Django Celery Periodic Task How to call Task method That is inside class

Question

I want to send periodic mail to certain user After the user has been registered to certain platform I tried to send email using celery which works fine and Now I want django celery to send periodic mail as of now I have set the email time period to be 15 seconds. Further code is here

celery.py

   app.conf.beat_schedule = {
    'send_mail-every-day-at-4': {
        'task': 'apps.users.usecases.BaseUserUseCase().email_send_task()',
        'schedule': 15
    }
   }

I have my Class in this way ->apps.users.usecases.BaseUserUseCase.email_send_task here is my usecases to send email

 class BaseUserUseCase:
    ##other code is skipped 

    @shared_task
    def email_send_task(self):
        print("done")
        return ConfirmationEmail(context=self.context).send(to=[self.receipent])

How do I call this email_send_task method am I doing right any help regarding this It is not working.

Answer 1

To enable class-based tasks:

1. Change your class to inherit from celery.Task
2. Change your @shared_task:email_send_task() to run()
3. Call Celery.register_task() for your class. The result would be the callable task.
4. Directly call the callable task from step-3 to manually enqueue tasks.

References:

• https://docs.celeryproject.org/en/4.0/whatsnew-4.0.html#the-task-base-class-no-longer-automatically-register-tasks
• https://docs.celeryproject.org/en/stable/userguide/application.html#breaking-the-chain
• https://docs.celeryproject.org/en/stable/userguide/application.html#abstract-tasks
• Register Celery Class-based Task

File structure

.
├── apps
│   └── users
│       └── usecases.py
└── my_proj
    ├── celery.py
    └── settings.py

celery.py

import os

from celery import Celery

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "my_proj.settings")  # Only if using Django. Otherwise remove this line.

app = Celery("my_app")

app.conf.update(
    imports=['apps.users.usecases'],
    beat_schedule={
        'send_mail-every-day-at-4': {
            'task': 'apps.users.usecases.BaseUserUseCase',
            'schedule': 5,
        },
    },
)

usecases.py

from celery import Task

from my_proj.celery import app


class BaseUserUseCase(Task):
    def __init__(self, context, recipient):
        self.context = context
        self.recipient = recipient

    def run(self, context=None, recipient=None):  # Optional arguments context and recipient only if you need to explicitly change it for some calls
        target_context = context or self.context
        target_recipient = recipient or self.recipient
        print(f"Send email with {target_context} to {target_recipient}")


BaseUserUseCaseTask = app.register_task(
    BaseUserUseCase(
        context={'setting': 'default'},
        recipient="default@email.com",
    )
)

Logs (Producer)

$ celery --app=my_proj beat --loglevel=INFO
[2021-08-20 09:50:22,193: INFO/MainProcess] Scheduler: Sending due task send_mail-every-day-at-4 (apps.users.usecases.BaseUserUseCase)
[2021-08-20 09:50:27,181: INFO/MainProcess] Scheduler: Sending due task send_mail-every-day-at-4 (apps.users.usecases.BaseUserUseCase)

Logs (Consumer)

$ celery --app=my_proj worker --queues=celery --loglevel=INFO

[tasks]
  . apps.users.usecases.BaseUserUseCase

[2021-08-20 09:50:22,206: INFO/MainProcess] Task apps.users.usecases.BaseUserUseCase[3bce46e8-98c0-410e-a156-83e293ba6337] received
[2021-08-20 09:50:22,207: WARNING/ForkPoolWorker-4] Send email with {'setting': 'default'} to default@email.com
[2021-08-20 09:50:22,207: WARNING/ForkPoolWorker-4] 

[2021-08-20 09:50:22,207: INFO/ForkPoolWorker-4] Task apps.users.usecases.BaseUserUseCase[3bce46e8-98c0-410e-a156-83e293ba6337] succeeded in 0.0002498120002201176s: None
[2021-08-20 09:50:27,183: INFO/MainProcess] Task apps.users.usecases.BaseUserUseCase[e1d2de2a-3e7d-4253-9641-41fd328a17ce] received
[2021-08-20 09:50:27,183: WARNING/ForkPoolWorker-4] Send email with {'setting': 'default'} to default@email.com
[2021-08-20 09:50:27,184: WARNING/ForkPoolWorker-4] 

[2021-08-20 09:50:27,184: INFO/ForkPoolWorker-4] Task apps.users.usecases.BaseUserUseCase[e1d2de2a-3e7d-4253-9641-41fd328a17ce] succeeded in 0.0001804589992389083s: None

---

If you want to change the context and recipient as a scheduled task.

celery.py

• Just change the following lines.

