Comment 30 for bug 1789654

Reviewed: https://review.openstack.org/647291
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=7a3b072442db74418fa7fe626c637627d219c71f
Submitter: Zuul
Branch: stable/queens

commit 7a3b072442db74418fa7fe626c637627d219c71f
Author: Matt Riedemann <email address hidden>
Date: Tue Sep 4 12:11:57 2018 -0400

    Document unset/reset wrinkle for *_allocation_ratio options

    This is a follow up to I43a23a3290db0c835fed01b8d6a38962dc61adce
    which makes the cpu/disk/ram_allocation_ratio config "sticky" in
    that once set to a non-default value, it is not possible to reset
    back to the default behavior (when config is 0.0) on an existing
    compute node record by unsetting the option from nova.conf. To
    reset back to the defaults, the non-0.0 default would have to be
    explicitly put into config, so cpu_allocation_ratio=16.0 for example.

    Alternatively operators could delete the nova-compute service
    record via the DELETE /os-services/{service_id} REST API and
    restart the nova-compute service to get a new compute_nodes record,
    but that workaround is messy and left undocumented in config.

    Change-Id: I908615d82ead0f70f8e6d2d78d5dcaed8431084d
    Related-Bug: #1789654
    (cherry picked from commit c45adaca5dd241408f1e29b657fe6ed42c908b8b)
    (cherry picked from commit a039f8397702d15718ebcec0fdb9cfeb6155f6a1)