Nonchalantly Perusing Magazines

    TypeScript icon, indicating that this package has built-in type declarations

    0.3.4 • Public • Published


    master-cluster is a utility to facilitate implementing node.js core cluster module in any project. I created this module as I use the cluster module in pretty much all my projects and wanted to remove the boilerplate code. It also provides hot reloading of files on the worker in development mode so that workers are restarted when code is changed.


    In boot.js:

    var MC = require('master-cluster')
      , worker = require.resolve('./server.js');
    MC.start({exec: worker});

    In server.js:

    var MC = require('master-cluster')
      , app = require('./app.js')
      , http = require('http');
    // set the handler that will be used for all new requests
    MC.setFnHandlers(app.index, shutdown);
    // create the server and pass MC run handler
    // workers are restarted automatically on crash
    var server = http.createServer(;
    server.listen(3000, function () {
      console.log("Listening on %d", 3000);
    function shutdown () {
        // optional - cleanly close db connections and other resources

    In app.js:

    function index (req, res) {
        // do something with the request and response
    exports.index = index;

    Convenience http server method

    The code above can be simplified if all you need is to start a http server.

    In server.js:

    var MC = require('master-cluster')
      , app = require('./app.js');
    MC.createHttpServer(app.index, 3000, shutdown, function () {
      console.log("Listening on %d", 3000);
    function shutdown () {
        // cleanly close db connections and other resources

    With express

    var app = require('express')();
    var MC = require('master-cluster');
    var responseTime = require('response-time');
    // setup middlewares, mount routes, etc.
    app.use(responseTime({ header: 'x-response-time' }));
    app.get('/', function (req, res) {
      res.end('Hello world');
    MC.createHttpServer(app, 3000);
    console.log('Server listening on %d', 3000);


    Following options can be passed to the master cluster configuration:

    • exec: file path to worker file (see exec option of cluster.setupMaster)
    • size: the number of workers to start, default is require("os").cpus().length
    • reload: boolean, default is false except when /^dev/.test(process.env.NODE_ENV)
    • logger: optional logger for errors (must implement error method)
    • isCluster: pass false to disable cluster and run master-only process. Setting exec is required in this case

    Reloader specific options:

    • cooldown: number of milliseconds to wait between file changes, default is 100ms
    • extensions: file extensions to watch for and reload on change, default to js
    • path: path to watch for change, default to current directory (.)

    Worker options:

    • killTimeout: timeout to kill the worker on uncaught exception (default 30s)
    • logger: optional logger for errors (must implement error method)

    Method handlers

    • start (options): start the master with cluster options
    • run (): worker http handler that runs the request
    • setFnHandlers (runFn, errorFn): set the run and error handlers
    • setOptions (options): set the options for the workers (logger and kill timeout)
    • createHttpServer (handler, port, onShutdown, onListening): create the http server and setup the run and error handlers


    • cluster: expose node.js cluster module


    This module is still experimental and subject to change. Please open issues for bugs and suggestions in github. Pull requests welcome.


    Jerome Touffe-Blin, @jtblin,


    master-cluster is copyright 2013 Jerome Touffe-Blin and contributors. It is licensed under the BSD license. See the include LICENSE file for details.


    npm i master-cluster

    DownloadsWeekly Downloads






    Unpacked Size

    13.8 kB

    Total Files


    Last publish


    • jtblin