基于FreeBSD内核的虚拟服务器研究与实现

服务器集群是实现高性能网络服务的有效结构,而报文转发技术是发挥服务器集群性能的关键。高效的报文转发技术使得集群的调度负载很轻,具有很高的可扩展性。IP隧道技术/直接路由是两种新颖而且高效的报文转发技术。FreeBSD是理想的网络服务器操作系统,但目前基于FreeBSD的集群调度系统均采用网络地址转换技术,系统可扩展性有限。本文讨论了基于FreeBSD操作系统内核,采用IP隧道/直接路由报文转发技术的虚拟服务器(FVS)系统的设计动机及实现,重点探讨了系统的体系结构及实现关键技术。我们基于FreeBSD-5.3内核实现了FVS系统,性能测试结果表明,该系统的调度负载很轻,有很好的可扩展性。     

存储过程技术及KingbaseES中的实现

PL／SQL语言是SQL标准的一个重要扩展，它的典型形式之一是数据库服务器支持存储过程。采用存储过程技术能够对应用逻辑进行封装，同时在客户机／服务器体系中能够明显改善性能。支持存储过程的系统必须解决存储过程的存储和执行两个核心问题。金鼎关系数据库系统KingbaseES在其3．0版本中，提供了过程SQL语言PL／SQL以支持存储过程的使用。本文将分析存储过程技术和KingbaseES对该技术的设计与实现。     

B/S安全性的关键技术研究

随着网络技术的高速发展、普及以及各种应用系统规模的不断扩大,传统上的C/S结构已经无法满足许多用户的需求,B/S（Browser/Server）模式即浏览器和服务器结构,这种三层客户/服务器模式应运而生,它分为3层框架：数据层、业务逻辑操作层以及表示层。服务器端（Server）实现了它主要的事务逻辑,使得客户端的负载能力大大减轻,从而更易于数据维护。但是由于它实现的是用户工作界面通过WWW浏览器来访问,在具有异地信息浏览和信息采集的灵活性的同时,也由于所有的数据传输都要通过公共的网络,因此在B/S模式下信息安全的研究也显得尤其重要。     

基于多层结构的应用系统设计与实现

为了解决将现有 C/S结构的系统过渡到 B/S结构而必须将原代码重写一遍的问题 ,因而产生了应用程序服务器 ,它包含企业逻辑的应用程序。给出了三层结构数据库系统的模型及一般的开发流程 ,并给出了一个使用 SQL Server和 C+ + Builder开发的应用实例     

电厂图档管理系统应用SQLite数据库的可行性研究

提出了在基于B／S的电厂图档管理系统中应用SQLite进行数据管理的方案。在介绍SQLite的特点及电厂图档管理系统架构的基础上,从电厂图档管理系统服务器端数据库、数据逻辑层、事务处理层以及SQLite自身局限性等方面来分析在该系统中应用SQLite数据库的可行性,并最终给出了基于SQLite数据库的电厂图档管理系统架构。     

SLA-Driven Clustering of QoS-Aware Application Servers

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     

A compact AES core with on-line error-detection for FPGA applications with modest hardware resources

This paper presents a compact, low-cost, on-line error-detection architecture for a 32-bit hardware implementation of the AES. The implemented AES is specially designed for FPGA-based embedded applications, since it is tuned to specific FPGA logic resources. The on-line error-detection is based on parity codes. The parity prediction is implemented in the AES encryption, decryption, and key expansion process. The developed solution has been upgraded to an efficient BIST with a high fault coverage and a low hardware overhead.     

Programmable context awareness framework

Context-awareness enables applications to provide end-users with a richer experience by enhancing their interactions with contextual information. Several frameworks have already been proposed to simplify the development of context-aware applications. These frameworks are focused on provisioning context data and on providing common semantics, definitions and representations of these context data. They assume that applications share the same semantic, which limits the range of use cases where a framework can be used, as that assumption induces a strong coupling between context management and application logic. This article proposes a framework that decouples context management from application business logic. The aim is to reduce the overhead on applications that run on resource-limited devices while still providing mechanisms to support context-awareness and behavior adaptation. The article presents an innovative approach that involves third-parties in context processing definition by structuring it using atomic functions. These functions can be designed by third-party developers using an XML-based programming language. Its implementation and evaluation demonstrates the benefits, in terms of flexibility, of using proven design patterns from software engineering for developing context-aware application.     

