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Subject: Re: [ws-tx] Issue 30 - One-way message replies
Isn't this related to
http://www.oasis-open.org/apps/org/workgroup/ws-tx/email/archives/200603/msg00091.html
?
And in which case, there's already a proposal on the table: define our
own endpoint type instead of wsa:ReplyTo and use that in this situation.
That's pretty much what we agreed at the f2f meeting (hence the issue).
Mark.
Doug Davis wrote:
>
> Alastair,
> Why not an option "C" - just define a new EPR (like 'i' from option
> "A") and just let the normal WS-Addr rules apply for everything else.
> That's very close to option "B", which , as you say, lines up with
> WS-Addr but doesn't overload wsa:ReplyTo - Tx defines its own EPR. I
> really don't think Tx needs to do anything other than define a new
> EPR. If Tx believes that the WS-Addr headers need to be contrained
> for, what appears to me to be, normal message flows then something is
> really wrong with WS-Addr because then all specs will need to do the
> same thing. But I don't think that's the case.
> thanks,
> -Doug
>
>
>
> *Alastair Green <alastair.green@choreology.com>*
>
> 04/03/2006 03:26 PM
>
>
> To
> Alastair Green <alastair.green@choreology.com>
> cc
> Bob Freund-Hitachi <bob.freund@hitachisoftware.com>, Doug
> Davis/Raleigh/IBM@IBMUS, Mark Little <mark.little@jboss.com>,
> ws-tx@lists.oasis-open.org
> Subject
> Re: [ws-tx] Issue 30 - One-way message replies
>
>
>
>
>
>
>
>
>
> In preparation for Thursday's meeting, I wanted to formulate a
> concrete change proposal along the lines of my last message (quoted
> below), but on checking it over, I believe I am mistaken on one key
> point. I say below:
>
> '[reply endpoint] cannot be set to "none" (that will blitz all
> responses)'
>
> I think that is wrong. If the [reply endpoint] is set to "none", it is
> still possible to have a [fault endpoint]. If the only kind of "reply"
> in the full WS-Addressing sense is a fault, then faults will not be
> thrown away, they will be sent using to the fault endpoint using
> [relationship] (message id etc).
>
> This would enable the use of a special [ws-tx conversation endpoint]
> instead of [reply endpoint], the difference being that use of the
> [ws-tx conversation endpoint] doesn't imply use of [relationship].
>
> However, given the necessary presence of [fault endpoint] and [message
> id] for fault processing it does beg the question: "why not use the
> WS-Addressing reply-processing model?" In other words, always specify
> [reply endpoint] and [message id] on /all/ messages, and then use that
> EPR for normal replies, amnesia cases, faults.
>
> To facilitate a clear discussion, I'd like to suggest two alternative
> resolutions of Issue 30:
> *
> Option A.*
>
> Retain status quo, with following qualifications/clarifications:
>
> i) use extension property [ws-tx conversation endpoint] (or [source
> endpoint]) instead of [reply endpoint] on non-terminal notification
> messages.
> ii) Set [reply endpoint] on all notification messages to "none" to
> avoid dragging in "anon" default.
> iii) Make clear that [fault endpoint] and [message id] must always be
> present (for terminal and non-terminal messages), and that WS-A
> predefined faults and WS-TX faults are sent, using [relationship] to
> the [fault endpoint] supplied on the message being responded to.
> iv) Retain MAY rule with respect to use of [ws-tx conversation
> endpoint] (or [source endpoint]).
> *
> Option B.*
>
> i) Specify a non-none ("physical address") value for [reply endpoint]
> for all messages, along with [message id].
> ii) omit [fault endpoint]
> ii) Send responses, if any (whether normal "conversational", WS-A
> predefined faults, WS-TX faults), to that EPR using [relationship],
> following MUST rule of WS-Addressing reply processing model.
>
> Option B has the advantage that it lines up WS-AT/BA messages with
> WS-C messages (one size fits all). It also leverages WS-Addressing in
> a straightforward way.
>
> Neither proposal is a "no-change" from the status quo.
