Introduction

Please answer the questions precisely and concisely. Every question can be answered in one or at most a few sentences. I will not have the patience to read long paragraphs or essays and you may lose credit for possibly correct answers.

Submission

Please submit your assignment prior to the due date & time via canvas.

Note: submissions must be plain text or PDF files or text entry within Canvas. Other formats, such as Microsoft Word, Apple Pages, or Adobe InDesign will not be accepted.

Reading/watching

(1) Raft: Understandable Distributed Consensus, The Secret Lives of Data.

This is a visualization of Raft in operation. You’ll have to click through the steps and there’s a sentence or two on each screen that explains what’s going on.

(2) Diego Ongaro and John Ousterhout, In Search of an Understandable Consensus Algorithm, 2014 USENIX Annual Technical Conference, June 2014.

This is the definitive paper on Reft. It’s 12 pages long but you can skip sections 5.4 (the last 4.75 pages) if you’re pressed for time. There’s also an extended version that’s a couple of pages longer if you want to read that.

(3) Optional: YouTube video: An Introduction to Raft (CoreOS Fest 2015) by Diego Ongaro

This is a talk about Raft by Diego Ongaro, the creator of Raft.

Questions

Question 1.  

What are the two timeout settings that control elections in Raft?

Question 2.  

Are there conditions where concurrent elections and hence a split vote may arise? If not, how is this prevented? If so, what happens?

Question 3.  

It is possible for a situation arise where there are multiple leaders. Why is this not a problem?

Question 4.  

What is the Log Matching Property in Raft?