Atomic Data Access in Distributed Hash Tables

Abstract

While recent proposals for distributed hashtables address the crucial issues of communication efficiency and load balancing in dynamic networks,they do not guarantee strong semantic on concurrent data accesses. While it is well known that guaranteeing availability and consistency in an asynchronou and failure prone network is impossible, we believe that guaranteeing atomic semantics is crucial for establishing DHT a a robust middleware service. In this paper, we describe a simple DHT algorithm that maintain the atomicity property regardless of timing, failures, or concurrency in the system. The livene of the algorithm, while not dependent on the order of operation in the system, requires that node failures do not occur and that the network eventually delivers all messages to intended recipients. We outline how state machine replication technique can be used to approximate these requirements even in failure-prone network,and examine the merit of placing the responsibility for fault-tolerance and reliable delivery below the level of the DHT algorithm.