RE: [ws-rx] i061 proposal / directions

["Gilbert Pilz" <Gilbert.Pilz@bea.com>]

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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.

 

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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