How to make tornado not block IO?

Question

Python

Good day, can you tell me why the tornado locks IO when executing the following code:

import time
import tornado.web
from tornado.ioloop import IOLoop
from tornado import gen
from tornado.concurrent import run_on_executor
from concurrent.futures import ThreadPoolExecutor

MAX_WORKERS = 4


class TestHandler(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

    @tornado.gen.coroutine
    def get(self):
        """ Request that asynchronously calls background task. """
        print('%s news handler accept' % time.time())
        res = yield self.background_task(time.time())
        self.write(str(res))


application = tornado.web.Application([
    (r"/", TestHandler),
])

application.listen(8888)
IOLoop.instance().start()

I know about gen.sleep, but how to make this code not block the application?

Answer 1

I think I know what's going on with you. Everything is fine with your code, not with the test method. Surely you open two tabs in the same browser and send requests from them. But neither Google Chrome nor Mozila Firefox will send a second request to the same address until they receive a response to the first one. Even if you run two windows. But IE11 sends two requests at the same time to the same address from the tabs without any problems. Try running two different browsers, or even better, use curl for tests.