Bumper: Sheltering Transactions from Conflicts

This paper addresses the issue of maximizing the efficiency and scalability of distributed transactional platforms, by introducing Bumper, a set of innovative techniques to minimize aborts of transactions in high-contention scenarios. At its core, Bumper relies on two key ideas: (1) sparing update transactions from spurious aborts when they access concurrently updated data, by attempting to serialize them in the past via a novel distributed concurrency control scheme that we call Distributed Time-Warping (DTW), and (2) avoiding aborts due to contention hot spots (that cannot be tackled by DTW) via a novel programming abstraction, called delayed actions, which allows to efficiently serialize, in an abort-free fashion, the execution of conflict-prone data manipulations. The techniques used in Bumper can be applied to a wide variety of transactional replication protocols to enhance their performance in contention intensive workloads. In this paper we show how they can be integrated with SCORe, a recent, highly-scalable genuine partial replication protocol. By means of an extensive evaluation using well-known benchmarks and a cluster of 160 nodes, we show that Bumper can boost performance up to 3x in conflict-intensive workloads, while imposing negligible (2.5%) overheads in uncontended scenarios.