does Express uses cluster by default? - node.js

Question

I try to use JMeter running benchmark on pure node.js and express server.
And the result is :
node.js = 600 RPS, express = 1200 RPS
while running benchmark, node.js server always use 1 cpu, but express server uses all.
Does this means that express server uses cluster by default ?
UPDATE : benchmark code
node.js
var http = require('http');
var Server = http.createServer(function(req, res){
res.write('I heard you !');
res.end();
}).listen(8000);
Express (3.8)
var express = require('express');
var app = express();
// ----------- middleware -------------
app.configure(function(){
app.use(express.bodyParser());
app.use(express.cookieParser());
app.use('/public',express.static(__dirname+'/files'));
});
// ----------- route-------------
app.get('/', function(req, res){
res.send('I heard you!')
});
app.listen(8000);

Answer 1

Express.js does not use cluster.
The reason you see more cores than a single being busy is very likely due to the node.js with express more efficiently offloading operations to other workers through async code.
You can use cluster with an express, but as long as you are not having scaling issues that is just unnecessary hassle.
Below is an example code (source):
// Include the cluster module
var cluster = require('cluster');
// Code to run if we're in the master process
if (cluster.isMaster) {
// Count the machine's CPUs
var cpuCount = require('os').cpus().length;
// Create a worker for each CPU
for (var i = 0; i < cpuCount; i += 1) {
cluster.fork();
}
// Code to run if we're in a worker process
} else {
// Include Express
var express = require('express');
// Create a new Express application
var app = express();
// Add a basic route – index page
app.get('/', function (req, res) {
res.send('Hello World!');
});
// Bind to a port
app.listen(3000);
console.log('Application running!');
}