Grid-based dynamic service overlays

Variations in service demand and resource availability on the Internet compel service operators to deploy and modify service overlays manually: installing new service instances, reconfiguring existing service instances and creating new connections. Service overlays are increasingly difficult to manage due to their size and coordination requirements for low latency, load balancing and high availability. An approach is required that adapts service overlays to demand and resource availability variations without the intervention of service operators. In this article, we propose a Grid-based architecture and an implementation that make dynamic service overlays possible. We have designed a layered Grid-based architecture: a collective layer that contains the service overlay component, a resource layer that contains the execution environment and service process components, a connectivity layer for communication among components and a fabric layer with programmable infrastructure mechanisms. The implementation makes use of Grid factories for creation of execution-environment and service-processes components, and Grid manager and Grid controller for service-overlay creation and control. Experiments have been performed which deployed, adjusted, modified and destroyed three kinds of service overlays, proxy cache hierarchy, chat server network and JXTA P2P application, over a world-wide programmable infrastructure. Response times of such dynamic operations measured in such experiments have been satisfactory, in the order of tens of seconds. Experiments show that execution environment preparation and code downloading are the mechanisms that contribute the larger overhead.