Re: [Netconf] [yang-doctors] YANG Doctor question: empty mandatory choice? (was RE: YangPush now)

[Kent Watsen <[e-mail]>]

Hi Juergen,


> Why is the transport leaf needed if the choice cases identify the transport? 

My understanding is that this leaf is needed (exclusively?) to support the
enforcement that all the transports for a given subscription use the same
transport.

I've also been asking about this, partly from the "difficultly to enforce"
reason Eric mentions (though see the "when" statement in Eric's 7/20 email
where he resolves this, I thought), but also from a "are we making this
more difficult than needed?" perspective.


> Why do all receivers of a subscription have to use the same transport?

This was something that Martin and Eric worked out before we did the first
Last Call.  Eric doesn't seem to know the particular reason, other than 
Martin seems to think it’s easier.

Thinking out loud, I can sort-of, but not really, understand the motivation
for wanting to enforce the same encoding (xml, json, etc.) across receivers
and, since some transports may require certain encodings (i.e. netconf-->xml,
coap-->cbor, etc.), it carries that the transports should be the same too?

What I don't like about this argument is:

1) It's not user-friendly.  If a server really does have to send similar 
   subscriptions to a set receivers using different transports and/or 
   encodings, we've introduced what looks like an artificial need to 
   duplicate the subscriptions for each unique transport+encoding 
   combination.

2) I don't understand the implementation issue.  My view is that slightly
   clever code that caches encodings used could do this in one loop.  
   Here's some pseudo-pythonic code:

   send-notification-to-receivers(receivers, native-notification):
     xml-notification=None
     json-notification=None
     for receiver in receivers:
       if receiver.encoding is XML:
         if xml-notification is None:
           xml-notification = to-xml(native-notification)
         receiver.send(xml-notification)
       if receiver.encoding is JSON:
         if json-notification is None:
           json-notification = to-json(native-notification)
         receiver.send(json-notification)

   
Kent // as a contributor