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陈红红 《计算机技术与发展》2009,19(7)
服务质量(Qos)描述了-个产品或服务满足消费者需求的能力.如何为不同类型的用户提供区分服务正在引起研究领域的关注.通过改进Web服务器应用软件来提供WebQoS支持是一种非常直观的Web QoS控制思路,但在实际应用中却存在着通用性和可扩展性等方面的局限.以此思路为出发点,将QoS控制部分功能提取出来,在一个前置服务器中去实现,该服务器置于客户端与Web服务器中间,主要负责完成Web请求的截取、QoS控制及请求转发.实验证明以引入前置服务器的方式实现Web请求的QoS控制,能够保证高级别用户请求的较高完成率以及较低响应延时,以低优先级请求的尽早拒绝防止了服务器过载,有效地实现web服务区分. 相似文献
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论文利用近似计算模型和WHC实时调度策略,设计了一个Web服务器能够提供区分服务和服务质量保证PIK机制。同时,通过修改ApacheWeb服务器软件,实现了对PIK机制的仿真研究。通过仿真实验表明,PIK机制是一个可行的和有效的Web服务器区分服务质量机制,它为Web服务器区分服务质量研究提供了模型框架。 相似文献
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目前普遍应用的在确定资源环境下的FCFS短信服务调度机制在处理请求过载的情况下难以保证服务质量.本文提出的系统自适应组网以及根据获益分析动态调整资源的模型.实验证明了对于提高服务器服务质量的有效性. 相似文献
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Web Services服务质量度量工具的研究 总被引:1,自引:0,他引:1
提出了一种基于API Hook技术的方法来对Web Services的服务质量(QoS)进行度量,该方法可以在Web服务的客户端和服务端度量多种QoS属性,具有客观化、自动化和轻量化的特点.还给出了一个基于该方法的度量工具原型实现. 相似文献
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Web集群服务器已被广泛用来提高Web服务器的性能。如何保证Web服务的服务质量(QoS)是一个迫切需要解决的问题。区分服务已成为QoS研究领域中的一个焦点。本文分析了Web请求服务时间的数字特性,并使用M/G/1 FCFS排队模型对Web服务器及Web集群服务器进行了建模。在对模型进行分析的基础上,设计并实现了一种异构Web集群服务器中的比例伸展因子区分服务的方案,并提出了基于概率空间的请求调度算法。请求被分成多个类,无论系统的负载如何,系统确保每类请求的平均伸展因子与事先给定的参数成正比。实际测试表明,所设计的方案满足相对区分服务的可预测性和可控制性的要求。 相似文献
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QoS (Quality of Service), which defines service quality such as latency, availability, timeliness and reliability, is important for web applications that provide real-time information, multimedia content, or time-critical services. Many web applications are best implemented by servers with a guaranteed server processing capacity. In this research, we study the QoS control issues using the current Web services standards. We propose a QoS-capable Web service architecture, QCWS, by deploying a QoS broker between Web service clients and providers. The functions of the QoS broker module include tracking QoS information about servers, making selection decisions for clients, and negotiating with servers to get QoS agreements. We have implemented a QCWS prototype using IBM WSDK, enhanced with simple QoS capabilities. We have measured the performance running under different service priorities. 相似文献
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Web QoS控制研究综述 总被引:49,自引:0,他引:49
Internet的服务模式正由传统的数据通信与信息浏览向电子交易与服务转变 ,Web服务器系统作为支持电子商务的核心设施 ,需要对不同的用户或HTTP请求提供区分服务和性能保证 ,因此必须具备建立和支持服务质量 (QualityofService ,QoS)控制的机制与策略 .该文综述了WebQoS控制的研究现状 ,包括Web请求的分类机制、Web服务器应用软件的QoS控制机制、操作系统的WebQoS控制机制、中间件的WebQoS控制机制以及Web服务器集群系统的QoS控制机制与策略 ,并分析了进一步的研究方向 . 相似文献
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Two recent advances have resulted in significant improvements in Web server quality-of-service. First, both centralized and distributed Web servers can provide isolation among service classes by fairly distributing system resources. Second, session admission control can protect classes from performance degradation due to overload. The goal of this work is to design a general "front-end" algorithm that uses these two building blocks to support a new Web service model, namely, multiclass services which control response latencies to within prespecified targets. Our key technique is to devise a general service abstraction to adaptively control not only the latency of a particular class, but also to bound the interclass relationships. In this way, we capture the extent to which classes are isolated or share system resources (as determined by the server architecture and system internals) and hence their effects on each other's QoS. For example, if the server provides class isolation (i.e., a minimum fraction of system resources independent of other classes), yet also allows a class to utilize unused resources from other classes, the algorithm infers and exploits this behavior, without an explicit low level model of the server. Thus, as new functionalities are incorporated into Web servers, the approach naturally exploits their properties to efficiently satisfy the classes' performance targets. We validate the scheme with trace driven simulations. 相似文献
