The Homeostasis Protocol

Abstract

Datastores today rely on distribution and replication to achieve improved performance and fault-tolerance. But correctness of many applications depends on strong consistency properties-something that can impose substantial overheads, since it requires coordinating the behavior of multiple nodes. This paper describes a new approach to achieving strong consistency in distributed systems while minimizing communication between nodes. The key insight is to allow the state of the system to be inconsistent during execution, as long as this inconsistency is bounded and does not affect transaction correctness. In contrast to previous work, our approach uses program analysis to extract semantic information about permissible levels of inconsistency and is fully automated. We then employ a novel homeostasis protocol to allow sites to operate independently, without communicating, as long as any inconsistency is governed by appropriate treaties between the nodes. We discuss mechanisms for optimizing treaties based on workload characteristics to minimize communication, as well as a prototype implementation and experiments that demonstrate the benefits of our approach on common transactional benchmarks.

Hampa: Solver-Aided Recency-Aware Replication

“…As the consistency decreases (staleness bound increases), the latency decreases (responsiveness increases). Warranties [38] and Homeostasis [47] allow local updates if they keep the validity of certain assertions. Although other replicas can rely on the validity of the assertions, the staleness of their state is not bounded.…”

“…These projects seem to be the steps towards reviving the same three pillars of consistency, i.e. integrity, convergence and recency, with as little coordination [7,35,47] as possible. CRDTs [48] revived convergence.…”

Conflict-Free Replicated Data Types CRDTs

“…A number of other works have proposed techniques to verify the correctness of distributed systems that run under weak consistency, identifying when coordination is necessary [46,10,62,33,73,6]. Some of these works focused on systems that use CRDTs.…”