[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]
Subject: Re: [ws-rx] DA and Protocol: is the date over?
I am confused. Quoting the Charter[1]:
The specific reliability assurances in the scope of the TC are:
* At Least Once: Messages are transferred at least one time or an
error is raised on at least one of the endpoints. It is possible
that some messages are transferred more than once.
Don't we have to create a useful protocol for that purpose? Again, this
protocol would be something upon which we would quite easily build the
RM-as-it-is-today protocol. Both protocols (or options within one
protocol, depending on our future terminology choice) would do one thing
well.
thanx,
doug
[1] http://www.oasis-open.org/committees/ws-rx/charter.php
On 19/08/05 12:56, Christopher B Ferris wrote:
>Doug,
>
>As I said in my previous response to this thread, I did not dispute the
>relevance of AtMostOnce,
>just that the protocol, as designed, was not intended to support that
>mode. Frankly, I think
>that it would be a mistake to try to repurpose the protocol to enable an
>ackless retryless
>AtMostOnce as I believe it opens up some potentially nasty gotchas and I
>think it would
>be detrimental to the purpose of holding to the agressive dates mapped out
>in the TC's
>charter.
>
>There's no reason why someone couldn't develop a *separate* protocol that
>simply
>provided for a monotonically increasing sequence identifier in a *separate
>namespace*
>to provide for ordered delivery only and permitted duplicate elimination
>(although, if you
>aren't doing retries, it isn't clear that there's much value in performing
>duplicate elimination
>at that level as there are no intentional retransmissions).
>
>I subscribe to the Curly principal. Do one thing, well. I think that we
>should keep the
>protocol simple and straightforward. I think that is where its greatest
>strengths lie.
>
>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
>
>Doug.Bunting@Sun.COM wrote on 08/19/2005 03:26:01 PM:
>
>
>
>>Chris,
>>
>>I am not sure about the elephant, the gun, or the gnat but I can see
>>great utility and efficiency in using a subset of the existing WS-RM
>>protocol when implementing at-most-once delivery or at-most-once /
>>in-order delivery between RMS and RMD. Those delivery assurances are
>>basically about identifying messages such that a recipient may
>>efficiently track duplicates and (in the second case) ignore messages
>>deemed "throwbacks". WS-A does not, to my knowledge, provide such
>>efficient identification. The WS-RM's monotonically increasing and
>>scoped sequence number is however well suited for implementing these RMS
>>
>>
>
>
>
>>to RMD delivery assurances.
>>
>>The question at hand seems to be whether our protocol should explicitly
>>support a no-Ack mode which may directly support the requested DA. That
>>would essentially mean separating the well-identified (or at-most-once)
>>concern from the acknowledged (or at-least-once) concern. Please let me
>>know if I am missing other concerns in this thread besides the
>>end-to-end (application level) delivery assurances.
>>
>>Oh, yes, we should probably also ask the higher level use case question
>>about whether our protocol or a supported and well-described subset
>>thereof should directly support at most once delivery assurances on the
>>wire. Saying "don't use RM" may be a negative answer to this question.
>>
>>thanx,
>>doug
>>
>>PS. I remember City Slickers but not every word of the dialogue. Could
>>you remind me about Curly's Law?
>>
>>On 18/08/05 12:40, Christopher B Ferris wrote:
>>
>>
>>
>>>Jacques,
>>>
>>>There's no doubt that there might be use cases for AtMostOnce delivery
>>>
>>>
>of
>
>
>>>messages *between* the
>>>RMS and RMD. However, as I recall someone (Umit?) saying either on the
>>>list or on IRC, that that isn't
>>>reliable messaging.
>>>
>>>I would agree.
>>>
>>>In fact, RM would be overkill, using an elephant gun to kill a gnat,
>>>especially if InOrder is not required.
>>>What possible purpose would an acknowledgement serve if the RMS didn't
>>>care that all of its
>>>messages were received, and if it were not doing retransmission of
>>>messages (because it didn't care
>>>one way or the other if the messages were all delivered)? Fire and
>>>
>>>
>forget
>
>
>>>is probably good enough
>>>for that use case. Ordered processing could be facilitated by
>>>
>>>
>inspecting
>
>
>>>timestamps and discarding
>>>messages that had a timestamp value less than the highest value already
>>>
>>>
>
>
>
>>>processed.
>>>
>>>Again, I think we need to keep in mind the separation of concerns that
>>>
>>>
>I
>
>
>>>mentioned in the F2F briefing.
>>>RM is concerned only with ensuring that messages are transmitted
>>>successfully from the RMS to the
>>>RMD. Period. While the source application may want that all of the
>>>messages be processed by the destination
>>>application, there is nothing that the RMD can do to ensure that
>>>guarantee. The destination application
>>>might be implemented as a separate, distributed component, and be taken
>>>
>>>
>
>
>
>>>off line (whether voluntarily
>>>or not) never to return, despite the fact that there are unprocessed,
>>>
>>>
>yet
>
>
>>>acknowledged, messages in the
>>>RMD's message store.
