Replicated data types

BurckhardtSebastian,; GotsmanAlexey,; YangHongseok,; ZawirskiMarek,

doi:10.1145/2578855.2535848

Cited by 23 publications

(2 citation statements)

References 28 publications

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“…Eventual consistency allows replicas of some data type to temporarily diverge and makes sure that these replicas will eventually converge to the same state in a deterministic way 2 . The conflict‐free replicated data type (CRDT) framework provides a principled approach to maintaining eventual consistency 1,2 . CRDTs are key components in modern geo‐replicated systems, such as Riak, 6 Redis‐Enterprise, 7 and Cosmos DB 8…”

Section: Introductionmentioning

confidence: 99%

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Model‐checking‐driven explorative testing of CRDT designs and implementations

Zhang

Huang

Wei

et al. 2023

J Software Evolu Process

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Internet‐scale distributed systems often replicate data at multiple geographic locations to provide low latency and high availability, despite node and network failures. According to the CAP theorem, low latency and high availability can only be achieved at the cost of accepting weak consistency. The conflict‐free replicated data type (CRDT) is a framework that provides a principled approach to maintaining eventual consistency among data replicas. CRDTs have been notoriously difficult to design and implement correctly. Subtle deep bugs lie in the complex and tedious handling of all possible cases of conflicting data updates. We argue that the CRDT design should be formally specified and model checked, to uncover deep bugs which are beyond human reasoning. The implementation further needs to be systematically tested. On the one hand, the testing needs to inherit the exhaustive nature of the model checking and ensures the coverage of testing. On the other hand, the testing is expected to find coding errors which cannot be detected by design level verification. Toward the challenges above, we propose the model‐checking‐driven explorative testing (MET) framework. At the design level, MET uses TLA+ to specify and model check CRDT designs. At the implementation level, MET conducts model‐checking‐driven explorative testing, in the sense that the test cases are automatically generated from the model‐checking traces. The system execution is controlled to proceed deterministically, following the model‐checking trace. The explorative testing systematically controls and permutes all nondeterministic choices of message reorderings. We apply MET in our practical development of CRDTs. The bugs in both designs and implementations of CRDTs are found. As for bugs which can be found by traditional testing techniques, MET greatly reduces the cost of fixing the bugs. Moreover, MET can find subtle deep bugs which cannot be found by existing techniques at a reasonable cost. Based on our practical use of MET, we discuss how MET provides us with sufficient confidence in the correctness of our CRDT designs and implementations.Conflict‐free replicated data type (CRDT) is a framework that provides a principled approach to maintaining eventual consistency among data replicas in distributed systems. CRDTs have been notoriously difficult to design and implement correctly. We propose model‐checking‐driven explorative testing (MET) framework for dealing with such problem. We apply MET in our practical development of CRDTs. MET successfully finds subtle deep bugs and provides us with sufficient confidence in the correctness of our CRDT designs and implementations.

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Section: Introductionmentioning

confidence: 99%

“…Large‐scale distributed systems often resort to replication techniques to achieve fault‐tolerance and load distribution 1–3 . For a large class of applications, user‐perceived latency and overall service availability are widely regarded as the most critical factors.…”

Section: Introductionmentioning

confidence: 99%

Model‐checking‐driven explorative testing of CRDT designs and implementations

Zhang

Huang

Wei

et al. 2023

J Software Evolu Process

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Replicated Data Types

Shapiro¹

2018

Encyclopedia of Database Systems

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Verifying Visibility-Based Weak Consistency

Krishna

Emmi

Enea

et al. 2020

Programming Languages and Systems

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Multithreaded programs generally leverage e cient and thread-safe concurrent objects like sets, key-value maps, and queues. While some concurrentobject operations are designed to behave atomically, each witnessing the atomic e ects of predecessors in a linearization order, others forego such strong consistency to avoid complex control and synchronization bottlenecks. For example, contains (value) methods of key-value maps may iterate through key-value entries without blocking concurrent updates, to avoid unwanted performance bottlenecks, and consequently overlook the e ects of some linearization-order predecessors. While such weakly-consistent operations may not be atomic, they still o er guarantees, e.g., only observing values that have been present. In this work we develop a methodology for proving that concurrent object implementations adhere to weak-consistency speci cations. In particular, we consider (forward) simulation-based proofs of implementations against relaxedvisibility speci cations, which allow designated operations to overlook some of their linearization-order predecessors, i.e., behaving as if they never occurred. Besides annotating implementation code to identify linearization points, i.e., points at which operations' logical e ects occur, we also annotate code to identify visible operations, i.e., operations whose e ects are observed; in practice this annotation can be done automatically by tracking the writers to each accessed memory location. We formalize our methodology over a general notion of transition systems, agnostic to any particular programming language or memory model, and demonstrate its application, using automated theorem provers, by verifying models of Java concurrent object implementations.

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Replicated data types

Cited by 23 publications

References 28 publications

Model‐checking‐driven explorative testing of CRDT designs and implementations

Model‐checking‐driven explorative testing of CRDT designs and implementations

Replicated Data Types

Verifying Visibility-Based Weak Consistency

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