Django : user online / offline - user None false even if user is online

I'm trying to know if my user are online or offline.

I got different apps. I'm using user app for all my users.

user/models.py

class UserProfile(models.Model):
    ...
    def last_seen(self):
        return cache.get('last_seen_%s' % self.user.username)
    
    def online(self):
        if self.last_seen():
            now = datetime.datetime.now()
            if now > (self.last_seen() + datetime.timedelta(seconds=settings.USER_ONLINE_TIMEOUT)):
                return False
            else:
                return True
        else: 
            return False

then I've created a new file:

user/middleware.py

import datetime
from django.core.cache import cache
from django.conf import settings
from django.utils.deprecation import MiddlewareMixin

class ActiveUserMiddleware(MiddlewareMixin):

    def process_request(self, request):
        current_user = request.user
        if request.user.is_authenticated():
            now = datetime.datetime.now()
            cache.set('seen_%s' % (current_user.username), now, 
                           settings.USER_LASTSEEN_TIMEOUT)

In my settings.py (monsite folder):

I added this to MIDDLEWARE

'user.middleware.ActiveUserMiddleware' 

Also at the bottom of my settings.py file I've added that: (and I don't really with what I've to replace LOCATION value)

CACHES = {
        'default': {
            'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
            'LOCATION': '127.0.0.1:11211',              
        }
    }

# Number of seconds of inactivity before a user is marked offline
USER_ONLINE_TIMEOUT = 300

# Number of seconds that we will keep track of inactive users for before 
# their last seen is removed from the cache
USER_LASTSEEN_TIMEOUT = 60 * 60 * 24 * 7  

I got this issue:

'bool' object is not callable

/home/dulo0814/monProjetDjango/user/middleware.py in process_request, line 10

UPDATE

user/middleware.py

    if request.user.is_authenticated:

monsite/settings.py (python manage.py createcachetable)

CACHES = {
        'default': {
            'BACKEND': 'django.core.cache.backends.db.DatabaseCache',
            'LOCATION': 'name_table',              
        }
    }

# Number of seconds of inactivity before a user is marked offline
USER_ONLINE_TIMEOUT = 300

# Number of seconds that we will keep track of inactive users for before 
# their last seen is removed from the cache
USER_LASTSEEN_TIMEOUT = 60 * 60 * 24 * 7

{{ user.userprofile.online }} = got None