数据库集群的"无应答严次序发布传播"复制策略

数据库集群服务器的关键技术是数据复制，本文在对比分布式文件系统、可靠型多播、对象组服务以及分布式内存等技术的基础上，提出了“无应答严次序发布传播”复制策略，“发布传播”类似但不同于“发布订阅”模型。该策略采用了IP多播、双钥锁和基于全局／局部／状态次序编号的次序管理机制。双钥锁允许加锁者或下一个申请者释放互斥锁。次序管理遵循4个原则来避免“乱序”、“意图歪曲”、“因果牵制”和“反向因果牵制”四个数据不一致问题。本文详细讨论了该策略的设计目标、主要问题及解决途径、特征、基本原则以及算法轮廓。

NASO Publish-propagate Replication Scheme for Clustered Database Server

Clustered Database Server (CDS) supports dynamic Web pages and allows online updating. Because each node of a CDS has the same copy of business-logical objects in spite of what atomic architecture is adopted, replication is essential. After commenting on some different techniques to achieve replication for CDS, such as DFS, reliable Multicast protocol, Groupware services and DSM, this paper puts forward a NASO Publish-Propagate Replication scheme. NASO stands for No-Acknowledgement-Strict-Order and Publish-Propagate is a paradigm close to but different from Publish-Subscribe paradigm. This scheme depends on IP Multicast protocol, Twin-Keys Locking mechanism and Sequence Management based on Global/Local/Status Order Numbers. By this replication scheme, either the lock-holder or the next applicant can unlock the corresponding exclusive locks. At the same time, four sequence-management rules are used to avoid divergence, intention violation, causal diversion and inverse causal diversion. This paper focuses on its design motives, main problems and their solutions, characteristics, basic rules and algorithm frames.