Resource-Aware Migratory Services in Wide-Area Shared Computing Environments

In this paper we present the design and evaluation of a system for deploying highly available and migratable services in shared infrastructures, such as the PlanetLab, where the available resource capacities at a node can fluctuate significantly. A migratable service can monitor its operating conditions and autonomously relocate itself to another node when the available resource capacities at the current node fall below certain acceptable limits. We utilize the autonomous mobile agent paradigm for building such migratable services. Such agents can monitor their operating conditions and follow various migration policies. We investigate here the mechanisms for service relocation, and client-side protocols to access migratory services. The "blackout periods'', i.e. the time during which the clients are unable to access a migrating service, need to be minimized and kept within some tolerable limits for services required to be highly available. We first present the design of a migratable service implemented using a mobile agent, and evaluate its performance in terms of the blackout periods and the service agent's abilities to autonomously migrate in the network. We replicate service agents to reduce the blackout periods, and develop the coordination protocols for autonomous agent migration in a group of service agents. We also present here our work for monitoring PlanetLab nodes for their available resource capacities in order to assist a migratory service in selecting a target node for relocation.