A visual process connector for Unix

Upconn a tool that lets Unix programmers visually describe the connections between the processes in a distributed program and then execute the distributed program, is described. Upconn consists of several modules and can be extended by adding to a library of tools rather than by adding many special features to Upconn itself. Upconn has three main uses. First, it lets researchers study distributed processing in common Unix environments, reducing the dependence on specialized environments. Second, it can be used for rapid prototyping of distributed applications. Third, Upconn is a learning tool that can help students focus on writing distributed programs without dealing with the complexities of the communication links     

基于分布式环境一种动态依赖关系发现的方法

本文提出了一种为分布式应用动态构造依赖性模型的方法。这个方法通过对系统进行主动干扰来获得建模的先验知识,然后基于贝叶斯网络构造方法,对分布式应用的组件间关系建立依赖性模型。和传统的被动建模技术不同的是,这种主动方法不需要事先对系统细节充分了解,它通过在运行环境中部署探针,捕捉和测量与部署的主动干扰相关的系统反馈,通过机器学习的方法识别分布式应用中构件间的动态调用的依赖关系,为分布式应用建立动态运行过程中的依赖性模型。动态建立的依赖性模型可用于分布式应用的运行时管理,用于分布式应用执行过程中的故障定位和恢复,对于分布式应用自主计算环境的实现,提供一种实用的方法。     

分布式虚拟环境平台(NPSNET-V)的研究

NPSNET-V由美国海军研究生院开发,其目标是逐步发展形成一个支持互联网上分布式虚拟环境的框架。目前,NPSNET-V是一个支持网络虚拟环境应用的、基于组件的、动态可扩展平台。本文论述了它的基本构思、组件框架、实体模型、典型架构、应用结构、设计启示等。     

Adaptive computing on the Grid using AppLeS

Ensembles of distributed, heterogeneous resources, also known as computational grids, have emerged as critical platforms for high-performance and resource-intensive applications. Such platforms provide the potential for applications to aggregate enormous bandwidth, computational power, memory, secondary storage, and other resources during a single execution. However, achieving this performance potential in dynamic, heterogeneous environments is challenging. Recent experience with distributed applications indicates that adaptivity is fundamental to achieving application performance in dynamic grid environments. The AppLeS (Application Level Scheduling) project provides a methodology, application software, and software environments for adaptively scheduling and deploying applications in heterogeneous, multiuser grid environments. We discuss the AppLeS project and outline our findings.     

Migration of active objects in proactive

ProActive, which supports active objects as the basic units of activity and distribution used for building applications using ProActive, is a Java library for parallel, distributed and concurrent computing. In this paper, we discuss an important distribution function—migration of objects—that is not readily available in many systems designed for implementing distributed applications. The migration is done in a scalable and secure way based-on ProActive. It has the ability to easily migrate computation, especially in heterogeneous environments. Moreover, it can be used for dynamic load balancing and dynamic deployment purposes to gain improved performance and flexibility of distributed applications.     

AMROEBA: Computational astrophysics modeling enabled by dynamic lambda switching

Many data and compute intensive Grid applications, such as computational astrophysics, may be able to benefit from networking supported by dynamically provisioned lightpaths. To date, the majority of high performance distributed environments have been based on traditional routed packet networks, provisioned as external services rather than as integrated components within those environments. Because this approach often cannot provide high performance capabilities required by these applications, an alternative distributed infrastructure architecture is being designed based on dynamic lightpaths, supported by optical networks. These designs implement communication services and infrastructure as integral components of distributed infrastructure. The resultant environments resemble large scale specialized instruments. Presented here is one such architecture, implemented on a wide-area, optical Grid test bed, featuring a closely integrated dedicated lightpath mesh. The test bed was used to conduct a series of experiments to explore its potential for supporting adaptive mesh refinement (AMR) astrophysics simulations. While preliminary, the results of these experiments indicate that this architecture may provide the deterministic capabilities required by a wide range of high performance distributed services and applications, especially for computational science.     

Real-time adaptive resource management

Distributed mission-critical environments employ a mixture of hard and soft real-time applications that usually expect a guaranteed range of quality of service (QoS). These applications have different levels of criticality and varied structures ranging from periodic independent tasks to distributed pipelines or event-driven modules. The underlying distributed system must evolve and adapt to the high variability in resource demands that competing applications impose. The current industry trend is to use commercial off-the-shelf (COTS) hardware and software components to build distributed environments for mission-critical applications. The paper considers how adding a middleware layer above the COTS components facilitates consistent management of system resources, decreases system complexity, and reduces development costs     

基于分布对象的离散事件仿真系统

分布对象技术将面向对象的概念揉合到分布计算中,使得基于对象的软件成员在分布异构环境中可重用、可移植和可互操作。文章把分布对象技术用于离散事件系统仿真中,通过对离散事件系统中分布对象的标识,分布对象间同步机制的讨论,提出了基于分布对象离散事件仿真系统的结构,定义了分布仿真对象的接口。     

