RACS-SADL: Robust and Understandable Randomized Consensus in the Cloud

TL;DR

RACS-SADL is a new randomized consensus protocol designed for cloud environments that maintains high performance and robustness under both normal and adversarial network conditions, improving throughput significantly over existing protocols.

Contribution

It introduces RACS, a robust, low-latency randomized consensus protocol inspired by Raft, with a throughput-optimized version SADL-RACS, enhancing cloud system resilience and performance.

Findings

RACS achieves 28k cmd/sec under adversarial conditions, nine times higher than Raft.

RACS matches Raft and Multi-Paxos performance under synchronous networks, with 200k cmd/sec and 300ms latency.

SADL-RACS attains 500k cmd/sec, 150% higher than Raft.

Abstract

Widely deployed consensus protocols in the cloud are often leader-based and optimized for low latency under synchronous network conditions. However, cloud networks can experience disruptions such as network partitions, high-loss links, and configuration errors. These disruptions interfere with the operation of leader-based protocols, as their view change mechanisms interrupt the normal case replication and cause the system to stall. We propose RACS, a novel randomized consensus protocol that ensures robustness against adversarial network conditions. RACS achieves optimal one-round trip latency under synchronous network conditions while remaining resilient to adversarial network conditions. RACS follows a simple design inspired by Raft, the most widely used consensus protocol in the cloud, and therefore enables seamless integration with the existing cloud software stack. Experiments with a prototype running on Amazon EC2 show that RACS achieves 28k cmd/sec throughput, ninefold higher than Raft under adversarial cloud network conditions. Under synchronous network conditions, RACS matches the performance of Multi-Paxos and Raft, achieving a throughput of 200k cmd/sec with a median latency of 300ms, confirming that RACS introduces no unnecessary overhead. Finally, SADL-RACS, a throughput-optimized version of RACS, achieves a throughput of 500k cmd/sec, delivering 150% higher throughput than Raft.