RE: [ws-rx] Use Case for having Reliability assurances at finer granularity than Port Type

["Patil, Sanjay" <sanjay.patil@sap.com>]

Can the Source really be unaware of the contract between the RM
Destination and the Application destination in all the cases? For
example, how does a Source RM decide bracketing a set of messages handed
by Source Application in different Sequences? Let us look at the
semantics of TerminateSequence. The contributed material says - The RM
Destination can safely reclaim any resources associated with the
Sequence upon receipt of the <TerminateSequence> message. Doesn't this
mean that the Source is *aware* of the potential state on the
Destination RM?

Consider that the Source Application has handed 10 messages to its
Source RM. Could the Source RM now independently decide whether all the
10 messages should be sent in one single Sequence or break them into
multiple Sequences? It is arguable that this decision be based on the
contract between Source RM and Source Application? But without the
Source RM being *sure* about the Destination RM's capabilities, why
should it care for spending resources in creating one single Sequence
for all the 10 messages. On the other hand, if the Source RM chooses to
split the 10 messages into different Sequences, then the Destination RM
can not possibly establish ordering of the messages received as part of
the different Sequences. Doesn't it seem logical that whenever the
Destination RM is willing to dedicate resources for ordering, etc, it
also advertises its corresponding capabilities. If this requirement
seems reasonable, then Tom's concern about not allowing advertisement of
RM policies per operation also seems reasonable to me! Let us at least
log this as a potential issue.

