Distributed Hash Table - PPCA 2025

Overview

A DHT is a distributed system that provides a lookup service similar to a hash table: (key, value) pairs are stored in the DHT, and any participating node can efficiently retrieve the value associated with a given key. The goal of a DHT is to store and retrieve data in a scalable, efficient and reliable manner.

There are many algorithms to implement DHT. For this project, you are required to implement Chord protocol and Kademlia protocol. You should write a report for about one page, probably about your architecture, innovation, features and references. As a bonus, you can also implement an application of DHT (for example: File-Transfer or Group-Chat-Room under local area network).

Tutorial

First, you should read the Environment Setup to setup your environment.

A naive implementation of dhtNode is provided in naive/node.go. You can use it as a reference. The code is well commented. It is suggested to read it carefully.

You can read the Tutorial for more information about Go, DHT and how to debug.

Scores

• 40% for the Chord Test
  • 30% Basic test: naive test without "force quit".
  • 10% Advance test: "Force quit" will be tested. There will be some more complex tests.
• 40% for the Kademlia Test (Same as above)
• 20% for a short report and code review
• Extra 10% for the application of DHT

Tests

Note: DHT tests cannot run successfully under Windows or WSL 1. See Environment Setup for more information.

Contact TA if you find any bug in the test program, or if you have some test ideas, or if you think the tests are too hard and you want TA to make it easier.

Basic Test

There are 5 rounds of test in total. In each round,

1. 20 nodes join the network. Then sleep for 10 seconds.
2. Put 150 key-value pairs, query for 120 pairs, and then delete 75 pairs. There is no sleep time between two contiguous operations.
3. 10 nodes quit from the network. Then sleep for 10 seconds.
4. (The same as 2.) Put 150 key-value pairs, query for 120 pairs, and then delete 75 pairs. There is no sleep time between two contiguous operations.

Advance Test

The advance test consists of "Force-Quit Test" and "Quit & Stabilize Test".

Force-Quit Test

The current test procedure is:

• In the beginning, 50 nodes join the network.
• Then put 500 key-value pairs.
• It follows by 9 rounds of force quit. In each round,
  1. 5 nodes force-quit from the network. There is 500ms of sleep time between each force-quit operation.
  2. Query for all key-value pairs.

Quit & Stabilize Test

The current test procedure is:

• In the beginning, 50 nodes join the network.
• Then put 500 key-value pairs.
• Next, every node will quit from the network:
  1. One node quits.
  2. After the node quitting from the network, there is 80ms of sleep time. And then 20 key-value pairs will be queried for.