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Subject: interposition
Hopefully this is all implicit in what everyone's assuming, but to try to
clarify what I mean by interposition and participation.
We all seem to be agreed that a participant takes part in the termination
protocol. However, a participant can't simply do sub-coordination: that's
different functionality. For example, a book purchasing participant can't
suddenly decide to sub-coordinate on behalf of other participants it may talk
to. The functionality required for sub-coordination is different from "straight
forward" participation. A sub-coordinator needs to be a proxy for the
coordinator, and this has implications on recovery and its interface (e.g., it
now has to have the enlist etc. interface, which a "normal" participant doesn't
need to have), as well as context propagation.
Therefore, being a subcoordinator is:
(i) a conscious choice of the implementer to provide that kind of
functionality.
(ii) a conscious choice of the application/participant to use that
functionality.
If a participant has the sub-coordinator interface and functionality then
you can (essentially) flick a switch and enable/disable that functionality.
However, if it doesn't then you can't. I am in no way saying that BTP should
mandate that all participants should be able to behave as subcoordinators. It's
a choice, and we should allow it. My original email of days ago was produced
because it appeared as though we were mandating the opposite, i.e., that no
participant could behave as a subcoordinator, and all participants, whether
directly or indirectly communicated with, had to register with the root (and
only) coordinator.
Mark.
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SENDER : Dr. Mark Little, Architect (Transactions), HP Arjuna Labs PHONE : +44 191 206 4538, FAX : +44 207 670 1964 EMAIL : mark@arjuna.com |
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