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Subject: Re: [ws-rx] i0019 - a proposal: (more complete)


Jacques,
    Anytime you can reduce the number of message types, it is always a good thing :-)

More specifically,
- In its current usage AckRequested may change the state at the RMD anyway, e.g., it may cause the RMD to start generating NAKs. So, I don't see the fact that it affects the sequence state to be a big issue.
- The purpose of Close is to make sure that the RMS and RMD are reconciled i.e. messages and corresponding acks are delivered. Using AckRequested seems to be appropriate for that.
- I don't see an issue with processing order between headers and body because both Sequence and the AckRequested are carried as headers. There may be an issue with the order in which Sequence and AckRequested headers get processed but this is an issue that already exists independent of this proposal.

Regards
Shivajee.

Jacques Durand wrote:

Shivajee:

I had considered something like this, and I know Doug had too. That would work, but I guess the tradeoff is a design that is a bit less consistent:

- AckRequested would then do much more than what it is supposed to do (would affect sequence state).

- Closing is a significant sequence operation, that normally should be designed the same way as CreateSequence, TerminateSequence were.

- the AckRequest can be bundled. The semantics of the processing order between headers and body becomes now important.

 

Regards,

jacques

 


From: Shivajee Samdarshi [mailto:shivajee@tibco.com]
Sent: Wednesday, August 24, 2005 5:53 PM
To: ws-rx@lists.oasis-open.org
Cc: Dan Leshchiner
Subject: [LIKELY JUNK]Re: [ws-rx] i0019 - a proposal: (more complete)

 

Here is a modification to this proposal that avoids having to add a new "Close" message.

As I understand it, the purpose of the "Close" message is two fold - one, is to notify the destination that there will be no more new messages on this sequence and two, is to solicit a final set of acks from the destination.

There is already an "AckRequested" message that allows the sender to solicit  acks from the destination. By adding a "Final" element with an optional "Complete" attribute to the "AckRequested" message we should be able to achieve what is proposed via the "Close" message.

<wsrm:AckRequested ...>
    <wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
    <wsrm:MessageNumber> xs:unsignedLong </wsrm:MessageNumber> ?
    <wsrm:Final Complete=xs:boolean?.. /> ?
</wsrm:AckRequested/>

Doug Davis wrote:


Jacque (et al),
  I'd like to hear your feedback on my formal proposal:  http://www.oasis-open.org/apps/org/workgroup/ws-rx/email/archives/200508/msg00160.html
thanks
-Doug


Jacques Durand <JDurand@us.fujitsu.com>

08/23/2005 08:19 PM

To

Christopher B Ferris/Waltham/IBM@IBMUS, ws-rx@lists.oasis-open.org

cc

 

Subject

RE: [ws-rx] i0019 - a proposal: (more complete)

 

 

 




Updating the M.O.U. for resolution of i019 and i028, based on feedback from Chris:

NOTE: I personally think the closing option <wsrm:Truncate/>? (remnant of "LastMessage") (proposed renamed wsrm:Complete/> here, see (e)) has little value and makes implementation more complex. But maybe I just miss a use case.

(a) [for i019 and i028] A new SeqAck boolean attribute @final is defined, and set to "true" by RMD only when sending Acks for a closed sequence.

(b) [for i019 and i028] The "Closed" state for a sequence, is defined as:
- the sequence will not accept anymore any message with a wsrm:Sequence header block  for this sequence.

- the RMD will still respond to other sequence-level operations for this sequence (Ack requests, close op, terminate op)

- any SeqAck sent back for such a sequence is tagged "final" (see (a)). Regardless of how the closing occurred (fault, request..) the RMS may query to get this final Ack again (e.g. by sending a "naked" AckRequested - no SOAP body, and wsa:Action=".../AckRequested". Or by sending a Close operation which is idempotent.)

(c)  [for i019] When a sequence fault is raised by RMD, the RMD may close the sequence (depending on the fault), but will never directly terminate the sequence. Along with a fault that just closed a sequence, a final SeqAck (see (a)) is sent back. The closing that takes place due to a fault is same as without <wsrm:Complete> option in <wsrm:Close> (see (e)).

