New issue - WS-BA: Coordinator informed immediately of autonomous partic

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Subject: New issue - WS-BA: Coordinator informed immediately of autonomous participant decision

Issue name -- WS-BA: Coordinator informed immediately of autonomous participant decision

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Target document and draft:

Protocol: WS-BA

Artifact: spec

Draft: BA spec cd 2

Link to the document referenced:

http://www.oasis-open.org/committees/download.php/18819/wstx-wsba-1.1-spec-cd-02.doc

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

Allow Closed and Compensated to be sent by a Participant from Completed state, triggering transitions to new states ("Auto-closed", "Auto-compensated"). If the "right" message arrives - i.e. Close or Compensate, respectively - resend the Closed or Compensated and transition to Ended. (The resend may not be needed - the earlier message may be perceived at the coordinator as the reply, but resending avoids forcing the coordinator to remember the first message) If the "wrong" message arrives (i.e. Compensate in Auto-closed, Close in Auto-compensate), send Fault and transit to Faulting, awaiting Faulted as usual.

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.)