How to fully utilise server capacity for Node.js Web Apps - node.js

Question

Does the latest Node.js version(4.2.3) supports multi threading now? Hard to find useful answers as most relevant discussions are from years ago.
How would a node.js cloud server handle node.js Web App requests? Say a 2-Core server runs a node.js app, does that mean no matter how heavy the traffic is, they all go through via a single core and the other core is always idle?
If the answer is yes, any recommendations of some third party libs could possibly achieve multi-threading for node.js Web Apps?
Thanks for the helps. In addition to the above question. I adopted the cluster code into an Express.js web app, it turns out the else block is not executed in the below code section.
var app = require('../app');
var debug = require('debug')('NewExpress:server');
var http = require('http');
var cluster = require('cluster');
var numCPUs = require('os').cpus().length;
if (cluster.isMaster) {
// Fork workers.
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
cluster.on('exit', function(worker, code, signal) {
console.log('worker ' + worker.process.pid + ' died');
});
} else {
/**
* Get port from environment and store in Express.
*/
var port = normalizePort(process.env.PORT || '3000');
app.set('port', port);
/**
* Create HTTP server.
*/
var server = http.createServer(app);
/**
* Listen on provided port, on all network interfaces.
*/
server.listen(port);
server.on('error', onError);
server.on('listening', onListening);
}
Any ideas how should I implement cluster in here?

Answer 1

You can use each of your cpus like this:
var cluster = require('cluster');
var numCPUs = require('os').cpus().length;
if (cluster.isMaster) {
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
} else {
startServer();
}
Update
To give a fuller example, you can throw this in index.js:
var express = require('express');
var app = express();
var cluster = require('cluster');
var numCPUs = require('os').cpus().length;
if (cluster.isMaster) {
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
} else {
startServer();
}
function startServer() {
var server = app.listen(3000, function () {
var port = server.address().port;
console.log('Example app listening at %s', port);
});
}
run node index.js in a terminal to start it up.
and it will log this with my 8 cpu monster:
Example app listening at 3000
Example app listening at 3000
Example app listening at 3000
Example app listening at 3000
Example app listening at 3000
Example app listening at 3000
Example app listening at 3000
Example app listening at 3000
Update 2
After seeing the question edit, I adapted your example. This should work
var http = require('http');
var express = require('express');
var app = express();
var cluster = require('cluster');
var numCPUs = require('os').cpus().length;
if (cluster.isMaster) {
// Fork workers.
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
cluster.on('exit', function(worker, code, signal) {
console.log('worker ' + worker.process.pid + ' died');
});
} else {
console.log('in else statement');
var port = '3000';
app.set('port', port);
var server = http.createServer(app);
server.listen(port);
}
and it should show this in the console
in else statement
in else statement
in else statement
in else statement
in else statement
in else statement
in else statement
in else statement
Let me know if this is not running for you.