Conflict-free Replicated Data Types

Conflict-free Replicated Data Types

Oct 2011 | Marc Shapiro, Nuno Preguiça, Carlos Baquero, Marek Zawirski
The paper "Conflict-free Replicated Data Types" by Marc Shapiro, Nuno Preguiça, Carlos Baquero, and Marek Zawirski introduces the concept of Conflict-free Replicated Data Types (CRDTs) to address the challenges of eventual consistency in large-scale distributed systems. The authors propose a formal Strong Eventual Consistency (SEC) model and define CRDTs as data types that satisfy certain mathematical properties, ensuring convergence in the presence of failures. CRDTs are designed to be self-stabilizing and scalable, with no need for remote synchronization. The paper discusses two main approaches: state-based and operation-based. State-based CRDTs use monotonic semilattices, where updates commute and merge operations compute the least upper bound. Operation-based CRDTs use commutativity, where concurrent operations commute and are delivered in causal order. The authors provide examples of CRDTs, such as sets with clean semantics and a directed graph CRDT, and demonstrate how these data types can be composed to build complex applications. The paper also explores the theoretical foundations of CRDTs, including their relationship to sequential consistency and fault tolerance. It highlights the advantages of CRDTs over traditional ad-hoc approaches to eventual consistency, providing a systematic study and theoretical foundation for their use in distributed systems. Future work is planned to further understand the computational capabilities of CRDTs, implement them in practical applications, and evaluate their performance.The paper "Conflict-free Replicated Data Types" by Marc Shapiro, Nuno Preguiça, Carlos Baquero, and Marek Zawirski introduces the concept of Conflict-free Replicated Data Types (CRDTs) to address the challenges of eventual consistency in large-scale distributed systems. The authors propose a formal Strong Eventual Consistency (SEC) model and define CRDTs as data types that satisfy certain mathematical properties, ensuring convergence in the presence of failures. CRDTs are designed to be self-stabilizing and scalable, with no need for remote synchronization. The paper discusses two main approaches: state-based and operation-based. State-based CRDTs use monotonic semilattices, where updates commute and merge operations compute the least upper bound. Operation-based CRDTs use commutativity, where concurrent operations commute and are delivered in causal order. The authors provide examples of CRDTs, such as sets with clean semantics and a directed graph CRDT, and demonstrate how these data types can be composed to build complex applications. The paper also explores the theoretical foundations of CRDTs, including their relationship to sequential consistency and fault tolerance. It highlights the advantages of CRDTs over traditional ad-hoc approaches to eventual consistency, providing a systematic study and theoretical foundation for their use in distributed systems. Future work is planned to further understand the computational capabilities of CRDTs, implement them in practical applications, and evaluate their performance.
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[slides and audio] Conflict-Free Replicated Data Types