In template, when I use
{% if topic.creator.is_authenticated %}
Online
{% else %}
Offline
{% endif %}
the users turn out to be always online, even when they has signed out a while ago. So I'm wondering how to check the online users correctly?
Thanks this excellent blog post, with slight modifications, I came up with a better solution, which uses memcache, hence less delay per request:
in models.py add:
from django.core.cache import cache
import datetime
from myproject import settings
and add these method the userprofile class:
def last_seen(self):
return cache.get('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
in userprofile folder add this middleware.py
import datetime
from django.core.cache import cache
from django.conf import settings
class ActiveUserMiddleware:
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 settings.py add 'userprofile.middleware.ActiveUserMiddleware',
to MIDDLEWARE_CLASSES
and also add:
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
and in profile.html:
<table>
<tr><th>Last Seen</th><td>{% if profile.last_seen %}{{ profile.last_seen|timesince }}{% else %}awhile{% endif %} ago</td></tr>
<tr><th>Online</th><td>{{ profile.online }}</td></tr>
</table>
That's it!
To test cache in the console, to make sure that memcache works fine:
$memcached -vv
$ python manage.py shell
>>> from django.core.cache import cache
>>> cache.set("foo", "bar")
>>> cache.get("foo")
'bar'
>>> cache.set("foo", "zaq")
>>> cache.get("foo")
'zaq'