(d) [for i028] A new "Close" operation (idempotent) for the RMS to close a sequence at any time. A final Ack is returned as response to the operation.

Request message will contain:
<wsrm:Close ...>

 <wsrm:Sequence ...>

   [as specified with MessageNumber = highest message number sent]

   ...

 </wsrm:Sequence>

 <wsrm:Complete/>?
 <!-- indicates whether the RMD should close gracefully (absent) or
"truncate" the Sequence -->

 ...

</wsrm:Close>Response will contain:

<wsrm:Closed ...>

 <wsrm:SequenceAcknowledgement final="true|false"? ...>

       [as specified]

       ...

 </wsrm:SequenceAcknowledgement>

 ...

</wsrm:Close>

(e) removing LastMessage feature, as it is kind of subsumed by the new Close operation. The presence of <wsrm:Complete/>? element (which is the Boolean opposite of <wsrm:Truncate/>? element Chris introduced) in <wsrm:Close> will cause the closing to be effective only when no message is missing below the greatest seqnum received so far at the time the closing request is received (meaning the sequence is complete). If  <wsrm:Complete/>? Is absent in <wsrm:Close>, the sequence would be closed immediately by RMD (no laggard message accepted.)

---- remaining to be discussed later, possibly as another issue or predicated to pending discussions and use cases:

(f) [improving fault termination case]  Sequence Faulted by RMD to never terminate directly a sequence, and to not even Close a sequence (except for "SequenceTerminated" fault) (see my recent mail to Doug D.) Most faults are "message-scope" faults not affecting seq integrity if the faulty message is just ignored (but faulted). RMS has always the choice of closing or not a Faulted sequence.

(g) [just a resource mgt issue for special case] Use of
TerminateSequence by RMS authorized even on non-complete sequences, assuming they have been Closed.

Regards,

Jacques

 

-----Original Message-----
From: Christopher B Ferris [
mailto:chrisfer@us.ibm.com]
Sent: Thursday, August 18, 2005 4:34 PM

To: ws-rx@lists.oasis-open.org

Subject: RE: [ws-rx] i0019 - a proposal: (more complete)

Please see my inline comments below.

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 08/18/2005 06:17:29 PM:

> To summarize where we are I think in resolving i019 and Proposed-01:
>
> Consensus on:

>
> (a)     [for i019] A final SeqAck tagged "final" sent by RMD when it
closes a sequence on Fault .
> The RMS may query to get this Ack again.

yes. we need specific language. Assume by "query" that you mean via a
"naked" AckRequested (no

SOAP body, and wsa:Action=".../AckRequested". I think that we also need to
be precisely clear

what the criteria for when the @final="true" (assume we want it to be a
boolean attribute) to be

required to be set, etc.

> (b)     [for Proposed-01] A new "Close" operation (idempotent) for the
RMS to freeze the state of
> a sequence on RMD and return a final Ack.

Yes, and predicated on resolution to i019 as above one would assume.

>
> Still on the table:

>
> (c ) [improving by simplifying] removing LastMessage feature, as it is
kind of subsumed by (b) above.

Think so, yes. I believe that Dug wanted to "sleep" on this still.
Frankly, <LastMessage/> is difficult
to implement unless you expose RM through to the application programming
model and even then, it is often

not until after the fact that you know which message is the last.

What I think is needed is a param in the Close() operation that indicates
whether or not

the RMS wants the RMD to process any further messages in the Sequence, and
also what the

RMS thinks is the highest message number in that Sequence. That way, we
have

effectively preserved the feature that signals to an RMD whether the
Sequence is to be

closed gracefully (normally), or whether it is to be truncated "as is",
etc.

<wsrm:Close ...>
 <wsrm:Sequence ...>

   [as specified with MessageNumber = highest message number sent]

   ...

 </wsrm:Sequence>

 <wsrm:Truncate/>?
 <!-- indicates whether the RMD should close gracefully (absent) or
"truncate" the Sequence -->

 ...

</wsrm:Close>

<wsrm:Closed ...>
 <wsrm:SequenceAcknowledgement final="true|false"? ...>

       [as specified]

       ...

 </wsrm:SequenceAcknowledgement>

 ...

