Comment 20 for bug 1456073

Reviewed: https://review.openstack.org/275420
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=f0bdb798fa14b7bd5649d98789e71803127dd9f7
Submitter: Jenkins
Branch: master

commit f0bdb798fa14b7bd5649d98789e71803127dd9f7
Author: Swaminathan Vasudevan <email address hidden>
Date: Tue Feb 2 12:44:16 2016 -0800

    DVR:Pro-active router creation with live migration

    Today DVR routers are created after a dvr service port is
    seen on a given node. But in the case of instance live
    migration, the creation of l3 routed networks on the
    destination node is delayed since we react to the event.

    This patch tries to proactively create routers on the
    destination node based on the portbinding profile info
    updated by the nova when the instance is on a pre-migration
    state.

    Nova calls setup_network_on_host during the pre-migration
    phase and we update the portbinding profile dict with
    an attribute 'migrating_to' as shown below

    port:{'binding:profile':{'migrating_to': 'host'}}

    where 'host' points to the 'destination' of the port.

    L3 plugin will verify the migration profile for the port on
    any port update and then take action to create routers in the
    respective agents if routers have not been created.

    If the live migration fails or if reverted, then the port
    binding profile attribute 'migrating_to' will be cleared from
    the port profile. In this case, the router and the fip namespace
    may be created on the destination node, but since the VM did
    not land on the destination node, it would not cause any issues,
    since the traffic will still be flowing out from the origination
    node, except for the existence of the router and fip namespace.

    For some reason if the creation of the router namespace and fip
    namespace fails, then the live migration may still proceed as
    it is now and the agent will create the router namespace and fip
    namespace reactively.

    The case were we report status back to Nova and Nova reacting
    to the setup_networks_on_host status will be handled in the
    upcoming release.

    This patch should not affect any upgrades with respect to the
    agent or server.

    Change-Id: Ibb62f012333cfdfd468bafdc0b4501aa46b4b54d
    Related-Bug: #1456073