>>>
>>>The point of RM is to ensure that all messages transmitted by the RMS
>>>
>>>
>are
>
>
>>>successfully *received* by
>>>the RMD. The RMS is responsible to retransmit unacknowledged messages.
>>>
>>>
>The
>
>
>>>RMD is responsible
>>>for acknowledging receipt of each message so that the RMS can
>>>
>>>
>discontinue
>
>
>>>retransmission of
>>>successfully received messages.
>>>
>>>That is the extent of the scope of the protocol. It does just that one
>>>thing (recall Curly's Law [1]). It's purpose
>>>is to provide better QoS than can be achieved using TCP/IP alone (which
>>>
>>>
>
>
>
>>>itself has reliability characteristics
>>>built-in, but offers no guarantees about anything above the TCP/IP
>>>
>>>
>layer).
>
>
>>>The same applies at the
>>>IP layer, and so on, down the OSI seven layer cake.
>>>
>>>If the application wants some assurance that the destination
>>>
>>>
>application
>
>
>>>received and processed
>>>(or faulted) the message, then you need an application-level message
>>>
>>>
>for
>
>
>>>that (e.g. a business-level
>>>ack).
>>>
>>>The DA has relevance at the RMD as it specifies the QoS contract that
>>>
>>>
>the
>
>
>>>RMD offers the application
>>>destination. In the case of AtMostOnce, it is saying "look, I'll do my
>>>best to ensure that you get all of the
>>>messages, but I may have limited resources and you MAY lose some
>>>
>>>
>messages.
>
>
>>>You want a better
>>>guarantee than that, try another RMD provider.".
>>>
>>>[1] http://www.imdb.com/title/tt0101587/
>>>
>>>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
>>>
>>>Jacques Durand <JDurand@us.fujitsu.com> wrote on 08/18/2005 03:08:31
>>>
>>>
>PM:
>
>
>>>
>>>
>>>
>>>>Since Anish opened this Pandora box, I must say I share his confusion
>>>>
>>>>
>>>>
>>>>
>>>about the rationale for
>>>
>>>
>>>
>>>
>>>>separating the protocol mechanism from DA.
>>>>That could well be the mother of all issues that we still need to
>>>>
>>>>
>>>>
>>>>
>>>discuss on WS-RM, surely
>>>
>>>
>>>
>>>
>>>>deserving its own thread here (so I resubjected the mail).
>>>>Chris may have some use cases or rationale for that, but we have not
>>>>
>>>>
>>>>
>>>>
>>>seen the detail of them yet.
>>>
>>>
>>>
>>>
>>>>On my side, I can see the case of a monitoring device that only needs
>>>>
>>>>
>>>>
>>>>
>>>AtMostOnce for sending its
>>>
>>>
>>>
>>>
>>>>measures (maybe combined with InOrder), and that cannot afford a
>>>>
>>>>
>>>>
>>>>
>>>resending mechanism that it does
>>>
>>>
>>>
>>>
>>>>not need, nor does it care about interpreting Acks. So the protocol
>>>>
>>>>
>>>>
>>>>
>>>would be affected by DA
>>>
>>>
>>>
>>>
>>>>here... (note that even with AtLeastOnce, the tuning of resending
>>>>
>>>>
>>>>
>>>>
>>>parameters depends on a Policy
>>>
>>>
>>>
>>>
>>>>assertion, and we could make the case that such parameters can be seen
>>>>
>>>>
>
>
>
>>>>
>>>>
>>>as DA QoS parameters.)
>>>
>>>
>>>
>>>
>>>>Anish, you are the one who started this...
>>>>Jacques
>>>>-----Original Message-----
>>>>From: Anish Karmarkar [mailto:Anish.Karmarkar@oracle.com]
>>>>Sent: Thursday, August 18, 2005 11:15 AM
>>>>To: Jacques Durand
>>>>Cc: 'Christopher B Ferris'; ws-rx@lists.oasis-open.org
>>>>Subject: Re: [ws-rx] NEW ISSUE, twin sister of i019
>>>>Jacques Durand wrote:
>>>>
>>>>
>>>>
>>>>
>>>>>Chris: inline <JD>
>>>>>
>>>>>A meta-comment for those who may worry about the amount of discussion
>>>>>
>>>>>
>
>
>
>>>>>triggered by just one (or two) issues among... about 20 remaining
>>>>>
>>>>>
>>>>>
>>>>>
>>>issues?
