Design And Implemention Of Publication And Subscription System Based On WSRF And WS-Notification

Benefit from the conception of Electronic Grid, Grid computing was given birth and developed rapidly in company with internet techniques. Various computing resources, storage, data and other specific resources, which are high-powered, geographically distributed and heterogeneous, are connected in Grid computing schema via internet to achieve optimized composition of resources dynamically and establish collaborate high-performance computing to solve huge application problems cooperatively, hence the name wide-area high-performance meta computing technology, a kind of distributed computing technology as well. A"Virtual Super Computer"is composed of all kinds of resources with distinctions among hardwares, operation systems, organizations and regions masked by Grid infrastructure, shared and managed transparently and efficiently by different users and organizations. Grid computing has powerful data processing capability and is capable of making full use of idle computing resources through internet.Certain system structure is needed to build a Grid system. Grid system structure must identify the basic conponent parts of Grid, clearly explain the relationship among parts and their mode of integration, describe the function, purpose, feature and running mechanism of parts. Grid system structure is the core technique of Grid, the skeleton and soul of Grid. A reasonable system structure can be used to design and build Grid, ensure the capability of Grid. The most influencing Grid system structure is the WS-Resource Framework. Grid needs to contain and use fuctions of web service. The capacity for user to accesss and operate the state-data is supplied by web service. Standards of managing service's state-data need to be defined for application to discover, monitor and interact with stateful resources in a standard and operable way. The purpose of proposing WS-Resource Framework is to standardize web service's capacity and introduce the conception"stateful"into web service. It means Grid group and web service group develop on the same foundation. The Web Services Resource Framework defines conventionsfor managing state in distributed systems based on Web Services, and WS-Notification defines topic-based publish/subscribe mechanisms.Web service is the best way to implement distributed service based on the Internet. However, common web service are usually non-state, which means they would not maintain state among multiple calls. In fact, web service do not keep the information persistent among communications. Therefore, when the grid components are realized in the form of web service, problems would arise. WSRF is designed to solve this problem by introducing the concept of WS-Resource. This paper implements a Globus Toolkit V4 (GT4) grid service, and it fulfils communication by using WS-Notification to publication and subscription mode. This grid service is operated by publishing and subscribing; it receives messages from the author, and transmits them to the editors subscribing related subjects. It is operated as a GT4 grid service, according to the WSN standard of publishing and subscribing behavior.This paper aims to develop GT4 grid service in the Eclipse environment. With proper plug-in units and configuration, Eclipse could manage all the development in a single program abstraction including coding, configuration and debugging. In Eclipse IDE,WS-Notification could be used to develop grid service prototype quickly. The ability of GT4 to make Resource Properties automatically as WSN subjects considerably simplifies the code of the system. The latest submitted information will be stored by grid service when users send a request to the service. When those messages are updated, which means the Source Properties are updated, GT4 will send the notification to the related subscribers automatically. Any user who subscribes related subjects will receive the latest message.Web service pairs could provide one or multiple state resources. WS-Resources could address by endpoint reference. The state of WS-Resources is maintained as a group called Resource Properties, with which the interfaces of Get, Set and Query interact. Providers for WS-Resource and WS-Notification portType are specified with the modification of WSDD configuration file. Thus two testing client services are set up: one is the author, who is to submit new messages to grid service; the other is the editor, who will receive notifications when new messages appear which match the subscribing conditions.Publication-subscription design mode is a general method of communication in Lose Coupling System. The Globus Toolkit V4 (GT4) grid service implemented in this paper is not only on the study of WSRF and WSN, realizing publication-subscription system as described by the standards of the WS-Notification series, but the service is also a good attempt to achieve fast development of grid service by WS-notification. This system is extremely suitable for the situation in which when the producer entity has any change, event and conditions related to the subject, the consumer who subscribes this subject hopes to get notifications. Publish-Subscribe design mode is a very powerful and common way to design Lose Coupling System service and system. WSN series standards could be very well used in web developing field. The functions fulfilled in this paper is only confined t very few of those functions, and it is hoped that this would serve as the foundation for research of more complex publication-subscription service systems.