Priority scheduling service for E-commerce web servers

Service scheduling is one of the crucial issues in E-commerce environment. E-commerce web servers often get overloaded as they have to deal with a large number of customers’ requests—for example, browse, search, and pay, in order to make purchases or to get product information from E-commerce web sites. In this paper, we propose a new approach in order to effectively handle high traffic load and to improve web server’s performance. Our solution is to exploit networking techniques and to classify customers’ requests into different classes such that some requests are prioritised over others. We contend that such classification is financially beneficial to E-commerce services as in these services some requests are more valuable than others. For instance, the processing of “browse” request should get less priority than “payment” request as the latter is considered to be more valuable to the service provider. Our approach analyses the arrival process of distinct requests and employs a priority scheduling service at the network nodes that gives preferential treatment to high priority requests. The proposed approach is tested through various experiments which show significant decrease in the response time of high priority requests. This also reduces the probability of dropping high priority requests by a web server and thus enabling service providers to generate more revenue.     

测控设备web网络服务器化研究

为实现利用Internet自带的客户端浏览器对现场设备进行远程监控的目的,设计并实施了新型web网络服务器化远程测控系统。系统中测控设备内嵌嵌入式web服务器,既能自身作为测控终端直接采集数据,又能通过CAN总线与其他测控器进行组网,实现类似网关的功能。硬件设计主要包括：嵌入式web服务器模块、测控器模块以及其接口模块设计与实施。软件设计主要选用Linux操作系统和嵌入式web服务器Boa实现CGI技术,设计添加CAN控制器驱动程序后完成IE浏览器与嵌入式web服务器以及测控器三者之间的通信。利用该系统进行温度测试,实验成功并能满足实时性,充分表明利用Internet浏览器、嵌入式web服务器组建并控制CAN网络的新型远程测控系统的先进性与可行性。     

嵌入式实时Web Server的动态调度算法研究

对嵌入式实时Web Server的网络任务活动特点进行了研究,将任务分为优先任务和普通任务两类,在此基础上利用M／M／1/K模型提出了保障优先任务接纳率的动态调度算法。该方法可以根据实时Web Server当前的任务量决定是否接纳普通任务,保证实时Web Server在优先任务安全运行的前提下,为网络中的其它客户开放资源。该算法已用于远程实验网站的任务调度(www．remot-lab．net)。     

嵌入式Web服务器端脚本引擎设计与实现

由于嵌入式设备的资源有限,RAM和ROM都非常小.为了在资源受限的情况下实现Web服务功能,在分析HTTP1.1的基础上,设计了一种简化的嵌入式Web服务器的软件结构.在参照MicrosoftASP技术的基础上,定义了实现嵌入式Web服务器端脚本解析的主要函数和接口,并给出了脚本引擎调用方法.结合C语言编程,成功地实现了HTTP连接和脚本解析.     

Web应用服务器中Web Service引擎的设计与实现

Web Service为程序之间的交互提供了基础,实现了独立于程序设计语言的一致化编程模型,并以通用的方法进行应用程序集成。分析了Web应用服务器实现Web Service的关键需求,阐述了在应用服务器中基于SOAP的Web Service引擎的设计与实现,介绍了实现Web Service引擎的若干关键技术和解决办法。Web Service引擎已在自主研发的OnceAS应用服务器中实现。     

嵌入式Web服务器软件的设计和实现

针对当前嵌入式Internet技术已成为嵌入式系统发展的新技术热点的情况,讨论了嵌入式设备接入Internet的方法,论述了实现嵌入式Web服务器的关键技术——HTTP协议和通用网关接口CGI,阐述了嵌入式Web服务器的特点及其设计思想,最后提出并在VxWorks实时操作系统环境下实现了的一种嵌入式Web服务器的方案,并给出了该嵌入式Web服务器的数据处理流程以及其主要模块和功能说明。     

光伏发电监控系统中嵌入式Web服务器的实现

为了提高光伏发电监控系统的响应速度和运行效率,设计并实现了一种高效的嵌入式Web服务器.系统浏览器客户端与服务器首次连接时,服务器发送JavaScript脚本到浏览器客户端,并在客户端创建AJAX引擎;该引擎采用异步交互的信息处理方式,实现监控页面实时数据的快速刷新;服务器采用基于回调函数的消息响应机制,处理客户端的请求并返回相应的响应消息;采用线性链表结构存储交互过程中需要的网页文件.该系统操作简单,运行效率高,可以满足光伏发电监控系统中数据频繁更新的需求.     

Task assignment in multiple server farms using preemptive migration and flow control

Existing task assignment policies proposed for assigning tasks in stand-alone server farms are not efficient in multiple server farm environments because they have not been designed to exploit the properties of such environments. With the emergence of high speed networks and operating systems that have features such as preemptive migration, the importance of designing task assignment policies for assigning tasks in multiple server farms has increased. Such policies can result in better overall performance compared to those that optimise performance in stand-alone server farms.This paper proposes a task assignment policy suitable for assigning tasks in multiple server farms. The proposed policy, called Multi-Cluster Task Assignment based on Preemptive Migration (MCTPM) is based on a multi-tier host architecture that reduces the variance of task sizes in host queues by processing tasks with similar sizes using a set of hosts that have a distinct task size range. MCTPM controls the traffic flow into server farms via a global dispatching device so as to optimise the performance. MCTPM supports preemptive task migration between servers in the same farm and between servers in different farms.Performance analysis of the proposed policy indicates that significant performance improvements are possible under a wide range of workload scenarios. For example, MCTPM outperforms existing policies such as MC-Random, MC-TAGSPM and MC-MTTPM by factors of 190, 5 and 10.5 respectively under certain scenarios.     