>>>
>>>
>>>
>>>
>>>>>I think that behind the issues discussed here is a fundamental
>>>>>discussion touching at the protocol model and meaning of delivery
>>>>>assurance. There are many aspects of the model behind WS-RM that were
>>>>>
>>>>>
>
>
>
>>>>>not apparent for all TC joiners, and I guess that explains the
>>>>>understanding process (and questioning) going on.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>One of the problems I have had in the past (till Chris explained that
>>>>the protocol is AtLeastOnce on the wire) was about Delivery Assurance
>>>>and how/why it does/doesn't affect the protocol on the wire. The
>>>>intention, as mentioned by Chris, that the protocol is AtLeastOnce on
>>>>the wire is not apparent from reading the spec (at least to me). There
>>>>
>>>>
>
>
>
>>>>are statements that contradict this or are misleading. For example,
>>>>Section 2, 2nd para:
>>>>"WS-ReliableMessaging provides an interoperable protocol that a
>>>>
>>>>
>Reliable
>
>
>>>>
>>>>
>>>
>>>
>>>
>>>>Messaging (RM) Source and Reliable Messaging (RM) Destination use to
>>>>provide Application Source and Destination a guarantee that a message
>>>>that is sent will be delivered. The guarantee is specified as a
>>>>delivery assurance. The protocol supports the endpoints in providing
>>>>these delivery assurances. It is the responsibility of the RM Source
>>>>and RM Destination to fulfill the delivery assurances, or raise an
>>>>error. The protocol defined here allows endpoints to meet this
>>>>guarantee for the delivery assurances defined below. "
>>>>At the very least there is an editorial issue here.
>>>>-Anish
>>>>--
>>>>
>>>>
>>>>
>>>>
>>>>>Once that is being clarified and maybe refined, I certainly hope we
>>>>>
>>>>>
>>>>>
>>>>>
>>>will
>>>
>>>
>>>
>>>
>>>>>not need to go through this level of discussion at each issue...
>>>>>
>>>>>Jacques
>>>>>
>>>>>
>>>>>-----Original Message-----
>>>>>From: Christopher B Ferris [mailto:chrisfer@us.ibm.com]
>>>>>Sent: Friday, August 12, 2005 5:30 AM
>>>>>To: ws-rx@lists.oasis-open.org
>>>>>Subject: RE: [ws-rx] NEW ISSUE, twin sister of i019
>>>>>
>>>>>Jacques,
>>>>>
>>>>>Taking an approach of "what is not forbidden is allowed" in
>>>>>
>>>>>
>>>>>
>>>>>
>>>implementing a
>>>
>>>
>>>
>>>
>>>>>spec will almost invariably
>>>>>lead to interoperability problems when applied to areas of the spec
>>>>>
>>>>>
>>>>>
>>>>>
>>>that
>>>
>>>
>>>
>>>
>>>>>prescribe what to do.
>>>>>
>>>>><JD> I didn't pretend to make this my motto - but we all know that
>>>>>
>>>>>
>>>>>
>>>>>
>>>this
>>>
>>>
>>>
>>>
>>>>>is a question that every developer faces from time to time... I guess
>>>>>
>>>>>
>
>
>
>>>>>this is one of those areas where the keyword "SHALL NOT" can help a
>>>>>
>>>>>
>>>>>
>>>>>
>>>lot.
>>>
>>>
>>>
>>>
>>>>>As to the point of using TerminateSequence on an incomplete Sequence,
>>>>>
>>>>>
>
>
>
>>>>>
>>>>>
>>>I
>>>
>>>
>>>
>>>
>>>>>don't disagree that there
>>>>>is utility in providing a means for the RMS to terminate a Sequence.
>>>>>
>>>>>
>>>>>
>>>>>
>>>That
>>>
>>>
>>>
>>>
>>>>>is what the SequenceTerminated
>>>>>fault is for. Note that either endpoint may issue the
>>>>>
>>>>>
>>>>>
>>>>>
>>>SequenceTerminated
>>>
>>>
>>>
>>>
>>>>>fault:
>>>>>Sequence Terminated
>>>>>This fault is sent by either the RM Source or the RM Destination to
>>>>>indicate that the endpoint that generates the fault has either
>>>>>
>>>>>
>>>>>
>>>>>
>>>encountered
>>>
>>>
>>>
>>>
>>>>>an unrecoverable condition, or has detected a violation of the
>>>>>
>>>>>
>>>>>
>>>>>
>>>protocol
>>>
>>>
>>>
>>>
>>>>>and as a consequence, has chosen to terminate the sequence. The
>>>>>
>>>>>
>>>>>
>>>>>
>>>endpoint
>>>
>>>
>>>
>>>
>>>>>that generates this fault should make every reasonable effort to
>>>>>
>>>>>
>>>>>
>>>>>
>>>notify
>>>
>>>
>>>
>>>
>>>>>the corresponding endpoint of this decision.
>>>>>
>>>>>This leads us back to issue i019 unless we raise and resolve an issue
>>>>>
>>>>>
>
>
>
>>>>>
>>>>>
>>>that
>>>
>>>
>>>
>>>
>>>>>says roughly: is the RMS *required* to retransmit messages
>>>>>that are unacknowledged.
>>>>>
>>>>><JD> mmmh, I never saw this as a key thing: retransmission - whether
>>>>>required or not - is a limited effort that can ultimately fail for
>>>>>whatever reason. Regardless of this effort, won't we inevitably face
>>>>>situations where there are gaps in the sequence that we have to live
>>>>>with till the end of the seq? But I think i019 stands regardless of
>>>>>
>>>>>
>>>>>
>>>>>
>>>this
>>>
>>>
>>>
>>>
>>>>>(see later).
