辅导data编程、讲解Python语言程序、讲解Java，c++编程

日期：2020-10-30 07:13

Assignment 3 - Paxos
PLEASE NOTE: If your code does not compile and run the awarded mark is an automatic zero. Our
expectation is that you are able to code and submit a tested and working copy of your code. There
will not be any partial marks and you are expected to debug and fix errors and test that your code
works on the Linux image at University (CATS machines or ssh remotely to uss.cs.adelaide.edu.au).
A quick note about the implementation of assignment 3. Please make sure that you watch the
video of the Paxos lecture, and clearly understand what the algorithm should be.
I am expecting you to implement this from scratch, meaning that you are not allowed to use
Zookeper and other tools. I also expect you to implement this in Java, as this is the language for
this course.
Assignment Description
Objective
To gain an understanding of consensus and voting protocols in the presence of failures of one or
more of the participants.
Welcome to the Suburbs Council Election!
This year, Suburbs Council is holding elections for council president. Any member of its nine person
council is eligible to become council president.
Member M1 – M1 has wanted to be council president for a very long time. M1 is very chatty over
social media and responds to emails/texts/calls almost instantly. It is as if M1 has an in-brain
connection with their mobile phone!
Member M2 – M2 has also wanted to be council president for a very long time, except their very long
time is longer than everybody else's. M2 lives in a remote part of the Suburbs and thus their internet
connection is really poor, almost non-existent. Responses to emails come in very late, and sometimes
only to one of the emails in the email thread, so it is unclear whether M2 has read/understood them
all. However, M2 sometimes likes to work at Café @ Bottom of the Hill. When that happens, their
responses are instant and M2 replies to all emails.
Member M3 – M3 has also wanted to be council president. M3 is not as responsive as M1, nor as late
as M2, however sometimes emails completely do not get to M3. The other councilors suspect that it’s
because sometimes M3 goes on retreats in the woods at the top of the Suburbs, completely
disconnected from the world.
Members M4-M9 have no particular ambitions about council presidency and no particular
preferences or animosities, so they will try to vote fairly. Their jobs keep them fairly busy and as such
their response times will vary.
How does voting happen: On the day of the vote, one of the councilors will send out an
email/message to all councilors with a proposal for a president. A majority (half+1) is required for
somebody to be elected president.
YOUR TASK:
Write a program that implements a Paxos voting protocol for Suburbs Council President that is fault
tolerant and resilient to various failure types, some of which are shown in the above. Communication
happens strictly via sockets. You are responsible for the message design.
Assessment
Your assignment will be marked out of 100 points, as following:
10 points - Paxos implementation works when two councillors send voting proposals at the same
time
30 points – Paxos implementation works in the case where all M1-M9 have immediate responses to
voting queries
30 points – Paxos implementation works when M1 – M9 have responses to voting queries suggested
by the profiles above, including when M2 or M3 propose and then go offline
20 points – Testing harness for the above scenarios + evidence that they work (in the form of printouts)
10 points for the quality of your code:
Code Quality Checklist
Do!
o write comments above the header of each of your methods, describing
o what the method is doing, what are its inputs and expected outputs
o describe in the comments any special cases
o create modular code, following cohesion and coupling principles
Don’t!
o use magic numbers
o use comments as structural elements (see video)
o mis-spell your comments
o use incomprehensible variable names
o have long methods (not more than 80 lines)
o allow TODO blocks
Bonus
10 points – Paxos implementation works with a number ‘n’ of councilors with four profiles of response
times: immediate; medium; late; never
50 points – (you can use these points in this assignment, or in any other subsequent assignment) –
Fast Byzantine Paxos implementation that works when councilors lie, collude, or intentionally do not
participate in some voting queries but participate in others.
You will need to submit:
Your code
Your testing harness + evidence that the above tests work
A readme file containing instructions about how to compile and run your code