Re: [netmod] Datastore leaf for yang instance data

[Balázs Lengyel <[e-mail]>]

On 2018. 11. 28. 16:43, Robert Wilton wrote:
>
> On 28/11/2018 15:32, Juergen Schoenwaelder wrote:
>> On Wed, Nov 28, 2018 at 03:27:26PM +0000, Robert Wilton wrote:
>>> On 28/11/2018 10:20, Juergen Schoenwaelder wrote:
>>>> On Wed, Nov 28, 2018 at 09:41:12AM +0000, Balázs Lengyel wrote:
>>>>>> I do not buy this story. Your software needs to decide somehow what
>>>>>> instance data means. A config true leaf in candidate means something
>>>>>> different than the same config true leaf in running and this yet 
>>>>>> again
>>>>>> means something different than the same config true leaf in 
>>>>>> operational.
>>>>>>
>>>>>> /js
>>>>> BALAZS: As I understood the WG decided that this draft should only 
>>>>> be about
>>>>> the format of the yang instance data. What the SW does with it is 
>>>>> out of
>>>>> scope. So considerations whether instance data should be loaded 
>>>>> into running
>>>>> or candidate or not at all, are outside the scope.
>>>> If you do not know what the instance data means, any attempt to use it
>>>> is kind of broken.
>>>>> I want to provide a datastore indicator, but how that should be 
>>>>> used (and
>>>>> thus what is exactly means) is out of scope.
>>>> I disagree. The datastore indicator is needed to understand what the
>>>> data means, i.e., to do anything meaningful with it.
>>> I think that a datastore indicator is useful sometimes.  E.g. it 
>>> might be
>>> helpful in some cases to know that the data was associated with a 
>>> particular
>>> datastore.
>>>
>>> But in the general case I think that this is just "data at rest", and
>>> probably the key thing to know is whether (i) the data relates to
>>> configuration, or (ii) the data relates to operational state.
>>>
>>> This could potentially be inferred from a datastore leaf, or perhaps 
>>> this
>>> distinction could more explicitly be made by a separate field, which 
>>> I would
>>> make an enumeration or identity, since there might be other types of 
>>> data in
>>> future, such as capability information or diagnostics.
>>>
>> I do not understand why a datastore leaf is not sufficient and why we
>> need yet something new. If ever needed, NMDA does allow us to define
>> new datastores.
>
> Because a distinction between "candidate" vs "running" vs "intended" 
> won't necessarily be that useful.  Although knowing "running" vs 
> "intended" would allow the client to know whether it is pre/post 
> template expansion and that might be useful.
>
> The second reason is that I don't know whether things like 
> capabilities and diagnostics will be new datastores or just part of 
> operational.  I don't think that either of these two areas have really 
> been properly worked out yet.  I presume that they will come over 
> time, once more network management becomes more automated.
>
> Thanks,
> Rob

BALAZS: You are right, that these areas are not worked out. That is 
exactly why they are out of scope. This is only about the format, and 
not about the usage. As we already have about 10 use cases with 
different needs, none of which are specified exactly, I want to avoid 
defining specific metadata for use cases we don't fully understand. 
Note: it is possible and documented that the metadata can be 
extended/augmented.

regards balazs

-- 
Balazs Lengyel                       Ericsson Hungary Ltd.
Senior Specialist
Mobile: [phone]              email: [e-mail]