>>>>>
>>>>>
>>>>>Note though that this changes the nature of the
>>>>>protocol significantly. My personal take on it is that the
>>>>>answer to the previous question is "yes" and that the only meaningful
>>>>>
>>>>>
>
>
>
>>>>>
>>>>>
>>>way
>>>
>>>
>>>
>>>
>>>>>of optimizing AtMostOnce DA with regards to messages on the wire (if
>>>>>
>>>>>
>
>
>
>>>>>
>>>>>
>>>that
>>>
>>>
>>>
>>>
>>>>>is what we want) is to permit the RMD to acknowledge messages that it
>>>>>
>>>>>
>
>
>
>>>>>
>>>>>
>>>has
>>>
>>>
>>>
>>>
>>>>>not received (e.g. pre-emptively filling in gaps) but that the
>>>>>RMS is still required to retransmit unacknowledged messages (just to
>>>>>
>>>>>
>>>>>
>>>>>
>>>keep
>>>
>>>
>>>
>>>
>>>>>the protocol simple).
>>>>>
>>>>><JD> Chris: isn't that rather weird ??? I hope we don't need to
>>>>>
>>>>>
>>>>>
>>>>>
>>>stretch
>>>
>>>
>>>
>>>
>>>>>the interpretation of acknowledgement (you seem to suggest that
>>>>>acknowledgement may have a different meaning depending on the DA in
>>>>>use). Note that i019 applies regardless of the DA in use: it only
>>>>>
>>>>>
>says
>
>
>>>>>
>>>>>
>>>
>>>
>>>
>>>>>that the RMS has no way to get an accurate account of *actually*
>>>>>received vs not-received messages at the time the Fault terminates
>>>>>
>>>>>
>the
>
>
>>>>>
>>>>>
>>>
>>>
>>>
>>>>>sequence on RMD (because the latest SequenceAck obtained by RMS may
>>>>>
>>>>>
>>>>>
>>>>>
>>>show
>>>
>>>
>>>
>>>
>>>>>unacknowledged messages for which we don't know what happened.) That
>>>>>
>>>>>
>>>>>
>>>>>
>>>can
>>>
>>>
>>>
>>>
>>>>>still be of great importance especially in the case of ExactlyOnce:
>>>>>knowing that a message was for sure never received by RMD, allows for
>>>>>
>>>>>
>
>
>
>>>>>
>>>>>
>>>a
>>>
>>>
>>>
>>>
>>>>>meaningful failure notice to SA on which it can act (and I think it
>>>>>would also for AtMostOnce, since you are using ack mechanism there
>>>>>
>>>>>
>>>>>
>>>>>
>>>too).
>>>
>>>
>>>
>>>
>>>>>As long as accuracy of final ack status is considered a valid
>>>>>expectation, i019 is a valid issue IMO. </JD>
>>>>>
>>>>>
>>>>>That would effectively provide the
>>>>>protocol with the "forget before" that is needed in order to allow
>>>>>
>>>>>
>for
>
>
>>>>>
>>>>>
>>>
>>>
>>>
>>>>>some messages to be dropped between the RMS and RMD without
>>>>>changing (and IMO significanltly over-complicating) the nature of the
>>>>>
>>>>>
>
>
>
>>>>>protocol.
>>>>>
>>>>><JD> I think this is precisely the crux of this issue: do we want the
>>>>>
>>>>>
>
>
>
>>>>>RMS to forget which messages were not received for the sequence when
>>>>>
>>>>>
>>>>>
>>>>>
>>>it
>>>
>>>
>>>
>>>
>>>>>terminates? (regardless on how it terminates) that seems to be the
>>>>>
>>>>>
>>>>>
>>>>>
>>>first
>>>
>>>
>>>
>>>
>>>>>question we need to address apparently.
>>>>>
>>>>>Cheers,
>>>>>Jacques
>>>>>
>>>>>Jacques Durand <JDurand@us.fujitsu.com> wrote on 08/11/2005 11:50:53
>>>>>
>>>>>
>>>>>
>>>>>
>>>PM:
>>>
>>>
>>>
>>>
>>>>>>Chris:
>>>>>>Maybe I am a bit obtuse here but I just did not take that whole
>>>>>>
>>>>>>
>>>>>statement itself in an exclusive
>>>>>
>>>>>
>>>>>>way (notwithstanding my notion of "complete" which was as good as
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>in
>>>
>>>
>>>
>>>
>>>>>dictionary.reference.com)...
>>>>>
>>>>>
>>>>>>I guess the "what is not forbidden is allowed" perspective. So I
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>think
>>>
>>>
>>>
>>>
>>>>>some editorial tightening
>>>>>
>>>>>
>>>>>>would help folks like me :-)
>>>>>> May I add, precisely because it is only about enabling RMD to
>>>>>>
>>>>>>
>>>>>efficiently reclaim resources
>>>>>
>>>>>
>>>>>>associated with the Sequence, I saw use cases where using
>>>>>>
>>>>>>
>>>>><TerminateSequence> may be as
>>>>>
>>>>>
>>>>>>legitimate for an incomplete sequence as for a complete one. So I
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>guess
>>>
>>>
>>>
>>>
>>>>>that is these use cases
>>>>>
>>>>>
>>>>>>that need be discussed - (let me download that Gil doc...)
