server.js

var connect = require ('connect');
var http = require ('http');
var mongodb = require('mongodb');
var MongoCluster = require('mongo-sharded-cluster');

var app = connect ();

app.use(connect.query());
app.use(connect.json({limit: '5mb'}));

if(process.env.FORWARD_URL) {
  console.log('>>> ', process.env.FORWARD_URL);
  var forwarder = require('./lib/middlewares/forward');
  app.use(forwarder(process.env.FORWARD_URL));
}

// add connect-ntp middleware, for the legacy support
// this does not works everywhere because, this doesn't
// works well with firewalls since this uses TCP over HTTP
app.use(require('connect-ntp')());

// new ntp middleware, simple sends the timestamp to the client
// this works well with firewalls, this is plain old HTTP
app.use(require('./lib/middlewares/simplentp')());
app.use(require('./lib/middlewares/cors-options'));

var port = process.env.PORT || 11011;
console.info('starting apm-engine on port', port);
http.createServer(app).listen(port);

//connect to mongo
var DBS = {};

MongoCluster.initFromEnv(function(err, cluster) {
  console.log('DDONE')
  if(err) {
    console.error('Error connecting to the Mongo Metrics Cluster');
    throw err;
  } else {
    DBS.metricsCluster = cluster;
    console.log("HERE");
    mongodb.MongoClient.connect(process.env.MONGO_URL, afterMongoURLConnected);
  }

});

function afterMongoURLConnected(err, db) {
  if (err) {
    throw err;
  } else {
    DBS.app = db;

    // parse JSON data sent using XDR with has data type set to text/plain
    // do this before appinfo otherwise required data will not be available
    app.use('/errors', require('./lib/middlewares/plaintext-body'));

    // extract appId and appSecret. Used by ratelimit.
    app.use(require('./lib/middlewares/appinfo'));

    // rate limit all requests from this point
    // limit => 15 req/s, traces => 100 traces/request
    // Note: Drops all requests without an appId.
    app.use(require('./lib/middlewares/ratelimit')({
      limit: 15,
      resetInterval: 1000,
      limitTotalTraces: 100
    }));

    // error manager handles errors sent from client (GET and POST)
    // all requests sent to /errors are considered as client side errors
    // it should be used before using the authentication middleware
    var stateManager = require('./lib/stateManager');
    var errorManager = require('./lib/middlewares/error-manager');
    app.use('/errors', errorManager(DBS.app, DBS.metricsCluster));

    // authenticare middleware
    // ping middleware must be used after the authentication middleware
    app.use(require('./lib/middlewares/authenticate')(DBS.app));
    app.use(require('./lib/middlewares/ping')());
    app.use(require('./lib/middlewares/logger')());
    app.use('/jobs', require('./lib/middlewares/jobs')(DBS.app));
    require('./lib/controller')(app, DBS.app, DBS.metricsCluster);

    // error middleware
    app.use(require('./lib/middlewares/onerror')());
  }
}