Comment 7 for bug 1258256

Reviewed: https://review.openstack.org/59560
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=0eb7e35fbfe5de5f9f00ff1a0cce1d6a61f3a902
Submitter: Jenkins
Branch: master

commit 0eb7e35fbfe5de5f9f00ff1a0cce1d6a61f3a902
Author: Dan Smith <email address hidden>
Date: Mon Dec 2 12:25:04 2013 -0800

    Make Serializer/Conductor able to backlevel objects

    This improves handling the situation where nova-api sends newer
    objects to an older compute node. In this case, the serializer detects
    the IncompatibleObjectVersion error and asks conductor to backlevel it.
    This means we call into a new method in conductor with the primitive
    object that we can't handle, and basically ask it to hydrate it and
    call obj_make_compatible() on our behalf and pass it back to us.

    This eliminates the need for API to know whether it's talking to
    an older compute and allows a newer conductor to assist older
    compute nodes during upgrades to a significant degree.

    Related-Bug: #1258256
    Change-Id: I4b17c8382619e4f73b83c026bf68549ac67a68a2