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I haven't had a chance to review this patch in detail yet, but am 
wondering if this is being integrated with ML2 as an extension driver? 
If so, that should clearly address how dictionaries are extended and 
input values are validated. If not, why?

-Bob

On 7/13/15 10:50 PM, Miguel Angel Ajo wrote:
> Inline reply (I've added to CC relevant people for ml2/plugin.py
> port_update extension
> handing -via git blame-) as they probably have an opinion here
> (specially the last
> two options).
>
> Kevin Benton wrote:
>> This sounds like a lot of overlap with the dict extend functions. Why
>> weren't they adequate for the QoS use case?
>
> Let me explain, I believe Mike exceeded the proposal with AFTER_READ,
> that's not the plan,
> even if we could do as he proposed,
>
> AFTER_READ dict extension is just a temporary workaround until we have
> a separate explicit
> api @armax is working on. Making explicit that your service is going
> to extend resources,
> and handled that in an ordered way is a good thing.
>
> Afterwards, the source of this review has came from ML2 implementation of
> AFTER_CREATE/AFTER_UPDATE notification for ports/nets.
>
> Let me explain:
>
>      As a decoupled, "mixinless" service extending core resources, we
> need to do two things:
>
> 1) Extending the core resources as other extensions would do, adding
> stuff to the port/network
> dicts, here's where it comes the current AFTER_READ dict extension,
> and future API making
> that more explicit and more controlled.
>
> 2) Verifying the extended values we receive on core resources, by
> registering to BEFORE_*
> callbacks. For example, if a tenant is trying to use a qos_profile_id
> he doesn't have access to,
> or that doesn't exist, we can cancel the operation by throwing an
> exception.
>
>       We need to extend the notifications for ports and networks, as
> that's not notified currently.
> Mike will work on that too in a separate patch.
>
>
> 3) Taking the finally extended values and store associations in database
>      (AFTER_UPDATE/AFTER_CREATE) so any later reads of the
> port/network will get the right
>      qos_profile_later in "after read".
>
>
> We have found that AFTER_CREATE/AFTER_UPDATE happens at plugin level
> (neutron/plugins/ml2/plugin.py / update_port) and that information
> passed down is
> very brief to our case (basically a "None" port if no ml2-know
> attribute is changed), and
> ml2 has to be aware of every single extension.
>
> Here there are two options:
>    a) we make ml2 also aware of qos_profile_id changes, complicating
> the business logic down
> there, or...
>
>    b) we send the AFTER_CREATE/UPDATE events, and we listen to the
> callback
> listeners to such notification, and they will tell us if there's any
> relevant field which must
> be propagated down to agents. Then it's up to the agents to use such
> field or not.
>
>
>    Mike's patch proposal is in the direction of (b), he's a long term
> thinker, I was proposing him
> to just go (a) for now, but let's discuss and find what's more right.
>
>
>> On Mon, Jul 13, 2015 at 7:58 AM, Mike Kolesnik<mkolesni at redhat.com>
>> wrote:
>>
>>> Hi,
>>>
>>> I sent a simple patch to check the possibility to add results to
>>> callbacks:
>>> https://review.openstack.org/#/c/201127/
>>>
>>> This will allow us to decouple the callback logic from the ML2
>>> plugin in
>>> the QoS scenario where we need to update the agents in case the
>>> profile_id
>>> on a port/network changes.
>>> It will also allow for a cleaner way to extend resource attributes as
>>> AFTER_READ callbacks can return a dict of fields to add to the original
>>> resource instead of mutating it directly.
>>>
>>> Please let me know what you think of this idea.
>>>
>>> Regards,
>>> Mike
>>>
>>>
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>>
>>
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