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

gistfile1.py

import time

import tornado
from tornado.concurrent import run_on_executor
from concurrent.futures import ThreadPoolExecutor   # `pip install futures` for python2

from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop
from tornado.web import Application, RequestHandler
from tornado import gen

MAX_WORKERS = 4


class Handler(tornado.web.RequestHandler):
    executor = ThreadPoolExecutor(max_workers=MAX_WORKERS)

    @run_on_executor
    def background_task(self, i):
        """ This will be executed in `executor` pool. """
        time.sleep(10)
        return i

    @gen.coroutine
    def get(self, idx):
        """ Request that asynchronously calls background task. """
        res = yield self.background_task(idx)
        self.write(res)


HTTPServer(Application([("/(\d+)", Handler)],debug=True)).listen(8888)

IOLoop.instance().start()