Django: how to create a signal using django?

I have a bidding system and there is an ending date for the bidding, i want users to bid against themselves till the ending of the bidding date.

The product creators are the ones to add the ending date which would be some date in the future, how can i write a django signal to check if the date that was added as the ending date is the current date, then i'll perform some operations like mark the highest bidder as winner.

This is my model

class Product(models.Model):
    user = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    price = models.DecimalField(max_digits=12, decimal_places=2, default=0.00)
    type = models.CharField(choices=PRODUCT_TYPE, max_length=10, default="regular")
    ending_date = models.DateTimeField(auto_now_add=False, null=True, blank=True)
    ...

class ProductBidders(models.Model):
    user = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    product = models.ForeignKey(Product, on_delete=models.SET_NULL, null=True, related_name="product_bidders")
    price = models.DecimalField(max_digits=12, decimal_places=2, default=1.00)
    date = models.DateTimeField(auto_now_add=True)

I believe that you cannot do this with Django signals alone. Django signals have triggers to detect operations like creating an instance, which you can use to invoke a task.

You might have to use something like Celery to do this. You can create a Celery task when you create a Product instance. (For this, you can use 'post_save' signal). At this time, you can pass an argument telling Celery when to run the task. However, if a user changes the 'ending_date', then you would have to have a mechanism to inform that to Celery as well.

Otherwise, you can run a Celery periodic task (using Celery Beat) which would filter Product instances periodically to check the 'ending_date' and perform your required operation if the instance meets the criteria.