How to pass environmental variable (database URL) in Tornado?

I have the elastic URL to be passed as a environmental variable to post method, I have declared the make_session_factory from tornado_sqlalchemy, and passed to requesthandler, how should I receive that in self, below is my code

class MyHandler(RequestHandler):
    _thread_pool = ThreadPoolExecutor(max_workers=10)

    def initialize(self, session_factory): 
      self.session_factory = session_factory

    @gen.coroutine
    def post(self):
        try:
            data = tornado.escape.json_decode(self.request.body)
            yield self.predict('mod1')
        except Exception:
            self.respond('server_error', 500)

    @concurrent.run_on_executor(executor='_thread_pool')
    def _b_run(self, mod, X):
        results = do some calculation
        return results

    @gen.coroutine
    def predict(self, mod):  
        model = mod(load from database)
        values = (load from database)
        results = yield self._b_run(model, values)
        self.respond(results)

    def respond(self, code=200):
        self.set_status(code)
        self.write(json.JSONEncoder().encode({
            "status": code
        }))
        self.finish()


def mod(model):
    #Elastic Client
    es = Elasticsearch([{'host': 'localhost', 'port': 9200}])
    ……...Load model
    return model


factory = make_session_factory(os.environ.get('DATABASE_URL', ''))
define('port', default=8888, help='Tornado port to listen on')

def make_app():  
    url = [(r"/pred", PredictionHandler)]
    return Application(url,session_factory=factory)

if __name__ == "__main__":
    application = make_app()
    http_server = HTTPServer(application)
    http_server.listen(options.port)
    IOLoop.current().start()

For now I have coded the URL in my mod function as localhost, 9200,

To pass that as environment variable I have created the factory and passed the factory as session_factory in my application,

I have to receive that in my requesthandler post method, so that I can pass to my predict method which in tern call my mod function, may I know how to receive that. I tried with initialize but not working properly.

Also found the other option using motor with tornado

import motor.motor_tornado
client = motor.motor_tornado.MotorClient('localhost', 9200)
db = motor.motor_tornado.MotorClient().test_database

application = tornado.web.Application([
    (r'/', MainHandler)
], db=db)

class MainHandler(tornado.web.RequestHandler):
    def get(self):
        db = self.settings['db']

Here also I have to receive in my post method

Any extra arguments you pass to the Application class will be available in self.settings from any of your request handlers.

So you can modify the initialize method like this:

def initialize(self): 
    self.session_factory = self.settings['session_factory']

# and just use `self.session_factory` in any other method where you need it