Middleware based data replication providing snapshot isolation

  • Authors:

  • Yi Lin;Bettina Kemme;Marta Patiño-Martínez;Ricardo Jiménez-Peris

  • Affiliations:

  • McGill Univ. Montreal;McGill Univ. Montreal;Univ. Politecnica de Madrid;Univ. Politecnica de Madrid

  • Venue:
  • Proceedings of the 2005 ACM SIGMOD international conference on Management of data
  • Year:
  • 2005

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Abstract

Many cluster based replication solutions have been proposed providing scalability and fault-tolerance. Many of these solutions perform replica control in a middleware on top of the database replicas. In such a setting concurrency control is a challenge and is often performed on a table basis. Additionally, some systems put severe requirements on transaction programs (e.g., to declare all objects to be accessed in advance). This paper addresses these issues and presents a middleware-based replication scheme which provides the popular snapshot isolation level at the same tuple-level granularity as database systems like PostgreSQL and Oracle, without any need to declare transaction properties in advance. Both read-only and update transactions can be executed at any replica while providing data consistency at all times. Our approach provides what we call "1-copy-snapshot-isolation" as long as the underlying database replicas provide snapshot isolation. We have implemented our approach as a replicated middleware on top of PostgreSQL replicas. By providing a standard JDBC interface, the middleware is completely transparent to the client program. Fault-tolerance is provided by automatically reconnecting clients in case of crashes. Our middleware shows good performance in terms of response times and scalability.