【作者】 邹德清；

【导师】 金海；

【作者基本信息】 华中科技大学 ， 计算机系统结构， 2004， 博士

【摘要】 网格是继传统互联网、Web之后的第三个大浪潮,可以称之为第三代互联网。传统互联网实现了计算机系统的连通,Web实现了网页的连通,而网格试图实现互联网上所有资源的全面连通。网格将成为未来的网络基础设施,几乎所有的应用都将基于网格。网格应用领域的重点目前已开始从单纯的科学计算转到科学计算和非科学计算并重上面来。服务网格需要为各类应用提供一种通用的、协同共享的标准中间件,开放式网格服务体系结构OGSA(Open Grid Service Architecture)的提出,标志着服务网格的研究进入了实质性的阶段。服务网格采用标准的“服务”方式,对各种类型应用提供统一的支持。Web服务资源框架WSRF(Web Services Resource Framework)的提出,加速了网格技术和Web services技术的融合,以及科研界和工业界、商业界研究的接轨,新的服务标准化道路正在逐步形成,基于服务网格平台和标准化协议的各种应用将充分发挥整合共享的优势。HowU信息处理平台正是基于服务网格的理念设计出来的。网格的理念已经逐步得到了社会的认同,但如何采用一种数学的方式来定义网格,对网格中发生的行为进行形式化的描述,这是网格研究者迫切需要解决的问题,此类问题的解决也能为网格的进一步研究和网格系统的开发提供理论指导。作为HowU信息处理平台的理论基础,网格形式化框架及行为规则模型VSP(虚拟组织V、服务池S以及物理资源池P)充分考虑了服务网格的本质特征:动态性、协同性以及服务质量,采用离散数学工具对网格框架进行形式化定义,采用ASM(Abstract State Machines)对网格的行为进行规则描述。如何有效组织、管理和获取服务及其信息是解决服务网格服务质量的一个关键因素。在当前国内外流行的网格信息服务的基础上,HowU信息服务器体系结构分为两个层次:多索引服务器结构和组织域信息服务。多索引服务器结构提供全局的服务路由,同时维持下级注册服务的可用性。组织域信息服务保证服务的当前信息有效性,用于组织域内服务的协商和调度决策。信息的发布是以“服务”为单位的,<WP=5>HowU信息服务器针对服务发布的关键信息──服务能力,提供了评估和预测的方法。针对服务的状态变化、交互机制及一致性问题,HowU信息服务器采用了全局时钟机制及灵活构建的方法。当前网格范围内的服务请求和调度已开始向规范化方向发展,与之相关的协议规范有:SLA(Service Level Agreement)、WS-Agreement和WS-Policy等。在上述协议和虚拟服务的基础上,HowU信息处理平台采用了规范描述和实现相分离的实时容错服务调度机制,并以数据服务为例对该机制进行了实现。数据服务采用了广域网的数据分片方式,提供了具有服务质量保证的数据发布和传输功能、基于文件重要程度和服务等级两种带宽分配策略以及相应的实时容错机制。地理协同标注系统是作为HowU信息处理平台的一个典型示例应用。在地理协同标注系统中,用户的一次协同标注活动可看成一次虚拟组织的活动。作为用户的一次会话过程,是有生命期的,部署在平台上则为一次虚拟组织的访问,用户在虚拟组织中的活动及其管理则表现为地图控制和标注、地图导入以及会话管理。地图导入是基于本平台的数据服务实现的,通过虚拟服务机制定位具体数据服务的物理位置,并采用了SLA机制来协商服务的提供以及服务质量监控和违例处理。会话的管理是基于GT3提供的服务实例展开的,用于维护虚拟组织中所有个体的状态,并提供协同操作功能和容错功能。更多还原

【Abstract】 Grid is regarded as the third generation Internet after traditional Internet and Web. Interconnection among computer hardwares is implemented by traditional Internet. World Wide Web solves the problems from interconnection among web pages. Grid tries to interconnect all the resources on the Internet. Grid will become network infrustructure in the future, almost all the applications will be developed and performed based on grid. The emphasis of grid application has transferred from single science computing into all kinds of applications. Service grid should provide a general, coordinated, standard middleware for all kinds of applications. As the emergence of Open Grid Service Architecture (OGSA), the research on service grid has a real beginning. Web Service Resource Framework (WSRF) accelerates the intergration between grid and Web services, and the association among science research, industry, and business. New way for service standardization is gradually formed, and all kinds of applications can communicate with each other based on grid platform and the standardized protocols. HowU information processing platform is designed and implemented based on service grid.The thought on “grid” is well accepted by the society, but how to define grid with mathematical tools and describe the actions in grid system formally is a large challenge for grid researchers. If such problems are solved perfectly, the further research on grid and the development of grid system will move towards the right way. As the theoretic base of HowU information processing platform, Three-level grid model, VSP model(Virtual organization, Service pool, and Physical resource pool), is proposed with full consideration to the properties of service grid, including dynamic characteristic, coordination, and Quality of Service. The VSP model has adopted discrete mathematics to define grid framework formally, and Abstract State Machine (ASM) is available to describe grid actions by rules.How to effectively organize, manage, and achieve services and their information is a key issue for solving the QoS issue of HowU information processing platform. Based on other popular grid information services, HowU information service is proposed. It is classified into two levels: multiple index server architecture (high level) and organization <WP=7>information service (low level). Multiple index server architecture provides global service routing, and maintains the usability of the low level information server. Organization information service is used to guarantee the validity of current service information, which is available for service negotiation and scheduling decision. A service is taken as the minimal unit of information publication. Service capability, which grid users pay more attentions to, is evaluated and predicted separately for various services. HowU information service provides global time mechanicsm and flexible construction method for solving the issues from service status changing, communication load, and consistency. Currently, service scheduling in grid system evolves towards standardization. There exist some related protocols, such as Service Level Agreement (SLA), WS-Agreement, and WS-Policy, and etc. Based on the above protocols and virtual service mechanism, HowU information processing platform adopts real-time, fault-tolerant service scheduling mechanism, which separates real-time fault-tolerant criterion from the real implementation. Data service is taken as a typical example based on this mechanism. The implementation details of real-time fault-tolerant data service are transparent to grid users. Data service focuses on QoS guarantees for data distribution and transferring, and provides two bandwidth distribution strategies: One is based on file importance, and the other is based on serving grade. In additional, a kind of global optimizing mechanism about file reliability is adopted in data service.Finally a typical demo application – geographical coordination markup system, is developed based on HowU information processing platform.更多还原