docs: function getMongoConnection(uri, mongodbConnection, cb) {
    logger.debug("getting mongodb connection");
    var mongoConn;
    if (mongodbConnection && typeof mongodbConnection.db === 'function') {
      process.nextTick(function() {
        logger.debug("creating the mongodb connection using the existing connection", {uri: uri});
        var dbName = getDbName(uri);
        mongoConn = mongodbConnection.db(dbName);
        return cb(undefined, mongoConn);
      });
    } else {
      logger.warn("creating a new mongodb connection", {uri: uri});
      return MongoClient.connect(uri, logger.ensureRequestId ? logger.ensureRequestId(cb) : cb);
    }
  }