>
> Alastair
>
> Alastair Green wrote:
> Bob,
>
> That's a useful summary.
>
> It seems that the impact for WS-TX (which explicitly eschews use of
> anonymous endpoints) is therefore:
>
> 1. Abolish the distinction between "request-response" and "one-way".
> None of our messages are best-attempt throwaways, and we would want to
> communicate predefined WS-A faults.
>
> 2. If we are going to have the apparatus in place for sending fault
> replies to a non-anon EPR then we might as well use that for WS-TX
> level faults (i.e. preserve that part of the status quo).
>
> 3. We might as well use the [reply endpoint] for all messages, so that
> ordinary and fault responses always have somewhere to go.
>
> 4. Therefore, we are indeed using the WS-A "reply processing model",
> for all messages.
>
> Background clarification/reasoning for the above:
>
> A. You didn't comment on the defaulting of the [reply endpoint] to
> anonymous. Am I right that it will /always/ default to "anonymous" if
> not specified, when using the XML infoset?
>
> B. If answer to A. is yes, then my summary is that WS-A recognizes
> three message exchange patterns:
>
> i) A message which will never be replied to at all ([reply endpoint] =
> none), which will not return standard faults (the destination is a
> sink or black hole)
>
> ii) Messages which will receive some kind of response, at minimum
> standard predefined faults, which specify (explicitly or by default)
> that [reply endpoint] = anonymous, and which can therefore omit
> message id. Delivery of the response is at some level synchronized: it
> holds a transport request-reply exchange open while a response is
> formulated.
>
> iii) Messages which will receive some kind of response, at minimum
> standard predefined faults, which specify either [reply endpoint] =
> "real address", or [fault endpoint] = "real address", and which have
> message ids. The underlying transport exchange concludes asap on
> receipt (just an ack); the response (ordinary or fault) uses a new
> transport-level exchange.
>
> B. iii) is a difficult beast, unless you use [reply endpoint]. I say
> that because [reply endpoint] cannot be set to "none" (that will blitz
> all responses); if it is not set to a "real address" then it defaults
> to "anonymous". If that is not what is required, then it must be set
> to a "real address". Ergo, B.iii) messages are extremely unlikely to
> exist unless [reply endpoint] is set. Which is the premise of my
> proposed actions for WS-TX in items 1 to 4 at the start of this mail.
>
> Alastair
>
> Bob Freund-Hitachi wrote:
> It is assumed that even a “one way” message when there is the
> potential of faults (nearly always I think), is in reality a
> request-response message with a potentially null response.
> The purpose of faultTo is to provide an address other than replyTo
> should the implementer decide that faults should go to a different place.
>
> Specialized (non general use cases) exist where responses are ALWAYS
> expected to be on a back-channel, thus the defaulting mechanism that
> is specified in WS-A and a somewhat grudging optional on messageid
> since in this case correlation may be preformed implicitly.
> In general, when messages may be sent and received asynchronously with
> respect to the lifetime of an underlying protocol specific
> backchannel, ReplyTo will be explicitly set to the desired value.
> In order to support either deployment scenario, then it is required to
> specify both replyTo as well as messageid in the sent messages so that
> returned replies, even if they are only fault messages, may be
> correlated through relatesTo.
>
> I don’t think that I have seen any one-way messages in the wild other
> than possibly of non-reliable logging-type messages where there is no
> particular concern about its receipt or faults it may produce
> Cheers
> -bob
>
>
>
> ------------------------------------------------------------------------
>
> *From:* Alastair Green [_mailto:alastair.green@choreology.com_] *
> Sent:* Tuesday, March 21, 2006 7:59 AM*
> To:* Doug Davis*
> Cc:* Mark Little; _ws-tx@lists.oasis-open.org_
> <mailto:ws-tx@lists.oasis-open.org>*
> Subject:* Re: [ws-tx] Issue 30 - One-way message replies
>
> Mark, Doug:
>
> I don't think that the section I quoted, tho' it appears in 3.4, is
> limited to the "reply processing model". It references section 3.2:
> /wsa:ReplyTo
>
> This OPTIONAL element (of type wsa:EndpointReferenceType) provides the
> value for the [reply endpoint] property. If this element is NOT
> present then the value of the [address] property of the [reply
> endpoint] EPR is _"http://www.w3.org/2005/08/addressing/anonymous"_
> <http://www.w3.org/2005/08/addressing/anonymous>.
