We will build a concurrent application to illustrate the functionality of Tornado. In this example, the tornado.concurrent module of Tornado has been used.

Listing 4.13 explains the code for a simple concurrent application using Tornado:

#!/usr/bin/env python 
# Python Network Programming Cookbook, Second Edition -- Chapter - 3 
# This program is optimized for Python 3.5.2. 
# It may run on any other version with/without modifications. 
 
import argparse 
import time 
import datetime 
 
import tornado.httpserver 
import tornado.ioloop 
import tornado.options 
import tornado.web 
 
from tornado import gen 
from tornado.concurrent import return_future 
 
class AsyncUser(object): 
    @return_future 
    def req1(self, callback=None): 
        time.sleep(0.1) 
        result = datetime.datetime.utcnow() 
        callback(result) 
 
    @return_future 
    def req2(self, callback=None): 
        time.sleep(0.2) 
        result = datetime.datetime.utcnow() 
        callback(result) 
 
 
 
class Application(tornado.web.Application): 
    def __init__(self): 
        handlers = [ 
            (r"/", UserHandler), 
        ] 
        tornado.web.Application.__init__(self, handlers) 
 
 
class UserHandler(tornado.web.RequestHandler): 
    @gen.coroutine 
    def get(self): 
        user = AsyncUser() 
        response1 = yield (user.req1()) 
        response2 = yield (user.req2()) 
        print ("response1,2: %s %s" %(response1, response2)) 
        self.finish() 
 
def main(port): 
    http_server = tornado.httpserver.HTTPServer(Application()) 
    print("Server listening at Port: ", port) 
    http_server.listen(port) 
    tornado.ioloop.IOLoop.instance().start() 
 
 
if __name__ == "__main__": 
    parser = argparse.ArgumentParser(description='Async Server Example') 
    parser.add_argument('--port', action="store",
     dest="port", type=int, required=True) 
    given_args = parser.parse_args()  
    port = given_args.port 
    main(port) 

Execute the following script to start the concurrent application:

$ python 4_13_tornado_conc_future.py --port=3333 

The following screenshot indicates the output of the execution: