tornado中，异步执行阻塞代码

import time
import datetime
import tornado.ioloop
import tornado.web
import tornado.gen
import tornado.concurrent
from concurrent.futures import ThreadPoolExecutor

class MainHandler(tornado.web.RequestHandler):
    executor = ThreadPoolExecutor(10)
    @tornado.gen.coroutine
    def get(self):
        future = ThreadPoolExecutor().submit(self.blocksleep)
        yield tornado.gen.with_timeout(datetime.timedelta(10), future,
                                       quiet_exceptions=tornado.gen.TimeoutError)
        self.write("Hello, world")

    @tornado.concurrent.run_on_executor
    def blocksleep(self):
        time.sleep(20)
        return


def make_app():
    return tornado.web.Application([
        (r"/", MainHandler),
    ])

if __name__ == "__main__":
    app = make_app()
    app.listen(8888)
    tornado.ioloop.IOLoop.current().start()