15-712: Advanced Operating Systems & Distributed Systems

Paxos

Prof. Phillip Gibbons

Spring 2021, Lecture 14 “Paxos Made Simple” Leslie Lamport 2001

“The Part-Time Parliament” Leslie Lamport 1989/1998 A familiar face

SigOps HoF citation (2012): The work (originally published in 1989) was independent and roughly concurrent with the Viewstamped Replication work also recognized this year. It describes the protocol in a more general setting, adds a correctness argument, and forms the basis for modern Paxos implementations.

2 “The Part-Time Parliament” [submitted 1990; published 1998]

Abstract

3 “Inspired by my success at popularizing the consensus problem by describing it with Byzantine generals, I decided to cast the algorithm in terms of a parliament on an ancient Greek island. Leo Guibas suggested the name Paxos for the island. I gave the Greek legislators the names of computer scientists working in the field, transliterated with Guibas's help into a bogus Greek dialect.

Writing about a lost civilization allowed me to eliminate uninteresting details and indicate generalizations by saying that some details of the parliamentary protocol had been lost. To carry the image further, I gave a few lectures in the persona of an Indiana-Jones-style archaeologist, replete with Stetson hat and hip flask.

My attempt at inserting some humor into the subject was a dismal failure. People who attended my lecture remembered Indiana Jones, but not the algorithm. People reading the paper apparently got so distracted by the Greek parable that they didn't understand the algorithm.” - Leslie Lamport

4 “The Part-Time Parliament”

“I submitted the paper to TOCS in 1990. All three referees said that the paper was mildly interesting, though not very important, but that all the Paxos stuff had to be removed. I was quite annoyed at how humorless everyone working in the field seemed to be, so I did nothing with the paper.”

[Real systems began using Paxos, follow-on papers were appearing, so Lamport tries to publish the same paper in 1998]

“Admittedly, the paper needed revision to take into account the work that had been published in the intervening years. As a way of both carrying on the joke and saving myself work, I suggested that instead of my writing a revision, it be published as a recently rediscovered manuscript, with annotations by [Editor-in-Chief] Keith Marzullo.”

5 “The Part-Time Parliament”

Keith Marzullo’s Annotation (right after the abstract)

6 “Viewstamped Replication: A New Primary Copy Method to Support Highly-Available Distributed Systems” Brian M. Oki, Barbara H. Liskov 1988

• Brian Oki (MIT PhD) – Industry, now at VMware

• Barbara Liskov (MIT) – NAE, NAS, AAAS – John von Neumann Medal – National Inventors Hall of Fame – ACM Turing Award 2008

7 “Viewstamped Replication: A New Primary Copy Method to Support Highly-Available Distributed Systems” Brian M. Oki, Barbara H. Liskov 1988

SigOps HoF citation (2012): The paper introduces a replication protocol very similar to what is now known as Paxos. That protocol has become the standard for consistent, fault-tolerant state-machine replication, and is widely used in data centers to keep the state consistent despite failures and reconfiguration.

8 Implementing Replicated Logs with Paxos https://www.youtube.com/watch?v=JEpsBg0AO6o

This is the link to the 66 minute video on Paxos by Prof. John Ousterhout of Stanford.

In class, we watched the first 31:51 of the video (Basic Paxos). – Note: video from 17:10 to 17:27 is blank

The lecture is part of the Raft User Study, an experiment to compare how students learn the Raft [Ongaro & Ousterhout, ATC’14] and Paxos consensus algorithms.

9 Discussion: Summary Question #1

• State the 3 most important things the paper says. These could be some combination of their motivations, observations, interesting parts of the design, or clever parts of their implementation.

10 Issues in Extending to Full Paxos

11 Discussion: Summary Question #2

• Describe the paper's single most glaring deficiency. Every paper has some fault. Perhaps an experiment was poorly designed or the main idea had a narrow scope or applicability.

12 Friday

Day of meetings to discuss project proposal ideas

Midterm Debrief 11:30-noon Monday

Fault Tolerance (III)

“Practical Byzantine Fault Tolerance” Miguel Castro and Barbara Liskov 1999

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