Load balancing policies without feedback using timed replicas

Abstract

Dispatching policies such as join the shortest queue (JSQ), join the queue with smallest workload (JSW), and their power of two variants are used in load balancing systems where the instantaneous queue length or workload information at all queues or a subset of them can be queried. In situations where the dispatcher has an associated memory, one can minimize this query overhead by maintaining a list of idle servers to which jobs can be dispatched. Recent alternative approaches that do not require querying such information include the cancel-on-start and cancel-on-complete replication policies. The downside of such policies however is that the servers must communicate either the start or the completion time instant of each service to the dispatcher and must allow the coordinated and instantaneous cancellation of all redundant replicas. In practice, the requirements of query messaging, memory, and replica cancellation pose challenges in their implementation and their advantages are not clear. In this work, we consider load-balancing policies that do not need to query load information, do not need memory, and do not need to cancel replicas. Our policies allow the dispatcher to append a timer to each job or its replica. A job or a replica is discarded if its timer expires before it starts receiving service. We analyze several variants of this policy which are novel and simple to implement. We numerically observe that the variants of the proposed policy outperform popular feedback-based policies for low arrival rates, despite no feedback from servers to the dispatcher.