import asyncmongo
import tornado.web

class Handler(tornado.web.RequestHandler):
    @property
    def db(self):
        if not hasattr(self, '_db'):
            self._db = asyncmongo.Client(pool_id='mydb', host='127.0.0.1', port=27017, maxcached=10, maxconnections=50, dbname='test')
        return self._db

    @tornado.web.asynchronous
    def get(self):
        self.db.users.find({'username': self.current_user}, limit=1, callback=self._on_response)
        # or
        # conn = self.db.connection(collectionname="...", dbname="...")
        # conn.find(..., callback=self._on_response)

    def _on_response(self, response, error):
        if error:
            raise tornado.web.HTTPError(500)
        self.render('template', full_name=response['full_name'])