[openstack-dev] About multihost patch review

Baldwin, Carl (HPCS Neutron) carl.baldwin at hp.com
Thu Aug 29 22:00:52 UTC 2013

On 8/28/13 11:28 AM, "Vishvananda Ishaya" <vishvananda at gmail.com> wrote:

>On Aug 26, 2013, at 6:14 PM, Maru Newby <marun at redhat.com> wrote:
>> On Aug 26, 2013, at 4:06 PM, Edgar Magana <emagana at plumgrid.com> wrote:
>>> Hi Developers,
>>> Let me explain my point of view on this topic and please share your
>>>thoughts in order to merge this new feature ASAP.
>>> My understanding is that multi-host is nova-network HA  and we are
>>>implementing this bp
>>>https://blueprints.launchpad.net/neutron/+spec/quantum-multihost for
>>>the same reason.
>>> So, If in neutron configuration admin enables multi-host:
>>> etc/dhcp_agent.ini
>>> # Support multi host networks
>>> # enable_multihost = False
>>> Why do tenants needs to be aware of this? They should just create
>>>networks in the way they normally do and not by adding the "multihost"
>> I was pretty confused until I looked at the nova-network HA doc [1].
>>The proposed design would seem to emulate nova-network's multi-host HA
>>option, where it was necessary to both run nova-network on every compute
>>node and create a network explicitly as multi-host.  I'm not sure why
>>nova-network was implemented in this way, since it would appear that
>>multi-host is basically all-or-nothing.  Once nova-network services are
>>running on every compute node, what does it mean to create a network
>>that is not multi-host?
>Just to add a little background to the nova-network multi-host: The fact
>that the multi_host flag is stored per-network as opposed to a
>configuration was an implementation detail. While in theory this would
>support configurations where some networks are multi_host and other ones
>are not, I am not aware of any deployments where both are used together.
>That said, If there is potential value in offering both, it seems like it
>should be under the control of the deployer not the user. In other words
>the deployer should be able to set the default network type and enforce
>whether setting the type is exposed to the user at all.

+1 for leaving it to the deployer and not the user.

>Also, one final point. In my mind, multi-host is strictly better than
>single host, if I were to redesign nova-network today, I would get rid of
>the single host mode completely.

+1 again.

>> So, to Edgar's question - is there a reason other than 'be like
>>nova-network' for requiring neutron multi-host to be configured
>> m.
>> 1: 
>>> I could be totally wrong and crazy, so please provide some feedback.
>>> Thanks,
>>> Edgar
>>> From: Yongsheng Gong <gongysh at unitedstack.com>
>>> Date: Monday, August 26, 2013 2:58 PM
>>> To: "Kyle Mestery (kmestery)" <kmestery at cisco.com>, Aaron Rosen
>>><arosen at nicira.com>, Armando Migliaccio <amigliaccio at vmware.com>,
>>>Akihiro MOTOKI <amotoki at gmail.com>, Edgar Magana
>>><emagana at plumgrid.com>, Maru Newby <marun at redhat.com>, Nachi Ueno
>>><nachi at nttmcl.com>, Salvatore Orlando <sorlando at nicira.com>, Sumit
>>>Naiksatam <sumit.naiksatam at bigswitch.com>, Mark McClain
>>><mark.mcclain at dreamhost.com>, Gary Kotton <gkotton at vmware.com>, Robert
>>>Kukura <rkukura at redhat.com>
>>> Cc: OpenStack List <openstack-dev at lists.openstack.org>
>>> Subject: Re: About multihost patch review
>>> Hi,
>>> Edgar Magana has commented to say:
>>> 'This is the part that for me is confusing and I will need some
>>>clarification from the community. Do we expect to have the multi-host
>>>feature as an extension or something that will natural work as long as
>>>the deployment include more than one Network Node. In my opinion,
>>>Neutron deployments with more than one Network Node by default should
>>>call DHCP agents in all those nodes without the need to use an
>>>extension. If the community has decided to do this by extensions, then
>>>I am fine' at
>>> I have commented back, what is your opinion about it?
>>> Regards,
>>> Yong Sheng Gong
>>> On Fri, Aug 16, 2013 at 9:28 PM, Kyle Mestery (kmestery)
>>><kmestery at cisco.com> wrote:
>>>> Hi Yong:
>>>> I'll review this and try it out today.
>>>> Thanks,
>>>> Kyle
>>>> On Aug 15, 2013, at 10:01 PM, Yongsheng Gong
>>>><gongysh at unitedstack.com> wrote:
>>>>> The multihost patch is there for a long long time, can someone help
>>>>>to review?
>>>>> https://review.openstack.org/#/c/37919/
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