Find your closest AWS region

AWSPingTest.js

'use strict';
(function() {
// inspired by cloudping.info
var regions = {
  'us-east-1': 'US-East (Virginia)',
  'us-east-2': 'US East (Ohio)',
  'us-west-1': 'US-West (California)',
  'us-west-2': 'US-West (Oregon)',
  'ca-central-1': 'Canada (Central)',
  'eu-west-1': 'Europe (Ireland)',
  'eu-west-2': 'Europe (London)',
  'eu-central-1': 'Europe (Frankfurt)',
  'ap-south-1': 'Asia Pacific (Mumbai)',
  'ap-southeast-1': 'Asia Pacific (Singapore)',
  'ap-southeast-2': 'Asia Pacific (Sydney)',
  'ap-northeast-1': 'Asia Pacific (Tokyo)',
  'ap-northeast-2': 'Asia Pacific (Seoul)',
  'sa-east-1': 'South America (São Paulo)',
  'cn-north-1': 'China (Beijing)',
};

var specialUrls = {
  'cn-north-1': 'http://dynamodb.cn-north-1.amazonaws.com.cn/'
};

function testUrl(region) {
  return (region in specialUrls ?
           specialUrls[region] : 'http://dynamodb.' + region + '.amazonaws.com/') + 
         'does-not-exist?cache-break=' +
            Math.floor(Math.random() * Math.pow(2, 52)).toString(36);
}

function callbackOnError(url, cb) {
  var img = new Image;
  img.onerror = cb;
  img.src = url;
}

function timestamp() {
  return (new Date()).getTime();
}

function pingRegion(region, cb) {
  var url = testUrl(region);
  // First failed request to prime connection
  callbackOnError(url, function() {
    // Second for measuring duration
    var start = timestamp();
    callbackOnError(url, function() {
      cb(timestamp() - start);
    });
  });
}

function pingAllRegions(doneCallback, progressCallback, _curr) {
  _curr = _curr || [];
  var regionNames = Object.keys(regions);
  if(_curr.length === regionNames.length)
    return doneCallback(_curr.sort(function(a, b) {
      return a.ping > b.ping ? 1 : -1;
    }));

  var nextRegion = regionNames[_curr.length];
  pingRegion(nextRegion, function(time) {
    _curr.push({
      name: nextRegion,
      title: regions[nextRegion],
      ping: time
    });

    if(typeof progressCallback === 'function')
      progressCallback(_curr.length / regionNames.length);

    pingAllRegions(doneCallback, progressCallback, _curr);
  });

}

this.AWSPingTest = pingAllRegions;

}).call(this);