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Hi Kevin,

On 2015/12/14 11:10, Kevin Benton wrote:
> Hi all,
>
> The availability zone code added a new field to the network API that 
> shows the availability zones of a network. This caused a pretty big 
> performance impact to get_networks calls because it resulted in a 
> database lookup for every network.[1]
>
> I already put a patch up to join the information ahead of time in the 
> network model.[2]
I agree with your suggestion. I believe that the patch can solve the 
performance issue.

> However, before we go forward with that, I think we should consider 
> the removal of that field from the API.
>
> Having to always join to the DHCP agents table to lookup which zones a 
> network has DHCP agents on is expensive and is duplicating information 
> available with other API calls.
>
> Additionally, the field is just called 'availability_zones' but it's 
> being derived solely from AZ definitions in DHCP agent bindings for 
> that network. To me that doesn't represent where the network is 
> available, it just says which zones its scheduled DHCP instances live 
> in. If that's the purpose, then we should just be using the DHCP agent 
> API for this info and not impact the network API.
I don't think so. I have three points.

1. Availability zone is implemented in just a case with Agent now, but 
it's reference implementation. For example, we should expect that 
availability zone will be used by plugin without agent.

2. In users view, availability zone is related to network resource. On 
the other hand, users doesn't need to consider Agent or operators 
doesn't like to enable users to do in the first place. So I don't agree 
with using Agent API.

3. We should consider whether users want to know the field. Originally, 
the field doesn't exist in Spec[3] but I added it according with 
reviewer's opinion(maybe Akihiro?). This is about discussion of use 
case. After users create resources via API with availability_zone_hints 
so that they achieve HA for their service, they want to know which zones 
are their resources hosted on because their resources might not be 
distributed on multiple availability zones by any reasons. In the case, 
they need to know "availability_zones" for the resources via Network API.

Thanks,
Hirofumi

[3]: https://review.openstack.org/#/c/169612/31

>
> Thoughts?
>
> 1. https://bugs.launchpad.net/neutron/+bug/1525740
> 2. https://review.openstack.org/#/c/257086/
>
> -- 
> Kevin Benton
>
>
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