are:
>>> 1. Other projects consuming glance_store -- this has become less
>>>likely to be
>>> useful.
>>> 2. another upload path for users for the convenience of tasks -- not
>>> preferable as we don't want to expose this library to users.
>>> 3. ease of addition of newer drivers for the developers -- drivers are
>>>only
>>> being removed since.
>>> 4. cleaner api / more methods that support backend store capabilities
>>>- a
>>> separate library is not necessarily needed, smoother re-factor is
>>>possible
>>> within Glance codebase.
>>>
>>> Also, the authN/Z complexities and ACL restrictions on the back-end
>>>stores
>>> can be potential security loopholes with the library and Glance
>>>evolution
>>> separately.
>>>
>>> In order to move forward smoothly on this topic in Liberty, I hereby
>>>request
>>> input from all concerned developer parties. The decision to keep this
>>>as a
>>> separate library will remain in effect if we do not come to resolution
>>>within 2
>>> weeks from now. However, if there aren't any significant use cases we
>>>may
>>> consider a port back of the same.
>>>
>>> Please find some corresponding discussion from the latest Glance weekly
>>> meeting:
>>> http://eavesdrop.openstack.org/meetings/glance/2015/glance.2015-08-06-
>>> 14.03.log.html#l-21
>>>
>>> --
>>>
>>> Thanks,
>>> Nikhil
>>>
>>>
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>>
>> 
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>
>As far as I know no one is actively trying to integrate glance_store
>into nova like what the cinder team did with os-brick.  I'm not entirely
>sure how glance_store drops into nova either.  The os-brick integration
>was pretty seamless since it was mostly duplicate code.
>
>I thought glance_store somehow got nova closer to using glance v2 but it
>seems that's not the case?

I would agree. It is not the case.

>
>And now there is a separate proposal to work on a new thing in nova's
>tree that's not python-glanceclient but gets nova to using glance v2
>(and v3?), which seems like more splintering.

I need to update that spec (maybe I¹ll do that now). The goal of ³the
seam² is not to create yet another thing to choose from. It¹s to have a
cleaner simpler more reusable interface to Glance that removes duplication
in Nova, Cinder, etc. and opens the door to being able to do things on the
client side that enhance reliability and performance later. There are
reasons to do it outside of python-glanceclient and to put
python-glanceclient on a deprecation path, but it¹s not strictly required
and warrants further discussion.

If you want to use Glance, talk to Glance, and oh btw, we have this single
library that has a clean interface, guarantees data consistency, handles
reliability bits, and all that jazz for services. We used to use some code
in Nova + python-glanceclient to do that and it was a bit of a mess, but
we cleaned that up. Yay!

>
>When the cinder team got nova to support cinder v2, it was Mike Perez
>taking over the change to add that support, so I'd expect the same type
>of effort from the glance team if they want to propagate newer versions
>of the glance API in order to deprecate v1.
>
>[1] https://review.openstack.org/#/c/194303/
>
>-- 
>
>Thanks,
>
>Matt Riedemann
>
>
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