基于C／S模式与网络计算体系结构的MIS开发研究

本文对MIS开发中的C／S模式与B／S模式进行了分析比较,对网络计算体系结构与Oracle Web服务器的Web技术进行了讨论,详细给出了运用C／S模式与网络计算体系结构相结合,利用Oracle Web服务器进行了一个企业管理信息系统的设计与实现过程,本文对在MIS开发中选取合适的体系结构以适应系统的安全性,灵活性及扩展性等方面要求作了有效尝试。     

J2EE资源集成的性能优化研究

J2EE应用服务器基于JCA规范为企业资源系统提供了一个统一的资-源集成解决方案。在JCA框架下,应用服务器提供连接管理、事务管理及安全管理等服务,这些服务是影响系统性能的重要因素。本文主要研究了应用服务器端在支持资源集成中与性能相关的几个关键问题,包括连接池管理和事务管理,提出了行之有效的优化策略。本文的工作已经应用到中科院软件所自主开发的J2EE应用服务器OnceAS中,取得了很好的效果。     

Asteroid: Scalable Online Memory Diagnostics for Multi-core,Multi-socket Servers

Memory diagnostics are important to improving the resilience of DRAM main memory. As bit cell size reaches physical limits, DRAM memory will be more likely to suffer both transient and permanent errors. Memory diagnostics that operate online can be a component of a comprehensive strategy to allay errors. This paper presents a novel approach, Asteroid, to integrate online memory diagnostics during workload execution. The approach supports diagnostics that adapt at runtime to workload behavior and resource availability to maximize test quality while reducing performance overhead. We describe Asteroid’s design and how it can be efficiently integrated with a hierarchical memory allocator in modern operating systems. We also present how the framework enables control policies to dynamically configure a diagnostic. Using an adaptive policy, in a 16-core server, Asteroid has modest overhead of 1–4 % for workloads with low to high memory demand. For these workloads, Asteroid’s adaptive policy has good error coverage and can thoroughly test memory.     

应用服务器外部资源集成研究

应用服务器是新一代Internet多层体系结构计算平台的核心部分，用于处理应用系统中的业务逻辑部分，通常采用组件方法，资源服务是应用服务器的重要组成部分，为组件提供可以访问的外部数据资源，本文研究了应用服务器的外部资源集成机制，建立了基于XA接口的外部资源系统集成模型，在此基础上设计了应用服务器的资源服务并实现了应用服务器和数据库系统的无缝集成。     

Design and Implementation of the Stony Brook Video Server

The system architecture of the Stony Brook Video Server (SBVS), which guarantees end-to-end real-time video playback in a client-server setting, is presented. SBVS employs a real-time network access protocol, RETHER, to use existing Ethernet hardware as the underlying communications media. The video server tightly integrates the bandwidth guarantee mechanisms for network transport and disk I/O. SBVS's stream-by-stream disk scheduling scheme optimizes the effective disk bandwidth without incurring significant scheduling overhead. To demonstrate the feasibility of the proposed architecture, we have implemented a prototype called SBVS-1, which can support five concurrent MPEG-1 video streams on an Intel 486DX2/EISA PC. To our knowledge, this system is the first video server that provides an end-to-end performance guarantee from the server's disks to the each user's display over standard Ethernet. This paper describes the implementation details of integrating network and I/O bandwidth guarantee mechanisms, and the performance measurements that drive and/or validate our design decisions. © 1997 by John Wiley & Sons, Ltd.     

J2EE平台中分布式事务互操作的研究与实现

RMI-IIOP协议扩展了J2EE应用服务嚣的应用领域。符合CORBAIDL规范的非Java语言编写的CORBA客户端可以通过IIOP协议与J2EE应用组件之间实现互操作。在分布式事务环境中,CORBA客户端通过IIOP协议调用应用服务嚣上的EJB组件时,应用服务嚣需要保证客户端的CORBA调用能正确到达EJB组件,并且事务上下文在客户端和服务器之间能够有效传播。本文基于应用服务嚣的JMX体系结构,设计了一个支持事务互操作的服务框架,实现了事务环境下基于IIOP协议对EJB的调用。它具有较好的灵活性和可重配性。并已经在中科院软件所研制的OnceAS应用服务嚣中得到了实现。     

On runtime adaptive tile defragmentation for resource management in many-core systems

