Cache updates in a peer-to-peer network of mobile agents

In open multi-agent systems, agents need resources provided by other agents but they are not aware of which agents provide particular resources. We consider a peer-to-peer approach, in which each agent maintains a local cache with information about k resources, that is for each of the k resources, an agent that provides it. However, when an agent or a resource moves, cache entries become obsolete. We propose a suite of cache update policies that combine pull-based invalidation that is initiated by the agent that maintains the cache with push-based invalidation that is initiated by the agent that moves. We study and compare variations of oblivious flooding-based push/pull along with an informed push approach where each agent maintains a list of the agents that have it cached. Our experimental results indicate that a novel variation of flooding for push where a moving agent propagates its new location to agents in its old neighborhood achieves good cache consistency with a small message overhead. The proposed policies are suitable for any peer-to-peer system where peers cache information about other peers and this information becomes obsolete.