Selective Delivery of Event Messages in Peer-to-Peer Topic-Based Publish/Subscribe Systems
Hiroki Nakayama, Dilawaer Duolikun, Tomoya Enokido, Makoto Takizawa · 2015
A distributed system is considered in an event-driven model where states of processes transit on occurrence of events. In this paper, we discuss a peer-to-peer (P2P) model of a topic-based publish/subscribe (P2PPS) system where each peer process (peer) pican both subscribe a subscription pi.S and publish an event message e with a publication e.P. The subscriptions and publications are specified in terms of topics, i.e. keywords. An event message e is notified to a target peer piwhose subscription pi.S includes a common keyword with the publication e.P. Each event message e carries a vector e:KV = 〈kv1, . . . , kvm〉 of keywords k1, . . . , km. An event message e1causally precedes an event message e2with respect to a subscription Siiff not only e1causally precedes e2but also e1·kvh2·kvhfor every keyword khin the publications e1.P and e2.P and the subscription pi.S. A pair of event messages e1and e2are unnecessarily ordered if e1.KV2.KV but e1does not causally precede e2. In this paper, we newly propose a keyword vector (KV) protocol where the linear clock or physical clock is used with keyword vector to reduce pairs of messages unnecessarily ordered. We evaluate the KV protocol and show the number of pairs of unnecessarily ordered messages is reduced.