Comment 12 for bug 1744361

Reviewed: https://review.openstack.org/540555
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=83ffc76edd360929925fc4bb66e5dcbf8254a30e
Submitter: Zuul
Branch: stable/pike

commit 83ffc76edd360929925fc4bb66e5dcbf8254a30e
Author: melanie witt <email address hidden>
Date: Thu Feb 1 22:27:57 2018 +0000

    Don't wait for vif plug events during _hard_reboot

    Originally, in change Id188d48609f3d22d14e16c7f6114291d547a8986 we
    added a re-initialization of volumes, encryptors, and vifs to hard
    reboot. When creating the libvirt domain and network, we were waiting
    for vif plug events from neutron when we replugged the vifs. Then, we
    started seeing timeouts in the linuxbridge gate job because compute
    was timing out waiting for plug events from neutron during a hard
    reboot.

    It turns out that the behavior of neutron plug events depends on what
    vif type we're using and we're also using a stale network info_cache
    throughout the hard reboot code path, so we can't be 100% sure we know
    which vifs to wait for plug events from anyway. We coincidentally get
    some info_cache refreshes from network-changed events from neutron,
    but we shouldn't rely on that.

    Ideally, we could do something like wait for an unplug event after we
    unplug the vif, then refresh the network_info cache, then wait for the
    plug event. BUT, in the case of the os-vif linuxbridge unplug method,
    it is a no-op, so I don't think we could expect to get an unplug
    event for it (and we don't see any network-vif-unplugged events sent
    in the q-svc log for the linuxbridge job during a hard reboot).

    Closes-Bug: #1744361

    Change-Id: Ib0cf5d55750f13d0499a570f14024dca551ed4d4
    (cherry picked from commit 236bb54493385bcfe2034e8b0fd7a387fa66635a)