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Subject: Re: [ws-rx] AS need for ordered delivery?


Marc,

I think making WSRM DA free would be a fine way to go, but it would 
solve only part of the problem. One of the important things related to 
reliable messaging is DAs (irrespective of whether it affects messages 
sent on the wire on not). The application, AS and AD rely on those 
semantics (and we already have usecases documented for that). One could 
envision completely eliminating DAs from WSRM but then one would have to 
invent additional mechanisms (layered on top of WSRM) so that AS and AD 
don't have to worry about the DAs just as WSRM allows them to be worry 
free about (at-least-once) reliability.

But the solution [1] to address this need seems to be fairly simple and 
does not complicate the protocol, IMO. It would go a long way in 
satisfying the developer/user community needs, and they are looking 
forward to the WSRM spec to do so.

The TC has already resolved issue i009 to include DAs in the policy 
assertion. This means that DAs are not private to the RMD/AD, although 
they don't affect the messages and are implemented by RMD/AD.

The question isn't: why would AS need to send a message in order if the 
AD didn't require it?
but: how does the AS indicate to the AD/RMD the DA for a Sequence that 
it (AD/RMD) already supports/requires.
Consider the case where the AD/RMD supports multiple DAs and declares 
them using wsp:ExactlyOne. How does the AS indicate to the AD/RMD which 
particular DA (of all the DAs the AD/RMD supports) is in effect for the 
Sequence.

There are two additional interesting case:
1) RMD intermediaries: The CS/CSR message set up the sequence. CS/CSR 
messages are signaling messages and do not indicate which operation is 
being invoked. An RMD intermediary will not know at that point which DA 
to use.
2) What happens when a DA is advertised in a WSDL and it applies to out 
messages? Essentially the service is acting as a AS/RMS for those 
messages but is asserting a DA.

Overall, I see DA as an important issue for the dev/user community, the 
solution seems rather simple and does not introduce additional protocol 
messages/elements. It seems like the cost/benefit ratio is quite low 
(much lower than the CloseSequence functionality that we have 
introduced, IMHO). If we don't address DAs then the users/dev community 
has to figure out how to layer this on top.

-Anish
--

[1] 
http://www.oasis-open.org/apps/org/workgroup/ws-rx/email/archives/200510/msg00263.html

Marc Goodner wrote:
> I'm retitling the thread because this issue and AI are closed.
> 
> Why would an AS need to send messages in order if the AD didn't require
> it? If the AD does need ordering it would request it of the RMD and the
> AS/RMS shouldn't need to care about the DA in effect as it has been
> taken care of at the destination.
> 
> 
> -----Original Message-----
> From: Gilbert Pilz [mailto:Gilbert.Pilz@bea.com] 
> Sent: Tuesday, October 25, 2005 8:58 PM
> To: Duane Nickull; Anish Karmarkar; Marc Goodner
> Cc: ashok.malhotra@oracle.com; ws-rx@lists.oasis-open.org
> Subject: RE: [ws-rx] Proposal for AI 40 and i024
> 
> I'm not sure if asking an RMD what DA it purports to provide is
> necessarily asking to "see beyond it". If I have an application that
> relies upon ordered delivery to function correctly and I deploy that
> service onto an infrastructure with an RMD implementation that
> can't/won't provide ordered delivery clearly I have made a mistake. The
> question is do I want that mistake to surface as a exception the first
> time a client tries to invoke the service (hey dude! this thing can't do
> ordered delivery!), or would I like the mistake to surface in all sorts
> of bizarre behaviour by the application?
> 
> - g
> 
> 
>>-----Original Message-----
>>From: Duane Nickull [mailto:dnickull@adobe.com] 
>>Sent: Thursday, October 20, 2005 5:37 PM
>>To: Anish Karmarkar; Marc Goodner
>>Cc: ashok.malhotra@oracle.com; ws-rx@lists.oasis-open.org
>>Subject: RE: [ws-rx] Proposal for AI 40 and i024
>>
>>
>>My sense of the F2F resolution was that the TC wanted to 
>>capture the fact that DAs, timeouts etc were "observed" 
>>
>>Anish:
>>
>>I do not think they really are unless the RMS can see past 
>>the service.
>>This is bad architecture IMO.  Talk to the interface but 
>>don't try to see beyond it.  
>>
>>D
>>
> 
> 
> 



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