基于网格服务异常处理的方法

网格服务是提供一组定义明确接口并遵守一定规范的Web服务。网格服务异常(exception)是指网格服务请求、响应和执行过程中可能发生的各种问题。网格服务异常处理的研究依赖于网格系统结构。本文首先对网格服务异常处理进行讨论,然后提出了用于网格服务异常处理的Ant/Bee-Back算法。     

面向服务软件异常处理过程的可终止性验证

大规模面向服务软件运行环境的动态性和不确定性使其异常处理逻辑复杂度高,导致异常处理过程的可终止性验证异常困难。而异常处理过程的可终止性是确保其正确性的重要基础,如果异常处理过程不能终止将导致面向服务软件无法正常运行。目前缺乏异常处理过程的可终止性验证方法,从而无法保证异常处理达到预期的目标。基于着色Petri网(colored Petri net,CPN)提出了一种面向服务软件异常处理过程的可终止性验证方法。该方法建立了包括正常流程和异常处理逻辑的异常层次CPN模型(hierarchy CPN model for exception handling,HCPN4EH)。基于此模型验证了异常处理过程的可终止性。通过一个实例说明了该方法的可行性和有效性。得到的可终止性验证结果可为进一步分析异常处理过程的正确性提供基础。     

服务网格中的事务服务及基于Petri网的正确性分析

面向服务的架构(SOA)推动着网格技术从科学计算走向商业领域,大部分商业应用需要事务的支持．该文提出了服务网格环境下用于事务管理的网格事务服务,它能够动态地发现执行子事务的网格服务;根据事务类型调用原子事务或聚合事务协调算法以保证这些服务在行动上实现期望的一致性．通过Petri网分析技术,将两种协调算法模型化为Petri网并验证了它们的正确性．网格事务服务可以提供较强的事务管理能力并将复杂的处理过程对用户透明,为网格技术的商业化提供了有效的支持．     

K/G:一种网格的使用模式体系结构及应用

传统的客户端／服务器模式通过请求/响应的数据交换方式为用户服务，网格系统的目的是让用户更加方便和高效地共享和使用广域的资源，这可能需要改变现有的计算机系统使用模式和评价方法，基于对网格的特性分析，提出一种K／G(grid key/grid)的网格使用模式体系结构，其关键特点是，用户将网格钥匙(grid key)接入连接网格的终端设备时，网格端的服务和数据实时地动态部署到网格终端为用户服务，还分析了这种使用模式体系结构如何体现网格的动态开放功能特征和高生产率服务的性能特征。     

面向服务应用中服务可用性及其引发的异常处理研究

面向服务应用倡导以松耦合的方式构建开放、动态的网络应用，系统对异常的检测和处理也由此面临许多新的挑战．分析了构建和运行面向服务应用的主要阶段中要面对的异常问题，重点探讨了在应用执行过程中由于服务的可用性问题引发的异常，并提出了一种基于案例匹配的异常处理方法．该方法应用到了奥运公众信息服务平台原型系统FLAME2008中，对其实际效果进行了评价．     

一种基于内存服务的内存共享网格系统

内存密集型应用对运行环境的物理内存要求严格,在物理内存不足时将会引发大量磁盘IO,降低系统性能．传统的网络内存致力于在集群内部通过共享空闲节点的物理内存解决该问题,但受集群负载和内部网络影响较大．通过结合网络内存和服务计算、网格计算等技术,提出一种基于内存服务的内存共享网格系统——内存网格,并分析和讨论了实现内存服务的关键技术和算法．内存网格弥补了网络内存的不足,扩展了网格计算的应用范围．通过基于真实应用运行状态的模拟,证明了内存网格与网络内存相比具有性能的提高．     

服务网格性能优化关键技术研究

服务网格(Service Mesh)是用于处理服务间通信的专用基础设施层.为了有效提升其性能,从并发处理模型和交互协议两个方面研究服务网格的性能优化方法,分别提出基于Reactor设计模式的服务网格高并发处理模型和面向服务网格的轻量级、自定义的代理交互协议,并实现一个服务网格原型系统.通过实验与当前主流的开源服务网格系统Linkerd和Envoy进行性能对比分析,实验结果表明该方法能够显著提升服务网格的并发处理性能,使实现的原型系统在并发处理和通信方面都有良好的性能表现.     

基于QoS的网格错误处理服务选择模型

在检测到错误发生的情况下,错误管理服务如何针对实际的不同网格应用程序,选择恰当的错误处理服务,是保证可靠网格容错能力的一个关键问题.针对网格计算环境下的错误处理需求,提出一种基于服务质量QoS的错误处理服务选择模型.在分析网格错误处理的相关背景及需求基础上,给出几种常用错误处理技术的形式化定义,提出相应的服务质量标准;将基于QoS的错误处理服务选择问题抽象为多属性决策问题,建立相应的决策模型.     

