Research On Resource Discovery In A Grid Environment

Resource is the major object of Grid, the aim of Grid is to provide transparent coherent access interface for users via managing all kinds of resources. In grid environment, the dynamic state, heterogeneity and distribution of virtual organization and resources, and the change with time of sharing model and conjunct way, which make the environment resources cannot be allocated beforehand, So usable resources and service information must be obtained in time. This is the work of resource discovery.This thesis studies the current resource discovery mechanism. In current grid environment, the typical resource discovery mechanisms are the resource discovery mechanism in the Globus that adopt MDS, the mechanism in the Condor passing by Matchmaker and the resource discovery mechanism based on rout in Vega Grid. Because grid and P2P are all orient to solve the resources integration and coordination used in a distributed environment, in many respects, they have a strong complementarity. The service discovery mechanism based on directory, flooding or distributed hash tables of the P2P network have also some adaptability to grid environment.With research and comparison of the existing resources discovery mechanism, the current resources discovery method can be divided into three types: concentrate type, distribute type and mixture type of resources discovery method. Because mixture type resources discovery connects the advantage of concentrate type discovery mechanism in system maintenance and resources discovery efficiency with the advantage of distribute type resources discovery in expanding of mechanism and credibility, hence this text puts forward a resource discovery model based on the layer structure, it divide resources and users into different organization by geographical position or administrant domain, it uses concentrative method to organize and inquiry resource information in the organization, but divides it into different virtual organization by the character of resources information, virtual organizations form distributed resource share method via constructing cover net. Besides this, it implements resource inquiry across virtual organization via connecting super nodes of virtual organization.Through analysis of the way overlay network is constructed in Gnutella system, a new method called cycle shift mode is proposed. The overlay network constructed in cycle shift way could guarantee the QoS of the resource discovery service, meanwhile the algorithm of message expanding-M-flooding is presented on the overlay network not only make the resource information disseminate to the whole network in a limited jumping number, but also significantly reduce redundant information by inserting the node marking in the message. So the resource discovery model with the level structure proposed in this thesis has good efficiency and reliability.