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# -*- coding: utf-8 -*-
"""
celery.local
~~~~~~~~~~~~
This module contains critical utilities that
needs to be loaded as soon as possible, and that
shall not load any third party modules.
Parts of this module is Copyright by Werkzeug Team.
:copyright: (c) 2009 - 2012 by Ask Solem.
:license: BSD, see LICENSE for more details.
"""
from __future__ import absolute_import
# since each thread has its own greenlet we can just use those as identifiers
# for the context. If greenlets are not available we fall back to the
# current thread ident.
try:
from greenlet import getcurrent as get_ident
except ImportError: # pragma: no cover
try:
from thread import get_ident # noqa
except ImportError: # pragma: no cover
try:
from dummy_thread import get_ident # noqa
except ImportError: # pragma: no cover
from _thread import get_ident # noqa
def try_import(module, default=None):
"""Try to import and return module, or return
None if the module does not exist."""
from importlib import import_module
try:
return import_module(module)
except ImportError:
return default
class Proxy(object):
"""Proxy to another object."""
# Code stolen from werkzeug.local.Proxy.
__slots__ = ('__local', '__args', '__kwargs', '__dict__', '__name__')
def __init__(self, local, args=None, kwargs=None, name=None):
object.__setattr__(self, '_Proxy__local', local)
object.__setattr__(self, '_Proxy__args', args or ())
object.__setattr__(self, '_Proxy__kwargs', kwargs or {})
if name is not None:
object.__setattr__(self, '__custom_name__', name)
@property
def __name__(self):
try:
return self.__custom_name__
except AttributeError:
return self._get_current_object().__name__
@property
def __module__(self):
return self._get_current_object().__module__
@property
def __doc__(self):
return self._get_current_object().__doc__
def _get_class(self):
return self._get_current_object().__class__
@property
def __class__(self):
return self._get_class()
def _get_current_object(self):
"""Return the current object. This is useful if you want the real
object behind the proxy at a time for performance reasons or because
you want to pass the object into a different context.
"""
if not hasattr(self.__local, '__release_local__'):
return self.__local(*self.__args, **self.__kwargs)
try:
return getattr(self.__local, self.__name__)
except AttributeError:
raise RuntimeError('no object bound to %s' % self.__name__)
@property
def __dict__(self):
try:
return self._get_current_object().__dict__
except RuntimeError: # pragma: no cover
raise AttributeError('__dict__')
def __repr__(self):
try:
obj = self._get_current_object()
except RuntimeError: # pragma: no cover
return '<%s unbound>' % self.__class__.__name__
return repr(obj)
def __nonzero__(self):
try:
return bool(self._get_current_object())
except RuntimeError: # pragma: no cover
return False
def __unicode__(self):
try:
return unicode(self._get_current_object())
except RuntimeError: # pragma: no cover
return repr(self)
def __dir__(self):
try:
return dir(self._get_current_object())
except RuntimeError: # pragma: no cover
return []
def __getattr__(self, name):
if name == '__members__':
return dir(self._get_current_object())
return getattr(self._get_current_object(), name)
def __setitem__(self, key, value):
self._get_current_object()[key] = value
def __delitem__(self, key):
del self._get_current_object()[key]
def __setslice__(self, i, j, seq):
self._get_current_object()[i:j] = seq
def __delslice__(self, i, j):
del self._get_current_object()[i:j]
