Using threads in flask web app

Question

I am developing a web app which has a service/task which might take a long time to finish. I am new to python and read that python has GIL, which means at one time only one thread can run irrespective of number of cores.

my pseudo code is like this

def service_xxx(self, data):
    thread = ThreadXXX(data)
    thread.start()
    self.threads[data.id] = thread

My questions is what happens when 100 requests comes ? Will flask framework run 100 user threads concurrently using all cores or its going to run 100 threads on single cores ?

Now serious. GIL is the reason I personally don't rely on threads when I need concurrency. I prefer multiprocessing. See http://stackoverflow.com/q/35616639/7699691 for more information. — Andrew Che, Mar 21 '17 at 23:20
You can integrate [Celery](http://www.celeryproject.org/) with Flask — stamaimer, Mar 22 '17 at 12:51
I am trying to understand how flask is handling these threads and also how requests are handled in each threads or not? — wayfare, Mar 22 '17 at 14:17

score 0 · Answer 1 · answered Mar 22 '17 at 05:21

Python (CPython) is not optimized for thread framework.You can keep allocating more resources and it will try spawning/queuing new threads and overloading the cores. You need to make a design change here:

Process based design:

Either use the multiprocessing module
Make use of rabbitmq and make this task run separately
Spawn a subprocess

Or if you still want to stick to threads:

Switch to PyPy (faster compared to CPython)
Switch to PyPy-STM (totally does away with GIL)

Using threads in flask web app

1 Answers1