> This seems to me to unambiguously enforce a default of anonymous when
> using the XML infoset.
>
> Section 3.4 simply reminds the reader that this rule exists and will
> apply (also) in the reply processing model (which I agree and
> understand we may not want to use -- that's why I raised this whole
> discussion in the first place).
>
> As for the question of where a fault goes to -- you raise an
> interesting dimension, Doug. :As I understand it there are two kinds
> of fault we could be talking about here:
>
> 1) An application-defined fault which the application contract
> determines should go to the fault-to EPR of a prior and related
> inbound message
> 2) A standard WS-Addressing fault, predefined in the WS-A SOAP binding
> spec
>
> Properties are provided by WS-Addressing to assist in delivering fault
> type 1). If you choose not to use them, then that's fine. The
> direction we seem to be heading in here is to define a WS-TX "fault"
> as "yet another WS-TX coordination protocol message with WS-TX-defined
> semantics, that happens to be generated when an inbound message causes
> a state machine to take an alternative path (generate a different
> message than it would when pursuing the normal, happy path)".
>
> However, the standard WS-Addressing faults do need to use the
> apparatus defined in WS-Addressing.
>
> Section 6 ("Faults") of the WS-A SOAP binding spec
> (_http://dev.w3.org/cvsweb/~checkout~/2004/ws/addressing/ws-addr-soap.html_
> <http://dev.w3.org/cvsweb/%7Echeckout%7E/2004/ws/addressing/ws-addr-soap.html>)
> reads, in part:
> Endpoints compliant with this specification MUST include the required
> message addressing properties serialized as SOAP headers in generated
> fault messages. Fault messages are correlated as replies using the
> [relationship] property as defined in Web Services Addressing 1.0 -
> Core[/_WS-Addressing-Core_/
> <http://dev.w3.org/cvsweb/%7Echeckout%7E/2004/ws/addressing/ws-addr-soap.html#WSADDR-CORE>].
> Note that omission of the [message id] property in an input message
> may impact the ability of a fault message receiver to correlate the
> fault message to the message that caused the fault message to be
> generated. Omission of the [fault endpoint] or [reply endpoint]
> properties in input messages may impact the delivery of a generated
> fault message
> So, to allow correct WS-Addressing predefined fault processing, all
> WS-A applications/implementations must specify message ids and at
> least a fault-to EPR. Arguably, if the [reply endpoint] is allowed to
> default to anonymous then the absence of a message id would not
> prevent the delivery of the fault (no correlation needed).
>
> However, it does appear that WS-A SOAP binding fault processing
> expects use of the whole "reply processing model" apparatus /with
> respect to standard faults/. This would militate against omission of
> fault-to and reply-to, an omission which I think you view as "normal"
> for one-ways.
>
> Therefore: we can properly avoid use of [reply endpoint], but it is
> far from clear that we can escape [fault endpoint] so easily.
>
> And, if we have to drag [fault endpoint], [message id] and
> [relationship] back in for this purpose, then it would appear that the
> difference between one-way and the full-scale "reply processing model"
> is more apparent than real. Are we coming full circle?
>
> If we default reply-to to anonymous (by omission), and live with the
> fact that faults must now travel on the anonymous back-channel, then I
> guess you could just about get away with ignoring the reply processing
> model. But that requires some heroic assumptions.
>
> The statement:
>
> "Fault messages are correlated as replies using the [relationship]
> property as defined in Web Services Addressing 1.0 -
> Core[/_WS-Addressing-Core_/
> <http://dev.w3.org/cvsweb/%7Echeckout%7E/2004/ws/addressing/ws-addr-soap.html#WSADDR-CORE>]."
