2016 USENIX Annual Technical Conference (USENIX ATC '16)

Consensus is at the core of many production-grade distributed systems. Given the prevalence of these systems, it is important to offer consensus as a cloud service. To match the multi-tenant requirements of the cloud, consensus as a service must provide performance guarantees, and prevent aggressive tenants from disrupting the others. Fulfilling this goal is not trivial without overprovisioning and under-utilizing resources.

We present Filo, the first system to provide consensus as a multi-tenant cloud service with throughput guarantees and efficient utilization of cloud resources. Tenants request an SLA by specifying their target throughput and degree of fault-tolerance. Filo then efficiently consolidates tenants on a shared set of servers using a novel placement algorithm that respects constraints imposed by the consensus problem. To respond to the load variations at runtime, Filo proposes a novel distributed controller that piggybacks on the consensus protocol to coordinate resource allocations across the servers and distribute the unused capacity fairly. Using a real testbed and simulations, we show that our placement algorithm is efficient at consolidating tenants, and while obtaining comparable efficiency and fairness, our distributed controller is ~5x faster than the centralized baseline approach.