Putting Order in Strong Eventual Consistency

Abstract

Conflict-free replicated data types (CRDTs) aid programmers develop highly available and scalable distributed systems. However, the literature describes only a limited portfolio of conflict-free data types and implementing custom ones requires additional knowledge of replication and consistency techniques. As a result, programmers resort to ad hoc solutions which are error-prone and result in brittle systems. In this paper, we introduce strong eventually consistent replicated objects (SECROs), a general-purpose data type for building available data structures that guarantee strong eventual consistency (SEC) without restrictions on the operations. To evaluate our solution we compare a realtime collaborative text editor built atop SECROs with a state-of-theart implementation that uses JSON CRDTs. This comparison quantifies various performance aspects. The results show that SECROs are truly general-purpose and memory efficient.

CScript: A distributed programming language for building mixed-consistency applications

“…This forces programmers to choose between availability (AP) and consistency (CP) in the event of a replicas of this RDT are guaranteed to converge to the same state. This paper complements our previous exposition of SECROs in [9] by proving convergence and showing that progress depends on the data type itself. Hence, we formulate a necessary condition for SECRO data types which enables us to give a general proof of progress.…”

“…Having introduced the CScript language and our SECRO data type, we now turn our attention to the replication algorithm behind SECROs. The detailed algorithm is explained in [9]. This paper provides the correctness proofs and presents only the parts of the algorithm that are relevant to the proofs.…”

“…Commit operations commute in order not to compromise availability. The detailed commit algorithm and its explanation can be found in [9].…”

OWebSync: Seamless Synchronization of Distributed Web Clients

“…But this only treats transient network disruptions where clients will come back online eventually, which is not necessarily the case for web clients. Strong Eventually Consistent Replicated Objects (SECROs) [47] are similar to operation-based CRDTs, but do not impose restrictions on commutativity of operations. However, by doing so, they need a global total order and cannot tolerate network disruptions.…”

Squirrel: an extensible distributed key-value store

“…Commutativity lies at the basis of (operation-based) conflict-free replicated data types (CRDTs) [20]. Other work proposed SECROs [7], an alternative data type ensuring SEC that can deal with non-commutative operations by keeping a totally ordered log of operations.…”