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import logging
from django.contrib.sessions.backends.base import (
CreateError, SessionBase, UpdateError,
)
from django.core.exceptions import SuspiciousOperation
from django.db import DatabaseError, IntegrityError, router, transaction
from django.utils import timezone
from django.utils.encoding import force_text
from django.utils.functional import cached_property
class SessionStore(SessionBase):
"""
Implement database session store.
"""
def __init__(self, session_key=None):
super().__init__(session_key)
@classmethod
def get_model_class(cls):
# Avoids a circular import and allows importing SessionStore when
# django.contrib.sessions is not in INSTALLED_APPS.
from django.contrib.sessions.models import Session
return Session
@cached_property
def model(self):
return self.get_model_class()
def load(self):
try:
s = self.model.objects.get(
session_key=self.session_key,
expire_date__gt=timezone.now()
)
return self.decode(s.session_data)
except (self.model.DoesNotExist, SuspiciousOperation) as e:
if isinstance(e, SuspiciousOperation):
logger = logging.getLogger('django.security.%s' % e.__class__.__name__)
logger.warning(force_text(e))
self._session_key = None
return {}
def exists(self, session_key):
return self.model.objects.filter(session_key=session_key).exists()
def create(self):
while True:
self._session_key = self._get_new_session_key()
try:
# Save immediately to ensure we have a unique entry in the
# database.
self.save(must_create=True)
except CreateError:
# Key wasn't unique. Try again.
continue
self.modified = True
return
def create_model_instance(self, data):
"""
Return a new instance of the session model object, which represents the
current session state. Intended to be used for saving the session data
to the database.
"""
return self.model(
session_key=self._get_or_create_session_key(),
session_data=self.encode(data),
expire_date=self.get_expiry_date(),
)
def save(self, must_create=False):
"""
Save the current session data to the database. If 'must_create' is
True, raise a database error if the saving operation doesn't create a
new entry (as opposed to possibly updating an existing entry).
"""
if self.session_key is None:
return self.create()
data = self._get_session(no_load=must_create)
obj = self.create_model_instance(data)
using = router.db_for_write(self.model, instance=obj)
try:
with transaction.atomic(using=using):
obj.save(force_insert=must_create, force_update=not must_create, using=using)
except IntegrityError:
if must_create:
raise CreateError
raise
except DatabaseError:
if not must_create:
raise UpdateError
raise
def delete(self, session_key=None):
if session_key is None:
if self.session_key is None:
return
session_key = self.session_key
try:
self.model.objects.get(session_key=session_key).delete()
except self.model.DoesNotExist:
pass
@classmethod
def clear_expired(cls):
cls.get_model_class().objects.filter(expire_date__lt=timezone.now()).delete()