Re: [wsn] Subscription leasing, garbage collection and scalability

[Steve Graham <sggraham@us.ibm.com>]

David:
ok, make a proposal.  Perhaps we
should consider incorporating any proposal here back into WSRL.  Potentially,
the solution you suggest may be more broadly applicable than just subscriptions?

sgg

++++++++
Steve Graham
(919)254-0615 (T/L 444)
STSM, On Demand Architecture
Member, IBM Academy of Technology
<Soli Deo Gloria/>
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David Hull <dmh@tibco.com> 05/24/2004 08:52 AM

To:        wsn@lists.oasis-open.org         cc:                 Subject:        [wsn] Subscription leasing, garbage collection and scalability

I believe the upshot of the previous exchange is,
if you expect a 
subscriber to make a lot of subscriptions, the lease time had better be
long or indefinite.  In fact, from the producer's point of view, if
you 
expect there to be a lot of subscriptions, period, the lease time had 
better be long or indefinite.

In other words, the only method that WS-BN provides for garbage 
collection of subscriptions should be effectively disabled precisely 
when it is most likely to matter.

I think the problem here is that WS-BN addresses subscription leasing 
and not garbage collection per se.  This doesn't mean that it should
try 
to provide all possible means of garbage collection, only that it should
specifically point out a need, allow for as wide a range of solutions as
is feasible, and point to subscription leasing (a la WS-RL) as one 
solution.  This is essentially the same road we went down with topics.

The more I consider leasing of individual subscriptions, the more 
potential technical issues I see.  Obviously, none of them is 
insurmountable -- they have all been addressed and solved in other 
contexts.  But each carries weight for the potential implementor.
 I'm 
willing to drill down on these a bit if needed, but I'm hoping we can 
avoid this and take a higher-level decision that leasing of individual
subscriptions, while useful in some contexts, should not be required or
be the only possible GC mechanism.

With that provisional assumption, the immediate question becomes how can
we allow for session-based garbage collection without adding undue 
weight to the WS-BN framework.  Sessions have their own technical
issues 
and implementation weight.