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OASIS Business Transaction Protocol: Multi-party Coordination for Commercial Collaborations

OASIS Business Transaction Protocol: Multi-party Coordination for Commercial Collaborations. peter.furniss@choreology.com alastair.green@choreology.com tony.fletcher@choreology.com March 2002. Goals. Inter-organizational multi-party coordination Targetting Web Services, but not only WS

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OASIS Business Transaction Protocol: Multi-party Coordination for Commercial Collaborations

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  1. OASIS Business Transaction Protocol:Multi-party Coordination for Commercial Collaborations peter.furniss@choreology.com alastair.green@choreology.com tony.fletcher@choreology.com March 2002

  2. Goals • Inter-organizational multi-party coordination • Targetting Web Services, but not only WS • Accommodate Long-running Transactions

  3. Requirements • Coordination of autonomous parties • Relationships are governed by contracts, rather than the dictates of a central design authority • Drop less ACID • Multiple possible successful outcomes to a transaction • Relaxed isolation, volatile results  • Interoperation • Using XML, over multiple communications protocols • Discontinuous service • Work unit lifespans exceed sub-system MTBFs 

  4. The key BTP roles Client side Service side Client Service Initiator/Terminator Application Enroller Protocol Factory Transaction Decider(Composer or Coordinator) Participant

  5. Ask Factory to Create top coordinator Client side Service side Client Service Initiator/Terminator Application BEGIN / BEGUN&CONTEXT Enroller Protocol Factory creates Coordinator Participant

  6. Send Application Message with CONTEXT Client side Service side Client Service CONTEXT Initiator/Terminator Application Enroller Protocol Factory Coordinator Participant

  7. Service creates and causes ENROL of Participant Client side Service side Client Service Initiator/Terminator Application Enroller Protocol ENROL / ENROLLED Factory creates Coordinator Participant

  8. Send Application Reply with CONTEXT_REPLY Client side Service side Client Service CONTEXT_REPLY Initiator/Terminator Application Enroller Protocol Factory Coordinator Participant

  9. CONFIRM_TRANSACTION Client side Service side Client Service Initiator/Terminator Application CONFIRM_TRANSACTION Enroller Protocol Factory Coordinator Participant

  10. Two-phase Confirmation: PREPARE phase Client side Service side Client Service Initiator/Terminator Application Enroller Protocol PREPARE / PREPARED Factory Coordinator Participant

  11. Two-phase Confirmation: Outcome phase Client side Service side Client Service Initiator/Terminator Application Enroller Protocol CONFIRM / CONFIRMED Factory Coordinator Participant

  12. TRANSACTION_CONFIRMED Reply Client side Service side Client Service Initiator/Terminator Application TRANSACTION_CONFIRMED Enroller Protocol Factory Coordinator Participant

  13. Cancellation • Example showed CONFIRM/CONFIRMED • Terminating application can also issue CANCEL_TRANSACTION • Or the CONFIRM_TRANSACTION can fail, leading to TRANSACTION_CANCELLED • CANCEL/CANCELLED exchange with Participant

  14. Service and Participant: Provisional effect and Counter-effect • Forward Operations create a provisional effect… • … and durably record information needed by Participant • Participant uses log to perform final effect or tocounter-effect Client side Service side Service A (provisional) Log of A finalise A CONFIRM counter A CANCEL Participant

  15. Provisional, final and counter effects • Provisional effect • Apparently – the application’s forward operation • Really – just do what is needed to do either final or counter • Do something, log (persist) information for final or counter • Final effect – action on CONFIRM • Final effect is action on CONFIRM • Complete the operation so it did happen • Use the information in the log, discard log • Counter effect – action on CANCEL • Counter-effect is action on CANCEL • Make it that the application did not happen (or unhappened) • Use the information in the log, discard the log • May be perfect or have side effects

  16. 2PC  ACID • Example #1: Compensation strategy • Provisional Effect includes committed database updates or message enqueues • E.g. debit credit card account • Final effect is no-op • Counter-effect involves compensatory action • E.g. contra-credit credit card • In whole or in part depending on business contract • Example #2: XA RM • Provisional Effect posits but does not commit database updates or MQPUTs • Final effect invoke xa_commit • Throw away RM undo logs • Counter-effect is to invoke xa_rollback • Process RM undo logs

  17. Service decides what a Participant covers • Service can combine provisional effects into one Participant • Single confirm or cancel signal • Application specific • Service had the right to create and enrol two participants Operation Group Client side Service side Service A B Log of A, B finalAB CONFIRM counterAB CANCEL Participant

  18. Superior-Inferior Relationship - outcome Superior PREPARE CONFIRM CANCEL Inferior ComposerCoordinatorSub-composerSub-coordinator PREPARED CONFIRMED CANCELLED Sub-composerSub-coordinatorParticipant

  19. Transaction Tree - 1 Inferior [Participant] Superior [e.g. Coordinator] Inferior [Participant] Inferior [Participant]

  20. Transaction Tree - 2 Inferior [Participant] Superior [e.g. Coordinator] Inferior/Superior [e.g. Sub-coordinator] Inferior [Participant] Inferior [Participant]

  21. Transaction Tree - 3 Inferior/Superior [e.g. Sub-coordinators] Inferior [Participant] Superior [Composer] Inferior [Participant] Inferior [Participant]

