Ensuring referential integrity under causal consistency

TL;DR

This paper demonstrates that causal consistency, a weaker form of consistency, is sufficient to ensure referential integrity in distributed object storage systems, supported by a CRDT model and formal verification.

Contribution

It introduces a CRDT-based approach that maintains referential integrity under causal consistency, challenging the assumption that stronger consistency models are necessary.

Findings

Causal consistency suffices for referential integrity

A CRDT model maintains RI under causal consistency

QuickCheck verified the model's correctness

Abstract

Referential integrity (RI) is an important correctness property of a shared, distributed object storage system. It is sometimes thought that enforcing RI requires a strong form of consistency. In this paper, we argue that causal consistency suffices to maintain RI. We support this argument with pseudocode for a reference CRDT data type that maintains RI under causal consistency. QuickCheck has not found any errors in the model.