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<div class="moz-cite-prefix">On 12/06/2013 10:46 AM, Mark
Washenberger wrote:<br>
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cite="mid:CAJyP2C8SrrDeRJMZq-sPGizvV3kGb9GDM6VgZJeeZwnZtFOMdg@mail.gmail.com"
type="cite">
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<div class="gmail_quote">On Thu, Dec 5, 2013 at 1:05 PM,
Vishvananda Ishaya <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:vishvananda@gmail.com" target="_blank">vishvananda@gmail.com</a>></span>
wrote:<br>
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<div class="im"><br>
On Dec 5, 2013, at 12:42 PM, Andrew Plunk <<a
moz-do-not-send="true"
href="mailto:andrew.plunk@RACKSPACE.COM">andrew.plunk@RACKSPACE.COM</a>>
wrote:<br>
<br>
>> Excerpts from Randall Burt's message of
2013-12-05 09:05:44 -0800:<br>
>>> On Dec 5, 2013, at 10:10 AM, Clint Byrum
<clint at <a moz-do-not-send="true"
href="http://fewbar.com" target="_blank">fewbar.com</a>><br>
>>> wrote:<br>
>>><br>
>>>> Excerpts from Monty Taylor's message of
2013-12-04 17:54:45 -0800:<br>
>>>>> Why not just use glance?<br>
>>>>><br>
>>>><br>
>>>> I've asked that question a few times,
and I think I can collate the<br>
>>>> responses I've received below. I think
enhancing glance to do these<br>
>>>> things is on the table:<br>
>>>><br>
>>>> 1. Glance is for big blobs of data not
tiny templates.<br>
>>>> 2. Versioning of a single resource is
desired.<br>
>>>> 3. Tagging/classifying/listing/sorting<br>
>>>> 4. Glance is designed to expose the
uploaded blobs to nova, not users<br>
>>>><br>
>>>> My responses:<br>
>>>><br>
>>>> 1: Irrelevant. Smaller things will fit
in it just fine.<br>
>>><br>
>>> 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.<br>
>>><br>
>><br>
>> Optimizations can be improved for various use
cases. The design, however,<br>
>> has no assumptions that I know about that would
invalidate storing blobs<br>
>> of yaml/json vs. blobs of kernel/qcow2/raw
image.<br>
><br>
> I think we are getting out into the weeds a little
bit here. It is important to think about these apis in
terms of what they actually do, before the decision of
combining them or not can be made.<br>
><br>
> I think of HeatR as a template storage service, it
provides extra data and operations on templates. HeatR
should not care about how those templates are stored.<br>
> Glance is an image storage service, it provides
extra data and operations on images (not blobs), and it
happens to use swift as a backend.<br>
<br>
</div>
This is not completely correct. Glance already supports
something akin to templates. You can create an "image"
with metadata properties that specifies a complex block
device mapping which would allow for multiple volumes and
images to connected to the vm at boot time. This is
functionally a template for a single vm.<br>
<br>
Glance is pretty useless if is just an "image storage"
service, we already have other places that can store bits
(swift, cinder). It is much more valuable as a searchable
repository of bootable templates. I don't see any reason
why this idea couldn't be extended to include more complex
templates that could include more than one vm.<br>
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<div><br>
</div>
<div>FWIW I agree with all of this. I think Glance's real
role in OpenStack is as a helper and optionally as a
gatekeeper for the category of "stuff Nova can boot". So
any parameter that affects what Nova is going to boot
should in my view be something Glance can be aware of.
This list of parameters *could* grow to include multiple
device images, attached volumes, and other things that
currently live in the realm of flavors such as extra
hardware requirements and networking aspects.</div>
<div><br>
</div>
<div>Just so things don't go too crazy, I'll add that since
Nova is generally focused on provisioning individual VMs,
anything above the level of an individual VM should be out
of scope for Glance.</div>
<div><br>
</div>
<div>I think Glance should alter its approach to be less
generally agnostic about the contents of the objects it
hosts. Right now, we are just starting to do this with
images, as we slowly advance on offering server side
format conversion. We could find similar use cases for
single vm templates.</div>
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</blockquote>
<br>
The average heat template would provision more than one VM, plus any
number of other cloud resources.<br>
<br>
An image is required to provision a single nova server;<br>
a template is required to provision a single heat stack.<br>
<br>
Hopefully the above "single vm" policy could be reworded to be
agnostic to the service which consumes the object that glance is
storing.<br>
<br>
<br>
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