PALE: Partially Asynchronous Agile Leader Election

TL;DR

This paper introduces PALE, a leader election algorithm designed for highly dynamic distributed systems operating under weak assumptions about message delays and clock synchronization, with proven correctness and efficiency.

Contribution

It presents a novel leader election algorithm that functions in dynamic environments with minimal assumptions, extending applicability to wireless and multi-region networks.

Findings

Algorithm operates under weak assumptions about delays and clock drifts.

Proven correctness and analyzed complexity in terms of time, space, and messages.

Supports extensions like multi-region, self-stabilization, and wireless networks.

Abstract

Many tasks executed in dynamic distributed systems, such as sensor networks or enterprise environments with bring-your-own-device policy, require central coordination by a leader node. In the past it has been proven that distributed leader election in dynamic environments with constant changes and asynchronous communication is not possible. Thus, state-of-the-art leader election algorithms are not applicable in asynchronous environments with constant network changes. Some algorithms converge only after the network stabilizes (an unrealistic requirement in many dynamic environments). Other algorithms reach consensus in the presence of network changes but require a global clock or some level of communication synchronization. Determining the weakest assumptions, under which leader election is possible, remains an unresolved problem. In this study we present a leader election algorithm that operates in the presence of changes and under weak (realistic) assumptions regarding message delays and regarding the clock drifts of the distributed nodes. The proposed algorithm is self-sufficient, easy to implement and can be extended to support multiple regions, self-stabilization, and wireless ad-hoc networks. We prove the algorithm's correctness and provide a complexity analysis of the time, space, and number of messages required to elect a leader.