Comment 3 for bug 1734838

Reviewed: https://review.openstack.org/523395
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=3e766e5bd429c6119c077b8be02360ae1e1ec8bd
Submitter: Zuul
Branch: master

commit 3e766e5bd429c6119c077b8be02360ae1e1ec8bd
Author: Wangpan <email address hidden>
Date: Tue Nov 28 19:48:21 2017 +0800

    Handle glance exception during rotating instance backup

    Glance image backends may return HTTPConflict in many cases
    during deleting image, for example, an rbd image is used for
    booting a new instance, or rbd image has snapshot(s).

    If user have already backed up instance to few numbers and then
    execute backup api with rotation 1, then nova will delete the
    previously created images exceeding rotation limit.
    During deleting these images, if the first one of the backup
    images are deleted failed with HTTPConflict or other exceptions,
    all images exceeding rotation limit will be left over.

    This patch handles ImageDeleteConflict and all other exceptions
    during deleting backup images, logs a message and continues
    deleting all of the remaining images.

    Closes-Bug: #1734838

    Change-Id: Ie8091fe3e0e4275717ddc50166345f1c9df4b889