Comment 9 for bug 1837635

Reviewed: https://review.opendev.org/679438
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=adac5d9b7a72b4edeba5357c6a47e7e528fcf775
Submitter: Zuul
Branch: stable/stein

commit adac5d9b7a72b4edeba5357c6a47e7e528fcf775
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Wed Jul 24 16:32:02 2019 +0000

    Delay HA router transition from "backup" to "master"

    As described in the bug, when a HA router transitions from "master" to
    "backup", "keepalived" processes will set the virtual IP in all other
    HA routers. Each HA router will then advert it and "keepalived" will
    decide, according to a trivial algorithm (higher interface IP), which
    one should be "master". At this point, the other "keepalived" processes
    running in the other servers, will remove the HA router virtual IP
    assigned an instant before

    To avoid transitioning some routers form "backup" to "master" and then
    to "backup" in a very short period, this patch delays the "backup" to
    "master" transition, waiting for a possible new "backup" state. If
    during the waiting period (set to the HA VRRP advert time, 2 seconds
    default) to set the HA state to "master", the L3 agent receives a new
    "backup" HA state, the L3 agent does nothing.

    Closes-Bug: #1837635

    Change-Id: I70037da9cdd0f8448e0af8dd96b4e3f5de5728ad
    (cherry picked from commit 3f022a193f66fde3bfd945af1119a60dfe91cb91)