>
> seems, on the face of it, to be normative. The qualifications in the
> following sentences about "impacting" the ability to deliver faults
> could be seen to weaken the force of that statement, but once again, I
> get that queasy feeling that one is in danger of bending and dodging
> the design intent of WS-Addressing.
>
> Alastair
>
>
> Doug Davis wrote:
>
> I don't think you want to do that because in the absence of a
> wsa:FaultTo, setting
> wsa:ReplyTo to "none" prevents you from getting back any fault
> messages - not
> Tx,non-related, faults, but other ones. These are just normal
> one-ways which
> people normally leave replyTo/faultTo blank - I see no reason to make
> them
> anything special but including a 'none' replyTo.
> -Doug
>
> *Alastair Green **_<alastair.green@choreology.com>_*
> <mailto:alastair.green@choreology.com>
>
> 03/21/2006 06:46 AM
>
>
> To
> Mark Little _<mark.little@jboss.com>_ <mailto:mark.little@jboss.com>
> cc
> _ws-tx@lists.oasis-open.org_ <mailto:ws-tx@lists.oasis-open.org>
> Subject
> Re: [ws-tx] Issue 30 - One-way message replies
>
>
>
>
>
>
>
>
>
>
>
>
> Mark,
>
> My point is that the WS-Addressing spec mandates that an absent
> reply-to causes the receiver to infer an anonymous response:
>
> Section 3.4 of the latest draft:
>
> *Note:*
>
> The [reply endpoint] message addressing property will always be
> present when using the XML Infoset representation since, in the
> absence of a wsa:ReplyTo element, the value of the [reply endpoint]
> message addressing property defaults to an EPR with an [address]
> property of _"http://www.w3.org/2005/08/addressing/anonymous"_
> <http://www.w3.org/2005/08/addressing/anonymous> - see section *_3.2
> XML Infoset Representation of Message Addressing Properties_*
> <http://dev.w3.org/cvsweb/%7Echeckout%7E/2004/ws/addressing/ws-addr-core.html?rev=1.51&content-type=text/html;%20charset=iso-8859-1#msgaddrpropsinfoset>.
>
>
> My understanding of this note, and of section 3.2, is that this
> inference MUST be drawn by a receiver, irrespective of any extension
> property like wsc:Response. Hence my proposal that we explicitly set
> wsa:ReplyTo to "none".
>
> Alastair
>
>
>
> Mark Little wrote:
> The discussion during the f2f concluded that we are indeed using
> wsa:ReplyTo in a way that, although probably legal, is not the way it
> was meant to be used and can lead to confusion (as we've seen here).
> So the first step in the process of removing that confusion, is to
> remove wsa:ReplyTo, which was my proposal. What we replace it with,
> and what the rules are around it, are the central points of the issue.
>
> Alastair Green wrote:
> Mark,
>
> Taking off from a comment in the last paragraph of my written
> contribution on this area during the F2F
>
> _http://www.oasis-open.org/apps/org/workgroup/ws-tx/email/archives/200603/msg00088.html_
>
>
> I think we need to address, in resolving this issue, the question of
> the [reply endpoint] value being defaulted to anonymous.
>
> The issue is about replacing wsa:ReplyTo in the case of "one ways that
> may ultimately have a response but aren't really request-response
> based messages" (to paraphrase). So in that case, we would be defining
> the rules around wsc:ReplyTo (just a name I've picked for this email
> so I can easily refer to it as being different to wsa:ReplyTo). As
> such, anonymous may not even play in that space. Why would we want an
> anonymous default? The current uses of wsa:ReplyTo really all assume
> that it was present on the message. I'd prefer a binary approach for
> wsc:ReplyTo.
>
>
> An absent [reply endpoint] property in the XML infoset representation
> becomes a receiver-inferred value of "anonymous" (actually, the URI
> that means anon).
>
> It seems preferable that we explicitly specify the value of "none"
> (again, a URI in truth).
