为Django项目中的可重用应用程序创建基于类的Celery任务

Question

Creating function based task is quite clean for Django project. Just create tasks.py in django app and start writing task like this example which is taken from official celery documentation at http://docs.celeryproject.org/en/latest/django/first-steps-with-django.html

from __future__ import absolute_import, unicode_literals
from celery import shared_task

@shared_task
def add(x, y):
    return x + y


@shared_task
def mul(x, y):
    return x * y

But sometimes function based tasks are tightly coupled and not very reusable. So i wanted to create class based celery task which is documented in official site. After following https://github.com/celery/celery/issues/3874 I could create sample task but I am not sure if its proper way to create class based task.

from __future__ import absolute_import, unicode_literals
from celery import shared_task, Task
import time
from celery import current_app


@shared_task
def add(x, y):
    time.sleep(5)
    return x + y


@shared_task
def mul(x, y):
    return x * y

# Sample class based task for testing
class AnotherTask(current_app.Task):
    name = 'tasks.another_task'
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def run(self):
        time.sleep(5)
        return self.x + self.y
# We need to manually register this class based task    
current_app.tasks.register(AnotherTask(3, 4))

I am able to call this task but each call result value is same

(workflow) alok@alok-MacBookAir:~/exp/expdjango/mysite$ ./manage.py shell
Python 3.6.3 (default, Oct  3 2017, 21:45:48) 
Type "copyright", "credits" or "license" for more information.

IPython 5.1.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: from polls.tasks import *

In [2]: r = AnotherTask(3,4).delay()

In [3]: r.get()
Out[3]: 7

In [4]: r = AnotherTask(5,6).delay()

In [5]: r.get()
Out[5]: 7

Is it a proper way to create and call class based task?

Answer 1

Class based tasks are actually instantiated only once per runtime. If you want your task to be parametrized, add arguments to the run method:

class AnotherTask(current_app.Task):
    name = 'tasks.another_task'

    def run(self, x, y):
        time.sleep(5)
        return x + y

Then you can call it like:

r = AnotherTask().delay(3, 4)
# Or
r = AnotherTask().apply_async(args=[3, 4])

This is also described in the docs on class based tasks , and in particular in the instantiation section .