An Event Service to Support Grid Computational Environments, Concurrency and Computation: Practice and Experience

We believe that it is interesting to study the system and software architecture of environments which integrate the evolving ideas of computational grids, distributed objects, web services, peer-to-peer networks and message oriented middleware. Such peer-to-peer (P2P) Grids should seamlessly integrate users to themselves and to resources which are also linked to each other. We can abstract such environments as a distributed system of “clients ” which consist either of “users ” or “resources ” or proxies thereto. These clients must be linked together in a flexible fault tolerant efficient high performance fashion. In this paper, we study the messaging or event system – termed GES or the Grid Event Service – that is appropriate to link the clients (both users and resources of course) together. For our purposes (registering, transporting and discovering information), events are just messages – typically with time stamps. The messaging system GES must scale over a wide variety of devices – from hand held computers at one end to high performance computers and sensors at the other extreme. We have analyzed the requirements of several Grid services that could be built with this model, including computing and education and incorporated constraints of collaboration with a shared event model. We suggest that generalizing the well-known publish-subscribe model is an attractive approach and here we study some of the issues to be addressed if this model is used in the GES. key words: distributed messaging, publish subscribe, guaranteed delivery, grid systems, peer-to-peer infrastructures and event distribution systems