>>>>>>Thanks,
>>>>>>Jacques
>>>>>>
>>>>>>
>>>>>>
>>>>>>-----Original Message-----
>>>>>>From: Christopher B Ferris [mailto:chrisfer@us.ibm.com]
>>>>>>Sent: Thursday, August 11, 2005 6:21 PM
>>>>>>To: ws-rx@lists.oasis-open.org
>>>>>>Subject: RE: [ws-rx] NEW ISSUE, twin sister of i019
>>>>>>Jacques,
>>>>>>The spec says at line 569:
>>>>>>"After an RM Source receives the <SequenceAcknowledgement>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>acknowledging
>>>
>>>
>>>
>>>
>>>>>>the complete range of messages in a Sequence, it sends a element,
>>>>>>
>>>>>>
>
>
>
>>>>>
>>>>>
>>>in
>>>
>>>
>>>
>>>
>>>>>the
>>>>>
>>>>>
>>>>>>body of a message to the RM Destination to indicate that the
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>Sequence is
>>>
>>>
>>>
>>>
>>>>>>complete, and that it will not be sending any further messages
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>related
>>>
>>>
>>>
>>>
>>>>>to
>>>>>
>>>>>
>>>>>>the Sequence. The RM Destination can safely reclaim any resources
>>>>>>associated with the Sequence upon receipt of the message."
>>>>>>The key word in the first sentence is "complete", wherein the
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>definition
>>>
>>>
>>>
>>>
>>>>>>of "complete" in this context is the fourth one here:
>>>>>> http://dictionary.reference.com/search?q=complete
>>>>>> 4. Absolute; total
>>>>>>I always thought that it was pretty unambiguous, but maybe I am
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>mistaken
>>>
>>>
>>>
>>>
>>>>>>and it should instead read:
>>>>>>After an RM Source receives the <SequenceAcknowledgement>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>containing a
>>>
>>>
>>>
>>>
>>>>>>single <AcknowledgementRange> element with an @Upper valued at the
>>>>>>
>>>>>>
>
>
>
>>>>>>MessageNumber of the <LastMessage> in a Sequence and the @Lower
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>valued
>>>
>>>
>>>
>>>
>>>>>at
>>>>>
>>>>>
>>>>>>"1".
>>>>>>That was certainly the intent.
>>>>>>The statement at 569 is followed up starting at line 580 with:
>>>>>>"/wsrm:TerminateSequence
>>>>>> This element is sent by an RM Source after it has received
>>>>>>
>>>>>>
>
>
>
>>>>>
>>>>>
>>>the
>>>
>>>
>>>
>>>
>>>>>>final <SequenceAcknowledgement> covering the full range of a
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>Sequence.
>>>
>>>
>>>
>>>
>>>>>It
>>>>>
>>>>>
>>>>>>indicates that the RM Destination can safely reclaim any resources
>>>>>>
>>>>>>
>
>
>
>>>>>related
>>>>>
>>>>>
>>>>>>to the identified Sequence. This element MUST NOT be sent as a
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>header
>>>
>>>
>>>
>>>
>>>>>>block."
>>>>>>This reinforces what I claimed on the call, that the purpose of
>>>>>>TerminateSequence is to allow the RMD to reclaim any resources
>>>>>>associated with the Sequence. It means that the RMS is done,
>>>>>>
>>>>>>
>finit,
>
>
>>>>>
>>>>>
>>>
>>>
>>>
>>>>>kaput
>>>>>
>>>>>
>>>>>>with that Sequence.
>>>>>>I don't think that you should read into a spec, content which is
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>simply
>>>
>>>
>>>
>>>
>>>>>>not there:
>>>>>>
>>>>>>
>>>>>>>I did NOT interpret it as:
>>>>>>>
>>>>>>>" an RM Source MUST NOT send <TerminateSequence> in other cases
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>where
>>>
>>>
>>>
>>>
>>>>>it
>>>>>
>>>>>
>>>>>>has not received full
>>>>>>
>>>>>>
>>>>>>>acknowledgement of the complete range of messages in a
>>>>>>>
>>>>>>>
>Sequence."
>
>
>>>>>
>>>>>
>>>
>>>
>>>
>>>>>>But, maybe that is what is needed:
>>>>>>"An RM Source MUST NOT send a <TerminateSequence> if it has any
>>>>>>expectation of ever receiving information from the RM Destination
>>>>>>about that Sequence after the <TerminateSequence> is transmitted."
>>>>>>
>>>>>>
>
>
>
>>>>>>Again, the purpose of the <TerminateSequence> is to enable the RMD
>>>>>>
>>>>>>
>
>
>
>>>>>
>>>>>
>>>to
>>>
>>>
>>>
>>>
>>>>>>efficiently reclaim any and all respources associated with
>>>>>>the Sequence. It isn't necessary that the RMD ever receive this
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>message,
>>>
>>>
>>>
>>>
>>>>>>as the resources can still be reclaimed either at the Sequence
>>>>>>
>>>>>>
>>>>>expiration
>>>>>
>>>>>
>>>>>>time or following a duration of inactivity, etc. However, the
>>>>>><TerminateSequence> message's purpose seems clear, to me at least.
