This project aims to provide a simple Scala implementation of Chord, a protocol and algorithm for a peer-to-peer distributed hash table.
It is intended for education purposes, and to better understand the Scala ecosystem.
This repo currently contains the following modules:
- core - core classes and algorithms that make up the Chord implementation
- demo - a simple websocket-based demo, which allows a Chord network to be visualised on a ring
- dht - a minimal Distributed Hash Table (DHT) based on the classes provided by core
The core module is being developed as a reusable Chord library, responsible for maintaining a node's location within a Chord overlay network. This approach, which is based on the protocol described in the Chord paper, allows the Chord network overlay layer to function independently of application-layer concerns such as replication.
The demo module is a single server demo application that can be used to experiment with Chord's network overlay concepts. It provides an RESTful interface for creating nodes, and a browser-based frontend for visualising a Chord ring.
The dht module implements a simple distributed hash table based on Chord. Note: This is a work in progress.
To start the demo server using SBT:
sbt "demo/runMain com.tristanpenman.chordial.demo.Demo"
Once the server has started, the browser-based interface should be accessible via http://127.0.0.1:4567. This page opens a WebSocket connection to the server, and will be updated with nodes and lines representing their successor relationships as they are added to the network.
Initially, the network will be empty:
You can click the 'Add Node' button to add new nodes to network.
Alternatively, nodes can be created via POST requests to the http://127.0.0.1:4567/nodes endpoint. Using cURL, you could create a new node like so:
curl -XPOST -w"\n" http://127.0.0.1:4567/nodes
This would create a new seed node. The response will contain a JSON representation of the new node:
{"nodeId":6,"successorId":6,"active":true}
Although this demo allows you to create multiple independent Chord networks within the same keyspace, you will generally want to create nodes that join an existing network. To create a node that is connected to an existing network, you can specify an existing node as a seed ID. For example:
curl -XPOST -w"\n" http://127.0.0.1:4567/nodes?seed_id=6
After several node insertions, you will end up with a visualisation similar to this:
The list of all existing nodes can be retrieved via a GET request:
curl -XGET -w"\n" http://127.0.0.1:4567/nodes
This will return a JSON array, where each element represents a node:
[{"nodeId":6,"successorId":59,"active":true}, {"nodeId":59,"successorId":6,"active":true}]
Chordial includes a basic test suite (growing all the time!), which can be run via SBT:
sbt test
This project is licensed under the Simplified BSD License. See the LICENSE file for more information.