Tornado concurrency limited to 6 connections?

Question

I have the following "dummy server" running:

import tornado.web
from tornado.ioloop import IOLoop
from tornado import gen 
import time

@gen.coroutine
def async_sleep(seconds):
    yield gen.Task(IOLoop.instance().add_timeout, time.time() + seconds)

class TestHandler(tornado.web.RequestHandler):

    reqnum = 0

    @gen.coroutine
    def get(self):
        reqnum = TestHandler.reqnum
        TestHandler.reqnum += 1
        for i in range(100):
            print(reqnum,end='')
            if reqnum == 0 : print()
            yield async_sleep(1)
        self.write(str(reqnum))
        self.finish()

if __name__ == '__main__' :

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

    application.listen(9999)
    IOLoop.instance().start()

So this should run fine for tons of concurrent connections, you'd think... But it doesn't. Starting the server and opening 16 tabs to it, you get:

Which is pretty perplexing. What's weirder still is that the correct result is printed on all tabs, 0-15. That's all the output to the console, though. No more arrived.

What the heck is happening?

Answer 1

I think it's a combination of two things:

The browser is limiting the number of connections to the server ( see the FAQ ). If you use separate browsers and not just tabs in one browser you should see more connections.
Python's stdout is line-buffered, so output is only written to the console when there is a newline. Once request 0 is finished, you no longer write newlines and so everything else is getting held in the buffer.

Tornado concurrency limited to 6 connections?

Question

1 answers

solution1
2 ACCPTED 2016-07-08 11:40:18

Tornado concurrency limited to 6 connections?

Question

1 answers

solution1 2 ACCPTED 2016-07-08 11:40:18

solution1
2 ACCPTED 2016-07-08 11:40:18