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作者: 赵劼
答辩日期: 2004
专业: 计算机软件与理论
授予单位: 中国科学院软件研究所
授予地点: 中国科学院软件研究所
学位: 博士
关键词: 中间件 ; Web应用服务器 ; 集群 ; 集群通信
其他题名: Design and Implementation of Cluster Communication System for Web Application Server
摘要: Web应用服务器为多层分布式企业级应用的开发、部署、集成、运行和维护提供了通用的基础设施。随着在网络计算环境下用户规模和数据量的增长,单个Web应用服务器往往不能满足性能、可靠性等方面的需求,需要借助集群技术以提高分布式系统的可用性、可扩展性和处理性能。可靠的集群通信是Web应用服务器信息交互的基础,然而目前应用服务器产品的集群通信系统普遍存在着自适应能力低、容错性较差、可重配能力不足等问题。本文围绕上述问题,探讨了Web应用服务器集群通信系统的设计与实现。首先,本文研究了维持集群结构一致性和正确性的关键问题。分析了Web应用服务器集群结构的应用需求,实现了自适应动态拓扑结构,在集群成员间维持拓扑视图的一致性,完成动态加入和优雅退出操作。提出了分布式对等管理机制,避免了性能和可用性瓶颈。利用管理服务器心跳信号侦测同名集群,通过管理服务器自动降级合并同名集群,保证集群的单一性。实现了失效监测链,在任意服务器失效情况下能够在有限时间内重组集群,同时在管理服务器失效后重新选举管理服务器,增强了集群的整体可用性。其次,本文研究了Web应用服务器集群消息传输的三类模型:PUB/SUB模型、恒定点一点传输模型和临时点一点传输模型,实现了基于集群协作的优化可靠多播,利用滑动窗口进行流控制。在局域网环境下扩展了GossiP算法,实现了分布式消息确认机制,同时依据动态拓扑视图的实时更新避免失效实例对消息的阻塞,在不可靠多播协议的基础上实现了消息的可靠传输。最后,本文描述了可灵活重配的集群通信系统CCSAS的具体实现。CCSAS利用XML结构化对象模型和Java虚拟机的运行时动态绑定机制,根据可配置组件参数和运行策略实现功能类实例的动态加载,赋予集群管理者灵活更改集群结构、备份策略、负载平衡机制等运行时规则的能力,实现了高度柔性的集群。论文的研究成果已应用于中科院软件所自主开发的基于J2EE规范的Web应用服务器OnceAs中。目前,OnceAs已成功用于电子政务、电子商务和ERP系统等领域。
英文摘要: Web application server(WAS) provides a common infrastructure for the development, deployment, integration, running and maintenance of multi-tier distributed enterprise applications. With the increase of user number and data volume in network computing environment, a single WAS cannot always satisfy the need for performance and reliability. It is necessary to improve the availability, scalability and processing capability of WAS with clustering technology. Reliable cluster communication is the base of WAS information exchange. However, there still exist problems such as low adaptability, deficient fault tolerance and lack of configurability in most cluster communication systems of today's application servers. This thesis focuses on these problems and studies the design and implementation of web application server cluster communication system. Firstly, this thesis studies the key issues of maintaining the consistency and correctness of cluster structure. It analyzes the application requirements of WAS cluster structure and implements an adaptive dynamic topology. The consistency of topology views is kept around the cluster members and graceful joining and leaving operations are performed. This thesis brings about a distributed noncentral management mechanism to avoid performance and availability bottleneck. Homonymous clusters are detected through heartbeat signals and merged by automatic administrative server degradation to keep the uniqueness of clusters. A fail-detect chain is implemented to reorganize the cluster in a limited period of time in case that any number of servers would fail. And a new administrative server would be selected if the original failed, which greatly improves the whole availability of clusters. Secondly, this thesis studies three types of models of WAS cluster message transport: PUB/SUB model, constant peer-to-peer model and temporary peer-to-peer model. It implements the optimized multicast based on cluster cooperation and uses sliding windows to fulfill flow-control. Gossip algorithm is extended in the LAN environment to facilitate the distributed message acknowledgement. Real-time update of dynamic topology view is used to prevent failed instances to block message transfer. Thus, reliable message exchange is implemented on top of unreliable multicast protocols. At last, this thesis describes the implementation of the flexibly configurable cluster communication system - CCS AS. In CCS AS, XML structural object model and Java dynamic binding mechanism are used to dynamically load instances of functionality class according to the component parameters and runtime policies, which grants the administrator of cluster capabilities of flexibly changing runtime rules such as cluster structure, backup policy and load balancing method. A cluster with great flexibility is achieved in this way. The CCSAS cluster communication system has been integrated in the J2EE web application server OnceAS which is developed independently by the Institute of Software, Chinese Academy of Sciences. Now OnceAS has been widely used in such fields as E-Government, E-Commerce and ERR.
语种: 中文
内容类型: 学位论文
Appears in Collections:中科院软件所

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Recommended Citation:
赵劼. Web应用服务器集群通信系统的设计与实现[D]. 中国科学院软件研究所. 中国科学院软件研究所. 2004-01-01.
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