Simulation-based analysis of middleware service impact on system reliability: Experiment on Java application server

Being a popular runtime infrastructure in the era of Internet, middleware provides more and more services to support the development, deployment and management of distributed systems. At the same time, the reliability of middleware services has a significant impact on the overall reliability of the system. Different services have different impacts and different service fault-tolerance solutions have different costs and risks. Therefore, the identification of the services that greatly affect the whole system reliability is the major obstacle to achieving reliable middleware-based systems. In this paper, we present an analytical framework to automatically reason and quantify such impacts when deploying the target system. In this framework, faults are represented by exceptions in modern programming languages; service failures are simulated by software fault injection; reliability impacts are measured by scenarios. This framework is demonstrated on multiple JEE application servers, including JBoss, JonAS and PKUAS. The experiments on two JEE blueprint applications, namely JPS and ECperf, show the feasibility, the applicability and the usability of this framework.     

Achieving Flexibility in Off-the-Shelf Middleware Services Integration

The development of component-based software engineering enables the construction of application servers by integrating reliable OTS middleware services. However it is di cult to achieve exibility in conventional hard coding way. In this paper, we propose a exible OTS middleware services integration framework to address this problem. In this framework, we de ne two kinds of modules: the middleware service contract module to represent the stable contract which speci es the abstract interaction logic between the application server and a kind of middleware services, and the middleware service implementation module to encapsulate the mutable implementation details of di erent OTS middleware services in a uni ed way. Additionally, we propose a module management mechanism to enable the application server to replace the OTS products at runtime via con guration. We implement the framework in a J2EE application server, and the evaluations show that our framework effectively reduces the cost and the time of maintaining and customizing the OTS middleware services-based application server.     

一种中间件服务容错配置管理方法

提出一种基于运行时刻软件体系结构的容错管理方法,支持开发者和管理员针对不同中间件服务失效定制合适的故障检测和修复机制.首先,运行时刻软件体系结构自动构造构件依赖视图和错误传播①视图,为理解和分析整个系统的可靠性提供全局视图;然后,操作运行时刻软件体系结构配置容错机制;最后利用AOP技术将容错机制插装到中间件中,使其具备指定的容错能力.上述过程在一个可视化工具的辅助下半自动实施,并在J2EE中间件上得到验证.     

J2EE中间件技术在电子政务系统中的应用

电子政务系统是建立在中间件平台之上的业务应用层系统,J2EE平台能够提供一个电子政务的框架,可以降低服务功能的成本和复杂性。本文介绍J2EE中间件技术在电子政务系统中的应用,并通过实例来说明省级电子政务系统的基本框架。     

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     

应用服务器中Web服务支持功能的设计与实现

随着Web服务技术的发展和步人实用，主流应用服务器给应用开发人员提供了在应用服务器上开发、部署和调用Web服务的功能。叙述了通过集成开源Web服务项目Axis的设计方案，在现有的符合J2EE1．3标准的应用服务器中增加Web服务支持功能，并说明了具体的实现结构，使得应用开发人员可以在该应用服务器上开发、部署和调用Web服务。     

MidCloud: an agent‐based middleware for effective utilization of replicated Cloud services

The Cloud relies heavily on resource replication to support the demands of the clients efficiently. Replicated Cloud services are distributed across large geographic areas and are accessible via the Internet. This paper describes MidCloud; an agent‐based middleware that provides Cloud clients with dynamic load balancing and fault tolerance mechanisms for effective utilization of replicated Cloud services and resources. MidCloud can be used to connect clients with multiple replicated Cloud services and provide fast and reliable service delivery from multiple replicas. Several approaches for load balancing and fault tolerance in distributed systems were introduced; however, they require prior knowledge of the environment's operating conditions and/or constant monitoring of these conditions at run time that allows the applications to adjust the load and redistribute the tasks when operational conditions change and when failures occur. These techniques work well when there is no high communication delay. Yet, this is not true in the Cloud, where data storage and computation servers are scattered all over the world and communication delays are usually very high. MidCloud deploys approaches to reduce the negative impact of high and dynamic delays on the Cloud servers and the Internet. The experimental results show the positive effects of using MidCloud to provide efficient load balancing and fault tolerance. Copyright © 2013 John Wiley & Sons, Ltd.     

