Open Stack

Hi,

I think one of the issues we're trying to solve here is duplication
reducing. Quotas in OpenStack commonly contain two parts: limits
management and limits enforcement.

If we're talking about library (delimiter) vs service (keystone or quota
service) for a duplication reducing in a limits management then IMO service is
more appropriate way because:

- Now we have API endpoint for limits
  management for the end user and we will need it in the future. Library can
  reduce an amount of code for such endpoint but can't totally eliminate it.
- Besides the code in services, we have api-ref, docs, and clients also
  and library can't reduce an effort for supporting those.
- Centralized limits management service can provide fresh and
  consistent API (see quota_class, quota_sets).

If we're talking about limits enforcement then it's more subtle thing.
I really agree with Jay that problem can be related to the cache for
usages. And I don't see the way how we can skip saving into reservation
table because we can easily define a moment of reservation with
reservation table but it can be hard with "real" objects like instance
as they have its own logic of creating.

I think a library can be appropriate if services like nova or cinder
have a possibility to deeply integrate external libraries (like django
apps). I mean if a library has own DB tables, cli commands, etc. it
can be seamlessly integrated to the main app. I'm not sure it's the
case for nova, for example. Therefore, for me, separate service
is the winner here too.

Sajeesh Cimson Sasi writes:

> Hi,
>     There was an ongoing project of delimiter for Cross Project Quota Management.
>     But I don't know the current status.
>     Kindly have a look at it.
>     https://review.openstack.org/#/c/284454/
>     More discussions are required on this.As more and more  projects or services are having the concept of    quotas,Quota as a service can also be thought of.Anyway more discussions are required on this topic.
>    best regards,
>     sajeesh
> ________________________________________
> From: Jay Pipes [jaypipes at gmail.com]
> Sent: 13 December 2016 18:55:14
> To: openstack-dev at lists.openstack.org
> Subject: Re: [openstack-dev] [keystone][nova]Quotas: Store resources and limits in the Keystone
>
> On 12/13/2016 08:09 AM, Kseniya Tychkova wrote:
>> Hi,
>> I would like to share a spec [1] with you.
>> The main idea of this spec is to start a discussion about quota
>> management in the OpenStack.
>>
>> Quotas are scattered across OpenStack services. Each service defines
>> it's own model and API for
>> managing resource's limits. Because of that, there are several problems:
>>
>>   * Names of the resources and resource-service mapping  are hardcoded.
>>     They are hardcoded in the service code (Nova, for example) and it
>>     should be hardcoded in the client code (Horizon, for example).
>>
>>   * There is no centralized quota management for OpenStack projects.
>>   * Cinder, Nova and Neutron support (or going to support) hierarchical
>>     quotas in different ways.
>>
>> There should be a single point of managing quotas in OpenStack.
>> Keystone looks like a proper place to store resource's limits because:
>>
>>   * Keystone stores projects
>>   * Limits are belong to project.
>
> Another excellent reason to store quota limits in Keystone is because
> virtually all non-list operations require some interaction with quota
> limits, and requiring Nova (or Cinder or Neutron) to call out to yet
> another service each time the user makes one of those non-list
> operations is sub-optimal when Nova is already making a call to Keystone
> for authentication.
>
> The alternative is to have a separate REST API service just for storing
> and returning the quota limits and have Nova, Cinder and Neutron call
> this new service each time a non-list operation is made. While this is
> possible, it's just yet another service that needs to be managed and
> deployed by all installations of OpenStack.
>
> Best,
> -jay
>
>> There are a lot of possible issues with “store limits in Keystone”
>> approach. But all of them can be discussed
>> and such discussion should lead to the good solution for quotas
>> management  in Openstack.
>>
>> Please take a look at the spec when you have time and share your ideas
>> or concerns.
>>
>> [1] https://review.openstack.org/#/c/363765/
>>
>>
>> Kind regards,
>> Kseniya
>>
>>
>>
>>
>>
>>
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>
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-- 
Thanks,

Andrey Volkov,
Software Engineer, Mirantis, Inc.