Hubraft concepts

Hubraft is a NodeJs partial implementation of The Raft Consensus Algorithm, aiming to fullfil the needs of resilient applications that can't run in parallel.

Hubraft does the election of nodes when the leader stop sending hearbeats, but does not implements data replication.

Install

npm install --save @pontal/hubraft

Initializing

const hubraft = require('@pontal/hubraft')(
    heartbeatInterval: 300, // optional
    minElectionTimeout: 800, // optional
    maxElectionTimeout: 1000, // optional
    name: 'master', // required
    host: 'master.example.com', // required
    port: 9899, // required
    nodes: [{ // required
        name: 'backup1',
        host: 'backup1.example.com',
        port: 9899,
    }, {
        name: 'backup2',
        host: 'backup2.example.com',
        port: 9899,
    }]
);

Options

• heartbeatInterval: (optional) in milliseconds, defaults to 300ms
• minElectionTimeout: (optional) in milliseconds, defaults to 800ms
• maxElectionTimeout: (optional) in milliseconds, defaults to 1000ms
• name: (required) slug that identifies the application node
• host: (required) the hostname/ip which application is running
• port: (required) port which hubraft should listen
• nodes: (required) other nodes of the application (array of name, host, port objects)

How it works

The Hubraft emits the following events :

• becomeLeader
• becomeFollower
• becomeCandidate

- becomeLeader

When the server is elected leader the event "becomeLeader" is sent to other servers, and to apply some type to behavior, use this script:

const hubraft = require('@pontal/hubraft');

let options = {...};

const hub = hubraft.init(options);

hub.eventEmitter.on('becomeLeader', () => {
	// Start your application
}); 

- becomeFollower

The event "becomeFollower" is sent when another server is elected leader, this way the current server is left in "Stand by", and just keeps listening to the leader's heartbeat

const hubraft = require('@pontal/hubraft');

let options = {...};

const hub = hubraft.init(options);

hub.eventEmitter.on('becomeFollower', () => {
	// Stop your system
});

- becomeCandidate

The event "becomeCandidate" is sent when the server was a "Follower" and the leader stops sending the heartbeat, and by default when a server becomes a "Candidate", he automatically asks for an election.

Tests

"Jest" needed.

npm test