基于J2EE平台集群服务的分布式缓存队列模型

集群缓存足提高J2FE(Java 2 Entcrprisc Edition)应用程序可扩展性能的关键技术,但目前J2EE提供的集群技术对于集群缓存的性能处理还存在一定的不足,该文在分析、12EE集群缓存技术的应用基础上,提出一种分布式缓存队列模型,可以有效地解决集群中的可靠性、可扩展性和失败转发等问题。实验表明,采用分布式缓存队列模型能提高集群的访问效率,是一种可行的解决方案。     

支持EJB动态分布的组件迁移模型与算法

Web应用服务器是Web计算环境下的新型中间件,为基于组件的分布式Web应用提供了基础运行平台.组件静态分布限制了事务性Web应用在运行期间适应执行环境变化的能力.为了满足Web应用的动态分布需求,Web应用服务器需在底层为组件提供一种动态迁移的能力.如何维持组件迁移前后的一致性是组件迁移中最棘手的问题之一.为解决此问题,定义了组件迁移一致性约束CMC(component migration constrains),并给出了在J2EE(Java 2 platform enterpnse edition)应用服务器中支持EJB(enterprise Java Bean)动态分布的组件迁移模型和SLB Copy,SFB_Copy,EB_Copy 3个迁移算法.分析得出SLB_Copy,SFB_Copy和EB_Copy均满足CMC约束.迁移模型和算法已在自主研制的Web应用服务器WebFrame2.0中实现,并已应用到自适应负载平衡、失效恢复等多个方面.     

Modeling and Analysis of Grid Service Reliability Considering Fault Recovery

The extreme complexity of grid system makes it extremely difficult to achieve high service reliability, and this situation is aggravated by the fact that many grid services need to perform time-consuming tasks that may require several days or even months of computation. To improve grid service reliability, this paper studies a fault recovery technique in grid systems and conducts in-depth research on grid reliability modeling and analysis with fault recovery. Grid failures considered in this paper are classified into two categories: unrecoverable failures and recoverable failures. Software reliability is taken into account as well. To make fault recovery more practical, certain constraints on fault recovery are introduced and grid service reliability models under these practical constraints are developed. Numerical examples are presented, and based on the results obtained, the impact of fault recovery as well as that of practical constraints on grid service reliability is discussed.     

Reconfigurable Service Composition and Categorization for Power-Aware Mobile Computing

The requirement of agile adaptation to varying resource constraints in mobile systems motivates the use of a service-oriented architecture (SOA), which can support the composition of two or more services to form a complex service. In this paper, we propose SOA-based middleware to support QoS control of mobile applications and to configure an energy-efficient service composition graph. We categorize services into two layers:functionality-centric services, which are connected to create a complex service to meet the user's intentions, and resource-centric services, which undertake distributed functionality-centric services in a way that increases the success rate of service composition while reducing contention at specific service nodes. We also present a service routing algorithm to balance the resource consumption of service providers on a service-overlay network. Through simulation of power-aware service composition using a realistic model based on ns-2 and traced data, we demonstrate that our approach can help both the mobile devices and the servers in a service-overlay network to reduce energy consumption without an increase in response time.     

J2EE平台上基于Web服务企业应用集成的研究

分析了传统点对点集成方案和中间件集成方案两种企业应用集成(EAI)架构的优缺点,阐述了Web Services(Web服务)给企业应用集成带来的革命性的变化以及Web Services在目前的技术条件下所不能解决的问题,提出了面向对象中间件基础上的Web服务集成方案并以J2EE为平台给出了一种全新的、面向服务层的、松耦合的企业应用集成框架,给出了实现该框架的原型系统,并展望了Web服务技术成熟后该框架的扩展。     

A Dependable ESB Framework for Service Integration

Service integration is an important issue in service-oriented computing. As an infrastructure for service-oriented architectures, the enterprise service bus (ESB) has been regarded as a promising way to support dynamic and agile service integration in distributed heterogeneous environments. The authors' ESB framework for large-scale service integration, JTangSynergy, adopts several mechanisms for providing effective and efficient dependability. It enables automated recovery from component failures and robust execution of composite services by checking service compatibility. The authors tested JTangSynergy in the Chinese Healthcare Service Integration project.     