A component framework for reusing a proprietary computer-aided engineering environment

Nowadays, it is becoming more frequent for engineers to deal with problems and situations that require specific software and the commercially available applications may not result adequate. Because of this, the reuse of software components is becoming a normal practice for improving the productivity of the software programmers, and the quality of the products that they develop. The employment of reusable components presents a number of advantages, such as the reduction in time necessary to develop new software, or the simplification of many computational tasks.There are some proprietary software environments in the engineering domain that are practically de facto standards, since they offer a broad functionality, robustness and constant updating. Therefore, those environments could be ideal candidates to be reusable components when developing new software. An example of this is Matlab, which can be encapsulated, in order to use it as a true reusable component. This will provide the user with efficient tools for designing his/her own applications.Moreover, there is an increasing importance for any software to offer distributed services. To perform this task, it is fundamental to have at one’s disposal reusable components that support Internet-based distributed applications and services development.In the present work, a software component framework that effectively encapsulates Matlab is described. This software allows developers the reuse of Matlab, for both local and distributed applications. To address those issues the .NET technology was employed. The component framework developed can be integrated in the toolbars of software development environments supporting the .NET framework. This facilitates the construction of applications that can reuse the components, since the software developers can use and test them and change their properties in design-time.     

GMATE: Dynamic Tuning of Parallel Applications in Grid Environment

Performance is a main issue in parallel application development. Dynamic tuning is a technique that changes certain applications’ parameters on-line to improve their performance adapting the execution to actual conditions. To perform that, it is necessary to collect measurements, analyze application behavior and carry out tuning actions during the application execution. Computational Grids present proclivity for dynamic changes in the environment during the application execution. Therefore, dynamic tuning tools are necessary to reach the expected performance indexes of applications on those environments. This paper addresses the dynamic tuning of parallel/distributed applications on Computational Grids. We analyze Grid environments to determine their characteristics and we present the development of dynamic tuning tool GMATE enabled for such environments. The performance analysis is based on performance models that indicate how to improve the application execution. A particular problem which provokes performance bottlenecks is the load imbalance in Master/Worker applications. A heuristic to dynamically tune granularity of work and number of workers is proposed. Finally, we describe the experimental validation of the performance model and its applicability on a set of real parallel applications.     

Metadata for Managing Grid Resources in Data Mining Applications

The Grid is an infrastructure for resource sharing and coordinated use of those resources in dynamic heterogeneous distributed environments. The effective use of a Grid requires the definition of metadata for managing the heterogeneity of involved resources that include computers, data, network facilities, and software tools provided by different organizations. Metadata management becomes a key issue when complex applications, such as data-intensive simulations and data mining applications, are executed on a Grid. This paper discusses metadata models for heterogeneous resource management in Grid-based data mining applications. In particular, it discusses how resources are represented and managed in the Knowledge Grid, a framework for Grid-enabled distributed data mining. The paper illustrates how XML-based metadata is used to describe data mining tools, data sources, mining models, and execution plans, and how metadata is used for the design and execution of distributed knowledge discovery applications on Grids.     

Evolvable concurrent processes

This paper presents a formal model of concurrent processes whose functions can be modified from the environments during execution. In many applications, it takes too much cost to stop the whole of the concurrent system working in distributed environments to update its components. Features of dynamic evolution that make it possible to modify functions of processes without termination are important. In this paper, a formal model of evolvable concurrent processes is presented using logical formulas of linear logic. The operational semantics is defined using a formal proof in a fragment of the sequent calculus of linear logic. A method for replacing the continuations of working processes by applications of inference rules of linear logic is presented.     

Simulation of SLA-based VM-scaling algorithms for cloud-distributed applications

Cloud Computing has evolved to become an enabler for delivering access to large scale distributed applications running on managed network-connected computing systems. This makes possible hosting Distributed Enterprise Information Systems (dEISs) in cloud environments, while enforcing strict performance and quality of service requirements, defined using Service Level Agreements (SLAs). SLAs define the performance boundaries of distributed applications, and are enforced by a cloud management system (CMS) dynamically allocating the available computing resources to the cloud services. We present two novel VM-scaling algorithms focused on dEIS systems, which optimally detect most appropriate scaling conditions using performance-models of distributed applications derived from constant-workload benchmarks, together with SLA-specified performance constraints. We simulate the VM-scaling algorithms in a cloud simulator and compare against trace-based performance models of dEISs. We compare a total of three SLA-based VM-scaling algorithms (one using prediction mechanisms) based on a real-world application scenario involving a large variable number of users. Our results show that it is beneficial to use autoregressive predictive SLA-driven scaling algorithms in cloud management systems for guaranteeing performance invariants of distributed cloud applications, as opposed to using only reactive SLA-based VM-scaling algorithms.     

