Re: [Netconf] subscription-id management across applications

[Juergen Schoenwaelder <[e-mail]>]

On Mon, Jul 09, 2018 at 09:34:17AM -0700, Andy Bierman wrote:
> On Mon, Jul 9, 2018 at 9:31 AM, Juergen Schoenwaelder <
> [e-mail]> wrote:
> 
> > On Mon, Jul 09, 2018 at 09:12:57AM -0700, Andy Bierman wrote:
> > > Hi,
> > >
> > > The configured subscriptions use a uint32 subscription-id.
> > > There is text in 5.2 about splitting the range for dynamic and configured
> > > subscriptions:
> > >
> > >    To support deployments including both configured and dynamic
> > >    subscriptions, it is recommended to split subscription identifiers
> > >    into static and dynamic halves.  That way it eliminates the
> > >    possibility of collisions if the configured subscriptions attempt to
> > >    set a subscription-id which might have already been dynamically
> > >    allocated.  A best practice is to use lower half the "identifier"
> > >    object's integer space when that "identifier" is assigned by an
> > >    external entity (such as with a configured subscription).  This
> > >    leaves the upper half of subscription identifiers available to be
> > >    dynamically assigned by the publisher.
> >
> > Why would a server accept a dynamic subscription that clashes with
> > a configured subscription?
> >
> >
> I don't think it would.
> The issue is how applications share the range allocated for configured
> subscriptions.

This is not how I read the text. Splitting between dynamic and
configured does not solve the problem you think needs to be solved.
The problem, which I think the text hints at, is a situation where a
saved configuration cannot be restored due to dynamic subscriptions
clashing. To avoid this, separating the number spaces for configured
and dynamic subscriptions may be a good idea.

I think applications creating subscriptions should coordinate by
picking random values and being prepared to handle a failure if the
randomly picked value is already taken. Given the number space,
clashes should be rare.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
Fax:   [phone]         <https://www.jacobs-university.de/>