The $k$-atomicity property can be used to describe the consistency of data operations in large distributed storage systems. The weak consistency guarantees offered by such systems are seen as a nec...

Although it has been commercially successful to deploy weakly consistent but highly-responsive distributed datastores, the tension between developing complex applications and obtaining only weak consistency guarantees becomes more and more severe. The almost strong consistency tradeoff aims at achieving both strong consistency and low latency in the common case. In distributed storage systems, we investigate the generic notion of almost strong consistency in terms of designing fast read algorithms while guaranteeing Probabilistic Atomicity with well-Bounded staleness (PAB). This problem has been explored in the case where only one client can write the data. However, the more general case where multiple clients can write the data has not been studied. In this article, we study the fast read algorithm for PAB in the multi-writer case. We show the bound of data staleness and the probability of atomicity violation by decomposing inconsistent reads into the read inversion and the write inversion patterns. We implement the fast read algorithm and evaluate the consistency-latency tradeoffs based on the instrumentation of Cassandra and the YCSB benchmark framework. The theoretical analysis and the experimental evaluations show that our fast read algorithm guarantees PAB, even when faced with dynamic changes in the computing environment.

background

/pdf/achieving-probabilistic-atomicity-with-well-bounded-4or02xtk8u.pdf

Computing $k$-Atomicity in Polynomial Time

Achieving Probabilistic Atomicity With Well-Bounded Staleness and Low Read Latency in Distributed Datastores

Both providers and consumers of distributed storage services benefit from the quantification of the severity of consistency violations. However, existing methods fail to capture a typical pattern of violation - the disorder among operations with reference to the ideally strong atomic execution. Such disorder are often seen in Internet applications based on distributed storage services, such as instant messaging. To this end, we use inversions in a permutation with reference to the totally-ordered permutation to measure the consistency of data. The $i$-atomicity model is proposed and a (pseudo-)polynomial verification algorithm for a restricted type of histories is proposed. The basic idea of the verification algorithm is brute-force search of the permutation with less than $i$ inversions, which requires exponential cost. Reasonable assumptions abstracted from applications scenarios can be leveraged to prune the search space, which yields an efficient polynomial verification algorithm.

background or methods

Inversion-based Measurement of Data Consistency for Read/Write Registers.

Large-scale replicated data type stores often resort to eventual consistency to guarantee low latency and high availability. It is widely accepted that programming over eventually consistent data stores is challenging, since arbitrary divergence among replicas is allowed. Moreover, pragmatic protocols actually achieve consistency guarantees stronger than eventual consistency, which can be and need to be utilized to facilitate the reasoning of and programming over replicated data types. Toward the challenges above, we propose the ViSearch framework for precise measurement of eventual consistency semantics. ViSearch employs the visibility-arbitration specification methodology in concurrent programming, which extends the linearizability-based specification methodology with a dynamic visibility relation among operations, in addition to the standard dynamic happen-before and linearization relations. The consistency measurement using ViSearch is NP-hard in general. To enable practical and efficient consistency measurement in replicated data type stores, the ViSearch framework refactors the existing brute-force checking algorithm to a generic algorithm skeleton, which further enables efficient pruning of the search space and effective parallelization. We employ the ViSearch framework for consistency measurement in two replicated data type stores Riak and CRDT-Redis. The experimental evaluation shows the usefulness and cost-effectiveness of consistency measurement based on the ViSearch framework in realistic scenarios.

Computing $k$-Atomicity in Polynomial Time

Citations

Achieving Probabilistic Atomicity With Well-Bounded Staleness and Low Read Latency in Distributed Datastores

Inversion-based Measurement of Data Consistency for Read/Write Registers.

ViSearch: Weak Consistency Measurement for Replicated Data Types

Related Papers (5)

Meta-analysis for Atomicity Violations under Nested Locking

On the k-Atomicity-Verification Problem

Probabilistically-Atomic 2-Atomicity: Enabling Almost Strong Consistency in Distributed Storage Systems

Monitoring Atomicity in Concurrent Programs

The fuzzylog: a partially ordered shared log