clusterhub

clusterhub

An attempt at giving multi process node programs a simple and efficient way to share data.

Usage

var cluster = require('cluster');
var numCPUs = require('os').cpus().length;
var hub = require('clusterhub');

if (cluster.isMaster) {
  // Fork workers.
  for (var i = 0; i < numCPUs; i++) {
    cluster.fork();
  }

} else {
  hub.on('event', function(data) {
    // do something with `data`
  });

  // emit event to all workers
  hub.emit('event', { foo: 'bar' });
}

Features

• Cluster agnostic. If you decide to include this in your app, it will work regardless of your app being used with cluster or not.
• Efficient event emitter system. If a process is listening to an event emitted from the same process, the listener will immediately be fired instead of waiting for the event to be broadcasted from the master.
• In process database. Each hub has its own instance of a redis-like database powered by EventVat.

Motive

Node.js is a perfect candidate to developing Date Intensive Real-time Applications. Load balancing in these applications can become complicated when having to share data between processes.

A remote database can be an easy solution for this, but it's not the most optimal. Communicating with a local process is several times faster than opening remote requests from a database. And even if the database is hosted locally, the overhead of communicating with yet another program is lessened.

clusterchat, a multi process chat applicationa that uses socket.io was made with clusterchat by allowing socket.io to sync its data using socket.io-clusterhub.

Note that this module is still experimental. It currently works by using a process's internal messaging system.

API

hub.createHub(id)

Clusterhub already comes with a default global hub. Use this if you want to create a custom hub.

Hub#destroy()

Call to disable hub from emitting and receiving remote messages/commands.

Hub#getWorkers()

Returns an array of all workers (child processes) spawned with cluster.fork().

Additionally, all functions from the regular EventEmitter are included. Plus a couple of extras.

Hub#emitLocal(event, [args...])

Use this to emit an event only to the current process.

Hub#emitRemote(event, [args...])

Use this to emit an event only to other worker processes and master. Or only to workers if the current process is the master.

hub.on('remotehello', function() {
  // hello from another process
});

hub.emitRemote('remotehello', { hello: 'there' });

All functions from EventVat are included as well. Their returned value can be accessed by providing a callback as the last argument. Or directly if used by the master.

worker process

hub.set('foo', 'bar', function() {
  hub.get('foo', function(val) {
    console.log(val === 'bar'); // true
  });
});

master process

var returnedVal = hub.incr('foo', function(val) {
  console.log(val === 1); // true
});

console.log(returnedVal === 1); // true

Install

npm install clusterhub

Tests

Tests are written with mocha

npm test

License

MIT