latency-recorder.js

var fs = require('fs');
var net = require('net');
var host = 'google.com';
var port = 80;
var limit = 6 * 60;
var interval = 10000;
var iterations = 1;
var results = [];
var out;

var connect = function (callback, prev, i) {
  var d = new Date();
  var conn = net.connect(port, host, function () {
    var now = new Date();
    var latency = now.getTime() - d.getTime();
    conn.end();
    if (i > 1) connect(callback, latency + prev, i - 1);
    else callback && callback(parseInt((latency + prev) / iterations));
  });
  conn.on('error', function () {
    callback && callback(9999);
  });
};

var summurize = function () {
  console.log('============================================================');
  console.log('Latency record from:\n%s\nto\n%s', results[0].date, results[results.length - 1].date);
  console.log('============================================================');
  console.log('Avg %d ms\tHigh %d ms\tLow %d ms', parseInt(sum/count), high, low);
  if (out) {
    out.end('Avg,High,Low,' + new Date() + '\n' + parseInt(sum/count) + ',' + high + ',' + low + '\n');
  }
}

var count = 0;
var sum = 0;
var recent = [];
var high = -1;
var low = 99999;

if (process.argv.length > 2) {
  for (var i = 2; i < process.argv.length; i++) {
    switch (process.argv[i]) {
      case '-l':
        limit = parseInt(process.argv[i+1]);
        i++;
        break;
      case '-i':
        interval = parseInt(process.argv[i+1]);
        i++;
        break;
      case '-I':
        iterations = parseInt(process.argv[i+1]);
        i++;
        break;
      case '-o':
        out = fs.createWriteStream(process.argv[i+1]);
        i++;
        break;
      case '-O':
        out = fs.createWriteStream('latency-' + new Date().getTime() + '.csv');
        break;
      case '-h':
        console.log('Usage: node latency-recorder [host[:port]] [-l limit] [-i interval] [-I iterations]');
        process.exit();
        break;
      default:
        var pat = /^(([0-9]+(\.[0-9]+){3})|([a-zA-Z]+(\.[a-zA-Z]+)+))(:[0-9]+)?$/;
        if (pat.test(process.argv[i])) {
          var target = process.argv[i].split(':');
          host = target[0];
          if (target.length > 1)
            port = target[1];
        } else {
          console.log('Usage: node latency-recorder [host[:port]] [-l limit] [-i interval] [-I iterations]');
          process.exit();
        }
    }
  }
}

console.log('Recording latency data to %s:%d', host, port);
if (out) out.write(host + ':' + port + ',' + new Date() + '\n');

var intervalID = setInterval(function () {
  connect(function (l) {
    var d = new Date();
    count++;
    sum += l;
    results.push({date: d, latency: l});
    if (out) out.write('' + d.getTime() + ',' + l + '\n');
    if (l > high) high = l;
    if (l < low) low = l;
    recent.push(l);
    if (recent.length > 10) recent.shift();
    var recentAvg = 0;
    for (var i = 0; i < recent.length; i++) recentAvg += recent[i];
    recentAvg = parseInt(recentAvg / recent.length);
    console.log('Now %d ms\tAvg %d ms\tHigh %d ms\tLow %d ms\tRAvg %d ms', l, parseInt(sum/count), high, low, recentAvg);
    if (count >= limit) {
      clearInterval(intervalID);
      summurize();
    };
  }, 0, iterations);
}, interval);