mongodb-promise.js

return Promise.try(function () {
     //return fs.readFileAsync(status.filename, 'utf8');
      return MongoClient.connectAsync(MONGODB_CONNECTION_STRING)
          .then(function(db){
              return db.collection("downloads").findOneAsync({key: status.filename});
          });
  }).then(function(content) {
    // ... 
  });