【作者】 杨开杰；

【导师】 徐汀荣；

【作者基本信息】 苏州大学 ， 计算机应用技术， 2009， 硕士

【摘要】 分布式技术的普遍应用,使传统的Web系统面临越来越大的挑战。客户端大量的并发请求导致服务器负载过重,业务逻辑和事务处理都受到影响。其中,并发访问情况下,响应速度慢和数据利用率低的问题大大制约了Web系统性能。在客户端和服务器之间加入中间层可解决上述问题,本文的中间层包括线程池、数据库连接池和分布式数据缓存三部分,与客户端和服务器组建成分布式池化数据缓存模型(DPDCM)。本模型的主要功能是用线程池处理客户端请求的业务逻辑,用连接池来优化数据库连接,用分布式缓存提高数据利用率。主要改进工作包含下面三部分:第一,针对用户并发的访问控制,本文采用多线程的并发控制技术设计线程池,通过对池中线程数量的动态优化调整来提升线程池性能,使其能处理更多并发请求;第二,针对频繁的数据库连接请求,文中的数据库连接池采取两种不同的复用连接策略,并建立具有延迟释放功能的应急池,以应对某段时间内的高并发请求连接的情况;第三,针对大量的相近数据访问,本文采用与传统数据缓存不同的分布式缓存方法,设计了DPDCM的缓存对象结构,改进了缓存替换算法和一致性维护策略,采用LRU-M替换算法和TTL与服务端失效模式相结合的一致性维护策略管理缓存,并对相关的技术进行了理论分析。本文将DPDCM应用到实际的社区论坛开发中,介绍了池化技术和分布式数据缓存的具体实现方法,最后对模型及其使用的技术进行了应用场景的设计和测试。实验表明,改进后的分布式池化数据缓存系统缩短了平均响应时间并提高了数据缓存命中率,本文解决方案比传统方法更适合如今的Web系统。更多还原

【Abstract】 The application of distributed technology has brought great challenges to conventional Web systems.A great number of simultaneous requests from clients give a big burden to servers and bring some problems on performance.In fact,the slow down of the reaction speed and low efficiency of data utilization have become the bottle-neck of system performance.The middle tier is imported between the clients and servers can solve these problems, including thread pool,database connection pool and distributed data cache three parts,the clients and the database with it together established the distributed pooling data cache model(DPDCM).The main function of this model is use the thread pool to deal with requests,use connection pool to optimize database connection,and use distributed cache to improve the efficiency of data utilization.The main improvements of this paper include the following three parts.First,this paper utilizes multi-threaded concurrency control technique to design the threads pool to manage the number of threads dynamically.Second,two kinds of different reuse strategies are used in database connection pool,and establish emergency pool with delayed releasing algorithm to deal with high concurrent request.Third,this paper designs the new structure of cache objects,improves LRU-M cache replacement algorithm and cache consistency management of the server failure mode and TTL combination.We also analyze the efficiency and feasibility of technologies in theory.This paper applies DPDCM to the development of community forums,and explains the realization methods.Finally utilizes the application scheme to test the performance of technologies in DPDCM.The results show that the improved distributed cache system shortens the reaction time and improves the rate of cache hit,so the new system is more suitable for today’s web systems than the tridational methods.更多还原