threaded_tornado.py

from functools import partial, wraps
from threading import Thread
from time import sleep

import tornado
from tornado.ioloop import IOLoop


def threaded(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        if 'callback' in kwargs:
            orig_cb = kwargs['callback']
        else:
            args, orig_cb = args[:-1], args[-1]
        io_loop = IOLoop.instance()
        def callback(*args, **kwargs):
            io_loop.add_callback(partial(orig_cb, *args, **kwargs))
        kwargs['callback'] = callback
        Thread(target=func, args=args, kwargs=kwargs).start()
    return wrapper


@threaded
def slow_func(callback):
    sleep(1)
    callback("Hello, world!")


class Handler(tornado.web.RequestHandler):

    @tornado.web.asynchronous
    @tornado.gen.engine
    def get(self):
        data  = yield tornado.gen.Task(slow_func)
        self.write(data)
        self.finish()

doesn't work with concurrent requests to the same handler