Odd behaviour with mongodb-native

presenter.js

#!/usr/bin/env node

console.warn();
console.warn('==============================');
console.warn(' Buffered Information Gateway');
console.warn('       Presenter v0.0.1 ');
console.warn('==============================');
console.warn();

/**
 * Load libraries
 */

console.warn('- Loading libraries');

console.warn(' `- Filesystem');
var fs = require('fs');

console.warn(' `- HTTP');
var http = require('http');

console.warn(' `- URL');
var url = require('url');

/**
 * Load config
 */

var config = JSON.parse(fs.readFileSync('config.json'));

// Create mongo object
require('assert').ok(config.db.database, 'Please define a database to use.');
if (config.db.poolSize === 'undefined') { config.db.poolSize = 1; }
var mongo = new (require('mongo-pool').MongoPool)({db: config.db.database, poolSize: config.db.poolSize});

/**
 * Load reports
 */

var reports = {};

reports.events = {
  collection: 'events',
  fields: ['imei', 'time_sent', 'time_recv', 'latitude', 'longitude'],
  query: {
    'imei': '<redacted>'
  }
};

console.warn('- Starting HTTP server on '+config.net.bind+':'+config.net.port);
var server = http.createServer(function(request, response) {
  var segments = url.parse(request.url).pathname.substr(1).split(/\//);

  response.on('finish', function() { console.log(JSON.stringify({time: new Date(), url: request.url, status: [response.statusCode, response.statusText]})); });

  response.setHeader('Content-Type', 'application/json');

  if (request.method != 'GET' && request.method != 'POST') {
    response.statusCode = 406;
    response.statusText = 'Invalid method';
    response.end(JSON.stringify({error: 'Invalid method'}));
    return;
  }

  if (segments.length != 1 || !segments[0].match(/^[0-9a-z\-]+$/)) {
    response.statusCode = 406;
    response.statusText = 'Invalid URI';
    response.end(JSON.stringify({error: 'Invalid URI'}));
    return;
  }

  var report_key = segments[0];
  if (!(report_key in reports)) {
    response.statusCode = 404;
    response.statusText = 'Unknown Report';
    response.end(JSON.stringify({error: 'Unknown Report'}));
    return;
  }
  report = reports[report_key];

  if (request.method == 'GET') {
    response.statusCode = 200;
    response.statusText = 'OK';
    response.end(JSON.stringify(report.fields));
    return;
  }

  if (request.method == 'POST') {
    var data = '';
    request.on('data', function(d) {
      data += d;
    });

    request.on('end', function() {
      try {
        obj = data.length ? JSON.parse(data) : {};
      } catch (e) {
        console.warn('[!] Error parsing JSON!');
        response.statusCode = 406;
        response.statusText = 'Malformed JSON';
        response.end();
        return;
      }

      mongo.getClient(function(client) {
        if (!client) {
          console.warn('[!] Error getting MongoDB client');
          response.statusCode = 500;
          response.statusText = 'Internal Server Error';
          response.end(JSON.stringify({error: 'Database error'}));
          return;
        }

        mongo.getCollection(report.collection, function(err, collection) {
          if (err) {
            console.warn('[!] Error getting collection: '+err.message);
            response.statusCode = 500;
            response.statusText = 'Internal Server Error';
            response.end(JSON.stringify({error: 'Database error'}));
            mongo.release(client);
            return;
          }

          // (report.query) is fine
          // (report.query, report.fields) results in an error (field list is mistaken for option object?)
          // (report.query, report.fields, {}) results in... odd things :(
          var cursor = collection.find(report.query, report.fields, {});
          if (!cursor) {
            console.warn('[!] Error getting cursor');
            response.statusCode = 500;
            response.statusText = 'Internal Server Error';
            response.end(JSON.stringify({error: 'Database error'}));
            mongo.release(client);
            return;
          }

          cursor.limit(5);

          cursor.toArray(function(err, results) {
            if (err) {
              console.warn('[!] Error iterating cursor: '+err.message);
              response.statusCode = 500;
              response.statusText = 'Internal Server Error';
              response.end(JSON.stringify({error: 'Database error'}));
              mongo.release(client);
              return;
            }

            response.statusCode = 200;
            response.statusText = 'OK';
            response.end(JSON.stringify({headers: report.fields, data: results}));
            mongo.release(client);
            return;
          });
        });
      });
    });

    return;
  }
});
server.listen(config.net.port, config.net.bind);
console.warn(' `- HTTP server ready');

console.warn();
console.warn('===================');
console.warn(' Server is running ');
console.warn('===================');
console.warn();