On 05/12/13 15:36 -0800, Mark Washenberger wrote:
On Thu, Dec 5, 2013 at 3:11 PM, Randall Burt <[email protected]> wrote: On Dec 5, 2013, at 4:45 PM, Steve Baker <[email protected]> wrote: On 12/06/2013 10:46 AM, Mark Washenberger wrote: On Thu, Dec 5, 2013 at 1:05 PM, Vishvananda Ishaya < [email protected]> wrote:
[snip]
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.
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.
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.
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.
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.
The average heat template would provision more than one VM, plus any
number of other cloud resources.
An image is required to provision a single nova server;
a template is required to provision a single heat stack.
Hopefully the above "single vm" policy could be reworded to be agnostic
to the service which consumes the object that glance is storing.
To add to this, is it that Glance wants to be *more* integrated and geared
towards vm or container images or that Glance wishes to have more intimate
knowledge of the things its cataloging *regardless of what those things
actually might be*? The reason I ask is that Glance supporting only "single
vm templates" when Heat orchestrates the entire (or almost entire) spectrum
of core and integrated projects means that its suitability as a candidate
for a template repository plummets quite a bit.
Yes, I missed the boat a little bit there. I agree Glance could operate as a
repo for these kinds of templates. I don't know about expanding much further
beyond the Nova / Heat stack. But within that stack, I think the use cases are
largely the same.
It seems like heat templates likely have built-in relationships with vm
templates / images that would be really nice track closely in the Glance data
model--for example if you wanted something like a notification when deleting an
image would invalidate a template you've created. Another advantage is the
sharing model--Glance is still aiming to become something of an image
marketplace, and that kind of sharing is something that I see being very useful
for Heat as well.
Does this response sound more in line? Sorry I'm still catching up on the
thread from before it was tagged with [Glance].
FWIW, during last week's meeting, we discussed a bit about image templates and what they should do. The discussion was oriented to having support for things like OVF. This sounds like a great opportunity to expand that concept to something that won't be useful just for nova but for Heat as well. As Mark mentioned, it's more about making glance aware about the difference between a template and an image and their types. None of this is written on stone. The discussion came out at the summit and we brought it up at one of our meetings. So, lets make sure we can cover the required needs. There's still no blueprint but I created this[0] etherpad where we could start writing the needs for Heat and other templates. I agree with Mark. I don't think Glance should expand much further beyond the Nova / Heat stack and akin. [0] https://etherpad.openstack.org/p/glance-templates Cheers, FF -- @flaper87 Flavio Percoco
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