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Subject: Issue 082 - WS-BA: Coordinator informed immediately of autonomous participant decision
This is identified as WS-TX
issue 082. Please ensure follow-ups have a subject line starting
"Issue 082 - WS-BA: Coordinator informed immediately of autonomous
participant decision". From: Peter Furniss
[mailto:peter.furniss@erebor.co.uk] sorry
- would have sent this one earlier, but there were complications ---------------------------------------------------- Issue
name -- WS-BA: Coordinator informed immediately of autonomous participant
decision Section
and PDF line number: section , lines Issue
type: Design Related
issues: A
Participant in Completed state that has had to finalise the application
information should be permitted to send Closed or Compensated immediately,
rather than wait to respond to the instruction from the coordinator. Services
involved in loosely-coupled business activities, of the sort targeted by WS-BA
are commonly more-or-less autonomous. They are cooperating in the Business
Activity, but there are other drivers and requirements on their behaviour. This
applies whether the systems involved in the Business Activity are from
different organizations (where the autonomy is obvious) or are just different
applications in one organization (where legacy applications, for example, often
have other, primary goals, and the Business Activity is an integration) Consequently,
it must be expected that services will reserve the right to make and apply
their own decision to the work they are responsible for, despite their promise
to await the decision of the controlling application. This is analogous to a
heuristic decision in a classic ACID transaction, but is likely to be more
common. Since
such an autonomous decision will threaten, and may (like a heuristic decision)
destroy the consistency target that led to use of WS-BA, it is important that
it can be signalled as soon as possible. If the warning arrives in time, it is
possible (given that Business Activities may be long-running) that the
controller can cope with the decision – either cancelling/compensating the
whole activity, or ensuring that the rebellious participant is accommodated
somehow. (This is especially likely with participant-completion) At
present, WS-BA does not give a chance for the participant to report an
autonomous decision, until it is informed of the coordinator’s decision. Since
WS-BA is based on one-way messages it would seem fairly straightforward to
allow the participant to reply before it is asked. If the answer is
"right", the protocol completes with this pre-emptive reply; if it is
"wrong", the relationship goes into the normal Fault/Faulted
exchange. Proposed
resolution At
the coordinator, receipt of Closed or Compensated in Completed state causes no
action and remains in the same state. It is not "ignored", because
this is the trigger for the coordinator/application to do something about the
situation, but there is no mandated protocol action. Receipt
at the coordinator of Closed or Compensated in the wrong state (Compensating,
Closing) is ignored - a Fault message will arrive later. (It is not worth
complicating matters further by allowing a pre-emptive Faulted, thought it
would work.)
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