</wsrm:Close>

> (d) [needed by i019 to allow querying again for Ack] Sequence faults do
not terminate sequences
> anymore. At best, they "close" them.

I think that as Close() is idempotent, that it can be issued repeatedly
until the RMS

gets a SequenceAcknowledgement with @final="true" in the Closed response.
A question though.

many implementations might find it unnatural to "receive" a Fault in
anything but a response

message. Granted, this is not a constraint of SOAP, but... We could also
provide Close

with the ability to carry Fault information for faults generated by the
RMS.

<wsrm:Close ...>
 <wsrm:Identifier>[Sequence Id]</wsrm:Identifier>

 <wsrm:MessageNumber>[value of highest MessageNumber
sent]</wsrm:MessageNumber>

 <wsrm:Truncate/>?
   <!-- indicates whether the RMD should close gracefully (absent) or
"truncate" the Sequence -->

 <soap:Fault>[yadda]</soap:Fault> | <soap12:Fault>[yadda]</soap12:Fault>?

 ...

</wsrm:Close>

Just a thought.

> (e) [improving fault termination case]  Sequence Faults to not even
Close a sequence (except for
> "SequenceTerminated" fault) (see my recent mail to Doug D.) Most faults
are "message-scope" faults

> not affecting seq integrity if message ignored. RMS has now choice to
close or not a Faulted sequence.

> (f)  [just a resource mgt issue for special case] Use of
TerminateSequence by RMS authorized even
> on non-complete sequences, assuming they have been Closed.

I think that this needs to be raised as a separate issue. I am still
firmly of the belief that

a Sequence operates in AtLeastOnce mode between RMS and RMD. I can see
closing a Sequence that

has gaps only in the case where the RMS is willing to see the Sequence end
with a SeqAck covering

the "complete range" of messages (e.g. it will retransmit unacked
messages) or in the case where
the Sequence has suffered some sort of fault (at either end) that prevents
it from being normally
completed (in which case it is "truncated" as above).

I still do not believe that we should be using the protocol in a manner
other than the one

I have described repeatedly.

>
> Do we agree on this status?

Not quite. Stefan mentioned that he has issues with regards to closing a
Sequence with

gaps in the context of InOrder (if I recall correctly from the call). He
indicated he

would send details of his concerns to the list.

>
> Jacques

>
> From: Jacques Durand
> Sent: Thursday, August 18, 2005 11:33 AM

> To: 'Christopher B Ferris'; ws-rx@lists.oasis-open.org

> Subject: RE: [ws-rx] i0019 - a proposal: (more complete)

>
> Chris:
> Extracting some of your answers from the logbook...
> >I think more correctly, the RMD, upon receipt of a Close() message MUST

> >NOT process any subsequent messages received for that Sequence that
have a
> >wsrm:Sequence header block  belonging to the closed Sequence.
> I think that's a precise statement for describing the Closed semantics.
> >Hmmm... I would be more inclined to eliminate LastMessage, as part of
the
> >proposal to close whichever issue this is related. That way, it can be
> > analyzed in its full glory. I too see Close() as a replacement for
> > <LastMessage/>.
> That is what I meant. I am all in favor of removing LastMessage feature
in this resolution, if
> that's not too much to do for closing this issue.

>
> >i019    Sequence termination on RMD generated Fault
> Better than current title, though I was also pleased with my own
proposal in a past mail:
> - I019: "Accurate final acknowledgement of a Sequence terminated on
Fault by RMD"
> - Proposed-01: "Accurate final acknowledgement of a Sequence with gaps
when RMS decides to stop using it."
>
> ...
> >I disagree, I think that it would be preferable that the
> > SequenceAcknowledgement MUST be marked as "final" to ensure that there
is
> > no ambiguity...
> Sounds good - indeed otherwise there may be some corner cases.
> >I don't quite understand. What rule? To the best of my knowledge, there
is
> > nothing in the spec that says that the TerminateSequence for a given
> > Sequence MUST NOT be sent  more than once by the RMS. However, I could
see
> > utility in making it clear that both Close() and TerminateSequence()
> > are idempotent operations and MUST be implemented as such.
> I meant the rule that TerminateSequence can only be used on fully
acknowledged (complete)
> sequences. It is definitely OK to send any of these ops more than once.
Idempotency reflects also
> in what is returned by these ops, if applicable.

