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Some functions should run asynchronously on the web server. Sending emails or data post-processing are typical use cases.
What is the best (or most pythonic) way write a decorator function to run a function asynchronously?
My setup is a common one: Python, Django, Gunicorn or Waitress, AWS EC2 standard Linux
For example, here's a start:
from threading import Thread def postpone(function): def decorator(*args, **kwargs): t = Thread(target = function, args=args, kwargs=kwargs) t.daemon = True t.start() return decorator desired usage:
@postpone def foo(): pass #do stuff 
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Yes it can multi-thread, but generally one uses Celery to do the equivalent. You can read about how in the celery-django tutorial. It is rare that you actually want to force the user to wait for the website.
And yes, most WSGI servers support multiprocessing and multithreading. Multiprocess is the common case.
Django itself does not determine whether it runs in one or more threads. This is the job of the server running Django. The development server used to be single-threaded, but in recent versions it has been made multithreaded.
Python doesn't support multi-threading because Python on the Cpython interpreter does not support true multi-core execution via multithreading. However, Python does have a threading library. The GIL does not prevent threading.
I've continued using this implementation at scale and in production with no issues.
Decorator definition:
def start_new_thread(function): def decorator(*args, **kwargs): t = Thread(target = function, args=args, kwargs=kwargs) t.daemon = True t.start() return decorator Example usage:
@start_new_thread def foo(): #do stuff Over time, the stack has updated and transitioned without fail.
Originally Python 2.4.7, Django 1.4, Gunicorn 0.17.2, now Python 3.6, Django 2.1, Waitress 1.1.
If you are using any database transactions, Django will create a new connection and this needs to be manually closed:
from django.db import connection @postpone def foo(): #do stuff connection.close() If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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