Running an async background task in Tornado

Question

Reading the Tornado documentation, it\'s very clear how to call an async function to return a response:

class GenAsyncHandler(RequestHandler):
    @gen.corou         


        

Answer 1

I have a time-consuming task in post request, maybe more than 30 minutes need, but client required return a result immediately.

First, I used IOLoop.current().spawn_callback. It works! but! If the first request task is running, second request task blocked! Because all tasks are in main event loop when use spawn_callback, so one task is synchronous execution, other tasks blocked.

Last, I use tornado.concurrent. Example:

import datetime
import time

from tornado.ioloop import IOLoop
import tornado.web
from tornado import concurrent

executor = concurrent.futures.ThreadPoolExecutor(8)


class Handler(tornado.web.RequestHandler):

    def get(self):
        def task(arg):
            for i in range(10):
                time.sleep(1)
                print(arg, i)

        executor.submit(task, datetime.datetime.now())
        self.write('request accepted')


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


if __name__ == "__main__":
    app = make_app()
    app.listen(8000, '0.0.0.0')
    IOLoop.current().start()

and visit http://127.0.0.1:8000, you can see it's run ok:

2017-01-17 22:42:10.983632 0
2017-01-17 22:42:10.983632 1
2017-01-17 22:42:10.983632 2
2017-01-17 22:42:13.710145 0
2017-01-17 22:42:10.983632 3
2017-01-17 22:42:13.710145 1
2017-01-17 22:42:10.983632 4
2017-01-17 22:42:13.710145 2
2017-01-17 22:42:10.983632 5
2017-01-17 22:42:16.694966 0
2017-01-17 22:42:13.710145 3
2017-01-17 22:42:10.983632 6
2017-01-17 22:42:16.694966 1
2017-01-17 22:42:13.710145 4
2017-01-17 22:42:10.983632 7
2017-01-17 22:42:16.694966 2
2017-01-17 22:42:13.710145 5
2017-01-17 22:42:10.983632 8
2017-01-17 22:42:16.694966 3
2017-01-17 22:42:13.710145 6
2017-01-17 22:42:19.790646 0
2017-01-17 22:42:10.983632 9
2017-01-17 22:42:16.694966 4
2017-01-17 22:42:13.710145 7
2017-01-17 22:42:19.790646 1
2017-01-17 22:42:16.694966 5
2017-01-17 22:42:13.710145 8
2017-01-17 22:42:19.790646 2
2017-01-17 22:42:16.694966 6
2017-01-17 22:42:13.710145 9
2017-01-17 22:42:19.790646 3
2017-01-17 22:42:16.694966 7
2017-01-17 22:42:19.790646 4
2017-01-17 22:42:16.694966 8
2017-01-17 22:42:19.790646 5
2017-01-17 22:42:16.694966 9
2017-01-17 22:42:19.790646 6
2017-01-17 22:42:19.790646 7
2017-01-17 22:42:19.790646 8
2017-01-17 22:42:19.790646 9

Want to help everyone!