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Lodi G. Panzieri F. Rossi D. Turrini E. 《IEEE transactions on pattern analysis and machine intelligence》2007,33(3):186-197
In this paper, we discuss the design, implementation, and experimental evaluation of a middleware architecture for enabling service level agreement (SLA)-driven clustering of QoS-aware application servers. Our middleware architecture supports application server technologies with dynamic resource management: application servers can dynamically change the amount of clustered resources assigned to hosted applications on-demand so as to meet application-level quality of service (QoS) requirements. These requirements can include timeliness, availability, and high throughput and are specified in SLAs. A prototype of our architecture has been implemented using the open-source J2EE application server JBoss. The evaluation of this prototype shows that our approach makes possible JBoss' resource usage optimization and allows JBoss to effectively meet the QoS requirements of the applications it hosts, i.e., to honor the SLAs of those applications 相似文献
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针对当前Web通用服务器性能评测工具并不能满足Web集群系统性能评测的需要,该文的研发重点在于构造一个高性能的支持QoS的Web集群服务器评测工具WC-Stress(WebClusterStress)。它的特点包括:可组装的组件结构;支持Web集群的评测需要:如区分服务;支持细粒度的QoS性能评测:如资源优化调度算法的支持;支持新的Web访问特征:如自相似请求的产生。最后给出了此评测工具对笔者设计的一种新型Web集群服务器的测试结果。 相似文献
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影响多媒体服务器性能的关键因素研究 总被引:7,自引:0,他引:7
在构建大规模视频服务系统时 ,基于层次型多服务器群的体系结构在吞吐率、可扩展性、经济性等方面都有其突出的优势 ,尤其适合于在因特网上的应用 .但是 ,要充分发挥和提高视频服务系统的性能 ,还要针对一些主要的瓶颈(如服务器磁盘 I/ O带宽与网络带宽 ) ,解决好一系列的问题 .本文分析了影响多媒体视频服务器性能的一些主要因素 ,如视频服务器的体系结构、服务器与客户端之间的数据传送方式、媒体数据在视频服务器存储子系统中的分布与放置方式、对磁盘访问请求的调度、单服务器中的缓存及多服务器间协同缓存的管理、接入控制策略、流调度策略等 ,这些因素对视频服务器的性能与吞吐率有着极大的影响 .本文还介绍了一些适用于大规模视频服务系统的性能优化技术 ,如广播、批处理等流调度策略 .在构建视频服务器系统时 ,只有综合考虑这些因素 ,才能真正提高服务器乃至整个视频服务系统的吞吐率 ,并较好地满足客户的 Qo S要求 相似文献
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《Journal of Network and Computer Applications》2002,25(1):57-68
The current Web service model treats all requests equivalently, both while being processed by servers and while being transmitted over the network. For some uses, such as multiple priority schemes, different levels of service are desirable. We propose application-level TCP connection management mechanisms for Web servers to provide two different levels of Web service, high and low service, by setting different time-outs for inactive TCP connections. We evaluated the performance of the mechanism under heavy and light loading conditions on the Web server. Our experiments show that, though heavy traffic saturates the network, high level class performance is improved by as much as 25–28%. Therefore, this mechanism can effectively provide QoS guaranteed services even in the absence of operating system and network support. 相似文献
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分析了几种服务器软件体系结构存在的优点与缺陷,设计了一种结合多进程并发与单进程事件驱动优点的对称式多进程事件驱动SMPED服务器体系结构。提出了一种新颖的连接调度算法,该算法根据服务器实际吞吐量进行连接分发和资源分配,试图实现服务器吞吐量最大化。仿真试验证明,SMPED服务器性能在多种网络条件下明显优于现行服务器。 相似文献
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Data centres which host Web services for other organisations and users in a Grid environment must provide for Quality of Service (QoS) requirements to be specified to ensure deployed services perform as desired. As services hosted by a data centre receive unpredictable rates of demand, servers must be allocated dynamically to service pools that are over utilised to avoid breaking QoS requirements. This work describes how a cost based stochastic model for resource allocation is used in data centre middleware to balance server utilisation, and how the model was used to enable a data centre to meet QoS requirements. The stochastic QoS model is compared to two other QoS models and is shown to be the most effective in a number of experiments. 相似文献