Seeing is Believing: A Client-Centric Specification of Database Isolation
Seeing is Believing: A Client-Centric Specification of Database Isolation
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DOI：
10.1145/3087801.3087802
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发表时间：
2017-07
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影响因子：
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通讯作者：
Natacha Crooks;Youer Pu;L. Alvisi;Allen Clement
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作者：
Natacha Crooks;Youer Pu;L. Alvisi;Allen Clement
本文介绍了第一个基于状态的隔离保证形式化。我们的方法基于一个简单的观察：应用程序将存储系统视为黑匣子，黑匣子会通过一系列状态进行转换，应用程序可以观察到其中的一个子集。根据这些状态定义隔离保证可以将定义从特定于实现的假设中解放出来。它立即明确了应用程序可以观察到的异常情况（如果有），从而弥合了当今隔离保证的定义方式和感知方式之间存在的差距。基于客户可观察状态的定义带来的清晰度带来了几个好处。首先，它使我们能够轻松比较不同但语义上接近的隔离保证的保证。我们发现，以前被认为是不同的几个众所周知的保证实际上是等效的，并且许多以前无与伦比的快照隔离风格可以组织在一个干净的层次结构中。其次，将定义从特定于实现的工件中解放出来可以建议更有效地实现相同的隔离保证。我们展示了以客户端为中心的并行快照隔离实施如何能够更好地应对级联减速（大规模数据中心的常见现象）。
This paper introduces the first state-based formalization of isolation guarantees. Our approach is premised on a simple observation: applications view storage systems as black-boxes that transition through a series of states, a subset of which are observed by applications. Defining isolation guarantees in terms of these states frees definitions from implementation-specific assumptions. It makes immediately clear what anomalies, if any, applications can expect to observe, thus bridging the gap that exists today between how isolation guarantees are defined and how they are perceived. The clarity that results from definitions based on client-observable states brings forth several benefits. First, it allows us to easily compare the guarantees of distinct, but semantically close, isolation guarantees. We find that several well-known guarantees, previously thought to be distinct, are in fact equivalent, and that many previously incomparable flavors of snapshot isolation can be organized in a clean hierarchy. Second, freeing definitions from implementation-specific artefacts can suggest more efficient implementations of the same isolation guarantee. We show how a client-centric implementation of parallel snapshot isolation can be more resilient to slowdown cascades, a common phenomenon in large-scale datacenters.