Primitives for distributed computing in a heterogeneous local areanetwork environment

Epsilon is a testbed for monitoring distributed applications involving heterogeneous computers, including microcomputers, interconnected by a local area network. Such a hardware configuration is usual but raises difficulties for the programmer. First, the interprocess communication mechanisms provided by the operating systems are rather cumbersome to use. Second, they are different from one system to another. Third, the programmer of distributed applications should not worry about system and/or network aspects that are not relevant for the application level. The authors present the solution chosen in Epsilon. A set of high-level communication primitives has been designed and implemented to provide the programmer with an interface independent of the operating system and of the underlying interprocess communications facilities. A program participating in a distributed application can be executed on any host without any change in the source code except for host names     

J2EE平台上消息驱动Bean对客户的响应与回传的实现

EJB是基于Java的服务器端组件架构技术,借助于EJB,开发者能够轻松构建企业的、分布式组件应用,并且能够开发架构灵活、运行可靠及安全的应用系统.在EJB规范中,客户可向中间件发送消息,而消息驱动Bean(MDB)能从中间件接收消息,从而客户与消息驱动Bean实现异步传输消息,形成松耦合的状态.介绍了消息发布客户与消息驱动Bean通过服务器互传消息的理论,给出了Java消息服务的请求/响应解决方案,并且在J2EE1.4平台上实现了消息驱动Bean将响应结果异步回传给生产消息的客户,而客户可以是应用程序,Servlet/JSP,或EJB本身.     

跨平台人机交互软件组件集成框架

提出一种跨平台的人机交互软件组件集成框架,包括三部分内容:一是人机交互软件的框架结构,包括引导程序、主框架、组件实体、消息总线.二是组件的管理方式,组件是跨平台的可单独加载的单元,引导程序将组件二进制代码加载到内存.框架通过虚函数体系动态地派生出不同组件实体对象,并以组件名为关键字散列挂载到消息总线上,组件对应的界面放置在主框架的界面容器内.三是基于领导者-追随者模型的组件状态切换和交互协同工作方式,组件通过鼠标或键盘操作响应获得焦点,进入领导活动状态,处理完事件后进入休眠追随状态.组件之间通过消息交互协同,并支持快速消息总线和事件循环总线.该框架在保护测控装置配置软件、工业控制编程软件进行了应用,实践表明基于该架构显著降低了组件间耦合关系,提高了开发效率和组件复用度.     

A configuration approach to parallel programming

This paper advocates a configuration approach to parallel programming for distributed memory multicomputers, in particular, arrays of transputers. The configuration approach prescribes the rigorous separation of the logical structure of a program from its component parts. In the context of parallel programs, components are processes which communicate by exchanging messages. The configuration defines the instances of these processes which exist in the program and the paths by which they are interconnected.

The approach is demonstrated by a toolset (Tonic) which embodies the configuration paradigm. A separate configuration language is used to describe both the logical structure of the parallel program and the physical structure of the target multicomputer. Different logical to physical mappings can be obtained by applying different physical configurations to the same logical configuration. The toolset has been developed from the Conic system for distributed programming. The use of the toolset is illustrated through its application to the development of a parallel program to compute Mandelbrot sets.     

The impact of distributed programming abstractions on application energy consumption

With battery capacities remaining a key physical constraint for mobile devices, energy efficiency has become an important software design consideration. Distributed programming abstractions (e.g., sockets, RPC, messages, etc.) are an essential component of modern software, but their energy consumption characteristics are poorly understood. The programmer has few practical guidelines to choose the right abstraction for energy-constrained scenarios. In this article, we report on the findings of a systematic study we conducted to compare and contrast major distributed programming abstractions in terms of their energy consumption patterns. By varying the abstractions with the rest of the functionality fixed, we measure and analyze the impact of distributed programming abstractions on application energy consumption. Based on our findings, we present a set of practical guidelines for the programmer to select an abstraction that satisfies the energy consumption constraints in place. Our other guidelines can steer future efforts in creating energy efficient distributed programming abstractions.     

