Specifying and Implementing an Eventual Leader Service for Dynamic Systems

The election of an eventual leader in an asynchronous system prone to process crashes is an important problem of fault-tolerant distributed computing. This problem is known as the implementation of the failure detector Omega. Nearly all papers that propose algorithms implementing such an eventual leader service consider a static system. In contrast this paper considers a dynamic system, i.e., a system in which processes can enter and leave. The paper has three contributions. It first proposes a specification of Ω suited to dynamic systems. Then, it presents and proves correct an algorithm implementing this specification. Finally, the paper discusses the notion of an eventual leader suited to dynamic systems. It introduces an additional property related to system stability. The design of an algorithm satisfying this last property remains an open challenging problem.