Thanks,
Sanjay 

>-----Original Message-----
>From: Christopher B Ferris [mailto:chrisfer@us.ibm.com] 
>Sent: Monday, Jun 27, 2005 15:20 PM
>To: Paul Fremantle
>Cc: wsrx
>Subject: Re: [ws-rx] Use Case for having Reliability 
>assurances at finer granularity than Port Type
>
>Tom writes:
>
>"The current protocol has no way to have the message sender signal what
>reliabilty qos should be applied to a message."
>
>Frankly, I don't get this requirement at all. Maybe it's my nature to 
>rebel when someone tells me what to do, but I really don't understand
>why you'd want to assert on a pairwise-basis, whether duplicates are
>eliminated, or the messages must be processed exactly once.
>
>If we have 4 nodes: A, B, C and D with D serving as the Destination 
>and A, B and C serving as the Source of messages to the service
>offered at D, why would A choose a quality of service different than
>B and/or C? Wouldn't it be FAR more likely that D would effect a 
>consistent QoS (again, as a contract between its RM Destination and
>its Application Destination roles) that A, B and C would avail 
>themselves
>of when using the RM protocol? Keep in mind that the protocol 
>is the same
>as perceived on the wire regardless of QoS effected at the destination 
>endpoint.
>
>Can someone come up with a valid use case that would require 
>the ability
>of the Source endpoint to assert the QoS on the part of the Destination
>where the QoS itself would likely vary from one Source endpoint to 
>another? 
>
>Furthermore, since effecting QoS would require some utilization of 
>resources
>at the Destination endpoint (e.g. durable store for 
>unprocessed messages)
>is it realistic to have the Source assert a requirement that the 
>Destination
>cannot meet because of constraints it might have on those resources?
>
>Personally, I would think that giving a Destination the ability to 
>advertise
>the QoS that is observed at the endpoint by virtue of the QoS contract 
>that the Application
>Destination has with the RM Destination combined with any capabilities 
>that the Application
>Destination itself (e.g. elimination of duplicates) and 
>allowing a Source
>endpoint to choose whether or not to use the service (e.g. 
>whether the QoS
>meets its expectations) is a more appropriate way to go.
>
>Cheers,
>
>Christopher Ferris
>STSM, Emerging e-business Industry Architecture
>email: chrisfer@us.ibm.com
>blog: http://webpages.charter.net/chrisfer/blog.html
>phone: +1 508 377 9295
>
>Paul Fremantle <pzf@uk.ibm.com> wrote on 06/27/2005 05:17:27 PM:
>
>> 
>> 
>> 
>> 
>> Tom
>> 
>> I agree that the current spec doesn't allow that. However, 
>in your use 
>case
>> below I imagine that the service provider could decide the 
>QoS required 
>per
>> operation type.
>> 
>> Paul
>> 
>> Paul Fremantle,
>> 
>> STSM, WebServices standards and architecture
>> Hursley WebServices Team
>> Consulting IT Specialist
>> IBM Hursley Lab (MP 189)
>>  Winchester, SO21 2JN, UK
>> 
>> ph+fax    44 (0) 1962 815 078
>> int ph: 245 078
>> pzf@uk.ibm.com
>> "God, however, has chosen the most perfect world, that is to 
>say the one
>> which is at the same time the simplest in hypotheses and the 
>richest in
>> phenomena." Liebniz
>> 
>> Tom Rutt <tom@coastin.com> on 27/06/2005 22:12:41
>> 
>> Please respond to tom@coastin.com
>> 
>> To:    Paul Fremantle/UK/IBM@IBMGB
>> cc:    wsrx <ws-rx@lists.oasis-open.org>
>> Subject:    Re: [ws-rx] Use Case for having Reliability 
>assurances at 
>finer
>>        granularity than Port Type
>> 
>> 
>> Paul Fremantle wrote:
>> 
>> >
>> >
>> >Tom
>> >
>> >Is that a correct reading of the specification? I thought that the
>> >restriction to portType is the WSRM Policy. Since the 
>policy does not
>> >define the GD, DE, or OD, then this does not affect those. As I 
>understand
>> >the submitted spec qos's are based on a private contract 
>between the RM
>> >destination and the application destination, which could 
>well be more
>> >finely grained than per porttype since it is not defined in 
>the spec or
>> >policy at all.
>> >
>> >
>> I did not want to put all the details in the first mail, but your
>> question begs that I bring up one of my
>> major concerns with the ws-reliable messageing protocol.
>> 
>> The current protocol has no way to have the message sender 
>signal what
>> reliabilty qos should be applied
>> to a message.  A simple mechanism, with a indication of the qos level
>> requested in the create sequence operation
>> would allow a sender to set up individual sequences for each 
>qos level
>> required.  If the receiving endpoint does not support the requested
>> level of Qos, a "not supported feature" fault can be returned.
>> 
>> Currently the spec seems to indicate that an endpoint will 
>apply its own
>> qos level appropriate with the application.
>> 
>> My point is that the protocol should enable a sender to express
>> different Qos levels per operation type on an endpoint.
>> 
>> If there is some other way to enable this (eg. policy or wsdl
>> decorations) I am open for discussion.
>> 
>> I just feel this is a requirement that is not met by the existing 
>protocol.
>> 
>> >Paul
>> >
>> >Paul Fremantle,
>> >
>> >STSM, WebServices standards and architecture
>> >Hursley WebServices Team
>> >Consulting IT Specialist
>> >IBM Hursley Lab (MP 189)
>> > Winchester, SO21 2JN, UK
>> >
>> >ph+fax    44 (0) 1962 815 078
>> >int ph: 245 078
>> >pzf@uk.ibm.com
>> >"God, however, has chosen the most perfect world, that is 
>to say the 
>one
>> >which is at the same time the simplest in hypotheses and 
>the richest in
>> >phenomena." Liebniz
>> >
>> >Tom Rutt <tom@coastin.com> on 27/06/2005 21:59:49
>> >
>> >Please respond to tom@coastin.com
>> >
>> >To:    wsrx <ws-rx@lists.oasis-open.org>
>> >cc:
>> >Subject:    [ws-rx] Use Case for having Reliability 
>assurances at finer
>> >       granularity than Port Type
>> >
>> >
>> >
>> >The current WS-reliable messaging contribution does not support the
>> >application of reliability quality of service
>> >at a finer granularity than port type.
>> >
>> >I provide an example interface definition (which would map to a WSDL
>> >port type)
>> >
>> >Interface (Broker){
>> >
>> >Operation Buy(in AccountNo, in StockName, in NumberOfShares):
>> >Operation Sell(in AccountNo, in StockName, in NumberOfShares);
>> >Operation UpdateInfo(in AccountNo, in CustomerAddress, in
>> CustomerPhoneNo);
>> >Operation query (in AccountNo, out SequenceOf {StockName, 
>NumberOfShares}
>> >}
>> >
>> >Buy and Sell need to be protected for guaranteed delivery, duplicate
>> >elim, and ordered delivery.
>> >
>> >UpdateInfo only needs to be protected for guaranteed delivery (it is
>> >idempotent).
>> >
>> >Query needs no reliability Qos.
>> >
>> >the query operation would not use ws-reliability at all.
>> >
>> >
>> >For this use case, the sender should be able to set up two 
>Reliability
>> >message sequences,
>> >one with all qos enabled,
>> >the other with only Guaranteed delivery enabled.
>> >
>> >
>> >--
>> >----------------------------------------------------
>> >Tom Rutt           email: tom@coastin.com; trutt@us.fujitsu.com
>> >Tel: +1 732 801 5744          Fax: +1 732 774 5133
>> >
>> >
>> >
>> >
>> >
>> >
>> 
>> 
>> --
>> ----------------------------------------------------
>> Tom Rutt           email: tom@coastin.com; trutt@us.fujitsu.com
>> Tel: +1 732 801 5744          Fax: +1 732 774 5133
>> 
>> 
>> 
>> 
>
>