Tornado Example: Delegating an blocking task to a worker thread pool from an asynchronous request handler

gistfile1.py

from time import sleep
from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop
from tornado.web import Application, asynchronous, RequestHandler
from multiprocessing.pool import ThreadPool

_workers = ThreadPool(10)

def run_background(func, callback, args=(), kwds={}):
    def _callback(result):
        IOLoop.instance().add_callback(lambda: callback(result))
    _workers.apply_async(func, args, kwds, _callback)

# blocking task like querying to MySQL
def blocking_task(n):
    sleep(n)
    return n

class Handler(RequestHandler):
    @asynchronous
    def get(self):
        run_background(blocking_task, self.on_complete, (10,))

    def on_complete(self, res):
        self.write("Test {0}<br/>".format(res))
        self.finish()

HTTPServer(Application([("/", Handler)],debug=True)).listen(8888)
IOLoop.instance().start()