Comment 10 for bug 1174591

Reviewed: https://review.openstack.org/110893
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=9677cf87cb831cfd344bc63cbee23be52392c300
Submitter: Jenkins
Branch: master

commit 9677cf87cb831cfd344bc63cbee23be52392c300
Author: Kevin Benton <email address hidden>
Date: Wed Jul 30 15:49:59 2014 -0700

    Option to remove routers from dead l3 agents

    Add a configuration-enabled periodic check to examine the
    status of all L3 agents with routers scheduled to them and
    admin_state_up set to True. If the agent is dead, the router
    will be rescheduled to an alive agent.

    Neutron considers and agent 'dead' when the server doesn't
    receive any heartbeat messages from the agent over the
    RPC channel within a given number of seconds (agent_down_time).
    There are various false positive scenarios where the agent may
    fail to report even though the node is still forwarding traffic.

    This is configuration driven because a dead L3 agent with active
    namespaces forwarding traffic and responding to ARP requests may
    cause issues. If the network backend does not block the dead
    agent's node from using the router's IP addresses, there will be
    a conflict between the old and new namespace.

    This conflict should not break east-west traffic because both
    namespaces will be attached to the appropriate networks and
    either can forward the traffic without state. However, traffic
    being overloaded onto the router's external network interface
    IP in north-south traffic will be impacted because the matching
    translation for port address translation will only be present
    on one router. Additionally, floating IPs associated to ports
    after the rescheduling will not work traversing the old
    namespace because the mapping will not be present.

    DocImpact

    Partial-Bug: #1174591
    Change-Id: Id7d487f54ca54fdd46b7616c0969319afc0bb589