__setattr__ = lambda x, n, v: setattr(x._get_current_object(), n, v)
__delattr__ = lambda x, n: delattr(x._get_current_object(), n)
__str__ = lambda x: str(x._get_current_object())
__lt__ = lambda x, o: x._get_current_object() < o
__le__ = lambda x, o: x._get_current_object() <= o
__eq__ = lambda x, o: x._get_current_object() == o
__ne__ = lambda x, o: x._get_current_object() != o
__gt__ = lambda x, o: x._get_current_object() > o
__ge__ = lambda x, o: x._get_current_object() >= o
__cmp__ = lambda x, o: cmp(x._get_current_object(), o)
__hash__ = lambda x: hash(x._get_current_object())
__call__ = lambda x, *a, **kw: x._get_current_object()(*a, **kw)
__len__ = lambda x: len(x._get_current_object())
__getitem__ = lambda x, i: x._get_current_object()[i]
__iter__ = lambda x: iter(x._get_current_object())
__contains__ = lambda x, i: i in x._get_current_object()
__getslice__ = lambda x, i, j: x._get_current_object()[i:j]
__add__ = lambda x, o: x._get_current_object() + o
__sub__ = lambda x, o: x._get_current_object() - o
__mul__ = lambda x, o: x._get_current_object() * o
__floordiv__ = lambda x, o: x._get_current_object() // o
__mod__ = lambda x, o: x._get_current_object() % o
__divmod__ = lambda x, o: x._get_current_object().__divmod__(o)
__pow__ = lambda x, o: x._get_current_object() ** o
__lshift__ = lambda x, o: x._get_current_object() << o
__rshift__ = lambda x, o: x._get_current_object() >> o
__and__ = lambda x, o: x._get_current_object() & o
__xor__ = lambda x, o: x._get_current_object() ^ o
__or__ = lambda x, o: x._get_current_object() | o
__div__ = lambda x, o: x._get_current_object().__div__(o)
__truediv__ = lambda x, o: x._get_current_object().__truediv__(o)
__neg__ = lambda x: -(x._get_current_object())
__pos__ = lambda x: +(x._get_current_object())
__abs__ = lambda x: abs(x._get_current_object())
__invert__ = lambda x: ~(x._get_current_object())
__complex__ = lambda x: complex(x._get_current_object())
__int__ = lambda x: int(x._get_current_object())
__long__ = lambda x: long(x._get_current_object())
__float__ = lambda x: float(x._get_current_object())
__oct__ = lambda x: oct(x._get_current_object())
__hex__ = lambda x: hex(x._get_current_object())
__index__ = lambda x: x._get_current_object().__index__()
__coerce__ = lambda x, o: x.__coerce__(x, o)
__enter__ = lambda x: x._get_current_object().__enter__()
__exit__ = lambda x, *a, **kw: x._get_current_object().__exit__(*a, **kw)
__reduce__ = lambda x: x._get_current_object().__reduce__()
class PromiseProxy(Proxy):
"""This is a proxy to an object that has not yet been evaulated.
:class:`Proxy` will evaluate the object each time, while the
promise will only evaluate it once.
"""
def _get_current_object(self):
try:
return object.__getattribute__(self, "__thing")
except AttributeError:
return self.__evaluate__()
def __maybe_evaluate__(self):
return self._get_current_object()
def __evaluate__(self):
try:
thing = Proxy._get_current_object(self)
object.__setattr__(self, "__thing", thing)
return thing
finally:
object.__delattr__(self, "_Proxy__local")
object.__delattr__(self, "_Proxy__args")
object.__delattr__(self, "_Proxy__kwargs")
def maybe_evaluate(obj):
try:
return obj.__maybe_evaluate__()
except AttributeError:
return obj
def release_local(local):
"""Releases the contents of the local for the current context.
This makes it possible to use locals without a manager.
Example::
>>> loc = Local()
>>> loc.foo = 42
>>> release_local(loc)
>>> hasattr(loc, 'foo')
False
With this function one can release :class:`Local` objects as well
as :class:`StackLocal` objects. However it is not possible to
release data held by proxies that way, one always has to retain
a reference to the underlying local object in order to be able
to release it.
