Efficient Synchronization of State-based CRDTs

TL;DR

This paper introduces an optimized synchronization method for delta-based CRDTs that reduces redundancy and improves efficiency by leveraging join decomposition techniques, outperforming existing algorithms.

Contribution

It identifies inefficiencies in current delta-based CRDT synchronization, applies join decomposition to optimize delta generation, and evaluates the improved algorithms.

Findings

Reduced synchronization overhead compared to previous methods.

Achieved more efficient delta propagation with less redundancy.

Demonstrated improved performance through empirical evaluation.

Abstract

To ensure high availability in large scale distributed systems, Conflict-free Replicated Data Types (CRDTs) relax consistency by allowing immediate query and update operations at the local replica, with no need for remote synchronization. State-based CRDTs synchronize replicas by periodically sending their full state to other replicas, which can become extremely costly as the CRDT state grows. Delta-based CRDTs address this problem by producing small incremental states (deltas) to be used in synchronization instead of the full state. However, current synchronisation algorithms for Delta-based CRDTs induce redundant wasteful delta propagation, performing worse than expected, and surprisingly, no better than State-based. In this paper we: 1) identify two sources of inefficiency in current synchronization algorithms for delta-based CRDTs; 2) bring the concept of join decomposition to state-based CRDTs; 3) exploit join decompositions to obtain optimal deltas and 4) improve the efficiency of synchronization algorithms; and finally, 5) evaluate the improved algorithms.