SpotLess: Concurrent Rotational Consensus Made Practical through Rapid View Synchronization

The emergence of blockchain technology has renewed the interest in consensus-based data management systems that are resilient to failures. To maximize the throughput of these systems, we have recently seen several prototype consensus solutions that optimize for throughput at the expense of overall implementation complexity, high costs, and reliability. Due to this, it remains unclear how these prototypes will perform in real-world environments. In this paper, we present SPOTLESS, a novel concurrent rotational consensus protocol made practical. Central to SPOTLESS is the combination of (1) a chained rotational consensus design for replicating requests with a reduced message cost and low-cost failure recovery that eliminates the traditional complex, error-prone view-change protocol; (2) the novel Rapid View Synchronization protocol that enables SPOTLESS to work in more general network assumptions, without a need for a Global Synchronization Time to synchronize view, and recover valid earlier views with the aid of non-faulty replicas without the need to rely on the primary; (3) a high-performance concurrent consensus architecture in which independent instances of the chained consensus operate concurrently to process requests with high throughput, thereby avoiding the bottlenecks seen in other rotational protocols. Due to the concurrent consensus architecture, SPOTLESS greatly outperforms traditional primary-backup consensus protocols such as PBFT (by up to 430%), NARWHAL-HS (by up to 137%), and HOTSTUFF (by up to 3803%). Due to its reduced message cost, SPOTLESS is even able to outperform RCC, a state-of-the-art high-throughput concurrent consensus protocol, by up to 23%. Furthermore, SPOTLESS is able to maintain a stable and low latency and consistently high throughput even during failures.