支持日志乱序提交的分布式一致性协议  

Distributed consistency protocol supporting log submission out-of-order

作　　者：王进[1] 李博涵[1] 吴佳骏 宋欣洋 WANG Jin;LI Bo-han;WU Jia-jun;SONG Xin-yang(College of Computer Science and Technology,Nanjing University of Aeronautics and Astronautics,Nanjing 211106,China)

机构地区：[1]南京航空航天大学计算机科学与技术学院,江苏南京211106

出　　处：《浙江大学学报（工学版）》2023年第2期320-329,共10页Journal of Zhejiang University：Engineering Science

基　　金：CCF-华为数据库系统创新研究计划资助项目(CCF HUAWEIDBIR2020001A)。

摘　　要：为了解决Raft算法中日志提交的严格串行化设计,提出一种Raft协议变体:并行提交Raft (PC-Raft). PCRaft在日志提交阶段运用流水线,重新设计日志缓冲区,实现日志的乱序提交.传输方式使用RDMA网络,在提高日志传输的并发性的同时加快传输速度.在日志执行阶段,采用批处理,将多条指令打包发送给状态机逐条执行.针对日志并行提交情况下会出现的幽灵复现问题,采用LSN与任期号结合的方式保证日志的安全性.针对日志乱序提交会出现的日志空洞问题,重新设计领导者选举算法,在选举中加入临时领导者,保证选举出的领导者能最快恢复日志.测试结果证明PC-Raft对比Raft在吞吐量方面有着明显的性能提升,同时延迟更低,并且在日志指令依赖频繁的情况下,吞吐量比现有基于Raft的变体更高,延迟也更低.A Raft protocol variant, parallel commit Raft(PC-Raft), was proposed, in order to solve the strict serialization design of log submission in Raft algorithm. In PC-Raft, pipeline was used in the log submission stage and the log buffer was redesigned to realize out-of-order submission of logs. The RDMA network was used as the transmission method to improve the concurrency of log transmission and speed up the transmission. In the log execution stage, batch processing was used to package multiple instructions and send them to the state machine for execution one by one. For the ghost recurrence problem that occurs, the combination of LSN and term number was used to ensure the security of the log. In order to solve the problem of log holes caused by disordered log submission,the leader election algorithm was redesigned, and temporary leaders were added to the election to ensure that the elected leaders can recover the logs as quickly as possible. Test results show that PC-Raft has a significant performance improvement in throughput compared with Raft, and the delay is lower. In the case of frequent log instruction dependency, the throughput is higher and the latency is lower compared with the existing Raft based variant.

关 键 词：一致性协议 Paxos RAFT PC-Raft 乱序提交 

分 类 号：TP311[自动化与计算机技术—计算机软件与理论]