How to share cache between a task and a view with Django?

Question

In my django project, I got a task running every 5 minutes (with Celery and Redis as a broker):

from django.core.cache import cache

@shared_task()
@celery.task(base=QueueOnce)
def cache_date():
    cache.set('date', datetime.now)
    print('Cached date : ', cache.get('date'))

And it's running fine, printing the new cached date everytime it runs

But then, somewhere in one of my views I try to do this :

from django.core.cache import cache

def get_cached_date():
    print('Cached date :', cache.get('date')

And then it prints "Cached date : None"

Here's my cache settings :

CACHES = {
   'default': {
      'BACKEND': 'django.core.cache.backends.filebased.FileBasedCache',
      'LOCATION': '/tmp/cache',
   }
}

I don't get it, why is the value available in one place and not in the other while I'm using a singe location file ? Am I trying to do something wrong?

UPDATE

@Satevg I use docker-compose, here is my file :

services:
  redis:
    image: redis

  worker:
    image: project
    depends_on:
      - redis
      - webserver
    command: project backend worker
    volumes:
    - cache:/tmp/cache

  webserver:
    image: project
    depends_on:
      - redis
    volumes:
      - cache:/tmp/cache

volumes:
  cache:

I tried to share the volumes like this, but when my task tries to write to the cache I get :

OSError: [Errno 13] Permission denied: '/tmp/cache/tmpAg_TAc'

When I look at the filesystems in both containers I can see the folder /tmp/cache, the web app can even write on it and when I look on the worker's container /tmp/cache folder I can see the updated cache

UPDATE2:

The webapp can write to the cache.

cache.set('test', 'Test')

On the worker's container, I can see the cache file on the /tmp/cache folder When the task tries to read from cache :

print(cache.get('test'))

It says :

None

When the task tries to write from cache it still gets Errno13

Answer 1

As we figured out in comments, celery and app are working in different docker containers.

django.core.cache.backends.filebased.FileBasedCache serializes and stores each cache value as a separate file. But these files are in different file systems.

The solution is to use docker volumes in order to share /tmp/cache folder between these two containers.