>
> I would have expected us to be more specific: if there's a wsc:ReplyTo
> present, then this is the destination that MAY/SHOULD/MUST be used for
> sending a response. The absence means that no response is needed - no
> default.
>
>
> This is explicit, intuitively what one would expect for a one-way in
> terms of HTTP handling, and avoids any ambiguity/under-specification
> if a different representation is used at some future point.
>
> The current wording banning use of anonymous reply-to addresses would
> then be replaced.
>
> I think we also need to ban use of message ids, and ban use of
> fault-to, i.e. make it clear (by omission or by explicit statement)
> that none of these aspects of the reply-processing rules and apparatus
> are being put to use. ("Ban" in this context could mean "make it clear
> that these properties, if present, will be ignored".)
>
> We had discussed at the f2f that wsa:FaultTo is really meant just for
> comms faults and "application faults" would be treated as messages.
> I'm not sure if that made it into the minutes.
>
>
> I think use of wsa:From tends to detract from the clarity obtained by
> defining an extension property for our special use.
>
> Mark.
>
>
> Yours,
>
> Alastair
>
>
> Mark Little wrote:
> Line 472 and 480.
>
> Mark.
>
>
> Ram Jeyaraman wrote:
>
> Mark,
>
>
>
> Could you please provide the PDF line numbers in the referred document
> that are relevant to this issue. Thanks.
>
>
>
> ------------------------------------------------------------------------
>
> *From:* Ram Jeyaraman [_mailto:Ram.Jeyaraman@microsoft.com_]
> *Sent:* Friday, March 17, 2006 2:48 PM
> *To:* _ws-tx@lists.oasis-open.org_ <mailto:ws-tx@lists.oasis-open.org>
> *Subject:* [ws-tx] Issue 30 - One-way message replies
>
>
>
> This is identified as WS-TX issue 30.
>
>
>
> Please ensure follow-ups have a subject line starting "Issue 30 -"
> (after any Re:, [ws-tx] etc.)
>
>
>
> ===================================
>
>
>
> Issue name: One-way message replies
>
>
>
> Issue type: spec
>
>
>
> Owner: Mark Little (_mark.little@jboss.com_
> <mailto:mark.little@jboss.com>)
>
> Reference documents:
>
> WS-AT specification: _
> __http://www.oasis-open.org/apps/org/workgroup/ws-tx/download.php/17044/http://www.oasis-open.org/apps/org/workgroup/ws-tx/download.php/17129/wstx-wsat-1.1-spec-wd-04.pdf_
> <http://www.oasis-open.org/apps/org/workgroup/ws-tx/download.php/17044/http:/www.oasis-open.org/apps/org/workgroup/ws-tx/download.php/17129/wstx-wsat-1.1-spec-wd-04.pdf>
> _<http://www.oasis-open.org/apps/org/workgroup/ws-tx/download.php/17044/http:/www.oasis-open.org/apps/org/workgroup/ws-tx/download.php/17129/wstx-wsat-1.1-spec-wd-04.pdf>_
>
>
> Description:
>
> Currently we use wsa:ReplyTo for one-way messages in a way which
> although legal in terms of the latest CR draft of WS-Addressing, has
> led to confusion on a number of occasions. As an example, one use of
> wsa:ReplyTo is on Prepare->Prepared, where Prepare has a wsa:ReplyTo
> but the Prepared message is a separate (not response) message, because
> it could be sent autonomously and not actually in response to Prepare.
> The issue is that as far as WS-Addressing is concerned, wsa:ReplyTo
> should really only be used in the case of the request-response MEP,
> which is clearly not the case here.
>
> Proposed Resolution:
>
> The rules for where and when wsa:ReplyTo should be included and used
> within WS-AT are well defined, and particularly in respect to the
> interoperability scenarios. I propose that we replace wsa:ReplyTo with
> something specific to WS-TX (perhaps wsc:ReplyTo, wsc:OnewayTo, or
> somesuch).
>
> Addendum:
>
> Max suggested at the Raleigh f2f another potential resolution: that we
> use wsa:From.
>
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