>
> Cheers,
> Jacques
> -----Original Message-----
> From: Christopher B Ferris [
mailto:chrisfer@us.ibm.com]
> Sent: Thursday, August 18, 2005 9:24 AM
> To: ws-rx@lists.oasis-open.org
> Subject: RE: [ws-rx] i0019 - a proposal: (more complete)
> I've interspersed some comments thoughout this post (including the
> included emails)
> 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 08/16/2005 07:50:07 PM:

> > Ooops, backtrack this: something is missing in your proposal Doug,
that
> I didn't catch before:
> > -          remember this is the issue where termination is on sequence

> Fault from RMD side: the
> > RMS does not even get a chance to do some closing.
> > -          So I think we should also give all Sequence Faults a
> "closing" semantics, rather than
> > an actual "termination" semantics. When getting the Fault, the RMS
knows
> the sequence has closed,
> > but can still send a "close" op to get a final Ack. Then it would have

> to Terminate the sequence
> > (unless it lets inactivity or expiration time kick-in).
> > -          Your proposal seems to be more appropriate for the twin
issue
>  - reworded Proposed-01
> > -, where RMS just wants the final tab after deciding to not use the
> sequence anymore, regardless
> > of gaps and regardless of termination process (expiration, inactivity,

> or TerminateSequence if allowed here)
> I agree, IMO, i019's title should possibly better reflect the
description,
> which clearly suggests
> that it is concerned with faults generated by the RMD. I would proposed
> re-titling the issue:
>         i019    Sequence termination on RMD generated Fault
> I agree that much of the discussion here is probably more relevant in
the
> context of
> proposed issue 01 for this week's call.
>
>

http://www.oasis-open.org/apps/org/workgroup/ws-rx/email/archives/200508/msg00084.html

> With that said, I still have further comments below.
> >
> > Jacques
> >
> >
> > From: Jacques Durand
> > Sent: Tuesday, August 16, 2005 3:20 PM
> > To: 'Doug Davis'; ws-rx@lists.oasis-open.org
> > Subject: RE: [ws-rx] i0019 - a proposal
> >
> > Doug:
> >
> > Overall that seems to do the trick.
> > More Inline <JD>
> >
> > A related comment:
> >
> > -          the use of LastMessage marker appears now like a subcase of

> closing, where the RMD will
> > close if (1) LastMessage was received, (2) all messages before were
> received.
> > -          After we are done with i019, I think we should reconsider
how
> useful LastMessage is (I
> > guess a separate issue). My expectation here is to keep the protocol
> simple. At least, I would
> > like i019 and your proposal to NOT be perceived as making the protocol

> more complex... as I
> > believe it makes it possible to trade one feature ("LastMessage") for
> another ("Close").
> Hmmm... I would be more inclined to eliminate LastMessage, as part of
the
> proposal to close
> whichever issue this is related. That way, it can be analyzed in its
full
> glory. I too see
> Close() as a replacement for <LastMessage/>. read on...
> >
> > Cheers,
> > Jacques
> >
> >
> > From: Doug Davis [
mailto:dug@us.ibm.com]
> > Sent: Sunday, August 14, 2005 4:26 PM
> > To: ws-rx@lists.oasis-open.org
> > Subject: [ws-rx] i0019 - a proposal
> >
> >
> > For issue 19 we're really dealing with the communication of the state
of
> the sequence between the
> > RMD and the RMS.  I think there are two situation we need to think
> about:
> > 1 - a sequence w/o gaps
> > 2 - a sequence with gaps
> >
> > #1 is easy, when the RMS receives an Ack for the full range of
messages
> that it has sent then it
> > knows that the sequence is complete and it can send a Terminate
knowing
> no new messages will be
> > accepted by the RMD.  In the absence of an ACK the RMS can always ask
> for one using an
> > AckRequested thereby determine the RMD's state.
> >
> > #2 seems to be the problem child.  Lost (or delayed) Acks and Messages

