With http pipelining this should take 100 - 200ms to run. actually takes over 10s.

test.js

// Code to test HTTP pipelining

var cluster = require('cluster')
var port =  50001; //port for server to listen on
var number_of_messages =  100; //number of client to server messages to send.
var delay =  100; //millisecons delay before server responds

function log(txt){
  console.log( new Date().toISOString() + ' ' + txt);
}

if(cluster.isMaster){
  //start the server
  var express = require('express');
  var app     = express();


  app.use("/resource", function(req,res){
    var req_message = "";
    req.on('data', function(chunk) { 
      req_message += chunk;
    }); //drain the req
    req.on('end', function() { 
      //add a pause here to fake some kind of latency
      log(req_message + " - server got message.");
      setTimeout(function(){
        res.send("OK " + req_message); 
        log(req_message + " - server sent response.");
      }, delay);
    });
  });


  app.listen(port, function() {
    log('Server with pid ' + process.pid + ' started. Listening on port ' + port + '.');
  });

  //fork a client
  cluster.fork();

  cluster.on("exit", function(client, code, signal){
    log('Client with pid ' + client.process.pid + ' stopped. Server with pid ' + process.pid + ' stopping.' );
    process.exit();
  })




}else{
  //start the client
  log('Client with pid ' + process.pid + ' started. Will connect to server on port ' + port + '.');
  
  var http = require('http');
  var async = require('async');
  var options = {hostname: 'localhost', port: port, method: 'POST', path: "/resource" };

  http.globalAgent.maxSockets = 1;

  function requester(req_message){
    return function(callback){
      var req = http.request(options, function(res){
        var res_message = "";
        res.on('data', function(chunk) { 
          res_message += chunk;
        });
        res.on('end', function() { 
          log(req_message + " - client got response (\"" + res_message +"\").");
          callback(null, req_message + " - complete");
        });
      });
      req.write(req_message);
      req.end();
      log(req_message + " - client sent message.");
    }
  }

  var functions = [];

  for (i=1;i<=number_of_messages;i++){
    functions.push(requester("HTTP Message " + i));
  }

  var end  = function(){ 
    log('Client with pid ' + process.pid + ' stopping.' );
    process.exit();
  }

  async.series(functions, end);

}