[openstack-dev] RFC: Recording/providing ISO image headers in glance

Daniel P. Berrange berrange at redhat.com
Tue Apr 9 08:18:51 UTC 2013

On Mon, Apr 08, 2013 at 10:59:32AM -0700, Mark Washenberger wrote:
> Sorry I missed this earlier, but, couldn't you just run "isoinfo" on
> the image data before you upload it to Glance, and add the properties
> you care about during image creation? We could document those property
> names and values (and maybe even validate them) to make sure they
> retain their canonical meaning.

You need to have something that apps can rely on existing for all
images and more importantly being correct. I don't think requiring
the users to manually set this is satisfactory. You also can't
assume that the user actually has the ISO locally - you can tell
Glance to pull images straight from a remote HTTP url, which makes
running isoinfo impossible.

> Otherwise, adding a hook to "inspect image and add relevant
> properties" doesn't really have a good place to fit into Glance at the
> moment, IMO.

Well that will have to be dealt with as part of the development
of this feature.

> On Fri, Apr 5, 2013 at 3:04 PM, Mark Atwood <mark.atwood at hp.com> wrote:
> > Instead of just for ISO9660, I know that other filesystem images and also
> > various VM storage images also define various metadata.  (I know that I've
> > read and written metadata for Virtual Box images using the GUI tool, for
> > example.)
> >
> > I think it makes sense to do this in such a way that Glance can make all
> > these metadatas from all image formats discoverable and displayable.

Yep, it of course makes sense to design it as a pluggable facility
to allow for different file types to have different default metadata.

> > On Wed, Jan 30, 2013 at 2:55 AM, Daniel P. Berrange <berrange at redhat.com>
> > wrote:
> >>
> >> Some apps have a need to be able to obtain ISO filesystem headers from
> >> images stored in glance. Now obviously they can just download the image
> >> (or part of it) and run 'isoinfo' on it, but this is really horrifically
> >> inefficient/wasteful of bandwidth. It would be desirable for glance to
> >> have explicit support for this in some way.
> >>
> >> I've written a short wiki page describing one approach, which is to
> >> make glance extract the data upon upload of an ISO and store it in
> >> some well-defined metadata properties against the image.
> >>
> >>     http://wiki.openstack.org/GlanceISOHeaders
> >>     https://blueprints.launchpad.net/glance/+spec/iso-image-metadata
> >>
> >> A completely different approach we be to ignore metadata properties
> >> and add an explicit API to glance which would extract it on-demand,
> >> but I feel this is a needlessly large amount of work & less convenient
> >> and flexible than simply using existing metadata properties.

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