>>>>>>
>>>>>>
>
>
>
>>>>>>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
>>>>>>Jacques Durand <JDurand@us.fujitsu.com> wrote on 08/11/2005
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>08:16:56 PM:
>>>
>>>
>>>
>>>
>>>>>>>Giovanni:
>>>>>>>
>>>>>>>I think you are right on the spot about the misunderstanding
>>>>>>>
>>>>>>>
>that
>
>
>>>>>
>>>>>
>>>we
>>>
>>>
>>>
>>>
>>>>>had
>>>>>
>>>>>
>>>>>>in the conf call today.
>>>>>>
>>>>>>
>>>>>>>Indeed, I interpreted this statement of the spec as nothing more
>>>>>>>
>>>>>>>
>
>
>
>>>>>
>>>>>
>>>than
>>>
>>>
>>>
>>>
>>>>>>the normal use for
>>>>>>
>>>>>>
>>>>>>>TerminateSequence, non-exclusive of other uses:
>>>>>>>
>>>>>>>"After an RM Source receives the <SequenceAcknowledgement>
>>>>>>>
>>>>>>>
>>>>>acknowledging
>>>>>
>>>>>
>>>>>>>The complete range of messages in a Sequence, it sends a
>>>>>>>
>>>>>>>
>>>>>><TerminateSequence>
>>>>>>
>>>>>>
>>>>>>>element, in the body of a message to the RM Destination to
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>indicate
>>>
>>>
>>>
>>>
>>>>>that
>>>>>
>>>>>
>>>>>>>the Sequence is complete, and that it will not be sending any
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>further
>>>
>>>
>>>
>>>
>>>>>>>messages related to the Sequence."
>>>>>>>
>>>>>>>I did NOT interpret it as:
>>>>>>>
>>>>>>>" an RM Source MUST NOT send <TerminateSequence> in other cases
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>where
>>>
>>>
>>>
>>>
>>>>>it
>>>>>
>>>>>
>>>>>>has not received full
>>>>>>
>>>>>>
>>>>>>>acknowledgement of the complete range of messages in a
>>>>>>>
>>>>>>>
>Sequence."
>
>
>>>>>
>>>>>
>>>
>>>
>>>
>>>>>>>Therefore we were not discussing on the same base of premises.
>>>>>>>
>>>>>>>Your speculation is right: I assumed that seq termination (an
>>>>>>>
>>>>>>>
>>>>>operation
>>>>>
>>>>>
>>>>>>that is more meaningful to
>>>>>>
>>>>>>
>>>>>>>RMD than to RMS, given that the ending of a sequence has already
>>>>>>>
>>>>>>>
>
>
>
>>>>>
>>>>>
>>>been
>>>
>>>
>>>
>>>
>>>>>>notified by LastMessage
>>>>>>
>>>>>>
>>>>>>>sending ) may be appropriate in some cases where not all
>>>>>>>
>>>>>>>
>messages
>
>
>>>>>
>>>>>
>>>have
>>>
>>>
>>>
>>>
>>>>>>been acked. My recent
>>>>>>
>>>>>>
>>>>>>>rewording of the issue clarifies this a bit, but is still based
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>on the
>>>
>>>
>>>
>>>
>>>>>>same interpretation of
>>>>>>
>>>>>>
>>>>>>>TerminateSequence, so I may need to shelve it and submit an
>>>>>>>
>>>>>>>
>issue
>
>
>>>>>
>>>>>
>>>on
>>>
>>>
>>>
>>>
>>>>>>TerminateSequence instead.
>>>>>>
>>>>>>
>>>>>>>Note: I believe your last paragraph below just illustrates the
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>need
>>>
>>>
>>>
>>>
>>>>>for
>>>>>
>>>>>
>>>>>>clearly stating the valid
>>>>>>
>>>>>>
>>>>>>>use cases as in Gil doc, so that we can sync up on these before
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>even
>>>
>>>
>>>
>>>
>>>>>>discussing the issues ...
>>>>>>
>>>>>>
>>>>>>>Regards,
>>>>>>>
>>>>>>>Jacques
>>>>>>>
>>>>>>>-----Original Message-----
>>>>>>>From: Giovanni Boschi [mailto:gboschi@sonicsoftware.com]
>>>>>>>Sent: Thursday, August 11, 2005 3:47 PM
>>>>>>>To: Jacques Durand; ws-rx@lists.oasis-open.org
>>>>>>>Subject: RE: [ws-rx] NEW ISSUE, twin sister of i019
>>>>>>>
>>>>>>>From the issue justification, "The specification is too lax on
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>the
>>>
>>>
>>>
>>>
>>>>>>>loophole that permits stray messages to
>>>>>>>"sneak-in" just before a termination, without any opportunity to
>>>>>>>
>>>>>>>
>
>
>
>>>>>
>>>>>
>>>be
>>>
>>>
>>>
>>>
>>>>>>>acknowledged"
>>>>>>>
>>>>>>>This is what the specification says:
>>>>>>>
>>>>>>>"After an RM Source receives the <SequenceAcknowledgement>
>>>>>>>
>>>>>>>
>>>>>acknowledging
>>>>>
>>>>>
>>>>>>>the
>>>>>>>complete range of messages in a Sequence, it sends a
>>>>>>>
>>>>>>>
>>>>><TerminateSequence>
>>>>>
>>>>>
>>>>>>>element, in the body of a message to the RM Destination to
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>indicate
>>>
>>>
>>>
>>>
>>>>>that
>>>>>
>>>>>
>>>>>>>the
>>>>>>>Sequence is complete, and that it will not be sending any
>>>>>>>
>>>>>>>
>further
>
>
>>>>>
>>>>>
>>>
>>>
>>>
>>>>>>>messages related to
>>>>>>>the Sequence."
