Comment 16 for bug 1753550

Reviewed: https://review.openstack.org/554703
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=6482165bb1f44f5c98d9361153d737c22c92112d
Submitter: Zuul
Branch: master

commit 6482165bb1f44f5c98d9361153d737c22c92112d
Author: Matt Riedemann <email address hidden>
Date: Tue Mar 20 17:15:42 2018 -0400

    Handle EndpointNotFound when building image_ref_url in notifications

    Change I4e755b9c66ec8bc3af0393e81cffd91c56064717 made the
    [glance]/api_servers option optional. If not set, we attempt
    to get the image service endpoint via keystoneauth adapter and
    the service catalog via the request context.

    Periodic tasks run without an actual token so there is no way
    to get the service catalog and the KSA adapter code to get the
    endpoint raises EndpointNotFound when trying to build the
    "image_ref_url" entry in the legacy instance notification payload.

    This change simply handles the EndpointNotFound and sets the
    image_ref_url to the instance.image_ref, which for non-volume-backed
    instances is the image id (for volume-backed instances it's an empty
    string).

    This doesn't affect versioned notifications since those don't use the
    "image_ref_url" entry in the payload that is created, they just have
    an "image_uuid" entry in the versioned notification payload which is
    populated via instance.image_ref.

    An upgrade impact release note is added in the case that some consuming
    service is actually relying on that legacy notification field being
    a URL and parsing it as such. The thinking here, however, is this is
    better than not sending the field at all, or setting it to None.

    Long-term this code all gets replaced with versioned notifications.

    Change-Id: Ie23a9c922776b028da0720c939846cba233ac472
    Closes-Bug: #1753550