Comment 15 for bug 1833902

Reviewed: https://review.opendev.org/670648
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=d9892abd2f096c05a2885a4902128941a24f5670
Submitter: Zuul
Branch: stable/rocky

commit d9892abd2f096c05a2885a4902128941a24f5670
Author: Artom Lifshitz <email address hidden>
Date: Wed Mar 20 10:38:12 2019 -0400

    Revert resize: wait for events according to hybrid plug

    Since 4817165fc5938a553fafa1a69c6086f9ebe311af, when reverting a
    resized instance back to the source host, the libvirt driver waits for
    vif-plugged events when spawning the instance. When called from
    finish_revert_resize() in the source compute manager, libvirt's
    finish_revert_migration() does not pass vifs_already_plugged to
    _create_domain_and_network(), making the latter use the default False
    value.

    When the source compute manager calls
    network_api.migrate_instance_finish() in finish_revert_resize(), this
    updates the port binding back to the source host. If Neutron is
    configured to use OVS hybrid plug, it will send the vif-plugged event
    immediately after completing this request. This happens before the
    virt driver's finish_revert_migration() method is called. This causes
    the wait in the libvirt driver to time out because the event is
    received before Nova starts waiting for it.

    The neutron ovs l2 agent sends vif-plugged events when two conditions
    are met. First the port must be bound to the host managed by the
    l2 agent and second, the agent must have completed configuring the
    port on ovs. This involves assigning the port a local VLAN for tenant
    isolation, applying security group rules if required and applying
    QoS policies or other agent extensions like service function chaining.

    During the boot process, we bind the port first to the host
    then plug the interface into ovs which triggers the l2 agent to
    configure it resulting in the emission of the vif-plugged event.
    In the revert case, as noted above, since the vif is already plugged
    on the source node when hybrid-plug is used, binding the port to the
    source node fulfils the second condition to send the vif-plugged event.

    Events sent immediately after port binding update are hereafter known
    as "bind-time" events. For ports that do not use OVS hybrid plug,
    Neutron will continue to send vif-plugged events only when Nova
    actually plugs the VIF. These types of events are hereafter known as
    "plug-time" events. OVS hybrid plug is a per agent setting, so for
    a particular host, bind-time events are an all-or-nothing thing for the
    ovs backend: either all VIF_TYPE=ovs ports have them, or no ovs ports
    have them. In general, a host will only have one network backend.
    The only exception to this is SR-IOV. SR-IOV is commonly deployed on
    the same host as other network backends such as OVS or linuxbridge.
    SR-IOV ports with VNIC_TYPE=direct-physical will always have only
    bind-time events. If an instance mixes OVS ports with hybrid-plug=False
    with direct physical ports, it will have both kinds of events.

    For same host resize reverts we do not update the binding host as the
    host does not change, as such for same host resize we do not receive
    bind time events. For same host revert we therefore do not wait for
    bind time events in the compute manager.

    This patch adds functions to the NetworkInfo model that return what
    kinds of events each VIF has. These are then used in the migration
    revert logic to decide when to wait for external events: in the
    compute manager, when binding the port, for bind-time events,
    and/or in libvirt, when plugging the VIFs, for plug-time events.

    (cherry picked from commit 7a7a223602ca5aa0aca8f65a6ab143f1d8f8ec1b)
    Conflicts in nova/tests/unit/objects/test_migration.py due to
    1cf3da87027d87251920c2df665b850abb31178e's addition of
    test_obj_make_compatible() and test_get_by_uuid().

    (cherry picked from commit 7a3a8f325ef6eaa97de1cf74efbaa0079f61a9e6)
    NOTE(artom) uuidsentinel was moved to oslo_utils.fixture in Stein, in
    Rocky it was still in nova.tests.

    Closes-bug: #1832028
    Closes-Bug: #1833902
    Co-Authored-By: Sean Mooney <email address hidden>
    Change-Id: I51673e58fc8d5f051df911630f6d7a928d123a5b