This document describes the current stable version of Celery (3.1). For development docs, go here.
Source code for kombu.utils
"""
kombu.utils
===========
Internal utilities.
"""
from __future__ import absolute_import, print_function
import importlib
import numbers
import random
import sys
from contextlib import contextmanager
from itertools import count, repeat
from functools import wraps
from time import sleep
from uuid import UUID, uuid4
try:
from uuid import _uuid_generate_random
except ImportError:
_uuid_generate_random = None
from kombu.five import items, reraise, string_t
from .encoding import default_encode, safe_repr as _safe_repr
try:
import ctypes
except:
ctypes = None # noqa
try:
from io import UnsupportedOperation
FILENO_ERRORS = (AttributeError, ValueError, UnsupportedOperation)
except ImportError: # pragma: no cover
# Py2
FILENO_ERRORS = (AttributeError, ValueError) # noqa
__all__ = ['EqualityDict', 'say', 'uuid', 'kwdict', 'maybe_list',
'fxrange', 'fxrangemax', 'retry_over_time',
'emergency_dump_state', 'cached_property',
'reprkwargs', 'reprcall', 'nested', 'fileno', 'maybe_fileno']
[docs]def symbol_by_name(name, aliases={}, imp=None, package=None,
sep='.', default=None, **kwargs):
"""Get symbol by qualified name.
The name should be the full dot-separated path to the class::
modulename.ClassName
Example::
celery.concurrency.processes.TaskPool
^- class name
or using ':' to separate module and symbol::
celery.concurrency.processes:TaskPool
If `aliases` is provided, a dict containing short name/long name
mappings, the name is looked up in the aliases first.
Examples:
>>> symbol_by_name('celery.concurrency.processes.TaskPool')
<class 'celery.concurrency.processes.TaskPool'>
>>> symbol_by_name('default', {
... 'default': 'celery.concurrency.processes.TaskPool'})
<class 'celery.concurrency.processes.TaskPool'>
# Does not try to look up non-string names.
>>> from celery.concurrency.processes import TaskPool
>>> symbol_by_name(TaskPool) is TaskPool
True
"""
if imp is None:
imp = importlib.import_module
if not isinstance(name, string_t):
return name # already a class
name = aliases.get(name) or name
sep = ':' if ':' in name else sep
module_name, _, cls_name = name.rpartition(sep)
if not module_name:
cls_name, module_name = None, package if package else cls_name
try:
try:
module = imp(module_name, package=package, **kwargs)
except ValueError as exc:
reraise(ValueError,
ValueError("Couldn't import {0!r}: {1}".format(name, exc)),
sys.exc_info()[2])
return getattr(module, cls_name) if cls_name else module
except (ImportError, AttributeError):
if default is None:
raise
return default
class HashedSeq(list):
"""type used for hash() to make sure the hash is not generated
multiple times."""
__slots__ = 'hashvalue'
def __init__(self, *seq):
self[:] = seq
self.hashvalue = hash(seq)
def __hash__(self):
return self.hashvalue
def eqhash(o):
try:
return o.__eqhash__()
except AttributeError:
return hash(o)
class EqualityDict(dict):
def __getitem__(self, key):
h = eqhash(key)
if h not in self:
return self.__missing__(key)
return dict.__getitem__(self, h)
def __setitem__(self, key, value):
return dict.__setitem__(self, eqhash(key), value)
def __delitem__(self, key):
return dict.__delitem__(self, eqhash(key))
def say(m, *fargs, **fkwargs):
print(str(m).format(*fargs, **fkwargs), file=sys.stderr)
if ctypes and _uuid_generate_random: # pragma: no cover
def uuid4():
# Workaround for http://bugs.python.org/issue4607
buffer = ctypes.create_string_buffer(16)
_uuid_generate_random(buffer)
return UUID(bytes=buffer.raw)
def uuid():
"""Generate a unique id, having - hopefully - a very small chance of
collision.
For now this is provided by :func:`uuid.uuid4`.
"""
return str(uuid4())
gen_unique_id = uuid
if sys.version_info >= (2, 6, 5):
def kwdict(kwargs):
return kwargs
else:
def kwdict(kwargs): # pragma: no cover # noqa
"""Make sure keyword arguments are not in Unicode.
This should be fixed in newer Python versions,
see: http://bugs.python.org/issue4978.
"""
return dict((key.encode('utf-8'), value)
for key, value in items(kwargs))
def maybe_list(v):
if v is None:
return []
if hasattr(v, '__iter__'):
return v
return [v]
def fxrange(start=1.0, stop=None, step=1.0, repeatlast=False):
cur = start * 1.0
while 1:
if not stop or cur <= stop:
yield cur
cur += step
else:
if not repeatlast:
break
yield cur - step
def fxrangemax(start=1.0, stop=None, step=1.0, max=100.0):
sum_, cur = 0, start * 1.0
while 1:
if sum_ >= max:
break
yield cur
if stop:
cur = min(cur + step, stop)
else:
cur += step
sum_ += cur
def retry_over_time(fun, catch, args=[], kwargs={}, errback=None,
max_retries=None, interval_start=2, interval_step=2,
interval_max=30, callback=None):
"""Retry the function over and over until max retries is exceeded.
For each retry we sleep a for a while before we try again, this interval
is increased for every retry until the max seconds is reached.
