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Subject: Re: [ws-rx] AnonURI and Offer and WS-Addressing

  please see:  http://dev.w3.org/cvsweb/~checkout~/2004/ws/addressing/ws-addr-soap.html?content-type=text/html;%20charset=utf-8#anonaddress
which is the latest editor's copy of WSA, and in particular:
When "http://www.w3.org/2005/08/addressing/anonymous" is specified for the response endpoint and the message is the http://www.w3.org/2003/05/soap/mep/InboundMessage property of a SOAP request-response MEP [SOAP 1.2 Part 2: Adjuncts], then any response MUST be the http://www.w3.org/2003/05/soap/mep/OutboundMessage property of the same instance of the SOAP request-response MEP [SOAP 1.2 Part 2: Adjuncts].

They've added quite a bit of clarifying text since the submitted version.  I think the "same instance" part makes it clear that the response MUST flow over the same http connection as the request.

Perhaps it would help if we summarized the list of options:

1 - prohibit anon replyTo if the response is expected to be sent using RM
2 - prohibit the use of RM when the wsa:To is anonymous - or said another way, when replyTo is anon the response is not sent using RM
3 - resend request until response is delivered/acked even if the request is acked
4 - don't ack a request until the response is sent
5 - define a new URI that allows a polling flow like Paul described in his previous note

Here are some comments on each:
1 and 2 might actually be the same thing but my intention was to say that in '1' you can't use anon replyTo if the response is sent reliably - so perhaps a Fault is generated.  In '2', if the replyTo is anon then no matter what the wsdl/policy... says, RM needs to be turned off for the response - it can still be sent but just not as part of an RM sequence.  Slightly different.
'3' is a change to what I believe is most people current view of the RM processing model because we'll resend ACKed messages.  It also will only work for one-req/one-res MEPs.  Out-only, or single-req/multiple-res may have issues.
'4' is a change to the RM processing model because the RMD will not ACK a message even if it is received.  Depending on how you view things this could mean that the RMD needs to lie about what it has and could cause messages to be resent because the RMD is waiting for a response before it will ACK the request.  Now, since the RMD gets to choose when it ACKs (meaning is it simply 'I got it' or something else it up to it), so to some this may not be lying but just a change to the ACK model of that RMD.
'5' doesn't require a change to the RM processing model but heads in the direction of ws-polling and can work w/o a change to the RM processing model and can work for all MEPs.  Even if we did pick this option we'd still need to say something in the RM spec about what should happen when anon replyTo is used (I'm guessing 1 or 2).

Are there any other options people think we need to add to the list?  Having all of the known choices in front of us might help focus the discussions.


Paul Fremantle <paul@wso2.com>

03/12/2006 04:43 AM

Bob Freund-Hitachi <bob.freund@hitachisoftware.com>
Doug Davis/Raleigh/IBM@IBMUS, wsrx <ws-rx@lists.oasis-open.org>
[ws-rx] AnonURI and Offer and WS-Addressing

Bob et al.

I've attached a document that outlines the flow and shows message exchanges for a given interaction. The key question is whether the interaction:

   RMD.AckRequested_EmptyBody -> EchoResponse_World_ackSeq_1_2_3

breaks the WS-Addressing spec.


Bob Freund-Hitachi wrote:

Just another log for the fireā€¦
In reading HTTP 1.1, I do not see anything that specifies that the response entity cannot be interpreted prior to its completion.  In principle, it seems to me that both ack and response could be sent on the same connection backchannel provided that it was not closed prematurely.  Is this how the implementations that work do it?

From: Doug Davis [mailto:dug@us.ibm.com]
Friday, March 10, 2006 1:36 AM
Paul Fremantle
Re: [ws-rx] An alternative approach to make anon reply-to and sync rm work



I think there are some problems with this - I still think this violates WSA.  There's a reason anon replyTo means, in essence, the http response flow of the request message.  The connection becomes the correlator between the request and the response - meaning if several anon requests come in the only way the server knows which client gets which response is thru the http connection.  In your scenario if there are two anon requests sent to the server using the same sequence and no responses sent, when the third connection is made (to carry the ackReq) how does the server know which client is initiating the request.  It can not simply assume that just because they shared the same sequence that they also share WSA state and that any response can be sent to any client.  The correlation is now lost.  



Paul Fremantle <paul@wso2.com>

03/09/2006 06:53 PM

wsrx <ws-rx@lists.oasis-open.org>
[ws-rx] An alternative approach to make anon reply-to and sync rm work



The biggest issue with the two way reliable HTTP + anonURI case is the
requirement to replay request messages to get responses.

Why is this a problem? Because it means that the client has to store
requests (if and only if the interaction is two-way) beyond getting an ack
for that request.

This means that the RMS has to "know" if this particular message
interaction is one-way or two way. This means that for example, a dumb
gateway can't do it without looking at WSDLs etc.

Why do we need to do this: because WSA states:

"For instance, the SOAP 1.2
HTTP binding puts the reply message in the HTTP response."

So I agree we should not put an application reply to message A in an
HTTP response to application message B.

However, if we added the following text to our spec:

"In the case where an offered sequence is used, the RMS may send an
<wsrm:AckRequested> header together with an empty SOAP body. A valid
response to this message MAY either contain an empty SOAP body, or MAY
contain a message for the *offered* sequence".

The result of this would be that the response message on the HTTP reply
would be a valid reply to the request message and therefore would not break the
WS-Addressing text above. Effectively WSRM would be defining what
the SOAP request/reply would be, and therefore "making it right"
with respect to the HTTP binding.

So, when things are going well the HTTP reply to any given request message would be the
correct response message. But in the case that this message got lost or
delayed, the RMS would have a choice. If it still had the message, and it
"knew" that the MEP was two-way, it could choose to resend the
original request OR it could send an empty body with an ackRequested

This also gives the offered sequence a message onto which to
piggyback Close and TerminateSequence requests, solving another problem.

More importantly it removes the need for
the RMS to "know" the MEP, because by the repeated application of empty-body ackRequests,
the RMS can get the offered sequence into a decent state.

The only compulsory implementation change I see is that the RMD would
have to be coded to know what this empty body + ackrequest means.

From the RMS I see this as optional. It is completely up to the RMS
whether it initiates a CS with Offer+AnonURI. So if an implementation doesn't support this,
it will never initiate such a channel. And if the RMS does initiate such
a channel, it will "know" it is in this mode, that it needs to send
occasional empty ackrequests until it can close down the offered sequence.

In addition we would have to remove the words that say Offer is simply an optimization,
because this usage makes a specific correlation between a sequence and offered sequence.



Paul Fremantle
VP/Technology, WSO2 and OASIS WS-RX TC Co-chair


"Oxygenating the Web Service Platform",


Paul Fremantle
VP/Technology, WSO2 and OASIS WS-RX TC Co-chair


"Oxygenating the Web Service Platform",
www.wso2.com[attachment "AnonURI+Offer.doc" deleted by Doug Davis/Raleigh/IBM]

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