Using cluster in an Expressjs app

Question

I\'m doing a little OJT on my first node project and, while I can stand up a simple server, the app is going to get hammered so using cluster seems like a good idea. I\'ve cobbl

Answer 1

Also take a look at cluster2. It's used by eBay and has an express example

var Cluster = require('cluster2'),
    express = require('express');

var app = express.createServer();

app.get('/', function(req, res) {
  res.send('hello');
});

var c = new Cluster({
  port: 3000,
});

c.listen(function(cb) {
  cb(app);
});

Answer 2

For anyone searching later, here's what I ended up with:

var cluster = require( 'cluster' );
var express = require( 'express' );
var path    = require( 'path' );

var port    = 3000;
var root    = path.dirname( __dirname );
var cCPUs   = require('os').cpus().length;

if( cluster.isMaster ) {
  // Create a worker for each CPU
  for( var i = 0; i < cCPUs; i++ ) {
    cluster.fork();
  }

  cluster.on( 'online', function( worker ) {
    console.log( 'Worker ' + worker.process.pid + ' is online.' );
  });
  cluster.on( 'exit', function( worker, code, signal ) {
    console.log( 'worker ' + worker.process.pid + ' died.' );
  });
}
else {
  var app    = express();
  var routes = require( './routes' )( app );

  app
    .use( express.bodyParser() )
    .listen( port );
}

I'm still very early in the node learning curve, but the server starts and appears to have a working running on each core. Thanks to JohnnyH for getting me on the right track.

Answer 3

Here is my draft of Cluster.js class. Note that we should catch port conflict when you start master process.

/*jslint indent: 2, node: true, nomen: true, vars: true */

'use strict';

module.exports = function Cluster(options, resources, logger) {
  var start = function () {
    var cluster = require('cluster');

    if (cluster.isMaster) {
      require('portscanner').checkPortStatus(options.express.port, '127.0.0.1', function (error, status) {
        if (status === 'open') {
          logger.log.error('Master server failed to start on port %d due to port conflict', options.express.port);
          process.exit(1);
        }
      });

      // Each core to run a single process.
      // Running more than one process in a core does not add to the performance.
      require('os').cpus().forEach(function () {
        cluster.fork();
      });

      cluster.on('exit', function (worker, code, signal) {
        logger.log.warn('Worker server died (ID: %d, PID: %d)', worker.id, worker.process.pid);
        cluster.fork();
      });
    } else if (cluster.isWorker) {
      var _ = require('underscore');
      var express = require('express');
      var resource = require('express-resource');

      // Init App

      var app = express();

      // App Property

      app.set('port', process.env.PORT || options.express.port);
      app.set('views', options.viewPath);
      app.set('view engine', 'jade');
      app.set('case sensitive routing', true);
      app.set('strict routing', false);

      // App Middleware

      app.use(express.favicon(options.faviconPath));
      app.use(express.logger({ stream: logger.stream() }));
      app.use(express.bodyParser());
      app.use(express.methodOverride());
      app.use(express.responseTime());
      app.use(app.router);
      app.use(require('stylus').middleware(options.publicPath));
      app.use(express['static'](options.publicPath));

      if (options.express.displayError) {
        app.use(express.errorHandler());
      }

      // App Format

      app.locals.pretty = options.express.prettyHTML;

      // App Route Handler

      if (!_.isUndefined(resources) && _.isArray(resources)) {
        _.each(resources, function (item) {
          if (!_.isUndefined(item.name) && !_.isUndefined(item.path)) {
            app.resource(item.name, require(item.path));
          }
        });
      }

      // Start Server

      var domain = require('domain').create();

      domain.run(function () {
        require('http').createServer(app).listen(app.get('port'), function () {
          logger.log.info('Worker server started on port %d (ID: %d, PID: %d)', app.get('port'), cluster.worker.id, cluster.worker.process.pid);
        });
      });

      domain.on('error', function (error) {
        logger.log.error(error.stack);
      });
    }
  };

  return {
    start: start
  };
};