class LockableModel(LockableModelFieldsMixin, LockableModelMethodsMixin):
""" LockableModel comes with three managers: ``objects``, ``locked`` and
``unlocked``. They do what you'd expect them to. """
objects = managers.Manager()
locked = managers.LockedManager()
unlocked = managers.UnlockedManager()
class Meta:
abstract = True
class Lock(models.Model):
""" LockableModel comes with three managers: ``objects``, ``locked`` and
``unlocked``. They do what you'd expect them to. """
objects = managers.Manager()
locked = managers.LockedManager()
unlocked = managers.UnlockedManager()
def __init__(self, *vargs, **kwargs):
super(Lock, self).__init__(*vargs, **kwargs)
self._state.locking = False
_locked_at = models.DateTimeField(db_column='locked_at',
null=True,
editable=False)
app = models.CharField(max_length=255, null=True)
model = models.CharField(max_length=255, null=True)
entry_id = models.PositiveIntegerField(db_index=True)
_locked_by = models.ForeignKey(auth.User,
db_column='locked_by',
related_name="working_on_%(class)s",
null=True,
editable=False)
_hard_lock = models.BooleanField(db_column='hard_lock',
default=False,
editable=False)
# We don't want end-developers to manipulate database fields directly,
# hence we're putting these behind simple getters.
# End-developers should use functionality like the lock_for method instead.
@property
def locked_at(self):
"""A simple ``DateTimeField`` that is the heart of the locking
mechanism. Read-only."""
return self._locked_at
@property
def locked_by(self):
"""``locked_by`` is a foreign key to ``auth.User``.
The ``related_name`` on the User object is ``working_on_%(class)s``.
Read-only."""
return self._locked_by
@property
def lock_type(self):
""" Returns the type of lock that is currently active. Either
``hard``, ``soft`` or ``None``. Read-only. """
if self.is_locked:
if self._hard_lock:
return "hard"
else:
return "soft"
else:
return None
@property
def is_locked(self):
"""
A read-only property that returns True or False.
Works by calculating if the last lock (self.locked_at) has timed out
or not.
"""
if isinstance(self.locked_at, datetime):
# tue -> time delta until expiration
_tue = timedelta(seconds=settings.LOCKING['time_until_expiration'])
if (datetime.today() - self.locked_at) < _tue:
return True
else:
return False
return False
@property
def lock_seconds_remaining(self):
"""
A read-only property that returns the amount of seconds remaining
before any existing lock times out.
May or may not return a negative number if the object is currently
unlocked. That number represents the amount of seconds since the last
lock expired.
If you want to extend a lock beyond its current expiry date, initiate
a new lock using the ``lock_for`` method.
"""
_tue = timedelta(settings.LOCKING['time_until_expiration'])
diff = _tue - (datetime.today() - self.locked_at)
return (diff.days * 24 * 60 * 60) + diff.seconds
def lock_for(self, user, hard_lock=True):
"""
Together with ``unlock_for`` this is probably the most important
method on this model. If applicable to your use-case, you should lock
for a specific user; that way, we can throw an exception when another
user tries to unlock an object they haven't locked themselves.
When using soft locks, any process can still use the save method
on this object. If you set ``hard_lock=True``, trying to save an object
without first unlocking will raise an ``ObjectLockedError``.
Don't use hard locks unless you really need them. See :doc:`design`.
The 'hard lock' flag is set to True as the default as a fail safe
method to back up javascript lock validations. This is useful when
the user's lock expires or javascript fails to load, etc.
Keep in mind that soft locks are set since they provide the user with
a user friendly locking interface.
"""
logger.debug("Attempting to initiate a lock for user `%s`" % user)
if not isinstance(user, auth.User):
raise ValueError("You should pass a valid auth.User to lock_for.")
if self.lock_applies_to(user):
raise ObjectLockedError(
"This object is already locked by another"
" user. May not override, except through the `unlock` method.")
else:
self._locked_at = datetime.today()
self._locked_by = user
self._hard_lock = self.__init_hard_lock = hard_lock
date = self.locked_at.strftime("%H:%M:%S")
# an administrative toggle, to make it easier for devs to extend `django-locking`
# and react to locking and unlocking
self._state.locking = True
logger.debug("Initiated a %s lock for `%s` at %s" %
(self.lock_type, self.locked_by, self.locked_at))
def unlock(self):
"""
This method serves solely to allow the application itself or admin
users to do manual lock overrides, even if they haven't initiated
these locks themselves. Otherwise, use ``unlock_for``.
"""
self._locked_at = self._locked_by = None
# an administrative toggle, to make it easier for devs to extend `django-locking`
# and react to locking and unlocking
self._state.locking = True
logger.debug("Disengaged lock on `%s`" % self)
def unlock_for(self, user):
"""
See ``lock_for``. If the lock was initiated for a specific user,
unlocking will fail unless that same user requested the unlocking.
Manual overrides should use the ``unlock`` method instead.
Will raise a ObjectLockedError exception when the current user isn't
authorized to unlock the object.
"""
logger.debug("Attempting to open up a lock on `%s` by user `%s`" %
(self, user))
self.unlock()
def lock_applies_to(self, user):
"""
A lock does not apply to the user who initiated the lock. Thus,
``lock_applies_to`` is used to ascertain whether a user is allowed
to edit a locked object.
"""
logger.debug("Checking if the lock on `%s` applies to user `%s`" %
(self, user))
# a lock does not apply to the person who initiated the lock
if self.is_locked and self.locked_by != user:
logger.debug("Lock applies.")
return True
else:
logger.debug("Lock does not apply.")
return False
def is_locked_by(self, user):
"""
Returns True or False. Can be used to test whether this object is
locked by a certain user. The ``lock_applies_to`` method and the
``is_locked`` and ``locked_by`` attributes are probably more useful
for most intents and
purposes.
"""
return user == self.locked_by
def save(self, *vargs, **kwargs):
super(Lock, self).save(*vargs, **kwargs)
self._state.locking = False