>>>>>>>
>>>>>>>This, at least to me, says pretty clearly that a conformant RMS
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>will
>>>
>>>
>>>
>>>
>>>>>not
>>>>>
>>>>>
>>>>>>>send TerminateSequence until all messages have been
>>>>>>>
>>>>>>>
>acknowledged,
>
>
>>>>>
>>>>>
>>>and
>>>
>>>
>>>
>>>
>>>>>>>that it will not send any new messages after sending
>>>>>>>
>>>>>>>
>>>>>TerminateSequence.
>>>>>
>>>>>
>>>>>>>To be sure, duplicates of messages previously sent (and
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>acknowledged)
>>>
>>>
>>>
>>>
>>>>>>>may arrive at the RMD after TerminateSequence. But these are
>>>>>>>duplicates, not unacknowledged messages.
>>>>>>>
>>>>>>>The specification has a definition of "normal termination" which
>>>>>>>
>>>>>>>
>
>
>
>>>>>>>requires that all messages be acknowledged, and therefore the
>>>>>>>
>>>>>>>
>>>>>"situation
>>>>>
>>>>>
>>>>>>>whereupon normal termination of a sequence some messages that
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>were
>>>
>>>
>>>
>>>
>>>>>>>previously send and never acknowledged..." is, by definition,
>>>>>>>impossible. The "accuracy of acknowledgments upon normal
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>sequence
>>>
>>>
>>>
>>>
>>>>>>>termination" is 100% perfect.
>>>>>>>
>>>>>>>Now, during the call today, Jacques seemed to suggest that what
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>was
>>>
>>>
>>>
>>>
>>>>>>>behind this is that a sender may need/want to terminate the
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>sequence
>>>
>>>
>>>
>>>
>>>>>>>prior to all messages being acked; this may well have merit, or
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>at the
>>>
>>>
>>>
>>>
>>>>>>>very least is worthy of discussion; the current spec clearly
>>>>>>>
>>>>>>>
>does
>
>
>>>>>
>>>>>
>>>not
>>>
>>>
>>>
>>>
>>>>>>>allow it, and it is well within the responsibility of the TC to
>>>>>>>
>>>>>>>
>>>>>consider
>>>>>
>>>>>
>>>>>>>such a change.
>>>>>>>
>>>>>>>But if the request is to change the definition of sequence
>>>>>>>
>>>>>>>
>>>>>termination,
>>>>>
>>>>>
>>>>>>>or maybe to provide an additional type of termination, the issue
>>>>>>>
>>>>>>>
>
>
>
>>>>>>>description should clearly say just that ("we should allow for
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>normal
>>>
>>>
>>>
>>>
>>>>>>>termination prior to acknowledgement of all messages"); but
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>nothing in
>>>
>>>
>>>
>>>
>>>>>>>the text of the issue suggests that we are looking for a change
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>in
>>>
>>>
>>>
>>>
>>>>>>>definition of normal termination.
>>>>>>>
>>>>>>>I don't know whether procedure allows revising the text of the
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>issue
>>>
>>>
>>>
>>>
>>>>>for
>>>>>
>>>>>
>>>>>>>clarity. As it stands now both the description and
>>>>>>>
>>>>>>>
>justification
>
>
>>>>>
>>>>>
>>>
>>>
>>>
>>>>>below
>>>>>
>>>>>
>>>>>>>contain statements that appear to me to be factually incorrect,
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>or at
>>>
>>>
>>>
>>>
>>>>>>>best highly misleading. It should not be surprising that this
>>>>>>>
>>>>>>>
>>>>>generates
>>>>>
>>>>>
>>>>>>>long discussions in the confcall about whether to even accept it
>>>>>>>
>>>>>>>
>
>
>
>>>>>
>>>>>
>>>as an
>>>
>>>
>>>
>>>
>>>>>>>issue.
>>>>>>>
>>>>>>>I will speculate that I may have an idea of what Jacques may be
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>after:
>>>
>>>
>>>
>>>
>>>>>>>a sender may, for a variety of reasons which we could discuss
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>(e.g. it
>>>
>>>
>>>
>>>
>>>>>>>is being shut down for maintenance longer than the sequence
>>>>>>>
>>>>>>>
>>>>>expiration),
>>>>>
>>>>>
>>>>>>>be forced to stop resending; if so, it would be nice to know
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>which
>>>
>>>
>>>
>>>
>>>>>>>messages actually got delivered or didn't, so that it may send
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>the
>>>
>>>
>>>
>>>
>>>>>>>undelivered ones again later in another sequence w/o duplicating
>>>>>>>
>>>>>>>
>
>
>
>>>>>
>>>>>
>>>them.
