test to show that client agent throttles to 5 connections by default.

parallelclient.js

var http = require('http');


var count = 0;
function get() {
  var i = count++;
  console.log("Starting request #" + i);
  var req = http.request({
    hostname: "localhost",
    port: 8080,
    path: "/",
    method: "GET"
  }, function (res) {
    console.log("Got response for request #" + i);
  });
  req.end();
}


for (var i = 0; i < 2000; i++) {
  get();
}

slowserver.js

var http = require('http');
var count = 0;
var server = http.createServer(function (req, res) {
  var i = count++;
  console.log("Received request #" + i);
  setTimeout(function () {
    res.writeHead(200, {
      "Content-Type": "text/plain",
      "Content-Length": 12
    });
    res.end("Hello World\n");
    console.log("Sent response for request #" + i);
  }, 500);
});
server.listen(8080, function () {
  console.log("Server listening at http://localhost:8080");
});