Exception handling in workflow management systems

Fault tolerance is a key requirement in process support systems (PSS), a class of distributed computing middleware encompassing applications such as workflow management systems and process centered software engineering environments. A PSS controls the flow of work between programs and users in networked environments based on a “metaprogram” (the process). The resulting applications are characterized by a high degree of distribution and a high degree of heterogeneity (properties that make fault tolerance both highly desirable and difficult to achieve). We present a solution for implementing more reliable processes by using exception handling, as it is used in programming languages, and atomicity, as it is known from the transaction concept in database management systems. We describe the mechanism incorporating both transactions and exceptions and present a validation technique allowing to assess the correctness of process specifications     

A configurable RMI mechanism for sharing distributed Java objects

Many distributed programming environments have been designed to support distributed shared objects over the Internet. Most of these environments (Java RMI and CORBA, for example), support client-server applications where distributed objects reside on servers, which execute all methods (remote or local) invoked on the objects. Traditional client-server models do not support client-side object caching and the local access it provides. We believe that object caching is critical to distributed applications, especially over the Internet, where latency and bandwidth are highly variable. We have developed a configurable and efficient remote method invocation mechanism that provides the same interface as Java RMI, while extending its functionality so that shared objects can be cached on the accessing nodes. The mechanism, called Javanaise, is based on the caching of clusters, which are groups of interdependent Java objects. We have implemented a prototype consisting of a preprocessor that generates the required proxy classes from the application interfaces and a run-time environment that uses system classes to manage the consistency of cluster replicas cached on client nodes. We describe the motivation for the work, the design choices made for the Javanaise clustering mechanism, the implementation principles for managing Javanaise clusters, and the results from three experiments that compare the performance of Javanaise with Java RMI     

A support platform for distributed multimedia applications

Abstract

Considerable progress has been made in the development of technologies to support distributed multimedia computing, such that there is now a wide range of pilot applications under development. The design of support systems which help in the development of multimedia applications is therefore an emerging area of research. This paper discusses the requirements of distributed multimedia applications with respect to their support environments. A number of experimental systems are then described which intend to provide the necessary facilities for multimedia applications. Particular focus is placed on the Lancaster system which provides multimedia support for open distributed systems.     

Automatic distributed workflow generation with GridMD library

GridMD is a C++ class library intended for constructing simulation applications and running them in distributed environments. The library abstracts away from details of distributed environments, so that almost no knowledge of distributed computing is required from a physicist working with the library. She or he just uses GridMD function calls inside the application C++ code to perform parameter sweeps or other tasks that can be distributed at run-time. In this paper we briefly review the GridMD architecture. We also describe the job manager component which submits jobs to a remote system. The C++ source code of our PBS job manager may be used as a standalone tool and it is freely available as well as the full library source code. As illustrative examples we use simple expression evaluation codes and the real application of Coulomb cluster explosion simulation by Molecular Dynamics.     

软件构件平台持久框架的设计与实现

在分布式企业应用中不可避免地要大量访问数据库,或者保存对象、构件的状态信息。软件构件平台上的持久化技术为此提供了一个透明、简洁、高效的途径。本文介绍了现有各种构件平台、各种开发环境下的持久化技术,分析比较了各种方式的优劣,并提出了StarCCM软件构件平台上持久化框架的设计与实现。     

一种新的分布事务处理模型与协议

本文提出了一种适合于当前网络环境客户机／服务器应用方式下的分布事务处理模型及基于远程过程调用（ＲＰＣ）的实现协议。分析与实验表明它不仅满足客户机／服务器 应用的具体特点与要求，而且可以克服各种两段式提交协议中由于协调者故障造成的阻塞，同时避免了三段式提交等协议为解决阻塞而引起的开销过大、实现复杂等问题。     

An integrated runtime QoS-aware middleware framework for distributed multimedia applications

Future-generation distributed multimedia applications are expected to be highly scalable to a wide variety of heterogeneous devices, and highly adaptive across wide-area distributed environments. This demands multiple stages of run-time support in QoS-aware middleware architectures, particularly, probing the performance of QoS parameters, instantiating the initial component configurations, and adapting to on-the-fly variations. However, few of the past experiences in related work have shown comprehensive run-time support in all of the above stages – they often design and build a middleware framework by focusing on only one of the run-time issues. In this paper, we argue that distributed multimedia applications need effective run-time middleware support in all these stages to be highly scalable and adaptive across a wide variety of execution environments. Nevertheless, the design of such a middleware framework should be kept as streamlined and simple as possible, leading to a novel and integrated run-time middleware platform to unify the probing, instantiation and adaptation stages. In addition, for each stage, the framework should enable the interaction of peer middleware components across host boundaries, so that the corresponding middleware function can be performed in a coordinated and coherent fashion. We present the design of such an integrated architecture, with a case study to illustrate how it is simple yet effective to monitor and configure complex multimedia applications.