  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.
