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题名:
发布订阅系统服务保障技术研究
作者: 郭祥丰
答辩日期: 2009-01-12
导师: 李京
专业: 计算机软件与理论
授予单位: 中国科学院软件研究所
授予地点: 软件研究所
学位: 博士
关键词: 发布订阅系统 ; 服务质量 ; 可靠性 ; 中间件 ; 准入控制 ; 事件分发
其他题名: Research on Service Guarantee of Publish/Subscribe Systems
分类号: 暂无
索取号: 暂无
部门归属: 软件工程技术研究开发中心
摘要: 随着分布式计算环境的出现和分布式应用的不断发展,发布/订阅作为一种新的通信模型为分布式应用提供了松散耦合的协同工作方式。这种通信模型为通讯的各方提供了时间上、空间上、控制流等方面的松散耦合,为应用的匿名访问提供了可能性,使得应用更加容易重新配置。与此同时,工业界也出现了相应的标准以及业界产品来实现这种通信模型。目前,发布订阅系统解决了很多基本的功能方面的问题,如数据模型、匹配算法和事件路由等;然而,随着部署于发布订阅系统中应用的不断增加,与系统非功能性相关的系统服务质量成为影响系统是否成功的重要因素。与发布订阅系统相关的非功能性的系统服务质量属性主要包括事件分发性能、顺序性、发送可靠性、优先级、安全性以及事务性等。本文主要关注于其中最重要的几个方面:事件分发性能、发送可靠性、顺序性。 首先,本文分析了事件分发的主要机制,包括订阅的组织、事件的匹配、路由等。已有的事件匹配分发优化策略多关注于订阅的内部特征进行优化,如覆盖优化和合并优化等。本文从应用的角度出发,将事件的分布特性、订阅的分布特性引入到事件匹配分发机制中;在订阅的组织中引入了过滤器的匹配代价以及匹配可能性,考虑不同订阅、不同过滤器的匹配次序对事件分发过程的影响,选取最优的匹配次序。我们证明了选取最优匹配次序问题是一个NP问题,给出了事件匹配分发优化贪心算法,并给出了一种用于数值型过滤器快速匹配的索引结构。 其次,在有限的代理网络资源下,当过多的发布者和订阅者进入系统中时,系统由于处理能力不足会引发事件过载问题。已有研究多采用尽力而为的方式进行处理,无法保障订阅者的订阅请求以及发布者的事件分发;为此,本文提出了一种准入控制机制RacsCBPS来解决发布订阅系统的事件过载问题。RacsCBPS 使用松散耦合的方式将事件的流量特征扩散到代理网络中去,然后针对订阅者发出的订阅进行资源需求计算,进而判定代理节点是否会造成事件过载。最后给出了一种分布式准入控制算法,解决了代理网络上的事件过载问题。 本文还研究了发布订阅系统的事件发送保证问题。事件发送保证可以分为两部分,即事件在代理网络中的传输保证以及事件在代理网络和客户端之间的传输保证。我们首先给出了一种代理网络上的事件发送保证协议,其中包括单节点发送保证协议和多代理节点发送保证协议;然后研究了移动客户端的发送保证问题,针对已有移动迁移协议的不足,提出了一种新的迁移保证协议,该协议可以保证事件分发的顺序性和可靠性。 最后,本文介绍了发布订阅原型系统,给出了原型系统的体系结构、主要组件以及功能实现,它对上述研究工作成果进行了实现和验证。
英文摘要: With the development of distributed computing and distributed applications, Publish/Subscribe, as a new communication model, provides a loosely coupled approach for the cooperation among distributed applications. Based on this model, the communication among the applications is loosely coupled in time, space and control. With this model, anonymous access among distributed components is possible and the reconfiguration of applications is much easier. Moreover, some corresponding standards and software products are developed in industry community. Now, Publish/Subscribe systems have solved many important functional problems, such as data model, event matching, event routing and so on. However, with the increasing number of the applications running on Publish/Subscribe systems, system qualities related to the non-functional features become the most important factors for the success of these systems.The non-functional features of Publish/Subscribe systems include the performance of event dispatching, the guarantee of events order, the reliability of event dispatching, event priority, security, transaction and so on. The system qualities concerned in this paper are the performance of event distribution, the reliability of event dispatching, and the guarantee of the events order. Firstly, we analyze the mechanism of event dispatching which includes the organization of subscriptions, events matching and events routing. Most existing optimizing strategies concern inner characters of subscriptions, such as cover optimization and merge optimization. In the paper, we consider characters of the event distribution and the subscription distribution in optimization. In the organization of subscriptions, we consider the cost of event matching and the possibility of successful event matching with the filter, and study the influence of the order of different subscriptions and different filters, such that the optimized event matching order can be found. We prove that event matching optimization problem is NP-hard. We present a greedy algorithm for the optimization of events dispatching and a numeric subscription index for fast event matching. Secondly, when large amount of publishers and subscribers participate in the systems, due to limited resource the publish/subscribe systems often result in events overload. In this paper, we propose an admission control mechanism RacsCBPS to solve the overload problem in publish/subscribe system. RacsCBPS disseminates the character of event flow to the broker network in a loosely coupled manner, and decides a broker overload or not through computing the demand of resources of a specific subscription. An admission control algorithm is presented for the event overload problem in publish/subscribe systems. Thirdly, we consider the guarantee of the events dispatching problem in publish/subscribe systems. The guarantee of the events dispatching problem can be divided into two parts: the guarantee of transportation in broker network and the guarantee of transportation between broker network and clients. We first present an event guarantee protocol in the broker network, and then give a cache based event guarantee protocol. The guarantee of the events dispatching of mobile clients is also considered in this paper. We propose a novel protocol to guarantee the dispatching order and dispatching reliability. Finally, we introduce a publish/subscribe prototype system, including its architecture, main components and the functions. This prototype system has implemented the approach presented in this paper.
内容类型: 学位论文
URI标识: http://ir.iscas.ac.cn/handle/311060/6654
Appears in Collections:软件工程技术研究开发中心 _学位论文

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Recommended Citation:
郭祥丰. 发布订阅系统服务保障技术研究[D]. 软件研究所. 中国科学院软件研究所. 2009-01-12.
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