FENECIA: failure endurable nested-transaction based execution of composite Web services with incorporated state analysis
FENECIA: failure endurable nested-transaction based execution of composite Web services with incorporated state analysis
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DOI：
10.1007/s00778-007-0076-8
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发表时间：
2007
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影响因子：
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通讯作者：
N. Lakhal;Takashi Kobayashi;H. Yokota
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作者：
N. Lakhal;Takashi Kobayashi;H. Yokota
人们对Web服务(WS)组合(WSC)范例的兴趣正在急剧增加。当实现面向服务的体系结构(Service-Oriented Architecture，SOA)的梦想实现时，分布式计算历史有望发生真正的转变。然而，要实现这样一个雄心勃勃的目标，还有很长的路要走。在本文中，我们支持这样的观点：当挑战WSC问题时，越早认识到故障的必然性并定义适当的故障处理机制，从复合WS(CWS)规范的非常早期阶段开始，就越有可能实现显著的可靠性增长。为了形式化这一愿景，我们提出了FENECIA框架(FENECIA，基于合并状态分析的组合Web服务的故障可容忍嵌套事务执行)框架。我们的框架从不同的角度处理WSC问题，以保证高水平的可靠性。特别是，它的目标是同时成为一种致力于故障处理的CWS规范、执行和服务质量(Qos)评估方法。在我们的框架的第一部分中，我们重点回答为WS体系结构量身定做的规范模型的需求。为此，我们引入了一种新的事务模型WS-SAGAS。WS-SAGAS引入了不属于WS体系结构支柱的关键概念，即任意嵌套、状态、生命度和补偿，以将容错CWS指定为递归嵌套事务的层次结构。此外，为了定义CWS执行语义，而不受基于XML的符号的阻碍，我们描述了一种文本符号，它从定义规则、可组合性规则和排序规则方面描述了WSC，并引入了图形和形式符号。这些规则提供了根据执行正确性验证依赖来形式化CWS的执行语义所需的坚实基础。为了确保CWS的可靠执行，我们在FENECIA架构的第二节中介绍了抛出，其中生成的CWS的执行控制在动态发现的引擎之间分发，这些引擎以对等方式通信。通过跟踪CWS的执行进度以及强制向前和向后恢复，可以在抛出中保证可靠的执行。在我们的方法的第三部分中，我们集中展示在获取更准确的CWS服务质量估计时，故障考虑是如何微不足道的。我们提出了一个模型来评估CWS的几个服务质量属性，这些属性被指定为WS-SAGAS事务并在抛出中执行。通过描述一个已实现的原型和一个案例研究，验证了我们的建议，并展示了它的可行性和广泛的适用性。
Interest in the Web services (WS) composition (WSC) paradigm is increasing tremendously. A real shift in distributed computing history is expected to occur when the dream of implementing Service-Oriented Architecture (SOA) is realized. However, there is a long way to go to achieve such an ambitious goal. In this paper, we support the idea that, when challenging the WSC issue, the earlier that the inevitability of failures is recognized and proper failure-handling mechanisms are defined, from the very early stage of the composite WS (CWS) specification, the greater are the chances of achieving a significant gain in dependability. To formalize this vision, we present theFENECIA (Failure Endurable Nested-transaction based Execution of Composite Web services with Incorporated state Analysis)framework. Our framework approaches the WSC issue from different points of view to guarantee a high level of dependability. In particular, it aims at being simultaneously a failure-handling-devoted CWS specification, execution, and quality of service (QoS) assessment approach. In the first section of our framework, we focus on answering the need for a specification model tailored for the WS architecture. To this end, we introduceWS-SAGAS, a new transaction model. WS-SAGAS introduces key concepts that are not part of the WS architecture pillars, namely,arbitrary nesting,state,vitality degree, andcompensation, to specify failure-endurable CWS as a hierarchy of recursively nested transactions. In addition, to define the CWS execution semantics, without suffering from the hindrance of an XML-based notation, we describe a textual notation that describes a WSC in terms ofdefinition rules,composability rules, andordering rules, and we introduce graphical and formal notations. These rules provide the solid foundation needed to formulate the execution semantics of a CWS in terms ofexecution correctness verification dependencies. To ensure dependable execution of the CWS, we present in the second section of FENECIA ourarchitecture THROWS, in which the execution control of the resulting CWS is distributed among engines, discovered dynamically, that communicate in a peer-to-peer fashion. A dependable execution is guaranteed in THROWS by keeping track of the execution progress of a CWS and by enforcing forward and backward recovery. We concentrate in the third section of our approach on showing how the failure consideration is trivial in acquiring more accurate CWS QoS estimations. We propose a model that assesses several QoS properties of CWS, which are specified as WS-SAGAS transactions and executed in THROWS. We validate our proposal and show its feasibility and broad applicability by describing an implemented prototype and a case study.