Comment 8 for bug 1531772

Reviewed: https://review.openstack.org/268697
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=725a93bb7663c47ecde324b011d5c582d4e94c3f
Submitter: Jenkins
Branch: stable/liberty

commit 725a93bb7663c47ecde324b011d5c582d4e94c3f
Author: Ihar Hrachyshka <email address hidden>
Date: Wed Jan 13 12:37:21 2016 +0100

    Make security_groups_provider_updated work with Kilo agents

    Initially, we bumped the required version for the agent endpoint from
    1.1 (the initial version that implemented security groups) to 1.3
    without considering that the code should work with old agents that do
    not yet know about the new devices_to_update argument.

    Actually, there was no need to bump the version: old agent side code
    already captures all unknown arguments that could be passed from the
    server, ignoring them:

    https://github.com/openstack/neutron/blob/608b54137fb67512c07099089ea7e074176e12df/neutron/agent/securitygroups_rpc.py#L155

    (^ the link shows the latest Kilo code as of writing)

    Note: some people may argue that the approach that is taken in Neutron
    to support backwards compatibility for server notifications is wrong,
    and we instead should adopt some stricter mechanism like nova version
    pinning. While that is a noble thing to do, it's out of scope for the
    patch that is designed to be easily backportable to stable/liberty.

    Note: some people may also argue that the patch should go straight into
    stable/liberty because we don't claim support for rolling upgrade
    scenarios that span multiple releases. That's indeed true, though my
    take on it is that if we have a way to handle more unofficial scenarios
    without more coding effort, it's worth doing it.

    Change-Id: I741e6e5c460658ac17095551040e67e8d1990812
    Closes-Bug: #1531772
    (cherry picked from commit f8f366024052a191eb0fc74af1643be15c541aef)