DNS(domain name system) query log analysis has been a popular research topic in recent years. CLOPE, the represented transactional clustering algorithm, could be readily used for DNS query log mining. However, the algorithm is inefficient when processing large scale data. The MR-CLOPE algorithm is proposed, which is an extension and improvement on CLOPE based on Map Reduce. Different from the previous parallel clustering method, a two-stage Map Reduce implementation framework is proposed. Each of the stage is implemented by one kind Map Reduce task. In the first stage, the DNS query logs are divided into multiple splits and the CLOPE algorithm is executed on each split. The second stage usually tends to iterate many times to merge the small clusters into bigger satisfactory ones. In these two stages, a novel partition process is designed to randomly spread out original sub clusters, which will be moved and merged in the map phrase of the second phase according to the defined merge criteria. In such way, the advantage of the original CLOPE algorithm is kept and its disadvantages are dealt with in the proposed framework to achieve more excellent clustering performance. The experiment results show that MR-CLOPE is not only faster but also has better clustering quality on DNS query logs compared with CLOPE.
大数据具有规模大、深度大、宽度大、处理时间短、硬件系统普通化和软件系统开源化特点.针对当前传统数据库在对大数据进行分析时系统性能严重下降、计算效率提升有限的问题,提出一种基于列存储的大数据分析系统物化策略(materialization strategies in MapReduce based on column-store,MSMC).首先,通过引入MapReduce物化代价估计模型,深入分析影响物化效率的各个因素.在此基础上设计了MapReduce分布式环境下的列存储文件格式(MapReduce column-store file,MCF),并在数据加载过程中采用协同定位策略实现对物化数据的存储优化.其次,分别针对不同的物化时机,构建了MapReduce早期物化策略(MapReduce early materialization strategy,MEMS)、MapReduce延迟物化策略(MapReduce late materialization strategy,MLMS)和MapReduce混合物化策略(MapReduce early-late materialization strategy,MELMS).利用自适应物化调整策略对其做了进一步优化.实验结果在证明算法有效的同时,也显示出算法在存储空间和负载能力上都有很好的表现.
