[Nsi-wg] Message Delivery Layer

[Henrik Thostrup Jensen]

On Thu, 6 Dec 2012, Jeroen van der Ham wrote:

> A feasible first step in my opinion would be to make acknowledgements 
> optional. Combined with a good query interface this already makes it 
> possible to operate a client NSA behind a firewall.

Are you suggesting to make callback optional and resolve to polling for 
updates? I.e., never getting a reserveConfirmed message from a reserve 
request.

(btw. I think polling is completely acceptable - most people who have 
build a distributed system with events are painfully aware that they 
sometime disappear and that one will have to resolve to polling as a 
fallback).

OR:

Thowing out the callback scheme, i.e., getting a reserveConfirmed as the 
direct reply to a reseve request. This will mean some potential 
long-standing requests (not that it is a problem), probabaly some minutes.

This can also be optional (replyTo -> yes to callback, no replyTo -> 
direct reply). I'd prefer not to have this dual behavior due to 
implementation complexity.

--

Originally we chose to have the callbacks as some of the commands could 
take a very long time to complete. I think this was especially for 
provision, which would not trigger until the link came up (could be 
weeks), however with the notification mechanism in NSI2, that is no longer 
the case (provisionConfirmed now indicates that all NSAs have acknowledged 
the provision request).

If we are willing to handle request delays of a couple of minutes (most 
will be faster), we could forgo the callbacks for requests, and only deal 
with callbacks for notifications like active and forcedEnd.


     Best regards, Henrik

  Henrik Thostrup Jensen <htj at nordu.net>
  Software Developer, NORDUnet