分布事务服务的一致性测试

作为J2EE应用服务器重要组成部分的分布事务管理器主要用于提供分布环境下的事务处理能力。文章拓宽了协议一致性测试的理论和技术的应用范围，探讨了分布事务服务的一致性测试，也给出了分布事务服务的形式化描述和非基于经验的测试序列的生成方案。     

An adaptive quality of service aware middleware for replicated services

A dependable middleware should be able to adaptively share the distributed resources it manages in order to meet diverse application requirements, even when the quality of service (QoS) is degraded due to uncertain variations in load and unanticipated failures. We have addressed this issue in the context of a dependable middleware that adaptively manages replicated servers to deliver a timely and consistent response to time-sensitive client applications. These applications have specific temporal and consistency requirements, and can tolerate a certain degree of relaxed consistency in exchange for better response time. We propose a flexible QoS model that allows clients to specify their timeliness and consistency constraints. We also propose an adaptive framework that dynamically selects replicas to service a client's request based on the prediction made by probabilistic models. These models use the feedback from online performance monitoring of the replicas to provide probabilistic guarantees for meeting a client's QoS specification. The experimental results we have obtained demonstrate the role of feedback and the efficacy of simple analytical models for adaptively sharing the available replicas among the users under different workload scenarios.     

电子商务系统的性能评测与数据存取优化

随着J2EE技术不断成熟,人们基于J2EE技术架构,建设电子商务系统。J2EE标准是一个开发的标准,用户可以从众多的J2EE服务器中进行选择,人们关心J2EE服务器的性能及其可扩展性。利用EcPerf测试套件对J2EE系统进行了性能测试,结合测试过程找出数据存取的性能瓶颈,并且通过实用的优化策略,提高系统性能。这些策略包括数据库查询处理、数据库系统的加锁模式、异步消息传递、以及运行环境的配置等。通过优化,系统性能有了大幅度的提升。     

容忍入侵的J2EE应用服务器设计与实现

针对现有J2EE应用服务器在容忍入侵方面的不足,提出一种具有容忍入侵功能特性的J2EE应用服务器的构建方法。通过在J2EE应用服务器组通信层构建安全的群组通信系统和在服务器内部设计容忍入侵拦截器、容忍入侵框架,实现了容忍入侵服务的透明加入及集成、插拔和扩展功能。该设计方案运用容忍入侵、群组通信及拦截器技术为解决分布式环境下J2EE应用服务器领域容忍入侵问题提供了一个简便有效的方法。     

一种移动开发中间件的设计和实现

移动开发正成为一个迅速发展的领域，然而由于移动环境的种种限制，为开发移动应用带来巨大挑战。中间件是一种行之有效的处理分布式异构平台的技术，可用于解决移动开发中碰到的很多问题。在J2EE架构之上提出了一种移动应用系统框架，并基于这种框架在传统中间件的基础上设计和实现了一种移动开发中间件。这种中间件能够屏蔽移动设备和运行平台的多样性，并能够处理移动网络的延迟和出错，使得移动系统的开发与在普通网络环境上一样便捷，从而达到提高移动应用开发效率的目的。     

J2EE development frameworks

Java 2 Enterprise Edition has excelled at standardizing many important middleware concepts. For example, J2EE provides a standard interface for distributed transaction management, directory services, and messaging. In addition, Java 2 Standard Edition (J2SE), which underpins J2EE, provides a largely successful standard for Java interaction with relational databases. However, the platform has failed to deliver a satisfactory application programming model. Many in the open source community, especially smaller vendors, have chosen the alternative of developing frameworks designed to simplify the experience of building J2EE applications. Popular frameworks such as Struts, Hibernate, and the Spring Framework play an important role in many of today's J2EE development projects.     

基于J2EE技术的企业异步通信解决方案

解释了为什么异步通信对于企业的体系结构来说是至关重要的。借助J2EE平台跨平台、中间件技术、多层结构等技术性能优点，采用了基于J2EE技术的Java消息服务（JMS）和消息驱动bean（MDB）的解决方案，用来实现应用程序各个部件之间的异步消息传递，从而达到在分布式企业级应用系统中，异步通信机制有效地协调各个部分子系统的工作的目的。