arXiv subjects

Christopher Meiklejohn

Publications and source records attributed to Christopher Meiklejohn.

7 recordsLinked to original sources

arXiv2024

Can My Microservice Tolerate an Unreliable Database? Resilience Testing with Fault Injection and Visualization

In microservice applications, ensuring resilience during database or service disruptions constitutes a significant challenge. While several tools address resilience testing for service failures, there is a notable gap in tools specifically designed for resilience testing of database failures. To bridge this gap, we have developed an extension for fault injection in database clients, which we integrated into Filibuster, an existing tool for fault injection in services within microservice applications. Our tool systematically simulates database disruptions, thereby enabling comprehensive testing and evaluation of application resilience. It is versatile, supporting a range of both SQL and NoSQL database systems, such as Redis, Apache Cassandra, CockroachDB, PostgreSQL, and DynamoDB. A defining feature is its integration during the development phase, complemented by an IntelliJ IDE plugin, which offers developers visual feedback on the types, locations, and impacts of injected faults. A video demonstration of the tool's capabilities is accessible at https://youtu.be/bvaUVCy1m1s.

cs.SE↗

arXiv2020

Composing and Decomposing Op-Based CRDTs with Semidirect Products

Operation-based Conflict-free Replicated Data Types (CRDTs) are eventually consistent replicated data types that automatically resolve conflicts between concurrent operations. Op-based CRDTs must be designed differently for each data type, and current designs use ad-hoc techniques to handle concurrent operations that do not naturally commute. We present a new construction, the semidirect product of op-based CRDTs, which combines the operations of two CRDTs into one while handling conflicts between their concurrent operations in a uniform way. We demonstrate the construction's utility by using it to construct novel CRDTs, as well as decomposing several existing CRDTs as semidirect products of simpler CRDTs. Although it reproduces common CRDT semantics, the semidirect product can be viewed as a restricted kind of operational transformation, thus forming a bridge between these two opposing techniques for constructing replicated data types.

cs.DC↗

arXiv2018

Partisan: Enabling Cloud-Scale Erlang Applications

In this work, we present an alternative distribution layer for Erlang, named Partisan. Partisan is a topology-agnostic distributed programming model and distribution layer that supports several network topologies for different application scenarios: full mesh, peer-to-peer, client-server, and publish-subscribe. Partisan allows application developers to specify the network topology at runtime, rather than encoding topology-specific concerns into application code. Partisan additionally adds support for more channels, enabling users to distribute messages over multiple channels, sometimes in parallel. We implement and evaluate Partisan in the Erlang programming language and use it in the evaluation of three scenarios. The first scenario compares the raw performance between Distributed Erlang and Partisan, and shows that Partisan performs on par with or better than Distributed Erlang. The second scenario demonstrates that distributing traffic over multiple connections enables Partisan to perform up to 18x better under normal conditions, and up to 30x better in situations with network congestion and high concurrency. The third scenario demonstrates, using existing applications, that configuring the topology at runtime allows applications to perform up to 13.5x better or scale to clusters of thousands of nodes over the general-purpose runtime distribution layer.

cs.DC↗

arXiv2018

Just-Right Consistency: reconciling availability and safety

By the CAP Theorem, a distributed data storage system can ensure either Consistency under Partition (CP) or Availability under Partition (AP), but not both. This has led to a split between CP databases, in which updates are synchronous, and AP databases, where they are asynchronous. However, there is no inherent reason to treat all updates identically: simply, the system should be as available as possible, and synchronised just enough for the application to be correct. We offer a principled Just-Right Consistency approach to designing such applications, reconciling correctness with availability and performance, based on the following insights:(i) The Conflict-Free Replicated Data Type (CRDTs) data model supports asynchronous updates in an intuitive and principled way.(ii) Invariants involving joint or mutually-ordered updates are compatible with AP and can be guaranteed by Transactional Causal Consistency, the strongest consistency model that does not compromise availability. Regarding the remaining, "CAP-sensitive" invariants:(iii) For the common pattern of Bounded Counters, we provide encapsulated data type that is proven correct and is efficient; (iv) in the general case, static analysis can identify when synchronisation is not necessary for correctness.Our Antidote cloud database system supports CRDTs, Transactional Causal Consistency and the Bounded Counter data type. Support tools help design applications by static analysis and proof of CAP-sensitive invariants. This system supports industrial-grade applications and has been tested experimentally with hundreds of servers across several geo-distributed data centres.

cs.DC↗

arXiv2016

Worlds of Events: Deduction with Partial Knowledge about Causality

Interactions between internet users are mediated by their devices and the common support infrastructure in data centres. Keeping track of causality amongst actions that take place in this distributed system is key to provide a seamless interaction where effects follow causes. Tracking causality in large scale interactions is difficult due to the cost of keeping large quantities of metadata; even more challenging when dealing with resource-limited devices. In this paper, we focus on keeping partial knowledge on causality and address deduction from that knowledge. We provide the first proof-theoretic causality modelling for distributed partial knowledge. We prove computability and consistency results. We also prove that the partial knowledge gives rise to a weaker model than classical causality. We provide rules for offline deduction about causality and refute some related folklore. We define two notions of forward and backward bisimilarity between devices, using which we prove two important results. Namely, no matter the order of addition/removal, two devices deduce similarly about causality so long as: (1) the same causal information is fed to both. (2) they start bisimilar and erase the same causal information. Thanks to our establishment of forward and backward bisimilarity, respectively, proofs of the latter two results work by simple induction on length.

cs.DC↗

arXiv2015

Declarative, Secure, Convergent Edge Computation

Eventual consistency is a more natural model than strong consistency for a distributed system, since it is closer to the underlying physical reality. Therefore, we propose that it is important to find a programming model that is both congenial to developers and supports eventual consistency. In particular, we consider that a crucial test for such a model is that it should support edge computation in a both natural and secure way. We present a preliminary work report with an initial solution, called Lasp, which resembles a concurrent functional language while naturally supporting an eventually consistent coordination-free distribution model.

cs.DC↗

arXiv2014

Vector Clocks in Coq: An Experience Report

This report documents the process of implementing vector clocks in the Coq proof assistant for extraction and use in the distributed Dynamo-inspired data store, Riak. In this report, we focus on the technical challenges of using Core Erlang code extracted from the proof assistant in a production-grade Erlang application, as opposed to verification of the model itself.

cs.DC↗