Re: [netmod] [Netconf] Alternative YANG library structure for 7895bis

[Andy Bierman <[e-mail]>]

On Mon, Dec 11, 2017 at 2:57 AM, Robert Wilton <[e-mail]> wrote:

> Hi,
>
> On 08/12/2017 18:01, Andy Bierman wrote:
>
> Hi,
>
> A library per datastore sounds too complicated.
> I prefer the proposal that was made at the IETF meeting that had
> a 'not-implemented-in' leaf-list and a single module list.
>
> The use case that this particular design doesn't work particularly well
> for is if you have a dynamic datastore that just contains a few modules
> that are not supported via the conventional datastores.
>
> I think that there are future uses cases where the set of modules used for
> a dynamic datastore could be really quite different and separate from
> conventional configuration.  E.g. if dynamic subscribers were managed
> through a dynamic configuration datastore rather than RADIUS.
>
>
> Why is it interesting to have a separate module list for regular modules
> and imported modules?
>
> Several reasons:
> 1) It means that the list of implemented modules have a single key and
> hence any references to an implemented module are cleaner/simpler.
>


IMO you are replacing universally meaningful keys  (module-name,
revision-date) with an arbitrary name,
It is not cleaner and not simpler for a client.


2) The model structure naturally more strictly enforces that only a single
> revision/version of a module is implemented.  (E.g. it prevents a server
> stating that two revisions of a module are both implemented).
>


How is that the case if the schema list includes its own module list?
You mean there is a "unique" statement in the outer list that insures that
a module/revision
shows up at most once in all instances of the inner module list?



> 3) I genuinely think that the list of implemented modules is more
> interesting to the client than the imported, but not implemented modules.
>


The conformance leaf was good enough.
Duplicating the module list and removing the conformance leaf is
aggressively non-backward compatible.



>
> For a server, I would design it to "implement" one revision of every
> module that it uses (including those that don't contain any data nodes,
> RPCs, actions, notifications, or deviations), and then the "import-only"
> list becomes the list of modules that the server implements to satisfy
> "import-by-revision" and these are stated in the implemented schema anyway.
>
>
> I prefer to keep the conformance leaf and not change the module list.
>
> NMDA needs to be possible to implement with a single schema tree such that
> a module
> is implemented in all datastores, or a subset of all datastores.
> Otherwise it probably won't
> get supported in clients.
>
> All solutions accommodate this requirement.
>


Seems to me all new solutions allow a server to violate the MUST in the
NMDA draft that
there is a superset of all modules.  A client has to look for every module
in a server-specific
set of named schema sets, and then reconcile all these sets.
I still prefer the single module list with a conformance leaf and a
leaf-list indicating
the supported (or unsupported) datastores.



> For me, some of the interesting design questions have revolved around:
> - is it better to reduce duplication in the list of modules reported at
> the cost of increased model complexity?
> - does the solution extend to schema mount?
> - how well does the solution cope with with configuration datastores that
> support very different sets of modules?
>
> To a lesser extent we have also been considering how well the solution
> extends to packaging and semantic versioning, but I think that it is quite
> tricky to know who these are going to pan out.  E.g. I think that the
> restriction that a given schema will only implement a single revision of a
> module will end up still holding, but I'm not sure that everyone has that
> same view point.
>
> Thanks,
> Rob
>
>
>

Andy


>
>
> Andy
>
>
>
> On Fri, Dec 8, 2017 at 9:21 AM, Kent Watsen <[e-mail]> wrote:
>
>> CC-ing NETCONF, where the draft is being worked on.
>>
>> Kent
>>
>>
>> On Fri, 2017-12-08 at 16:34 +0100, Juergen Schoenwaelder wrote:
>> > On Fri, Dec 08, 2017 at 04:19:28PM +0100, Vladimir Vassilev wrote:
>> > >
>> > > Yes. The default value for yang-library-datastore leaf is
>> ds:operational
>> > > (the only possible one for the ds:operational datastore). This is
>> backward
>> > > compatible. If one needs different model for 'running', etc. then a
>> new
>> > > datastore identity has to be defined  and set in place of the default
>> value.
>> > > Then this identity can be used to read the yang-library data with
>> > > <get-data>.
>> > >
>> >
>> > Sorry, but I have to ask this: How do I obtain the schema for the
>> > datastore (lets call it <running-library>) that reports the schema for
>> > <running>? Is there another <running-library-library> datastore? Will
>> > the recursion end? Perhaps it does since <running-library-library>
>> > might have itself listed as the schema defining datastore. I guess
>> > Lada will like these kind of meta and meta-meta datastores.
>>
>> Not really. Metadata needn't be in datastores.
>>
>> Lada
>>
>> >
>> > /js
>> >
>> --
>> Ladislav Lhotka
>> Head, CZ.NIC Labs
>> PGP Key ID: 0xB8F92B08A9F76C67
>>
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