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Subject: Re: [ws-tx] Issue 041 - WS-AT: Invalid events should not cause definedtransitions
Commit Decision in the PV means: the participant inquired of itself (of
the "application" that is driven by the state machine) whether it was
ready to prepare, rollback or send read-only. Commit Decision = the
participant has answered its own enquiry with "yes, I want to prepare". The least comprehensible in the PV is "All Forgotten" which means: I am going to send read-only and then forget this transaction. It might be easier to think of this as "Read Only Decision". Alastair Peter Furniss wrote: Alastair asked "Peter, I don't understand how a message like this could be used to respond to internal events. To whom would it be delivered?" I was imprecise - it wouldn't actually be sent as a result of the internal event, but a currently illegal internal event (e.g. Rollback Decision in PreparedSuccess state) would cause a transition to Aborting (or a variant of Aborting), InconsistentInternalState would then be an appropriate response to Commit. (Similarly for Commit Decision going to Committing state [1]) However, that would be a heuristic decision and heuristic report, which is out of charter. Peter ([1]: what is Commit Decision supposed to mean for the participant side - it surely can't mean the same thing when it occurs in Preparing as it does in Committing. - this is really a 048 question) -----Original Message----- From: Alastair Green [mailto:alastair.green@choreology.com] Sent: 12 May 2006 10:27 To: Mark Little Cc: Peter Furniss; Ram Jeyaraman; ws-tx@lists.oasis-open.org Subject: Re: [ws-tx] Issue 041 - WS-AT: Invalid events should not cause defined transitions I think it's pretty obvious that these two messages are intended for the same purpose (protocol error; non-conformant counterpart, all bets are off). I would like to see an explanation from the original author companies for this duplication, and a proper argument that it is not redundancy. Without that it seems very clear the AT message should go. I also agree that no state transition should follow a protocol error, i.e. the approach taken in Peter's sparse + text solution is correct. Sparse versus verbose is a stylistic question. Peter, I don't understand how a message like this could be used to respond to internal events. To whom would it be delivered? Alastair Mark Little wrote:+1 Peter Furniss wrote:I agree that distinguishing circumstances of faults is generally a good thing. Equally, one can also have too much of a good thing :-) But the problem with InconsistentInternalState is that the definitionin the text doesn't correspond with the use in the state table. Definition says its when the participant cannot fulfil its obligations. That presumably would be apply when a participant has gone prepared but now cannot obey the Commit or Rollback it receives (which sounds suspiciously like a heuristic warning which would be out of charter for this TC). But the use in the state tables is that Participant sends it when it receives contradictory messages from the coordinator - sending both Rollback and Commit (in either order). That would seem to be no different from any of the other InvalidState circumstances = "I am receiving messages that should not happen in the state I am now in - either you have sent a message you shouldn't have done or I've made astate transition I shouldn't have done". Receiving InvalidState should certainly cause an alert - but it's a pretty serious one, because someone isn't conformant - the parties aren't talking WS-AT any more. InconsistentInternalState could be used in other circumstances, aligned with its definition. It might even appear in the state table - perhaps as action triggered from an internal event (which currentlyappears as N/A, curiously) Peter --------------------------------------------------------------------- --- *From:* Ram Jeyaraman [mailto:Ram.Jeyaraman@microsoft.com] *Sent:* 06 May 2006 01:42 *To:* ws-tx@lists.oasis-open.org *Subject:* RE: [ws-tx] Issue 041 - WS-AT: Invalid events should not cause defined transitions As a consumer of a fault, I would rather receive a more specific fault such as InconsistentInternalState, since it offer more specificinformation and helps distinguish from other possible error states. Specifically, upon receipt of an InconsistentInternalState fault, theconsumer may send an alert containing the specific cause, which is otherwise not possible, if it receives a more generic fault. Why should this fault be removed? --------------------------------------------------------------------- --- *From:* Ram Jeyaraman [mailto:Ram.Jeyaraman@microsoft.com] *Sent:* Tuesday, March 28, 2006 10:25 AM *To:* ws-tx@lists.oasis-open.org *Subject:* [ws-tx] Issue 041 - WS-AT: Invalid events should not causedefined transitions This is identified as WS-TX issue 041. Please ensure follow-ups have a subject line starting "Issue 041 - WS-AT: Invalid events should not cause defined transitions". --------------------------------------------------------------------- --- *From:* Peter Furniss [mailto:peter.furniss@erebor.co.uk] *Sent:* Monday, March 27, 2006 1:33 PM *To:* ws-tx@lists.oasis-open.org *Subject:* [ws-tx] New issue: WS-AT: Invalid events should not cause defined transitions Issue name -- WS-AT: Invalid events should not cause defined transitions PLEASE DO NOT REPLY TO THIS EMAIL OR START A DISCUSSISON THREAD UNTILTHE ISSUE IS ASSIGNED A NUMBER. The issues coordinators will notify the list when that has occurred. Target document and draft: Protocol: WS-AT Artifact: spec Draft: AT spec cd 1 Link to the document referenced: http://www.oasis-open.org/committees/download.php/17311/wstx-wscoor-1 .1-spec-cd-01.pdf http://www.oasis-open.org/committees/download.php/17325/wstx-wsat-1.1 -spec-cd-01.pdf Section and PDF line number: ws-at section 10, lines 503/505 coordinator table: Committed/Active, Committed/Preparing pariticipant table: Commit/Active, Commit/Preparing ws-at: seciton 6.1, line 371 Issue type: Design/Editorial Related issues: Issue Description: The receipt of a message when the receiver is in a state such that the event cannot occur between correct implementations should not cause a state transition and allow the transaction to complete "successfully". There is no need to distinguish "InvalidState" and "InconsistentInternalState". Issue Details Background InvalidState is defined in WS-Coordinator as being an unrecoverable condition, and in all the cases where it is a defined response in the WS-AT tables can only occur if one of the implementations is broken/bugged (apart than the volatile Prepared/None case, see separate issue). Providing a defined state transition, as if the circumstance were expected and could be recovered from is inappropriate. There can be no graceful completion of the protocol -it has gone fundamentally wrong. This does not preclude an implementation from attempting to tidy up and protecting its own resources, but there should be no required state transition for the implementation. The protocol exchange has gone off the map. The use of InconsistentInternalState to distinguish two cases where an invalid event occurs is unnecessary (and the definition in line 371 does not align with the use in the table - it is probably the coordinator that has been sending wrong messages). The use of InvalidState is appropriate in all cases. Proposed resolution The clearest solution would be to make invalid cells in the state tables empty, for the cells currently shown as InvalidState or InconsistentInternalState, and also for the N/A cells and explain this with text: "Where a cell is shown as empty - if the row is for an Inbound Event, an WS-C Invalid State faultshould be returned. The subsequent behaviour of the implementation isundefined. - if the row is for an Internal Event, event cannot occur in thisstate. A TM should view these occurences as serious internal consistency issues." Having invalid cells empty makes it significantly easier to read and check the state tables. It becomes much clearer that they are essentially "sparse" and the path through the table can be followed more easily. |
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