Comment 5 for bug 1533454

Reviewed: https://review.openstack.org/265685
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=472d84d25cee0694500e583845718a4f377cc75c
Submitter: Jenkins
Branch: master

commit 472d84d25cee0694500e583845718a4f377cc75c
Author: LIU Yulong <email address hidden>
Date: Mon Jan 11 12:02:55 2016 +0800

    Catch PortNotFound after HA router race condition

    When neutron server deleted all the resources of a
    HA router, L3 agent can not aware that, so race
    happened in some procedure like this:
    1. Neutron server delete all resources of a HA router.
    2. RPC fanout to L3 agent 1 in which the HA router was
       master state.
    3. In l3 agent 2 'backup' router set itself to masert
       and notify neutron server a HA router state change
       notify.
    4. PorNotFound rasied in updating router HA port status.

    How the step 2 and 3 happens?
    Consider that l3 agent 2 has much more HA routers than l3 agent 1,
    or any reason that causes l3 agent 2 gets/processes the deleting
    RPC later than l3 agent 1. Then l3 agent 1 remove HA router's
    keepalived process will soonly be detected by backup router in
    l3 agent 2 via VRRP protocol. Now the router deleting RPC is in
    the queue of RouterUpdate or any step of a HA router deleting
    procedure, and the router_info will still have 'the' router info.
    So l3 agent 2 will do the state change procedure, AKA notify
    the neutron server to update router state.

    This patch is mainly to deal with the race by catching the
    PorNotFound exception in neutron-server side.

    Change-Id: I34d7347595bfceb8a70685672a6287e1a44ede6b
    Closes-Bug: #1533454
    Related-Bug: #1523780