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On Aug 27, 2013, at 3:27 PM, Tom Fifield <tom at openstack.org> wrote:

> On 27/08/13 15:23, Maru Newby wrote:
>> 
>> On Aug 26, 2013, at 9:39 PM, Yongsheng Gong <gongysh at unitedstack.com> wrote:
>> 
>>> First 'be like nova-network' is a merit for some deployments.
>> 
>> I'm afraid 'merit' is a bit vague for me.  Would you please elaborate?
> 
> One area of 'merit' in this area is for migration from nova-network to
> neutron. If there's something exactly analogous to something that
> already exists, its easier to move across.

I apologize for being unclear, but I don't think there is any question that neutron needs a multi-host HA capability.  The question is not  one of function, but of implementation.  

I don't believe that the design of a feature being proposed for neutron should be acceptable simply because it reuses an implementation strategy used by nova-network.  Neutron's architecture may allow different decisions to be made, and we may have learned from nova-network's example.  In any case, reviewers need to understand the 'why' behind design decisions, and it doesn't appear to me that there is sufficient documentation justifying the current proposal's approach.  Only once we have more information will we be able to make an educated decision as to the quality of the proposal.


m.


> 
>> 
>>> second, To allow admin to decide which network will be multihosted at runtime will enable the neutron to continue using the current network node (dhcp agent) mode at the same time.
>> 
>> If multi-host and non- multi-host networks are permitted to co-exist (because configuration is per-network), won't compute nodes have to be allowed to be heterogenous (some multi-host capable, some not)?  And won't Nova then need to schedule VMs configured with multi-host networks on compatible nodes?  I don't recall mention of this issue in the blueprint or design doc, and would appreciate pointers to where this decision was documented.
>> 
>> 
>>> 
>>> If we force the network multihosted when the configuration enable_multihost is true, and then administrator wants to transfer to normal neutron way, he/she must modify the configuration item and then restart.
>> 
>> I'm afraid I don't follow - are you suggesting that configuring multi-host globally will be harder on admins than the change under review?  Switching to non multi-host under the current proposal involves reconfiguring and restarting of an awful lot of agents, to say nothing of the db changes.
>> 
>> 
>> m. 
>> 
>> 
>>> 
>>> 
>>> 
>>> On Tue, Aug 27, 2013 at 9:14 AM, 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" extension.
>>> 
>>> 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?
>>> 
>>> So, to Edgar's question - is there a reason other than 'be like nova-network' for requiring neutron multi-host to be configured per-network?
>>> 
>>> 
>>> m.
>>> 
>>> 1: http://docs.openstack.org/trunk/openstack-compute/admin/content/existing-ha-networking-options.html
>>> 
>>> 
>>>> 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
>>>> https://review.openstack.org/#/c/37919/11/neutron/extensions/multihostnetwork.py
>>>> 
>>>> 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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