Consistency Oracles: Towards an Interactive and Flexible Consistency Model Specification

Many modern distributed storage systems emphasize availability and partition tolerance over consistency, leading to many systems that provide weak data consistency. However, weak data consistency is difficult for both system designers and users to reason about. Formal specifications offer precise descriptions of consistency behavior, but they require expertise and specialized tools to apply to real software systems. In this paper, we propose and describe consistency oracles, an alternative way of specifying the consistency model of a system that provides interactive answers, making them easier and more flexible to use in a variety of ways. A consistency oracle mimics the interface of a distributed storage system, but returns all possible values that may be returned under a given consistency model. This allows consistency oracles to be directly applied in the testing and verification of both distributed storage systems and the client software that uses those systems.We would like to thank Eyal de Lara, Michael Stumm, Michelle Wong, Zhen Huang and the participants of the HotOS workshop for their helpful comments on this work. The research in this work is supported by a Tier 2 Canada Research Chair and an NSERC Discovery Grant. Beom Heyn Kim and Sukwon Oh are both supported by Bell Graduate Scholarships

ChIP: a Choreographic Integration Process

International audienceOver the years, organizations acquired disparate software systems, each answering one specific need. Currently, the desirable outcomes of integrating these systems (higher degrees of automation and better system consistency) are often outbalanced by the complexity of mitigating their discrepancies. These problems are magnified in the decentralized setting (e.g., cross-organizational cases) where the integration is usually dealt with ad-hoc "glue" connectors, each integrating two or more systems. Since the overall logic of the integration is spread among many glue connectors, these solutions are difficult to program correctly (making them prone to misbehaviors and system blocks), maintain, and evolve. In response to these problems, we propose ChIP, an integration process advocating choreographic programs as intermediate artifacts to refine high-level global specifications (e.g., UML Sequence Diagrams), defined by the domain experts of each partner, into concrete, distributed implementations. In ChIP, once the stakeholders agree upon a choreographic integration design, they can automatically generate the respective local connectors, which are guaranteed to faithfully implement the described distributed logic. In the paper, we illustrate ChIP with a pilot from the EU EIT Digital project SMAll, aimed at integrating pre-existing systems from government, university, and transport industry