Type-Checking CRDT Convergence

Conflict-Free Replicated Data Types (CRDTs) are a recent approach for keeping replicated data consistent while guaranteeing the absence of conflicts among replicas. For correct operation, CRDTs rely on merge function that is commutative, associative and idempotent. Ensuring such algebraic properties satisfied by implementations, however, left to programmer, resulting in process complex error-prone. While techniques based testing, automatic verification model, mechanized or handwritten proofs available, we lack an able verify concrete CRDT implementations. In this paper, present Propel, programming language with type system captures required implementation. The Propel deduces case analysis induction: sum types guide enable induction free. Propel’s key feature its capacity reason about (a) terms rewrite rules (b) derive equality inequality expressions from properties. We provide implementation as Scala embedding, implement several CRDTs, them compare four state-of-the-art tools. Our evaluation shows automatically deduce relevant common implementations found open-source libraries even cases which competitors timeout.