Django celery task: Newly created model DoesNotExist
asynchronous, celery, django, django-celery
Solution
These answers need to be updated. Django now has `transaction.on_commit()` which is built for this exact problem, they even provide an example with a task:
transaction.on_commit(lambda: some_celery_task.delay('arg1'))
https://docs.djangoproject.com/en/2.1/topics/db/transactions/#django.db.transaction.on_commit
Problem
Why is a model instance I've created, when queried from a celery task started directly afterwards, not found? For example: ``` # app.views model = Model.objects.create() # I create my lovely model in a view from app.tasks import ModelTask # I import my Async celery task ModelTask.delay(model.pk) # I start the task ``` That all looks fine, and surely if I queried at any point after the `create()` call the model should exist in the database. Update 1: I'm using the default `transaction.autocommit` behaviour, that Django provides, for my view. But the task below throws an `ObjectDoesNotExist` exception: ``` # app.tasks class ModelTask(Task): def run(self, model_pk): from app.models import Model Model.objects.get(pk=model_pk) ``` In my tests, as expected, `model_pk` is a correct positive integer ID. Conclusion I assume there is some asynchronous/"separate process" issues arising here, but I don't know what it is. If feel as though there is some obvious mistake I'm making. I don't think that database transactions are the answer, because Django's default "autocommit" approach ensures DB actions are performed as soon as the `create()` method is called.