Application-independent reconciliation for nomadic applications

  • Authors:
  • Marc Shapiro;Antony Rowstron;Anne-Marie Kermarrec

  • Affiliations:
  • Microsoft Research Ltd., Cambridge CB2 3NH, United Kingdom;Microsoft Research Ltd., Cambridge CB2 3NH, United Kingdom;Microsoft Research Ltd., Cambridge CB2 3NH, United Kingdom

  • Venue:
  • EW 9 Proceedings of the 9th workshop on ACM SIGOPS European workshop: beyond the PC: new challenges for the operating system
  • Year:
  • 2000

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Abstract

We describe attempts to build an application-independent model to support reconciliation of diverged replicas of shared objects. While replicas are disconnected from one another, actions on the shared objects are recorded in a log. An action is composed of a precondition, an operation and a postcondition. When reconnecting, the system attempts to reconcile the divergent replicas, in several phases. A symbolic phase merges the separate logs, creating one or more schedules, such that preconditions from one log remain true despite the postconditions introduced by the other. Then, a simulation phase checks the possible outcomes by actually applying the schedules to scratch copies of the shared objects. Finally, a selection phase allows users or applications to select one of the candidate schedules.Our approach supports sharing general objects, where one update may reference multiple objects (not just a single file or database). Compared to previous work on log-based reconciliation, our logs capture more semantic information and provide the application with more powerful and finer control over the outcome of reconciliation.