网格工作流技术综述

将工作流技术应用到网格领域中。作为复杂网格应用的一种编程模式是出现网格工作流这一概念的目的。但网格动态、异构、分布的运行环境给传统工作流技术的应用带来了许多新的挑战。其中，主要包括活动的协调、数据流管理、服务的动态绑定、事务性与异常处理、流程的验证和优化以及流程运行的监测等方面的内容，针对这些问题，文章从工作流生命周期的角度出发，并结合具体相关的研究项目作出较为深入的分析，并指出了可行的解决方向。     

CGSP作业管理器合成服务的QoS优化模型及求解

服务网格为松散的分布式服务提供了一个“电子市场”,使整合这些来自不同地方的异构的、动态的资源成为可能．CGSP的作业管理器提供了一个网格环境下的服务合成工具．在CGSP作业管理器早期开发和使用的实践中,作者发现合成服务难以提供预期的服务质量将成为CGSP网格服务合成技术走向实用化所面临的重要挑战．为此文章提出了一种合成服务的QoS优化模型．此模型的主要特点是：(1)服务虚拟化;(2)可扩展的QoS度量;(3)基于多度量的合成服务全局QoS优化．为此建立了数学模型并给出了两种求解算法．用程序对模型进行了模拟,分析了测试结果,然后从求解速度和优度两个方面比较了两种算法的优劣,并针对此模型在CGSP作业管理器中的实现给出了讨论．     

Toward a modular and efficient distribution for Web service handlers

Over the last few decades, distributed systems have architecturally evolved. One recent evolutionary step is SOA. The SOA model is perfectly engendered in Web services, which provide software platforms for building applications as services. Web services utilize supportive capabilities such as security, reliability, and monitoring. These capabilities are typically provisioned as handlers, which incrementally add new features. Even though handlers are very important, the method of utilization is crucial for obtaining potential benefits. Every attempt to support a service with an additional handler increases the chance of an overwhelmingly crowded handler chain. Moreover, a handler may become a bottleneck because of its comparably higher processing time. In this paper, we present the Distributed Handler Architecture to provide an efficient, scalable, and modular architecture. The performance and scalability benchmarks show that the distributed and parallel handler executions are very promising for suitable handler configurations. The paper is concluded with remarks on the fundamentals of a promising computing environment for Web service handlers. Copyright © 2012 John Wiley & Sons, Ltd.     

Efficient Java exception handling in just‐in‐time compilation

Java uses exceptions to provide elegant error handling capabilities during program execution. However, the presence of exception handlers complicates the job of the just‐in‐time (JIT) compiler, while exceptions are rarely used in most programs. This paper describes two techniques for reducing such complications. First, we delay the translation of an exception handler until the exception really occurs. This on‐demand translation of exception handlers allows more optimizations when translating the main flow, without being hindered by constraints caused by the exception flows. Secondly, for those exceptions that are actually thrown during program execution we insert exception‐type check code and a direct branch to the translated exception handlers. This exception handler prediction is motivated by an observation that frequently thrown exceptions are likely to be handled by the same exception handlers, so this will eliminate the exception processing overhead of the Java virtual machine. Our experiments indicate that the code quality of the main flow is no longer affected by the presence of exception handlers. Also, frequently thrown exceptions can be efficiently handled by the exception handler prediction. Copyright © 2004 John Wiley & Sons, Ltd.     

Dynamic state restoration using versioning exceptions

We explore the semantics and analysis of a new kind of control structure called a versioning exception that ensures the state of the program, at the point when an exception handler is invoked, reflects the program state at the point when the handler is installed. Versioning exceptions provide a transaction-like versioning semantics to the code protected by a handler: modifications performed within the dynamic context of the corresponding handler are versioned, and committed to the store only if the computation completes normally. Similar to the role of backtracking in logic programming, this facility allows unwanted effects of computations to be discarded when exceptional or undesirable conditions are detected. We define a novel points-to analysis to efficiently track changes to the store within handler-protected scopes. The role of the analysis is to facilitate optimizations that minimize the number of locations which must be restored when a versioning exception is raised. The analysis is defined by a reachability approximation over locations that indicates which objects have been potentially modified within a handler scope. The analysis is defined for programs which support first-class procedures, locations, and exceptions.     