> can play havoc with the
> > RMS's perception of what the final state of the sequence is.  For
> example, it may believe that
> > message #3 (out of 6) was lost and doesn't care any more (for some
> reason), so it sends a
> > TerminateSequence.
> >
> > <JD> I thought TerminateSequence can't be sent out unless RMS get all
> messages acknowledged ?
> > (hey, I am not the only one reading the spec in a "lax" way !! ;-)
> Let us assume that for purposes of discussion, #2 is taken in the
context
> of an RMS generated
> fault that results in premature termination of the Sequence by the RMS,
> yet it wants an accurate
> accounting of the final state as perceived by the RMD and it wants to
> ensure that no further messages
> are processed.
> >
> >  However, if message #3 is just slow, and arrives at the RMD after the

> sending of the Terminate
> > but before it arrives then the RMD's sequence state will differ from
the
> RMS's.  Sending a final
> > Ack back to the RMS might not be sufficient since that might be lost
as
> well.
> >
> > <JD> In fact, the termination case for i019 is more of a SequenceFault

> that, at the time it occurs
> > on RMD, leaves the RMS without an idea whether some missing messages
> were received since it got
> > its last SequenceAck. But the solution is the same.
> >
> >
> > So, I'd like to propose the following:
> >
> > Add a "Final" marker to the SequenceAck header (per Dan's
suggestions).
> The inclusion of this
> > element in the Ack is the RMD's way of telling the RMS that no new
> messages will be accepted into
> > this sequence.  This is true regardless of there being gaps in it or
> not.
> > Define a new operation: "Close".  The RMS can send a "Close" to the
RMD
> indicating that it would
> > like to shutdown the sequence and request that no new messages be
> accepted.  Notice that this is
> > similar to a TerminateSequence in that they both shutdown the sequence

> but unlike a TerminateSeq,
> > the "Close" will not do any resource reclamation - it just halts the
> delivery/processing of any
> > new messages.
> >
> > <JD> semantics of Close is: sequence will reject any future message
(in
> effect freezing its state)
> > except "operation" messages such as Close and TerminateSequence, to
> which it should respond as appropriate.
> I think more correctly, the RMD, upon receipt of a Close() message MUST
> NOT process any subsequent
> messages received for that Sequence that have a wsrm:Sequence header
block
> belonging to the closed
> Sequence.
> >
> >
> > So, going back to situation #2, the RMS wants to close down the
sequence
> despite there being gaps.
> > It will send a "Close" to the RMD, which in turn responds with
"Closed"
> plus an Ack.  Note that
> > the Ack will include the "Final" marker.
> >
> > <JD> if the Closed is always accompanied by the SeqAck, then this Ack
> can be considered as final
> > ("Final" marker is only cosmetic).
> I disagree, I think that it would be preferable that the
> SequenceAcknowledgement MUST be marked
> as "final" to ensure that there is no ambiguity... the SequenceAck
*could*
> technically just be
> piggy-backed by the implementation and represent state that is not, in
> fact, final. I believe that
> we would be better served leaving no doubt by making it a requirement
that
> the SeqAck be marked
> "final".
> >
> >  If this message (or the Close) is lost the RMS is free to send it
over
> and over until it gets an
> > Ack+Final since processing multiple ones has no negative impact.  Upon

> receipt of the Ack+Final
> > the RMS can then safely send a TerminateSequence without fear of any
new
> messages arriving and
> > changing its perception of the gaps in the sequence.
> > <JD> that means we change the rule of usage for TerminateSequence too.

> I don't quite understand. What rule? To the best of my knowledge, there
is
> nothing in the spec
> that says that the TerminateSequence for a given Sequence MUST NOT be
sent
> more than once by the
> RMS. However, I could see utility in making it clear that both Close()
and
> TerminateSequence()
> are idempotent operations and MUST be implemented as such.
> >
> >
> > Note that sending a "Close" for a sequence that doesn't have gaps
> doesn't cause any harm either -
> > its an optional message that _can_ flow right before a
> TerminateSequence.
> > Thoughts?  If people like this I'll write up a more formal proposal
> (spec changes).
> >
> > <JD> I'm OK with this.
> > -Jacques
> >
> >
> > thanks
> > -Doug

 




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