  22. Coordination Hub: control and outcome relationships Client Service Client Service Application Initiator/Terminator control Enroller outcome Protocol Transaction Decider(Composer or Coordinator) Participant Factory Coordination Hub

  23. Shipping Atom  Goods Atom  Cohesions: The Concept Buyer Services Inferior Coordinators Superior Cohesion Terminator Superior Composer #1 Inferior Participant #2 Inferiors Participants

  24. Shipping Atom  Goods Atom  Cohesions: PREPARE both Atoms Buyer Services Inferior Coordinators Superior Cohesion Terminator Superior Composer #1 PREPARE P PREPARE_INFERIORS #1, #2 Inferior Participant P #2 PREPARE PREPARE Inferiors Participants

  25. Shipping Atom  Goods Atom  Cohesions: both are PREPARED Buyer Services Inferior Coordinators Superior Cohesion Terminator Superior Composer #1 P’d #1 PREPARED P’d INFERIOR_ STATUSES Inferior Participant P’d #2 P’d #2 PREPARED PREPARED Inferiors Participants

  26. Shipping Atom  Goods Atom  Cohesions: CONFIRM #1 (  CANCEL #2) Buyer Services Inferior Coordinators Superior Cohesion Terminator Superior Composer CONFIRM #1 CONFIRM CONFIRM_TRANSACTION #1 Inferior Participant CANCEL #2 CANCEL CANCEL Inferiors Participants

  27. Shipping Atom  Goods Atom  Cohesions: #1 CONFIRMED, #2 CANCELLED Buyer Services Inferior Coordinators Superior Cohesion Terminator Superior Composer #1 CO’d #1 CONFIRMED CO’d INFERIOR_ STATUSES Inferior Participant CA’d #2 CA’d #2 CANCELLED CANCELLED Inferiors Participants

  28. Cohesions rely on “Open-top” Coordinator “Open-top” Atom Coordinators Cohesion Terminator Cohesion Composer #1 PREPARE / PREPARED CONFIRM_TRANSACTION #1 CONFIRM / CONFIRMED #1 CO’d INFERIOR_ STATUSES PREPARE / PREPARED #2 CA’d CANCEL / CANCELLED #2

  29. S S S S O O O O Example: Cross-company Securities Trading Stock and option – from different market makers Hedge Fund ABN Amro Nomura Commerz DKB

  30. S S S S O O O O Example: Cross-company Securities Trading Each market maker makes two guaranteed time-qualified quotes = PREPARED, from 2 participants each Hedge Fund ABN Amro Nomura Commerz DKB

  31. S S S S O O O O Example: Cross-company Securities Trading Hedge fund chooses one of each, cancels the others (or lets them timeout) Hedge Fund         ABN Amro Nomura Commerz DKB

  32. Participant time-out • Inferior can limit duration of its preparedness • Inferior threatens to auto-cancel or confirm after (at least) n seconds • Inferior qualifies the PREPARED message • Prevents coordinator hogging service provider’s resources • Independent organization likely to demand this power • Risks contradiction – which will be reported • Superior can negotiate the time limit • Superior qualifies the PREPARE message • Prevents service wasting coordinator’s time

  33. Failure Recovery • Protocol incorporates recovery after failure • Superior system, Inferior system or network may fail • Must try to re-establish Superior-Inferior relationship • Allows outcomes to be replayed • Standard “presumed abort” protocol • No durable record (log) equals absence of decision • Default decision (in absence of evidence to contrary): CANCEL • Bi-directional recovery initiation • Superior can attempt to contact logged Inferiors • Inferior can attempt to contact logged Superior

  34. Active phase recovery • Allows Superior/Inferior re-synch after failures • Standard 2PC protocols allow recovery only after prepared • BTP treats failure as a potential interruption • Standard 2PC protocols treat any failure as cause to cancel • Permitted, not required • Presume-abort still applies – just it isn’t compulsory • Useful for long-running transactions • Useful with interruptible communications

  35. Messaging • All BTP messages are XML documents • Can be compounded for optimization • “One-shot requests”: only 2 WAN messages instead of 6 • Application response + ENROL/PREPARE • “One wire” application topologies • All traffic between two business entities over a single, authenticated link • Binding of abstract set to SOAP • Defined in the specification • Other bindings are possible • To any underlying communications protocol stack

  36. Qualifiers • Qualifiers can be embedded in messages • Some are defined within BTP specification • Implementers/applications can define their own • Identified by URI • Allows extensions to protocol messages • trading parties could use to add security data • Implementor could use to add full nested transactions • Allows application data to travel with protocol • Example: confirm a two-way quote • Must include “buy” or “sell” in CONFIRM

  37. Business Transactions and Business Process • BTP complements BP/Collaboration frameworks • A coordinated, mutually understood outcome requires • Special messages and acknowledgements • Consistent, durable record of decisions • Asynchronous failure recovery operations • These features are tricky, error-prone and intrusive • “Build or buy” • BTP lets business people concentrate on business process • Puts housekeeping work in the background • Minimizes application exchanges • Reduces complexity of collaborative process schemas or scripts • Reduces conformance testing • Deploy new trading protocols or conventions more quickly

  38. Internal Business Process Internal Business Process Collaboration Process BTP BTP Collaboration Process Do Business Together with Business Transactions • Ensuring Collaboration for XML Services

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