Δ-CRDTs: making δ-CRDTs delta-based

Abstract

Replication is a key technique for providing both fault tolerance and availability in distributed systems. However, managing replicated state, and ensuring that these replicas remain consistent, is a non trivial task, in particular in scenarios where replicas can reside on the client-side, as clients might have unreliable communication channels and hence, exhibit highly dynamic communication patterns. One way to simplify this task is to resort to CRDTs, which are data types that enable replication and operation over replicas with no coordination, ensuring eventual state convergence when these replicas are synchronized. However, when the communication patters, and therefore synchronization patterns, are highly dynamic, existing designs of CRDTs might incur in excessive communication overhead. To address those scenarios, in this paper we propose a new design for CRDTs which we call Δ-CRDT, and experimentally show that under dynamic communication patters, this novel design achieves better network utilization than existing alternatives.