Django Execute Function When DateTimeField Equals Current Date And Time

So I have implemented a subscription product to my website. When they start the subscription, the current date and time is stored into the database. When they cancel the subscript

Solution 1:

Without Celery, installed on UNIX system providing CRON (cron doku: e.g. https://www.computerhope.com/unix/ucrontab.htm):

1. write a Command https://docs.djangoproject.com/en/2.1/howto/custom-management-commands/ that fetches the objects for which cancel_date is in the past and that have not been cancelled yet. (If you do the lookup with datetime.now() (a very precise lookup with the finest granularity), you would have to be more than lucky to find anything.)

You should add another date field that tells you when the system actually ran the cancellation, and you should allow both the cancel_date and cancelled_date to be null.

# models.py
class Subscriptions(models.Model):
    subscription_id = models.AutoField(primary_key=True)
    start_date = model.DateTimeField(auto_now_add=True)
    cancel_date = model.DateTimeField(auto_now_add=False, null=True)
    cancelled_date = model.DateTimeField(null=True)
    person_id = model.ForeignKey('Persons')

# under myapp/management/command/cancellation.py
class CancellationCommand(BaseCommand):
    def handle(self, *args, **options):
        now = datetime.now()
        to_cancel_qs = Subscriptions.objects.exclude(
            cancelled_date__isnull=False).filter(
            cancel_date__lte=now)
        for sub in to_cancel_qs.all():
            # do your cancelling
            sub.cancelled_date = now
            sub.save()
        # or: to_cancel_qs.update(cancelled_date=now)
        

2. install a cron job that runs this command via ./manage.py your_command at a regular time