Abstract
Current techniques for reconciling disconnected changes to optimistically replicated data often use version vectors or related mechanisms to track causal histories. This allows the system to tell whether the value at one replica dominates another or whether the two replicas are in conflict. However, current algorithms do not provide entirely satisfactory ways of repairing conflicts. The usual approach is to introduce fresh events into the causal history, even in situations where the causally independent values at the two replicas are actually equal. In some scenarios these events may later conflict with each other or with further updates, slowing or even preventing convergence of the whole system.
To address this issue, we enrich the set of possible actions at a replica to include a notion of explicit conflict resolution between existing events, where the user at a replica declares that one set of events dominates another, or that a set of events are equivalent. We precisely specify the behavior of this refined replication framework from a user’s point of view and show that, if communication is assumed to be “reciprocal” (with pairs of replicas exchanging information about their current states), then this specification can be implemented by an algorithm with the property that the information stored at any replica and the sizes of the messages sent between replicas are bounded by a polynomial function of the number of replicas in the system.
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References
Parker Jr., D.S., Popek, G.J., Rudisin, G., Stoughton, A., Walker, B.J., Walton, E., Chow, J.M., Edwards, D., Kiser, S., Kline, C.: Detection of mutual inconsistency in distributed systems. IEEE Trans. Software Eng (USA) SE-9(3), 240–247 (1983)
Malkhi, D., Terry, D.: Concise version vectors in winFS. In: Fraigniaud, P. (ed.) DISC 2005. LNCS, vol. 3724, pp. 339–353. Springer, Heidelberg (2005)
Kang, B.B., Wilensky, R., Kubiatowicz, J.: The hash history approach for reconciling mutual inconsistency. In: 23rd IEEE International Conference on Distributed Computing Systems (ICDCS 2003) (2003)
Foster, J.N., Greenwald, M.B., Kirkegaard, C., Pierce, B.C., Schmitt, A.: Schema-directed data synchronization. Technical Report MS-CIS-05-02, University of Pennsylvania, Supersedes MS-CIS-03-42 (2005)
Pierce, B.C., et al.: Harmony: A synchronization framework for heterogeneous tree-structured data (2006), http://www.seas.upenn.edu/~harmony/
Foster, J.N., Greenwald, M.B., Kirkegaard, C., Pierce, B.C., Schmitt, A.: Exploiting schemas in data synchronization. Journal of Computer and System Sciences (to appear, 2006); Extended abstract in Database Programming Languages (DBPL) (2006)
Demers, A., Greene, D., Hauser, C., Irish, W., Larson, J., Shenker, S., Sturgis, H., Swinehart, D., Terry, D.: Epidemic algorithms for replicated database maintenance. In: Proceedings of PODC 1987 (1987)
Fidge, C.: Logical time in distributed computing systems. Computer 24(8), 28–33 (1991)
Mattern, F.: Virtual time and global states of distributed systems. In: Cosnard, M., et al. (eds.) Parallel and Distributed Algorithms: proceedings of the International Workshop on Parallel & Distributed Algorithms, pp. 215–226. Elsevier Science Publishers B.V, Amsterdam (1989)
Kumar, P.: Coping with conflicts in an optimistically replicated file system. In: 1990 Workshop on the Management of Replicated Data, Houston, TX, pp. 60–64 (1990)
Satyanarayanan, M., Kistler, J.J., Kumar, P., Okasaki, M.E., Siegel, E.H., Steere, D.C.: Coda: A highly available file system for a distributed workstation environment. IEEE Transactions on Computers 39(4), 447–459 (1990)
Kumar, P., Satyanarayanan, M.: Flexible and safe resolution of file conflicts. In: Proceedings of the annual USENIX 1995 Winter Technical Conference, New Orleans, LA, pp. 95–106 (1995)
Guy, R.G., Reiher, P.L., Ratner, D., Gunter, M., Ma, W., Popek, G.J.: Rumor: Mobile data access through optimistic peer-to-peer replication. In: Proceedings of the ER Workshop on Mobile Data Access, pp. 254–265 (1998)
Ekenstam, T., Matheny, C., Reiher, P.L., Popek, G.J.: The Bengal database replication system. Distributed and Parallel Databases 9(3), 187–210 (2001)
Baldoni, R., Raynal, M.: A practical tour of vector clock systems. IEEE Distributed Systems Online 3(2) (2002), http://dsonline.computer.org/0202/features/bal.htm
Pierce, B.C., Vouillon, J.: What’s in Unison? A formal specification and reference implementation of a file synchronizer. Technical Report MS-CIS-03-36, Dept. of Computer and Information Science, University of Pennsylvania (2004)
Almeida, P.S., Baquero, C., Fonte, V.: Panasync: dependency tracking among file copies. In: EW 9: Proceedings of the 9th workshop on ACM SIGOPS European workshop, pp. 7–12. ACM Press, New York (2000)
Sarin, S.K., Lynch, N.A.: Discarding obsolete information in a replicated database system. IEEE Transactions on Software Engineering 13(1), 39–47 (1987)
Wuu, G.T.J., Bernstein, A.J.: Efficient solutions to the replicated log and dictionary problems. In: Principles of Distributed Computing, pp. 233–242 (1984)
Howard, J.H.: Reconcile user’s guide. Technical Report TR99-14, Mitsubishi Electronics Research Lab. (1999)
Richard, B., Nioclais, D.M., Chalon, D.: Clique: A transparent, peer-to-peer replicated file system. In: Chen, M.-S., Chrysanthis, P.K., Sloman, M., Zaslavsky, A. (eds.) MDM 2003. LNCS, vol. 2574, pp. 351–355. Springer, Heidelberg (2003)
Saito, Y., Shapiro, M.: Replication: Optimistic approaches. Technical Report HPL-2002-33, HP Laboratories Palo Alto (2002)
Terry, D.B., Theimer, M.M., Petersen, K., Demers, A.J., Spreitzer, M.J., Hauser, C.H.: Managing update conflicts in Bayou, a weakly connected replicated storage system. In: Proceedings of the 15th ACM Symposium on Operating Systems Principles (SOSP-15), Copper Mountain Resort, Colorado, pp. 172–183 (1995)
Kermarrec, A.M., Rowstron, A., Shapiro, M., Druschel, P.: The IceCube approach to the reconciliation of diverging replicas. In: ACM SIGACT-SIGOPS Symposium on Principles of Distributed Computing (PODC), Newport, Rhode Island, pp. 210–218 (2001)
Ceri, S., Houtsma, M.A.W., Keller, A.M., Samarati, P.: Independent updates and incremental agreement in replicated databases. Distributed and Parallel Databases 3(3), 225–246 (1995)
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Greenwald, M.B., Khanna, S., Kunal, K., Pierce, B.C., Schmitt, A. (2006). Agreeing to Agree: Conflict Resolution for Optimistically Replicated Data. In: Dolev, S. (eds) Distributed Computing. DISC 2006. Lecture Notes in Computer Science, vol 4167. Springer, Berlin, Heidelberg. https://doi.org/10.1007/11864219_19
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DOI: https://doi.org/10.1007/11864219_19
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