The guardian model and primitives for exception handling in distributed systems

This work presents an abstraction called guardian for exception handling in distributed and concurrent systems that use coordinated exception handling. This model addresses two fundamental problems with distributed exception handling in a group of asynchronous processes. The first is to perform recovery when multiple exceptions are concurrently signaled. The second is to determine the correct context in which a process should execute its exception handling actions. Several schemes have been proposed in the past to address these problems. These are based on structuring a distributed program as atomic actions based on conversations or transactions and resolving multiple concurrent exceptions into a single one. The guardian in a distributed program represents the abstraction of a global exception handler, which encapsulates rules for handling concurrent exceptions and directing each process to the semantically correct context for executing its recovery actions. Its programming primitives and the underlying distributed execution model are presented here. In contrast to the existing approaches, this model is more basic and can be used to implement or enhance the existing schemes. Using several examples we illustrate the capabilities of this model. Finally, its advantages and limitations are discussed in contrast to existing approaches.     

Exception handlers in functional programming languages

Constructs for expressing exception handling can greatly help to avoid clutter in code by allowing the programmer to separate the code to handle unusual situations from the code for the normal case. The author proposes a new approach to embed exception handlers in functional languages. The proposed approach discards the conventional view of treating exceptions, as a means of effecting a control transfer; instead, exceptions are used to change the state of an object. The two types of exceptions, terminate and resume, are treated differently. A terminate exception, when raised, is viewed as shielding the input object. On the other hand, a resume exception designates the input object as curable and requires the immediate application of a handler function. This approach enables the clean semantics of functions raising exceptions without associating any implementation restriction and without loss of the referential transparency and the commutativity properties of functions     

Toward modular verifiable exception handling

Recognizing that an error condition is an intrinsic part of the abstract type to which the operation that detects the condition belongs, an attempt is made to specify and implement error condition detection and handling within the framework of the Alphard form, a construct for encapsulation of data type specification and implementation. The essence of the problem is this: while error condition detection is done by the operation in the form, only the user of the type can determine the meaning of the condition with respect to the way the type is used. Thus, the user must be able to specify the handler. Unfortunately, programming the handler often requires access to encapsulated implementation details which are hidden from the user.After discussing the general issues of exception handling, modularity, and abstract data types, this paper proposes a solution for one category of exceptions, namely errors. Specifically an externally visible condition name is the link between an error's occurrence and some externally visible but internally programmed handler for it. Issues raised by this partial solution, including those of proof rules, are discussed.     

A hierarchical exception handler binding mechanism

A mechanism is proposed for binding exception handlers to exceptions. Hierarchical exception classes can be defined and changed during program execution. In addition, the action taken when an exception of a particular class is raised depends upon the type of the current exception handler for that class. The mechanism can be implemented in programming languages that allow runtime determination of an identifier's binding; most dynamically scoped programming languages meet this criterion.     

一种基于本体和Agent的网格服务发现机制

在动态的网格计算环境中分布着大量不同类型的网格服务。快速、准确地进行网格服务发现是影响网格计算性能的关键因素。本文提出了基于本体和Agent的网格服务发现机制,它具有良好的扩展性和完备性。该模型采用Agent代理技术进行服务搜索,不同的代理能够提供不同虚拟组织的本体知识库;利用本体论语义进行服务的匹配,从而实现智能化的服务发现。     

网格服务及调用模型研究

开放网格服务体系结构（OGSA）是在Globus网格计算工具包和Web Service技术融合的基础上提出的一套规范和标准.OGSA以服务为中心,将一切都抽象为服务,网格服务是OGSA的基本概念.在介绍了网格服务的思想之后,分析了OGSA的架构体系,讨论了网格服务的组成以及典型标准接口的功能描述,研究了创建网格服务实例的过程,提出了一个网格服务调用模型,并对其处理过程进行了描述.     

A model of grid service capacity

Computational grids （CGs） are large scale networks of geographically distributed aggregates of resource clusters that may be contributed by distinct organizations for the provision of computing services such as model simulation, compute cycle and data mining. Traditionally, the decision-making strategies underlying the grid management mechanisms rely on the physical view of the grid resource model. This entails the need for complex multi-dimensional search strategies and a considerable level of resource state information exchange between the grid management domains. In this paper we argue that with the adoption of service oriented grid architectures, a logical service-oriented view of the resource model provides a more appropriate level of abstraction to express the grid capacity to handle incoming service requests. In this respect, we propose a quantification model of the aggregated service capacity of the hosting environment that is updated based on the monitored state of the various environmental resources required by the hosted services. A comparative experimental validation of the model shows its performance towards enabling an adequate exploitation of provisioned services.