Synchronization of Peers in Peer-to-Peer Publish/Subscribe Systems
Hiroki Nakayama, Dilawaer Duolikun, Tomoya Enokido, Makoto Takizawa · 2015
In distributed systems, a group of multiple processes are cooperating with one another by exchanging messages in networks. In this paper, we consider a peer-to-peer (P2P) model of a topic-based publish/subscribe (P2PPS) system composed of peer processes (peers). Each peer pi can both subscribe a subscription pi. S and publish an event message e with a publication e.P, which are specified in terms 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.V = (V1, , Vm) of keywords k1, , km. An event message e1causally precedes an event message e2with respect to a subscription Siiff e1causally precedes e2with respect to the send-receive relation and e1.Vh2.Vhfor every keyword khin the publications e1.P and e2.P and the subscription pi.S. If a pair of event messages e1and e2are ordered so that e1precedes e2even if e1does not causally precede e2, the event messages e1and e2are unnecessarily ordered. In this paper, every pair of messages are causally delivered to every common target peer by using the linear clock and keyword vector to reduce pairs of messages unnecessarily ordered. We evaluate the keyword vectors in terms of number of messages unnecessarily ordered.