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Subject: RE: [ws-tx] Proposed AT CP state table
Here is the normalized state table that represents the
case where duplicate Commit or Rollback message would receive Unknown
Transaction. I believe that this does not prevent a coordinator implementation
from returning Committed or Aborted, if it chooses to, during the transitory 2PC
time window.
-----Original Message----- Dear all, Ram and I have been working on the AT CP state table
issue, and I think we've converged to a considerable degree, but not fully. I'm attaching my proposal. There are two points outstanding between Choreo and
Microsoft: 1. Should a participant sending Aborted, leading to an
active state rollback (cell Rollback Decision/Active) induce a "Send
Aborted" action (not shown in my proposal)? This would mean that a CP participant would receive a
spontaneous Aborted outcome message before it had sent Commit or Rollback to
the coordinator. I do not object to this per se, but am worried that this turns
a request-response model into a full one-way model, which would preclude a thin
client implementation of a CP participant (on which point I have raised a
separate issue). 2. Should the state table show Committing and Aborting
states, allowing a precise response (Committed or Aborted) to be returned
during the processing of the 2PC protocol across the underlying participants?
This is the approach in my proposal. Ram, I believe, accepts that it is legitimate for an
implementation to do this (our product does so), but thinks that the transition
to state None should occur immediately that Aborted is received, or internal
event Commit Decision arises, thereby removing the Committing and Aborting
states in the proposed table. This would mean that any duplicate Commit or Rollback
message would receive Unknown Transaction. If I can be persuaded that this
approach does not prevent returning Committed or Aborted after the None
transition (i.e. that the implementation was free to communicate outcome
knowledge if it happened to still have it) then I would be happy with that, but
I believe that this approach would in fact make that illegal (because contrary
to the state table). Yours, Alastair |
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