.. versionadded:: 0.6.1
"""
local.__release_local__()
class Local(object):
__slots__ = ('__storage__', '__ident_func__')
def __init__(self):
object.__setattr__(self, '__storage__', {})
object.__setattr__(self, '__ident_func__', get_ident)
def __iter__(self):
return iter(self.__storage__.items())
def __call__(self, proxy):
"""Create a proxy for a name."""
return Proxy(self, proxy)
def __release_local__(self):
self.__storage__.pop(self.__ident_func__(), None)
def __getattr__(self, name):
try:
return self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name)
def __setattr__(self, name, value):
ident = self.__ident_func__()
storage = self.__storage__
try:
storage[ident][name] = value
except KeyError:
storage[ident] = {name: value}
def __delattr__(self, name):
try:
del self.__storage__[self.__ident_func__()][name]
except KeyError:
raise AttributeError(name)
class LocalStack(object):
"""This class works similar to a :class:`Local` but keeps a stack
of objects instead. This is best explained with an example::
>>> ls = LocalStack()
>>> ls.push(42)
>>> ls.top
42
>>> ls.push(23)
>>> ls.top
23
>>> ls.pop()
23
>>> ls.top
42
They can be force released by using a :class:`LocalManager` or with
the :func:`release_local` function but the correct way is to pop the
item from the stack after using. When the stack is empty it will
no longer be bound to the current context (and as such released).
By calling the stack without arguments it returns a proxy that resolves to
the topmost item on the stack.
"""
def __init__(self):
self._local = Local()
def __release_local__(self):
self._local.__release_local__()
def _get__ident_func__(self):
return self._local.__ident_func__
def _set__ident_func__(self, value):
object.__setattr__(self._local, '__ident_func__', value)
__ident_func__ = property(_get__ident_func__, _set__ident_func__)
del _get__ident_func__, _set__ident_func__
def __call__(self):
def _lookup():
rv = self.top
if rv is None:
raise RuntimeError('object unbound')
return rv
return Proxy(_lookup)
def push(self, obj):
"""Pushes a new item to the stack"""
rv = getattr(self._local, 'stack', None)
if rv is None:
self._local.stack = rv = []
rv.append(obj)
return rv
def pop(self):
"""Removes the topmost item from the stack, will return the
old value or `None` if the stack was already empty.
"""
stack = getattr(self._local, 'stack', None)
if stack is None:
return None
elif len(stack) == 1:
release_local(self._local)
return stack[-1]
else:
return stack.pop()
@property
def stack(self):
"""get_current_worker_task uses this to find
the original task that was executed by the worker."""
stack = getattr(self._local, 'stack', None)
if stack is not None:
return stack
return []
@property
def top(self):
"""The topmost item on the stack. If the stack is empty,
`None` is returned.
"""
try:
return self._local.stack[-1]
except (AttributeError, IndexError):
return None
class LocalManager(object):
"""Local objects cannot manage themselves. For that you need a local
manager. You can pass a local manager multiple locals or add them later
by appending them to `manager.locals`. Everytime the manager cleans up
it, will clean up all the data left in the locals for this context.
The `ident_func` parameter can be added to override the default ident
function for the wrapped locals.
.. versionchanged:: 0.6.1
Instead of a manager the :func:`release_local` function can be used
as well.
.. versionchanged:: 0.7
`ident_func` was added.
"""
def __init__(self, locals=None, ident_func=None):
if locals is None:
self.locals = []
elif isinstance(locals, Local):
self.locals = [locals]
else:
self.locals = list(locals)
if ident_func is not None:
self.ident_func = ident_func
for local in self.locals:
object.__setattr__(local, '__ident_func__', ident_func)
else:
self.ident_func = get_ident
def get_ident(self):
"""Return the context identifier the local objects use internally for
this context. You cannot override this method to change the behavior
but use it to link other context local objects (such as SQLAlchemy's
scoped sessions) to the Werkzeug locals.
.. versionchanged:: 0.7
You can pass a different ident function to the local manager that
will then be propagated to all the locals passed to the
constructor.
"""
return self.ident_func()
def cleanup(self):
"""Manually clean up the data in the locals for this context. Call
this at the end of the request or use `make_middleware()`.
"""
for local in self.locals:
release_local(local)
def __repr__(self):
return '<%s storages: %d>' % (
self.__class__.__name__,
len(self.locals)
)
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