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Subject: RE: [ws-rx] i061 proposal / directions
- From: "Gilbert Pilz" <Gilbert.Pilz@bea.com>
- To: "Doug Davis" <dug@us.ibm.com>, <ws-rx@lists.oasis-open.org>
- Date: Mon, 23 Jan 2006 15:41:27 -0800
[text sizes changed to make
them readable]
Doug said:
If an RMS uses it then it knows how to
handle the http backchannel
for acks. If the RMD accepts it
then it knows how to use it
too. If neither side faults on its
use then I don't see the issue.
As Chris said, the RMD is always
free to fault on its use and an
RMS is always free to use a
non-anonymous URI. Both sides actually
have a lot of
control here. My proposal simply states what both
sides can
expect if it is used - if they don't like it they don't
have to
use it - but at least its written down what people should
expect.
I'm a little confused by this statement. In my mental
model of this issue, the use of the anonymous URI in the AcksTo EPR is only a
problem in cases where the AS/RMS subsequently "uses the sequence to engage
in"* message exchanges for which there is no backchannel (e.g. one-way
operations using a SOAP/HTTP implementation which does not put SOAP
envelopes in the HTTP response). If the AS/RMS uses the sequence for messages
conforming to a synchronous "send a SOAP request over HTTP, wait for the SOAP
reply in the HTTP response" pattern there is no problem because there is a
backchannel for acknowledgements to return upon. Thus it seems unnecessarily
restrictive for an RMS to forgo all uses of the anonymous URI
for the AcksTo EPR simply because it "knows" that, in some cases,
there is no SOAP backchannel.
*
Note; when I say "uses the sequence to engage in" I am implying that every
message that carries a SOAP header with the same <wsrm:Identifier> is
part of some logical application-level abstraction and that all the
messages with that identifier will conform to the same interaction pattern. I
know that this does not match your model of independent, intermediary RMS/RMD
pairs that carry all "traffic that is to be transmitted reliably" between two
clusters of services.
All of this still
begs the question of how someone implementing an RMS or an RMD "knows" that the
use of the anonymous URI in the AcksTo EPR might be problematic? The only thing
we say about the AcksTo EPR in the current spec is (lines 262-264 of
wsrm-1.1-spec-cd-02) is:
- Implementations MUST NOT use an endpoint reference in the AcksTo
element that would prevent the sending of Sequence Acknowledgements back to
the RM Source. For example, using the WS-Addressing "none" IRI would make it impossible for the
RM Destination to ever send Sequence Acknowledgements.
The proposal listed here (http://docs.oasis-open.org/ws-rx/issues/ReliableMessagingIssues.xml#i061)
does not mention the possibility that there may not be a SOAP backchannel
for the acknowledgements to flow back on. I'm wondering how we expect a
developer to know precisely when and where the use of the anonymous URI in the
AcksTo EPR might be problematic when our spec says nothing about the
subject?
- g
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