Incremental consistency guarantees for replicated objects

The Paper

https://www.usenix.org/system/files/conference/osdi16/osdi16-guerraoui.pdf

Summary by Adrian Colyer on the Morning Paper here: https://blog.acolyer.org/2017/01/13/incremental-consistency-guarantees-for-replicated-objects/

Format

We start at 6:10, don't be late!

The discussion lasts for about 1 to 1.5 hours, depending upon the paper.

• Read the paper (done before you arrive)

• Introductions (name, and background)

• First impressions (1-2 minutes this is what I thought)

• Structured review (we move through the paper in order, everyone gets a chance to ask questions, offer comments, and raise concerns)

• Free form discussion

• Nominate and vote on the next paper

• Adjourn for food and/or drink at Steamworks (https://www.google.ca/maps?ion=1&espv=2&q=steamworks&bav=on.2,or.&biw=1674&bih=956&dpr=2&um=1&ie=UTF-8&sa=X&ved=0ahUKEwjTpLXtqb_MAhVC0mMKHWLiBLcQ_AUIBigB)

Abstract

Programming with replicated objects is difficult. Developers must face the fundamental trade-off between consistency and performance head on, while struggling with the complexity of distributed storage stacks. We introduce Correctables, a novel abstraction that hides most of this complexity, allowing developers to focus on the task of balancing consistency and performance. To aid developers with this task, Correctables provide incremental consistency guarantees, which capture successive refinements on the result of an ongoing operation on a replicated object. In short, applications receive both a preliminary—fast, possibly inconsistent—result, as well as a final—consistent—result that arrives later.

We show how to leverage incremental consistency guarantees by speculating on preliminary values, trading throughput and bandwidth for improved latency. We experiment with two popular storage systems (Cassandra and ZooKeeper) and three applications: a Twissandrabased microblogging service, an ad serving system, and a ticket selling system. Our evaluation on the Amazon EC2 platform with YCSB workloads A, B, and C shows that we can reduce the latency of strongly consistent operations by up to 40% (from 100ms to 60ms) at little cost (10% bandwidth increase, 6% throughput drop) in the ad system. Even if the preliminary result is frequently inconsistent (25% of accesses), incremental consistency incurs a bandwidth overhead of only 27%.

Getting There

Stage 3 Systems is near the Vancouver City Centre Canada Line Station, or the Chinatown/Stadium Sky Train station, and there is pay parking available. Enter into the lobby, if no one is there to take you up the elevator, hang on if it's before 6:10, otherwise use the comments to get a hold of us.