>>>
>>>
>>>
>>>
>>>>>>>AckRequested does not serve this purpose because, unless the
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>sequence
>>>
>>>
>>>
>>>
>>>>>is
>>>>>
>>>>>
>>>>>>>actually terminated, there may be more message out there in
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>flight
>>>
>>>
>>>
>>>
>>>>>which
>>>>>
>>>>>
>>>>>>>will actually arrive at the RMD and be delivered. But I'm just
>>>>>>>speculating, the issue doesn't say that.
>>>>>>>
>>>>>>>Jacques, please clarify.
>>>>>>>
>>>>>>>Giovanni.
>>>>>>>
>>>>>>>________________________________________
>>>>>>>From: Jacques Durand [mailto:JDurand@us.fujitsu.com]
>>>>>>>Sent: Thursday, August 04, 2005 6:50 PM
>>>>>>>To: ws-rx@lists.oasis-open.org
>>>>>>>Subject: [ws-rx] NEW ISSUE, twin sister of i019
>>>>>>>
>>>>>>>I realize that we should probably discuss this new issue in
>>>>>>>
>>>>>>>
>>>>>conjunction
>>>>>
>>>>>
>>>>>>>with i019, i.e. before closing on i019.
>>>>>>>(it is stating a similar problem, but for normal termination
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>cases.)
>>>
>>>
>>>
>>>
>>>>>>>Daniel:
>>>>>>>With the perspective of this new issue, I am leaning more toward
>>>>>>>
>>>>>>>
>
>
>
>>>>>
>>>>>
>>>your
>>>
>>>
>>>
>>>
>>>>>>>proposal to mark as "last" the final sequence status.
>>>>>>>
>>>>>>>
>>>>>>>Jacques
>>>>>>>
>>>>>>>
>>>>>>>Title: Accuracy of acknowledgement status upon normal sequence
>>>>>>>termination
>>>>>>>
>>>>>>>Description: The specification does not address the situation
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>where
>>>
>>>
>>>
>>>
>>>>>upon
>>>>>
>>>>>
>>>>>>>normal
>>>>>>>termination of a sequence, some message that were previously
>>>>>>>
>>>>>>>
>sent
>
>
>>>>>
>>>>>
>>>and
>>>
>>>
>>>
>>>
>>>>>>>never acknowledged
>>>>>>>(for which RM Source had stop any resending effort) has been
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>received
>>>
>>>
>>>
>>>
>>>>>>>late by RM Destination,
>>>>>>>e.g. between the sending of the last SequenceAcknowledgement and
>>>>>>>
>>>>>>>
>
>
>
>>>>>before
>>>>>
>>>>>
>>>>>>>the reception of
>>>>>>>a TerminateSequence message. This is the twin sister of issue
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>i019
>>>
>>>
>>>
>>>
>>>>>which
>>>>>
>>>>>
>>>>>>>deals with a similar
>>>>>>>problem but in case of fault termination.
>>>>>>>
>>>>>>>Justification: Normal termination is actually a fairly common
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>event
>>>
>>>
>>>
>>>
>>>>>>>(compared to sequence fault)
>>>>>>>and it is expected that sequences will be terminated even if
>>>>>>>
>>>>>>>
>they
>
>
>>>>>
>>>>>
>>>have
>>>
>>>
>>>
>>>
>>>>>>>missing messages.
>>>>>>>The specification is too lax on the loophole that permits stray
>>>>>>>
>>>>>>>
>>>>>messages
>>>>>
>>>>>
>>>>>>>to
>>>>>>>"sneak-in" just before a termination, without any opportunity to
>>>>>>>
>>>>>>>
>
>
>
>>>>>
>>>>>
>>>be
>>>
>>>
>>>
>>>
>>>>>>>acknowledged.
>>>>>>>
>>>>>>>Target: core
>>>>>>>Type: design
>>>>>>>
>>>>>>>Proposal: A final acknowledgement status could be sent back that
>>>>>>>
>>>>>>>
>
>
>
>>>>>>>reflects the exact state
>>>>>>>at termination time. That could be done by sending (or by making
>>>>>>>
>>>>>>>
>
>
>
>>>>>>>available for polling
>>>>>>>even after the sequence is terminated) a last
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>SequenceAcknowledgement
>>>
>>>
>>>
>>>
>>>>>>>element, at the time
>>>>>>>the RM Destination terminates the sequence (either at reception
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>of
>>>
>>>
>>>
>>>
>>>>>>>TerminateSequence,
>>>>>>>or due to timeout). Such a SequenceAcknowledgement element
>>>>>>>
>>>>>>>
>should
>
>
>>>>>
>>>>>
>>>have
>>>
>>>
>>>
>>>
>>>>>a
>>>>>
>>>>>
>>>>>>>"last" marker.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>>>
>
>
>
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]