[openstack-dev] [ironic] support for various glance image reference formats - do we need them all?

Pavlo Shchelokovskyy pshchelokovskyy at mirantis.com
Thu Aug 10 07:20:16 UTC 2017

HI Dmitry,

On Tue, Aug 8, 2017 at 7:13 PM, Dmitry Tantsur <dtantsur at redhat.com> wrote:

> Hi!
> Thanks for raising this.
> On 08/07/2017 02:47 PM, Pavlo Shchelokovskyy wrote:
>> Hi all,
>> currently our GlanceImageService seems to support several ways of
>> defining a reference to glance image:
>> 1) simple image UUID [0]
>> 2) image UUID prefixed with 'glance://' protocol [1] (well, actually
>> anything starting with 'glance://' and ending with '/<uuid>')
>> 3) full REST path to the image (as in http://<glance-api>/v2/images/<image-uuid>),
>> also used to extract the glance API address [2]
>> Support for #3 must surely be removed, as we are moving to API endpoint
>> discovery from keystone catalog.
>> Besides I am pretty sure this code path can not actually be reached
>> currently, as the 'is_glance_image' will ignore such image refs and return
>> False for those [3], and 'get_image_service' would also not return the
>> GlanceImageService instance for such image refs [4].
>> Hence the question - if it is unusable anyway now, should we execute the
>> standard deprecation process when removing support for it or just remove
>> right away?
> If unsure, always use the standard process ;) Unless somebody is ready to
> set up DevStack, and try it out, and prove that it's completely and
> hopelessly broken.

Did just that [0] - hacked up our tempest configuration so that the 'http'
url for whole disk image used for *HttpLink standalone tests leads to
<glance-endpoint>/v2/images/<uuid> [1].
As I kind of expected, both *HttpLink standalone tests failed, right on
validating of the deploy interface when trying to do a HEAD on that URL
instead of 'glance image show', receiving 401 [2].
On a side note, it seems our logging is insufficient in this parts, as I
could not find any relevant logs in ironic-conductor even at debug level,
all that's there are final RPC processing error logs from api.

So I am quite confident that this code paths [3] in service_utils is a dead
end indeed :-/

[0] https://review.openstack.org/#/c/492184/

>> As for the #1 and #2 I do not see any big difference between those, and
>> proposed deprecating and eventually removing support for #2 ('glance://'
>> scheme) as part of [5]. Two people in review already raised a concern about
>> removing such support.
> To be honest, I like glance://<uuid> more, as it makes it obvious where
> the image is coming from vs http://. I don't mind removing it too much,
> but I guess supporting it is not a lot of code, right?

That's not too much burden indeed, as long as we actually do only that - as
I said, right now it is more like "glance://<anything>/uuid"

>> Thus I'd like to ask a broader audience - do we need support for glance
>> image references in 'glance://*<UUID>' form? Is it actually used somewhere?
>> What are the benefits of having it besides simple UUID?
>> [0] http://git.openstack.org/cgit/openstack/ironic/tree/ironic/c
>> ommon/glance_service/service_utils.py#n149
>> [1] http://git.openstack.org/cgit/openstack/ironic/tree/ironic/c
>> ommon/glance_service/service_utils.py#n155
>> [2] http://git.openstack.org/cgit/openstack/ironic/tree/ironic/c
>> ommon/glance_service/service_utils.py#n160
>> [3] http://git.openstack.org/cgit/openstack/ironic/tree/ironic/c
>> ommon/glance_service/service_utils.py#n208
>> [4] http://git.openstack.org/cgit/openstack/ironic/tree/ironic/c
>> ommon/image_service.py#n267
>> [5] https://review.openstack.org/#/c/467728
>> Cheers,
>> --
>> Dr. Pavlo Shchelokovskyy
>> Senior Software Engineer
>> Mirantis Inc
>> www.mirantis.com <http://www.mirantis.com>
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Dr. Pavlo Shchelokovskyy
Senior Software Engineer
Mirantis Inc
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