Before an application can be actually launched in a many-core system, the first thing that needs to be done is to get the application mapped to a number of tiles (cores). Such online application mapping process may unfortunately lead to a serious resource leak problem, referred as tile fragmentation, that free (uncommitted) tiles from any single contiguous region are just inadequate to accommodate the performance needs of an incoming application, although the total number of free tiles may still exceed what is required to service this application. When applications have to be mapped to noncontiguous tiles due to fragmentation, there will be obvious performance penalty due to increased communication distances. As a result, defragmentation that consolidates fragmented tiles needs to be routinely exercised, and this defragmentation process must not introduce high computation overhead that otherwise can adversely impact the system performance. In this paper, we propose a task migration-based adaptive tile defragmentation algorithm that helps consolidate running applications through online task migration. This algorithm relocates the applications’ tile regions so that a contiguous free tile region is formed and maintained. By doing so, future applications can be mapped to a region with low communication distance. Both the computation overhead and quality of defragmentation result of the proposed algorithm are adaptively set in response to the system workloads. Enabled by its low overhead, the proposed defragmentation algorithm is an effective resource management enhancement to the existing runtime task-to-tile mapping methods, with as much as 3× system throughput improvement observed in some experiments.     

Design and analysis of a demand adaptive and locality aware streaming media server cluster

The wide availability of broadband networking technologies such as cable modems and DSL coupled with the growing popularity of the Internet has led to a dramatic increase in the availability and the use of online streaming media. With the “last mile” network bandwidth no longer a constraint, the bottleneck for video streaming has been pushed closer to the server. Streaming high-quality audio and video to a myriad of clients imposes significant resource demands on the server. In this work, we propose a demand adaptive and locality aware (DALA) clustered media server architecture that can dynamically allocate resources to adapt to changing demand and also maximize the number of clients serviced by the server cluster. Moreover, our design exploits temporal locality among requests by dispatching newly arriving requests to servers that are already servicing prior requests for those objects, thereby extracting the benefits of locality. We explore the efficacy of the DALA clustered architecture through both performance models and simulations. Evaluation of the models and simulation results show that DALA exhibits significant performance gains when compared to static schemes. Furthermore, our simulation results show that DALA is highly adaptive, and has a low system overhead. Our results demonstrate that DALA is a simple, yet effective approach for designing clustered media servers.     

SelfMotion: A declarative approach for adaptive service-oriented mobile applications

Modern society increasingly relies on mobile devices. This explains the growing demand for high quality software for such devices. To improve the efficiency of the development life-cycle, shortening time-to-market while keeping quality under control, mobile applications are typically developed by composing together ad-hoc developed components, services available on-line, and other third-party mobile applications. Applications are thus built as heterogeneous compositions, whose characteristics strongly depend on the components and services they integrate. To cope with unpredictable changes and failures, but also with the various settings offered by the plethora of available devices, mobile applications need to be as adaptive as possible. However, mainstream adaptation strategies are usually defined imperatively and require complex control strategies strongly intertwined with the application logic, yielding to applications that are difficult to build, maintain, and evolve. We address this issue by proposing a declarative approach to compose adaptive heterogeneous mobile applications. The advantages of this approach are demonstrated through an example inspired by an existing worldwide distributed mobile application, while the implementation of the proposed solution has been validated through a set of simulations and experiments aimed at illustrating its performance.     

基于JMX的组件管理平台的研究与实现

设计了一种基于JMX(Java管理扩展)的组件管理平台;该管理平台作为一个具有良好扩展性的服务器端组件容器,结构上采用JMX为系统总线,将JNDI(Java名称与目录接口)及JTA(Java事务接口)等底层服务封装而成的可管理组件置入总线,利用该总线提供的资源管理器对外界提供服务,达到封装性和扩展性的目的;实践证明,该系统使繁杂的业务逻辑开发变得简单,使企业级应用的扩展能力得到增强,其满足企业级应用的快速、低成本及扩展性的要求。     

支持四层结构的电子商务数据管理模型的研究

1.引言今天,因特网已经培植成为一个全球市场,众多企业供应商和消费者通过因特网作为介质交换各种各样的数据。因特网不但成为广告载体,而且成为商品和服务集中的全球市场,从电子图书到传统出版物,从旅游计划到金融服务。总体上电子商务可以分成两大类:企业-消费者(B2C)商务和企业-企业(B2B)商务。数据管理主要提供了数据处理功能,例如数据