Comment 16 for bug 1289931

Reviewed: https://review.openstack.org/182327
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=706cbf40f5f8c6f756277057c92bf41f1ef1cd80
Submitter: Jenkins
Branch: master

commit 706cbf40f5f8c6f756277057c92bf41f1ef1cd80
Author: John Griffith <email address hidden>
Date: Tue May 12 08:03:27 2015 -0600

    Check type match on create from source/snap

    We used to allow creating from source/snap and specifying a
    different type than the originating resource when doing so.
    Once we started getting more drivers and more multi-backend
    configurations, we implemented a check in volume.api that
    took this away (broke it). There have been a number of
    arguments about whether this should be allowed or not, and
    that it could fail after the rpc call leaving the user with
    nothing more than a "failed" volume and no explanation as to
    why.

    This patch allows the capability, but checks validity at the
    API layer before issuing the create call. There are two
    requirements for the new type specification to be valid:
    1. There is only one backend (cinder-volume) topic configured
    2. Both types in question specify the same volume_backend_name
    If neither of these requirements are met, the user will receive
    an "invalid type" error explaining that the type combination is
    not compatible and that they should omit the type argument altogether.

    Change-Id: I08bc5e9a8800ce3b27c7db90b7bff86d7d14359a
    Closes-Bug: #1289931