Exploiting the concept of traffic shaping to improve distributed systems under node dynamics

With rapid growth in end hosts´ processing, storage, and bandwidth capacities, the last decade has witnessed tremendous research efforts in building distributed systems to utilize end-host capacity. However, end-host capacities are known for their inherent dynamics such that the end-host participants may often switch between online and offline status due to join, departure, and failure events. To improve system performance in presence of node dynamics, some researchers have taken the approach of recruiting stable nodes or grouping unstable nodes together in order to form an adequate number of stable servers. Nevertheless, such selection/grouping processes may stifle the system scalability or cause the associated overhead to kick-in. In this paper, we exploit the concept of traffic shaping to improve distributed systems under node dynamics. Our contribution is twofold. First, our simulation results show that node dynamics´ effect on the system is not absolute but determined by the input workload´s characteristics as well. To the best of our knowledge, no study has yet evaluated such fundamental performance issues of distributed systems under node dynamics. Based on our observations, we conclude that instead of raising the node-recruiting standard, reducing the job size or smoothing out the job arrival rate can also improve dynamic distributed systems in terms of system throughput and job failure rate at the cost of higher response time. We have also a centralized leaky-bucket controller in our simulation program as proof of concept.