A new approach to developing and implementing eager database replication protocols

Abstract

Database replication is traditionally seen as a way to increase the availability and performance of distributed databases. Although a large number of protocols providing data consistency and fault-tolerance have been proposed, few of these ideas have ever been used in commercial products due to their complexity and performance implications. Instead, current products allow inconsistencies and often resort to centralized approaches which eliminates some of the advantages of replication. As an alternative, we propose a suite of replication protocols that addresses the main problems related to database replication. On the one hand, our protocols maintain data consistency and the same transactional semantics found in centralized systems. On the other hand, they provide flexibility and reasonable performance. To do so, our protocols take advantage of the rich semantics of group communication primitives and the relaxed isolation guarantees provided by most databases. This allows us to eliminate the possibility of deadlocks, reduce the message overhead and increase performance. A detailed simulation study shows the feasibility of the approach and the flexibility with which different types of bottlenecks can be circumvented.

Managing Multiple Isolation Levels in Middleware Database Replication Protocols

“…Many data replication protocols have been published for years [5,6,11,22], and they have always been centred on a single isolation level. Indeed, when multiple isolation levels have been presented [11], a separate protocol has been designed for each of them.…”

“…Indeed, when multiple isolation levels have been presented [11], a separate protocol has been designed for each of them. There is no problem with this approach, since it makes possible a thorough description, discussion or justification for each protocol.…”

Pronto: High availability for standard off-the-shelf databases

“…The approach in [28] is to modify the underlying databases so that all write locks for a transaction can be acquired in a single atomic step.…”

Rigorous Design of Fault-Tolerant Transactions for Replicated Database Systems Using Event B

“…The algorithms ensuring globally ordered delivery of messages may be coupled with the provisions to provide fault tolerance in the event of failures. Several approaches has been proposed for management of replicated data using group communication primitives [5,18,20,26,30]. The application of formal methods to a replication algorithm is considered in [16].…”

“…Though serializability is the highest correctness criteria, it is too restrictive in practice. Various degrees of isolation to address this problem has been studied in [20].…”