Wait-Free Publish/Subscribe Using Atomic Registers

Abstract

We model wait-free publish/subscribe using multiple-reader, single-writer atomic registers as the sole inter-process communication primitive. The system supports dynamic publishers/subscribers, content-based matching, and durable subscriptions. Publication to M subscribers requires O(M) atomic register operations by the publisher and O(1) similar operations by each subscriber. We also contribute: (a) A wait-free, constant-space, producer-consumer solution, that extends an earlier solution [1] to atomic reads/writes of finite, N -valued integers, where N is the queue size. (b) A conversion of our and earlier fixed-space queues into wait-free, variable-capacity, FIFO communication links which can increase and decrease space upon need from no traffic backlog to O(N ^K) backlog, while minimally consuming Ω(N) space. K is a programmable constant. (c) A proof of the correctness of our solution. We show that our system requires only boolean to N-valued, multiple-reader, single-writer registers, making it applicable in shared and distributed memories [2].