1. keepalived vrrp/conntrackd

High availability features will be implemented as extensions or drivers.A first extension/driver will be based on VRRP.

A new scheduler will be also added in order to be able to spawn multiple instances of a same router in many places.

Conntrackd will be used to maintain the TCP sessions going through the router. One instance of conntrackd per virtual router, then one per namespace.

Blueprints:  https://blueprints.launchpad.net/neutron/+spec/l3-high-availability
wiki:        https://wiki.openstack.org/wiki/Neutron/L3_High_Availability_VRRP
analysis:    http://blog.csdn.net/quqi99/article/details/18799877

2. neutron DVR based multi-host l3-agent

Provide Distributed Virtual Routing functionality with OVS, to improve the performance.

在Openstack中L3router会造成流量集中的问题。不论东西向还是南北向的流量都需要流过网络节点的虚拟路由器。为了解决流量集中的问题，社区正在开打分布式虚拟路由器(DVR)的feature。

https://blueprints.launchpad.net/neutron/+spec/neutron-ovs-dvr
    https://wiki.openstack.org/wiki/Neutron/DVR_L2_Agent
    http://m.blog.csdn.net/blog/maoliping455mlp455/36899391
    http://blog.csdn.net/quqi99/article/details/20711303

3. Neutron Multi-host DHCP and L3

Goal here is to have a DHCP implementation that provides the same properties as nova-network's "multi_host" functionality, where the DHCP server for a particular VM runs directly on the same hypervisor as the VM itself (with the exception of when a VM migrates).

This blueprints is in drafting, and will not merge in upstream.

https://blueprints.launchpad.net/neutron/+spec/quantum-multihost

4. crontab using neutron-client

http://m.blog.csdn.net/blog/maoliping455mlp455/23428897

So this when we neutron-l3-agent is down, we can see that it will not affect the existed VMs. And we can easily use monitd to make process "neutron-l3-agent" is always alive. We can use the following script, and run a crontab(every 10 sec) on the server which installed neutronclient (But not on the controller nodes):

#!/usr/bin/python

from neutronclient.v2_0 import client as neutronclient

TENANT_NAME="admin"

USERNAME="admin"

PASSWORD="admin"

AUTH_URL="https://10.224.159.107:443/v2.0/"

neutron = neutronclient.Client(auth_url=AUTH_URL,

                               username=USERNAME,

                               password=PASSWORD,

                               tenant_name=TENANT_NAME)

agents = neutron.list_agents()

alive_l3_agents = []

dead_l3_agents = []

for agent in agents['agents']:

    if agent['binary'] == 'neutron-l3-agent' and agent['alive'] == True:

        alive_l3_agents.append(agent)

    if agent['binary'] == 'neutron-l3-agent' and agent['alive'] != True:

        dead_l3_agents.append(agent)

if len(alive_l3_agents) == 0 :

    print "No active L3"

if len(dead_l3_agents) == 0 :

    print "No dead L3"

routers = neutron.list_routers()

dead_routers = []

for dead_l3_agent in dead_l3_agents:

    dead_routers = neutron.list_routers_on_l3_agent(dead_l3_agent['id'])

    for dead_router in dead_routers['routers']:

        neutron.remove_router_from_l3_agent(dead_l3_agent['id'], dead_router['id'])

        print "remove_router_from_l3_agent : L3 id is %s, router id is %s" %(dead_l3_agent['id'], dead_router['id'])

        # Currently, only add to the first alive agent

        neutron.add_router_to_l3_agent(alive_l3_agents[0]['id'], {"router_id":dead_router['id']})

        print "add_router_to_l3_agent : L3 id is %s, router id is %s" %(alive_l3_agents[0]['id'], dead_router['id'])

5. HA of other components

(1) Database: active-passive (pacemarker + DRBD); active-active (Galera)
    http://blog.csdn.net/quqi99/article/details/9392789

(2) MQ: MQ cluster
    http://blog.csdn.net/quqi99/article/details/9394121

(3) Cinder: Local File System (Raid10 + LVM); Distrubte File System (Ceph)
    http://blog.csdn.net/quqi99/article/details/9396413
     http://blog.csdn.net/quqi99/article/details/10894833

(4) All stateless services, like (keystone|glance|nova|neutron)-api, nova-schedule etc (haproxy + pacemarker)

(5) l3-agent: VRRP + keeplived + ip conntracked
    https://blueprints.launchpad.net/neutron/+spec/l3-high-availability
    http://blog.csdn.net/quqi99/article/details/18799877