...
    beat_schedule={
        'send_mail-every-day-at-4': {
            'task': 'apps.users.usecases.BaseUserUseCase',
            'schedule': 5,
            'kwargs': {
                'context': {'setting': 'custom'},
                'recipient': "custom@email.com",
            },
        },
    },
...

Logs (Consumer):

[2021-08-20 09:54:36,530: INFO/MainProcess] Task apps.users.usecases.BaseUserUseCase[6b69b79b-6764-4d83-ad24-9b0723dd8c79] received
[2021-08-20 09:54:36,531: WARNING/ForkPoolWorker-4] Send email with {'setting': 'custom'} to custom@email.com
[2021-08-20 09:54:36,531: WARNING/ForkPoolWorker-4] 

[2021-08-20 09:54:36,532: INFO/ForkPoolWorker-4] Task apps.users.usecases.BaseUserUseCase[6b69b79b-6764-4d83-ad24-9b0723dd8c79] succeeded in 0.0012146830003985087s: None
[2021-08-20 09:54:41,498: INFO/MainProcess] Task apps.users.usecases.BaseUserUseCase[a20d34e7-3214-4130-aba2-5544238096d0] received
[2021-08-20 09:54:41,499: WARNING/ForkPoolWorker-4] Send email with {'setting': 'custom'} to custom@email.com
[2021-08-20 09:54:41,499: WARNING/ForkPoolWorker-4] 

[2021-08-20 09:54:41,500: INFO/ForkPoolWorker-4] Task apps.users.usecases.BaseUserUseCase[a20d34e7-3214-4130-aba2-5544238096d0] succeeded in 0.00047696000001451466s: None

---

If you intend to call the task manually eg from one of the Django views:

>>> from apps.users.usecases import BaseUserUseCaseTask
>>> BaseUserUseCaseTask.apply_async()
<AsyncResult: fd347270-59b8-4cec-8772-cf82a79e60df>
>>> BaseUserUseCaseTask.apply_async(kwargs={'context': {'setting': 'manual'}, 'recipient': "manual@email.com"})
<AsyncResult: 13d9df7e-e1c4-4f50-847f-72a413404c82>

Logs (Consumer):

[2021-08-20 09:57:19,324: INFO/MainProcess] Task apps.users.usecases.BaseUserUseCase[fd347270-59b8-4cec-8772-cf82a79e60df] received
[2021-08-20 09:57:19,324: WARNING/ForkPoolWorker-4] Send email with {'setting': 'default'} to default@email.com
[2021-08-20 09:57:19,324: WARNING/ForkPoolWorker-4] 

[2021-08-20 09:57:19,325: INFO/ForkPoolWorker-4] Task apps.users.usecases.BaseUserUseCase[fd347270-59b8-4cec-8772-cf82a79e60df] succeeded in 0.00026283199986210093s: None
[2021-08-20 12:35:29,238: INFO/MainProcess] Task apps.users.usecases.BaseUserUseCase[13d9df7e-e1c4-4f50-847f-72a413404c82] received
[2021-08-20 12:35:29,240: WARNING/ForkPoolWorker-4] Send email with {'setting': 'manual'} to manual@email.com
[2021-08-20 12:35:29,240: WARNING/ForkPoolWorker-4] 

[2021-08-20 12:35:29,240: INFO/ForkPoolWorker-4] Task apps.users.usecases.BaseUserUseCase[13d9df7e-e1c4-4f50-847f-72a413404c82] succeeded in 0.000784056000156852s: None

Answer 2

I am not 100% sure but below should work for you

Function class:

class BaseUserUseCase:
    def __init__(self):
        self.context = {}
        self.receipent = ""

Add a task.py file in project folder:

import datetime
import logging
from path_to.celery import app
from rest_framework import status

from path_to import BaseUserUseCase


@app.task
def email_send_task(self):
        context = BaseUserUseCase.context
        receipent = BaseUserUseCase.receipent
        print("done")
        return ConfirmationEmail(context=context).send(to=[receipent])

Configure a celery.py file:

from __future__ import absolute_import, unicode_literals
import os
from celery import Celery
# set the default Django settings module for the 'celery' program.
from celery.schedules import crontab

# set the default Django settings module for the 'celery' program.
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'project.settings')

app = Celery('project_name')

# Using a string here means the worker doesn't have to serialize
# the configuration object to child processes.
# - namespace='CELERY' means all celery-related configuration keys
#   should have a `CELERY_` prefix.
app.config_from_object('django.conf:settings', namespace='CELERY')

# Load task modules from all registered Django app configs.
app.autodiscover_tasks()
# # add cron beat
app.conf.beat_schedule = {
    'send-email-celery-task': {
        'task': 'app_name.tasks.email_send_task',
        'schedule': crontab(hour=0, minute=1)
    },
}

Could you please try and let me know if it works for you?