chord2

chord2

chord2 is a ring-based peer-to-peer protocol.

Installation

$ npm install chord2

Quick start

First you need to add a reference to chord2.

var Chord = require('chord2');

Then create a new node by calling the constructor function and specifying the host and the port to listen on.

Additionally, you need to specify a private key and a certificate. Please note that these values must be strings that contain data in .pem format.

var chord = new Chord({
  host: 'localhost',
  port: 3000,
  privateKey: '...',
  certificate: '...'
});

Optionally you may specify a metadata property to attach arbitrary data to a node. These metadata will be available to others when asking for information about the node. You may use it, e.g., to store information on services a node offers.

var chord = new Chord({
  host: 'localhost',
  port: 3000,
  privateKey: '...',
  certificate: '...',
  metadata: {
    foo: 'bar'
  }
});

Configuring housekeeping

By default, a node tries to do housekeeping around every 30 seconds. If you need to change this, provide a property called serviceInterval.

var chord = new Chord({
  host: 'localhost',
  port: 3000,
  privateKey: '...',
  certificate: '...',
  serviceInterval: '10s'
});

Please note that this affects the way the protocol works. Hence setting the serviceInterval property should be avoided in most cases.

Joining a Chord ring

To join another node, call the join function and provide the host and the port of the node you want to join.

chord.join({
  host: 'localhost',
  port: 4000
}, function (err) {
  // ...
});

To get the status of a node call its status function.

console.log(chord.status());
// => 'lonely' or 'unbalanced' or 'joined'

Finding the responsible node

If you want to find the node responsible for a value, call the getNodeFor function and provide the value as a string.

As a result you will get information on the node itself as well as its metadata. If no metadata have been set, an empty object is returned.

chord.getNodeFor('foobar', function (err, node, metadata) {
  // ...
});

Detecting changes in your neighborhood

To detect whether the successor or predecessor of a node changed, subscribe to the changed-successor and changed-predecessor events. Please note that the predecessor may be undefined.

chord.on('changed-successor', function (successor) {
  // ...
});

chord.on('changed-predecessor', function (predecessor) {
  // ...
});

Running the build

This module can be built using Grunt. Besides running the tests, this also analyses the code. To run Grunt, go to the folder where you have installed chord2 and run grunt. You need to have grunt-cli installed.

$ grunt

License

The MIT License (MIT) Copyright (c) 2012-2015 the native web.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.