Analysis of web server log files and attack detection

Problems of web application security and antihacker protection are very topical. Queries that users send to a web application via the Internet are registered in log files of the web server. Analyzing log files allows detecting anomalous changes that take place on the web server and identifying attacks. In this work, different methods are used to analyze log files and detect anomalies. The proposed methods allow detecting anomalous queries received from malicious users in log files of the web server.     

面向教学的Web服务器的设计与实现

本文设计并实现了一个面向教学的且支持程序员级别动态网页二次开发的Web服务器。     

Web缓存服务器技术研究与应用

Web缓存服务器系统正在Internet及局域网上广泛地应用,对它所采用的技术做了较深入的讨论,指出利用Web Cache技术,可减少网络流量,节约资金,提高带宽利用率;同时在Cache服务器端进行内容分析过滤,可提高过滤质量和效率,有效防止有害信息的进一步传播。     

基于ARM嵌入式Web服务器的设计与实现

分析了基于ARM的嵌入式Web服务器,介绍了其设计和实现的主要技术,并且通过模拟应用来验证设计的可用性。     

基于服务器推送技术和XMPP的WebIM系统实现

为解决现有Web IM系统中大量用到AJAX周期请求而产生的系统消息延迟,以及客户端和服务器端通信量大的问题,提出了以服务器推送技术作为基础的Web IM系统,并选择XMPP作为服务器和客户端的通信协议.在比较AJAX和Comet 技术原理的基础上,给出了Comet技术实现HTTP长连接的策略.通过一个原型WebIM系统,验证了Comet技术在Web IM 系统中使用的确可以有效地解决大量AJAX周期请求的问题.     

嵌入式Web服务器的设计及其CGI实现

由于嵌入式设备的资源有限,RAM和ROM都非常小,在资源受限的情况下实现Web服务功能是非常困难的.在分析HTTP1.1的基础上,讨论了嵌入式Web服务器的特点及设计思想,提出了一种简化的嵌入式Web服务器的软件结构.重点描述了嵌入式Web服务器中CGI的实现方法.最后,结合C语言编程成功地实现了HTTP连接.     

A multi-layer client–server queueing network model with non-hierarchical synchronous and asynchronous messages

We analyze a multi-layered queueing network that models a client–server system where clients and servers communicate via synchronous and asynchronous messages. The servers are organized in groups such that they form a multi-layered structure. The messaging pattern is non-hierarchical, i.e., a client can send a message to a server belonging to any layer, and a server from a layer-i may issue messages to a server belonging to any higher layer, j>i. The queueing network is analyzed approximately using a decomposition algorithm. Numerical tests show that the approximation algorithm has a good accuracy.     

Performance Analysis of a Client–Server System Using Queueing Networks: A Case Study

Queueing networks have been widely used to evaluation performance of mainframe computer systems. In contrast, few results have been reported for modern open systems, so it was not clear whether queueing networks are useful for modern systems or not. We think this situation has partly been due to lack of handy evaluation tools. This paper presents tow tools that we developed to evaluate open system performance. On is a measuring tool that is capable of accurately obtaining the service times of system resources requested by an application transaction. The other is an estimating tool which calculates various performance measures based on queueing network models. This paper also describes a case study in which the performance of a medium-sized UNIX client–server system (up to 24 clients) is estimated using the tools and these estimates are then compared with experimental results. The estimates closely agree with the measured results and are accurate enough for practical applications. Based on this, we conclude that queueing network models are also useful for modern systems.     

Web服务器通用性能测试系统的设计与实现

性能测试系统能够在应用系统遭受实际压力之前测算出系统能够承受的负荷，作者设计并实现了一个Web服务器的性能测试系统，该系统能够模拟真实的用户行为对各种Web服务器进行大用户量访问测试，为WEB服务器的性能评估提供数据依据，本文介绍了此系统的设计思路和关键技术，并介绍了该系统在清华大学选课系统测试中的实际应用情况。     

Power and performance control of soft real-time web server clusters

This paper presents a novel way to control power consumption and performance in a multi-tier server cluster designed for e-commerce applications. The requests submitted to these server systems have a soft real-time constraint, given that although some can miss a pre-defined deadline, the system can still meet an agreed upon performance level. Clusters of servers are extensively used nowadays and, with the steep increase in the total power consumption in these systems, economic and environmental problems have been raised. We present ways of decreasing power expenditure, and show the implementation of a SISO (Single Input Single Output) controller that acts on the speed of all server nodes capable of dynamic voltage and frequency scaling (DVFS), with QoS (Quality of Service) being the reference setpoint. For QoS, we use the request tardiness, defined as the ratio of the end-to-end response time to the deadline, rather than the usual metric that counts missed deadlines. We adjust the servers operating frequencies to guarantee that a pre-defined p-quantile of the tardiness probability distribution of the requests meet their deadlines. Doing so we can guarantee that the QoS will be statistically p. We test this technique in a prototype multi-tier cluster, using open software, commodity hardware, and a standardized e-commerce application to generate a workload close to that of the real world. The main contribution of this paper is to empirically show the robustness of the SISO controller, presenting a sensibility analysis of its parameters. Experimental results show that our implementation outperforms other published state-of-the-art cluster implementations.     

WWW系统性能分析

本文提出了一个简单高水平的开放网络模型,得出了一些ＷＷＷ服务器性能的结论,并分析了多服务器系统,定义了ＷＷＷ服务器处理能力的上限,分析了文件的大小、服务 器的速度、网络带宽等因素对ＷＷＷ服务器性能的影响,最后,评价了几种改善ＷＷＷ服务器性能的方法。