分布式系统的通信和对共享资源互斥访问的研究与实现

【作者】 赖周建；

【导师】 刘心松；

【作者基本信息】 电子科技大学 ， 计算机系统结构， 2006， 硕士

【摘要】 随着人们对信息日益增长的需求,信息服务提供者们的服务器系统面临着巨大的速度和容量压力。各种价格高居不下的大型服务器虽然能够缓解这种压力,可是仍然无法足够应付越来越高的访问频率。因此借助于网络的飞速发展,分布式系统应运而生。为了满足众多信息服务提供者对高性能、高性价比、高可扩展性的分布式服务器系统的需求,我们将对本研究室已经实现的、基于Linux内核的、具有自主知识产权的分布式系统DPS(俗称打不烂)进行全面的升级。DPS的升级目标是为用户提供一个更大流量,更高性能,更可靠的服务器系统。并且从目前宽带视频点播(BOD)方面的应用,扩展到电子政务,电子商务等领域。本文前半部分讨论了分布式系统的特征和设计问题,然后简要介绍了LINUX内核的相关技术,最后给出了DPS的设计特征和框架。后半部分详细讨论了通信机制(LKCC)的升级,互斥算法的重新设计和实现。主要包括以下内容:LKCC会话的改进,在LKCC增加组播和对紧急数据的优先发送功能,新的互斥算法(DPHC)的提出以及实现和测试。LKCC以UDP协议为基础,在此基础上采用了OTP协议,通过会话来完成数据的可靠传输。为了改善系统的性能和满足用户的需求,将原来OTP协议中会话的一一应答改成了组应答方式;由于DPS系统的资源存在多个副本,所以在LKCC中加入了组播功能;又因为当系统繁忙时,某些紧急数据得不到优先发送,降低了系统的性能,所以本文又实现了对紧急数据的优先发送。DPHC算法是一种采用自动迁移容错的、根据资源选择仲裁者的互斥算法。该算法将不同锁对象(共享资源)的仲裁者分布到了系统中的各个节点,让每个仲裁者都像集中式算法中的控制者一样的工作,因此,该算法具有集中式算法的消息量和分布式算法的负载均衡。而且当请求加锁的进程发现它的仲裁者失效以后,会马上为锁对象产生一个新的仲裁者并向它发送请求消息,如果节点相继失效,直到只剩下它自己时,它仍然能够产生仲裁者,就是它自己,这种自动迁移容错方法使得它还具有分布式算法的容错度。更多还原

【Abstract】 With the increasing information requirement, server system of ISP(internet server provider) is being faced with tremendous tension. Some exorbitant great server could be resolve the question, but can’t come up with the increasing frequency of accessing. With the rapid development of the computer network, distributed applications become main stream gradually. In order to meet the need of distributed and parallel server system, which has high performance, high scalability and with a reasonable price, we have entirely developed DPS that is a distributed and parallel system based on Linux kernel. BOD server system is just a typical example, in future DPS will be applied in electron government affair and business affairs and so on.In the first part of this thesis,we firstly discuss some design issues and character in distributed system and then introduce some Linux kernel information briefly,lastly describe the framework and the character of DFS。In the second part,this thesis describe the upgrade of LKCC and the implement of net mutual exclusion,including the ameliorating of communication session mechanism,the implement of multi-send and preferential sending of emergent message, and DPHC algorithm.LKCC,a Linux Kernel Concurrent Communication mechanism,uses Object Transfer Protocol to send and receive data。In order to improving system processing capability and to response client requests, session mechanism is changed;because a great of source have several copy, multi-send is added;because DPS often has great load, some emergent message cannot be send duly;capability of system is depressed, message PRI is added to LKCC.DPHC uses auto-transfer to imply dependability and chooses interceder by the name of source. Because it distributes interceders of different source to each node in system, lets each interceder work as controlling node in centralizing control arithmetic, it has message number of centralizing control arithmetic and load equilibrium of distributed arithmetic. Characteristic of auto-transfer brings dependability of distributed arithmetic, because while a node has down, other nodes’requests that had been sent to it can send to other nodes by producing new interceder. So DPHC can satisfy completely need of dependability.更多还原