As far as I can tell when you specify:

dhcp_agents_per_network = X > 1

The server binds the network to all the agents (up to X), which means that
you have multiple instances of dnsmasq serving dhcp requests at the same
time. If one agent dies, there is no fail-over needed per se, as the other
agent will continue to server dhcp requests unaffected.

For instance, in my env I have dhcp_agents_per_network=2, so If I create a
network, and list the agents serving the network I will see the following:

neutron dhcp-agent-list-hosting-net test

+--------------------------------------+--------+----------------+-------+

| id                                   | host   | admin_state_up | alive |

+--------------------------------------+--------+----------------+-------+

| 6dd09649-5e24-403b-9654-7aa0f69f04fb | host1  | True           | :-)   |

| 7d47721a-2725-45f8-b7c4-2731cfabdb48 | host2  | True           | :-)   |

+--------------------------------------+--------+----------------+-------+

Isn't that what you're after?

Cheers,
Armando

On 21 October 2014 22:26, Noel Burton-Krahn <n...@pistoncloud.com> wrote:

> We currently have a mechanism for restarting the DHCP agent on another
> node, but we'd like the new agent to take over all the old networks of the
> failed dhcp instance.  Right now, since dhcp agents are distinguished by
> host, and the host has to match the host of the ovs agent, and the ovs
> agent's host has to be unique per node, the new dhcp agent is registered as
> a completely new agent and doesn't take over the failed agent's networks.
> I'm looking for a way to give the new agent the same roles as the previous
> one.
>
> --
> Noel
>
>
> On Tue, Oct 21, 2014 at 12:12 AM, Kevin Benton <blak...@gmail.com> wrote:
>
>> No, unfortunately when the DHCP agent dies there isn't automatic
>> rescheduling at the moment.
>>
>> On Mon, Oct 20, 2014 at 11:56 PM, Noel Burton-Krahn <n...@pistoncloud.com
>> > wrote:
>>
>>> Thanks for the pointer!
>>>
>>> I like how the first google hit for this is:
>>>
>>> Add details on dhcp_agents_per_network option for DHCP agent HA
>>> https://bugs.launchpad.net/openstack-manuals/+bug/1370934
>>>
>>> :) Seems reasonable to set dhcp_agents_per_network > 1.  What happens
>>> when a DHCP agent dies?  Does the scheduler automatically bind another
>>> agent to that network?
>>>
>>> Cheers,
>>> --
>>> Noel
>>>
>>>
>>>
>>> On Mon, Oct 20, 2014 at 9:03 PM, Jian Wen <wenjia...@gmail.com> wrote:
>>>
>>>> See dhcp_agents_per_network in neutron.conf.
>>>>
>>>> https://bugs.launchpad.net/neutron/+bug/1174132
>>>>
>>>> 2014-10-21 6:47 GMT+08:00 Noel Burton-Krahn <n...@pistoncloud.com>:
>>>>
>>>>> I've been working on failover for dhcp and L3 agents.  I see that in
>>>>> [1], multiple dhcp agents can host the same network.  However, it looks
>>>>> like I have to manually assign networks to multiple dhcp agents, which
>>>>> won't work.  Shouldn't multiple dhcp agents automatically fail over?
>>>>>
>>>>> [1]
>>>>> http://docs.openstack.org/trunk/config-reference/content/multi_agent_demo_configuration.html
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> OpenStack-dev mailing list
>>>>> OpenStack-dev@lists.openstack.org
>>>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Best,
>>>>
>>>> Jian
>>>>
>>>> _______________________________________________
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>>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>>>>
>>>>
>>>
>>> _______________________________________________
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>>>
>>
>>
>> --
>> Kevin Benton
>>
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>
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