:param fun: The function to try
:param catch: Exceptions to catch, can be either tuple or a single
exception class.
:keyword args: Positional arguments passed on to the function.
:keyword kwargs: Keyword arguments passed on to the function.
:keyword errback: Callback for when an exception in ``catch`` is raised.
The callback must take two arguments: ``exc`` and ``interval``, where
``exc`` is the exception instance, and ``interval`` is the time in
seconds to sleep next..
:keyword max_retries: Maximum number of retries before we give up.
If this is not set, we will retry forever.
:keyword interval_start: How long (in seconds) we start sleeping between
retries.
:keyword interval_step: By how much the interval is increased for each
retry.
:keyword interval_max: Maximum number of seconds to sleep between retries.
"""
retries = 0
interval_range = fxrange(interval_start,
interval_max + interval_start,
interval_step, repeatlast=True)
for retries in count():
try:
return fun(*args, **kwargs)
except catch as exc:
if max_retries and retries >= max_retries:
raise
if callback:
callback()
tts = float(errback(exc, interval_range, retries) if errback
else next(interval_range))
if tts:
for _ in range(int(tts)):
if callback:
callback()
sleep(1.0)
# sleep remainder after int truncation above.
sleep(abs(int(tts) - tts))
def emergency_dump_state(state, open_file=open, dump=None):
from pprint import pformat
from tempfile import mktemp
if dump is None:
import pickle
dump = pickle.dump
persist = mktemp()
say('EMERGENCY DUMP STATE TO FILE -> {0} <-', persist)
fh = open_file(persist, 'w')
try:
try:
dump(state, fh, protocol=0)
except Exception as exc:
say('Cannot pickle state: {0!r}. Fallback to pformat.', exc)
fh.write(default_encode(pformat(state)))
finally:
fh.flush()
fh.close()
return persist
[docs]class cached_property(object):
"""Property descriptor that caches the return value
of the get function.
*Examples*
.. code-block:: python
@cached_property
def connection(self):
return Connection()
@connection.setter # Prepares stored value
def connection(self, value):
if value is None:
raise TypeError('Connection must be a connection')
return value
@connection.deleter
def connection(self, value):
# Additional action to do at del(self.attr)
if value is not None:
print('Connection {0!r} deleted'.format(value)
"""
def __init__(self, fget=None, fset=None, fdel=None, doc=None):
self.__get = fget
self.__set = fset
self.__del = fdel
self.__doc__ = doc or fget.__doc__
self.__name__ = fget.__name__
self.__module__ = fget.__module__
def __get__(self, obj, type=None):
if obj is None:
return self
try:
return obj.__dict__[self.__name__]
except KeyError:
value = obj.__dict__[self.__name__] = self.__get(obj)
return value
def __set__(self, obj, value):
if obj is None:
return self
if self.__set is not None:
value = self.__set(obj, value)
obj.__dict__[self.__name__] = value
def __delete__(self, obj):
if obj is None:
return self
try:
value = obj.__dict__.pop(self.__name__)
except KeyError:
pass
else:
if self.__del is not None:
self.__del(obj, value)
def reprkwargs(kwargs, sep=', ', fmt='{0}={1}'):
return sep.join(fmt.format(k, _safe_repr(v)) for k, v in items(kwargs))
def reprcall(name, args=(), kwargs={}, sep=', '):
return '{0}({1}{2}{3})'.format(
name, sep.join(map(_safe_repr, args or ())),
(args and kwargs) and sep or '',
reprkwargs(kwargs, sep),
)
@contextmanager
def nested(*managers): # pragma: no cover
# flake8: noqa
"""Combine multiple context managers into a single nested
context manager."""
exits = []
vars = []
exc = (None, None, None)
try:
try:
for mgr in managers:
exit = mgr.__exit__
enter = mgr.__enter__
vars.append(enter())
exits.append(exit)
yield vars
except:
exc = sys.exc_info()
finally:
while exits:
exit = exits.pop()
try:
if exit(*exc):
exc = (None, None, None)
except:
exc = sys.exc_info()
if exc != (None, None, None):
# Don't rely on sys.exc_info() still containing
# the right information. Another exception may
# have been raised and caught by an exit method
reraise(exc[0], exc[1], exc[2])
finally:
del(exc)
def shufflecycle(it):
it = list(it) # don't modify callers list
shuffle = random.shuffle
for _ in repeat(None):
shuffle(it)
yield it[0]
def entrypoints(namespace):
try:
from pkg_resources import iter_entry_points
except ImportError:
return iter([])
return ((ep, ep.load()) for ep in iter_entry_points(namespace))
class ChannelPromise(object):
def __init__(self, contract):
self.__contract__ = contract
def __call__(self):
try:
return self.__value__
except AttributeError:
value = self.__value__ = self.__contract__()
return value
def __repr__(self):
try:
return repr(self.__value__)
except AttributeError:
return '<promise: 0x{0:x}>'.format(id(self.__contract__))
def escape_regex(p, white=''):
# what's up with re.escape? that code must be neglected or someting
return ''.join(c if c.isalnum() or c in white
else ('\\000' if c == '\000' else '\\' + c)
for c in p)
def fileno(f):
if isinstance(f, numbers.Integral):
return f
return f.fileno()
def maybe_fileno(f):
"""Get object fileno, or :const:`None` if not defined."""
try:
return fileno(f)
except FILENO_ERRORS:
pass
