Celery. Task no simultaneous execution

decorators.py

from functools import wraps

from django.core.cache import cache

from celery.five import monotonic


CACHE_LOCK_EXPIRE = 10


def no_simultaneous_execution(f):
    """
    https://stackoverflow.com/a/59301422/8342448
    
    Decorator that prevents a task form being executed with the
    same *args and **kwargs more than one at a time.
    """
    @wraps(f)
    def wrapper(self, *args, **kwargs):
        # Create lock_id used as cache key
        lock_id = '{}-{}-{}'.format(self.name, args, kwargs)
        print('Lock id:', lock_id)

        # Timeout with a small diff, so we'll leave the lock delete
        # to the cache if it's close to being auto-removed/expired
        timeout_at = monotonic() + CACHE_LOCK_EXPIRE - 3
        print('Timeout at:', timeout_at)

        # Try to acquire a lock, or put task back on queue
        lock_acquired = cache.add(lock_id, True, CACHE_LOCK_EXPIRE)
        print('Lock acquired', lock_acquired)

        if not lock_acquired:
            print('Apply async', self)
            self.s(*args).apply_async(countdown=3)
            return

        print('Run', f)
        try:
            f(self, *args, **kwargs)
        finally:
            # Release the lock
            if monotonic() < timeout_at:
                cache.delete(lock_id)

    return wrapper

handlers.py

from .tasks import sync_order_task
...


@receiver(post_save, sender=Order)
def post_save_order_handler(sender, instance: 'Order', **kwargs):
    if not instance.is_created:
        sync_order_task.delay(instance.pk)

tasks.py

from .decorators import no_simultaneous_execution
...

@app.task(bind=True, name="sync_order_task")
@no_simultaneous_execution
def sync_order_task(self, pk: str):
    OrderModel = apps.get_model('order', 'Order')
    order = OrderModel.objects.get(pk=pk)

    try:
        sync_order = SyncOrder()
        sync_order.sync(order.pk)
        logger.info(
            f'Order #pk: {order.pk} was synced.'
        )
    except Exception as e:
        _error_handler(e, order)
        raise self.retry(exc=e, countdown=COUNTDOWN_TIMEOUT)