tornado_ex.py

#!/usr/bin/env python

import tornado.httpserver
import tornado.ioloop
import tornado.web
import multiprocessing
import random
import time

__author__ = 'Brian McFadden'
__email__ = '[email protected]'

class AsyncHandler(tornado.web.RequestHandler):   
    @tornado.web.asynchronous
    def get(self):
        print "New request: entering AsyncHandler.get"
        # Creating a pipe returns two file descriptors (one for each end).
        fd1, fd2 = multiprocessing.Pipe()
        self.pipe = fd1
        fno = fd1.fileno()
        # Create a process for the sleepy function. Provide one pipe end.
        p = multiprocessing.Process(target=sleepy, args=(fd2,))
        p.start()
        iol = tornado.ioloop.IOLoop.instance()
        iol.add_handler(fno, self.async_callback(self._finish), iol.READ)
        print "Leaving AsyncHandler.get."
    
    def _finish(self, fd, event):
        print "Entering AsyncHandler._finish"
        tornado.ioloop.IOLoop.instance().remove_handler(fd)
        val = self.pipe.recv()
        self.pipe.close()
        self.write(val)
        self.write(random_num())
        print "Finishing the request."
        self.finish()

class MainHandler(tornado.web.RequestHandler):    
    def get(self):
        print "New request: entering MainHandler.get"
        self.write(random_num())
        print "Finishing the request."

def random_num():    
    n = random.random()
    return "Here is a random number to show change: {0}".format(n)

def sleepy(pipe):    
    time.sleep(5)
    pipe.send("Now I'm awake.")
    pipe.close()
    return

if __name__ == '__main__':
    application = tornado.web.Application([
        (r"/", MainHandler),
        (r"/async", AsyncHandler),
    ])
    http_server = tornado.httpserver.HTTPServer(application)
    http_server.listen(8888)
    print 'The HTTP server is listening on port 8888.'
    tornado.ioloop.IOLoop.instance().start()