Tools for distributed application management

The issues of managing distributed applications are discussed, and a set of tools, the meta system, that solves some longstanding problems is presented. The Meta model of a distributed application is described. To make the discussion concrete, it is shown how NuMon, a seismological analysis system for monitoring compliance with nuclear test-ban treaties is managed within the Meta framework. The three steps entailed in using Meta are described. First the programmer instruments the application and its environment with sensors and actuators. The programmer then describes the application structure using the object-oriented data modeling facilities of the authors' high-level control language, Lomita. Finally, the programmer writes a control program referencing the data model. Meta's performance and real-time behavior are examined     

Dynamic end-to-end QoS management middleware for distributed multimedia systems

In this paper, we present a separable, reusable middleware solution that provides coordinated, end-to-end QoS management over any type of service component, and can use existing (legacy) QoS management solutions (by using wrappers) in a distributed multimedia system. Our middleware solution incorporates strategic and tactical QoS managers, and supports protocols and messages between tactical managers and managed application components, and between QoS managers in the management hierarchy. Strategic QoS managers take a global view of QoS provided by a set of application components within the manager's policy domain. Tactical QoS managers provide local control over application components. We introduce the concept of QoS policy domains to scope the authority of a strategic QoS manager. We describe how the management hierarchy is dynamically configured and reconfigured based on runtime needs of the application.     

一种大规模分布式应用性能分析系统

在网格和云计算环境下,由于平台和网络环境的复杂性,使得对大规模分布式应用的有效监控和性能分析变得非常困难。为此,提出一种基于数据流管理的大规模分布式应用性能分析系统,利用消息队列收集、缓冲和分发追踪消息,使用分布式实时处理框架分析和追踪消息。将该系统部署到一个Petabyte级别的分布式数据管理系统中,通过事例演示追踪消息的重要性。应用结果表明,该系统能够满足大规模分布式应用环境下大数据量处理能力和实时性的要求,为监控并分析系统性能、预测用户行为等提供了较好的平台支持。     

一种易部署的Android应用程序动态监测方案

Android应用程序动态监测方案通常有3种实现形式:1)定制ROM镜像;2)在获取设备Root权限的情况下,修改系统文件或者利用ptrace技术对目标进程注入代码;3)重打包APK。这3种方式都是以侵入式方式实现,依赖于系统环境,难以部署到不同的设备上。针对上述问题,文中提出了一种基于插件化技术的非侵入式动态监测方案。该方案将监测系统以宿主App形式发布并安装到目标设备上;将待监测应用以插件形式加载到宿主App环境中运行,同时由宿主App加载相应的监控模块,完成对待监测App应用行为的动态监测。在待监测应用作为插件运行前,预先启动一个进程,通过动态代理方式对该进程中的Binder服务代理对象进行替换,将Binder服务请求重定向到虚拟服务进程中的虚拟服务进行处理,从而使待监测应用中的四大组件能在预先启动的进程中运行。然后,在待监测应用Application的初始化过程中加载Java层和Native层监控模块,完成监控。根据该思想,在VirtualApp沙箱基础上实现了原型系统AndroidMonitor,并在Nexus5设备上对其进行测试。实验结果表明,与其他方案相比,该方案虽然会使...     

一个基于持续消息的分布式工作流管理模型

提出了一种新的分布式结构,在这个结构中,排除了工作流系统对一个集中式数据库的依赖,而是用持续消息的方法将与过程执行有关的信息存储起来,使过程的执行是完全分布式的,并且每个节点都是各自独立的。采用这种方式能增强对错误的恢复能力以及构造系统的灵活性和扩展性。     

An overview of the Nexus distributed operating system design

Nexus is a distributed operating system designed to support experimental research in fault-tolerance techniques and object-oriented programming in distributed systems. The Nexus programming environment consists of objects, which are instances of abstract data types. Inheritance of types and multiple implementations for a type are supported by the system. Operations on objects are invoked, based on the remote-procedure-call paradigm and executed as atomic actions with provisions for application-controlled checkpointing and restart within actions. Nexus also supports parallel remote procedure calls. Interobject communication and location transparency in accessing objects is supported by the Nexus kernel     

Component Management in a Dynamic Architecture

Modern distributed programming environments commonly restrict programmers to a single form of inter-component configuration of an application. However, these distributed applications are prone to evolve drastically during their lifetime, to take into account the new users requirements, the technological evolution, or to improve the performance of the application. Evolution involves changes related to the application architecture, the software implementation, or the physical location of software components in a distributed environment during the application execution. In this paper, we describe an original approach for the dynamic application management which fulfills the above requirements with minimal perturbation. In order to prove the advantage of our approach, we have implemented a prototype of this service by extending a CORBA environment.     

多租户高可用并行任务调度框架

描述了一种多租户高可用并行任务调度框架MTHPT的设计思想、体系结构和实现技术,MTHPT包括3部分：任务定义与配置、异步并行任务调度模式、消息告警与监视.任务调度引擎和任务执行组件采用分开部署、异步并行调度和快速回调的模式,快速释放调度引擎占用的线程资源,解决了部分任务执行周期长、定时任务无法按时执行等影响业务系统性能的问题.任务调度配置提供了多租户应用模式.实验分析及评估表明,MTHPT提高了应用系统的任务调度并行调度效率和稳定性.     

Application-dependent dynamic monitoring of distributed andparallel systems

Achieving high performance for parallel or distributed programs often requires substantial amounts of information about the programs themselves, about the systems on which they are executing, and about specific program runs. The monitoring system that collects, analyzes, and makes application-dependent monitoring information available to the programmer and to the executing program is presented. The system may be used for off-line program analysis, for on-line debugging, and for making on-line, dynamic changes to parallel or distributed programs to enhance their performance. The authors use a high-level, uniform data model for the representation of program information and monitoring data. They show how this model may be used for the specification of program views and attributes for monitoring, and demonstrate how such specifications can be translated into efficient, program-specific monitoring code that uses alternative mechanisms for the distributed analysis and collection to be performed for the specified views. The model's utility has been demonstrated on a wide variety of parallel machines     

Analyzing the effectiveness of fault-management architectures in layered distributed systems

Fault management infrastructure in distributed systems includes manager processes and agents with various kinds of interactions for monitoring and surveillance of the status of the application software and hardware. The system architecture now includes these additional components and interactions, and they affect the system availability. This paper describes an architecture model called MAMA (Model for Availability Management Architecture) with an architecture definition language MAMA-dl for the combination of the application and management parts, and its analysis. The analysis extends the Fault Tolerant Layered Queueing Model to account for propagation of knowledge of the system state in the management sub-architecture. The model is demonstrated on a problem of placement of manager tasks in a system.     

ARMADA Middleware and Communication Services

Real-time embedded systems have evolved during the past several decades from small custom-designed digital hardware to large distributed processing systems. As these systems become more complex, their interoperability, evolvability and cost-effectiveness requirements motivate the use of commercial-off-the-shelf components. This raises the challenge of constructing dependable and predictable real-time services for application developers on top of the inexpensive hardware and software components which has minimal support for timeliness and dependability guarantees. We are addressing this challenge in the ARMADA project.ARMADA is set of communication and middleware services that provide support for fault-tolerance and end-to-end guarantees for embedded real-time distributed applications. Since real-time performance of such applications depends heavily on the communication subsystem, the first thrust of the project is to develop a predictable communication service and architecture to ensure QoS-sensitive message delivery. Fault-tolerance is of paramount importance to embedded safety-critical systems. In its second thrust, ARMADA aims to offload the complexity of developing fault-tolerant applications from the application programmer by focusing on a collection of modular, composable middleware for fault-tolerant group communication and replication under timing constraints. Finally, we develop tools for testing and validating the behavior of our services. We give an overview of the ARMADA project, describing the architecture and presenting its implementation status.     

网络诊听系统

网络诊听是计算机网络系统管理体系中的重要组成部分。它通过截获共享广播信道中所有传输的报文，对网络实时信息和历史信息进行监控和统计分析，为网络健康性能状态的分析、调整提供有力的实用工具。该文重点研究分布式网络实时监测软件的关键问题。     

一个基于CORBA的图形用户界面体系结构及实例

随着网络计算技术的发展,软件的结构变为表示／处理／数据库分离的三级模式。表示与处理的分离导致了用户界面与应用计算间的通信成为开发交互式系统图形用户界面的关键。本文为分布式交互图形应用的开发提供了一个基于公用对象需求代理结构ＣＯＲＢＡ的用户界面体系结构,ＣＯＲＢＡ是为分布式对象系统中间件制定的一个互操作标准。在这个结构中,一些被称为代理的面向对象交互式图形构件被设计用来为图形的表示与交互提供有效的解