diff options
Diffstat (limited to 'src/leap')
| -rw-r--r-- | src/leap/common/decorators.py | 160 | ||||
| -rw-r--r-- | src/leap/common/tests/test_check.py | 1 | ||||
| -rw-r--r-- | src/leap/common/tests/test_memoize.py | 76 |
3 files changed, 237 insertions, 0 deletions
diff --git a/src/leap/common/decorators.py b/src/leap/common/decorators.py new file mode 100644 index 0000000..2ef6711 --- /dev/null +++ b/src/leap/common/decorators.py @@ -0,0 +1,160 @@ +# -*- coding: utf-8 -*- +# decorators.py +# Copyright (C) 2013 LEAP +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. +""" +Useful decorators. +""" +import collections +import datetime +import functools +import logging + +logger = logging.getLogger(__name__) + + +class _memoized(object): + """ + Decorator. + + Caches a function's return value each time it is called. + If called later with the same arguments, the cached value is returned + (not reevaluated). + """ + + # cache invalidation time, in seconds + CACHE_INVALIDATION_DELTA = 1800 + + def __init__(self, func, ignore_kwargs=None, is_method=False, + invalidation=None): + + """ + :param ignore_kwargs: If True, ignore all kwargs. + If tuple, ignore those kwargs. + :type ignore_kwargs: bool, tuple or None + :param is_method: whether the decorated function is a method. + (ignores the self argument if so). + :type is_method: True + """ + self.ignore_kwargs = ignore_kwargs if ignore_kwargs else [] + self.is_method = is_method + self.func = func + + if invalidation: + self.CACHE_INVALIDATION_DELTA = invalidation + + # TODO should put bounds to the cache dict so we do not + # consume a huge amount of memory. + self.cache = {} + self.cache_ts = {} + + def __call__(self, *args, **kwargs): + """ + Executes the call. + + :tyoe args: tuple + :type kwargs: dict + """ + def ret_or_raise(value): + """ + Returns the value except if it is an exception, + in which case it's raised. + """ + if isinstance(value, Exception): + raise value + return value + + if self.is_method: + # forget about `self` as key + key_args = args[1:] + else: + key_args = args + + if self.ignore_kwargs is True: + key = key_args + else: + key = (key_args, frozenset( + [(k, v) for k, v in kwargs.items() + if k not in self.ignore_kwargs])) + + if not isinstance(key, collections.Hashable): + # uncacheable. a list, for instance. + # better to not cache than blow up. + logger.warning("Key is not hashable, bailing out!") + return self.func(*args, **kwargs) + + if key in self.cache: + if self._is_cache_still_valid(key): + value = self.cache[key] + logger.debug("Got value from cache...") + return ret_or_raise(value) + else: + logger.debug("Cache is invalid, evaluating again...") + + # no cache, or cache invalid + try: + value = self.func(*args, **kwargs) + except Exception as exc: + logger.error("Exception while calling function: %r" % (exc,)) + value = exc + self.cache[key] = value + self.cache_ts[key] = datetime.datetime.now() + return ret_or_raise(value) + + def _is_cache_still_valid(self, key, now=datetime.datetime.now): + """ + Returns True if the cache value is still valid, False otherwise. + + For now, this happen if less than CACHE_INVALIDATION_DELTA seconds + have passed from the time in which we recorded the cached value. + + :param key: the key to lookup in the cache + :type key: hashable + :param now: a callable that returns a datetime object. override + for dependency injection during testing. + :type now: callable + :rtype: bool + """ + cached_ts = self.cache_ts[key] + delta = datetime.timedelta(seconds=self.CACHE_INVALIDATION_DELTA) + return (now() - cached_ts) < delta + + def __repr__(self): + """ + Return the function's docstring. + """ + return self.func.__doc__ + + def __get__(self, obj, objtype): + """ + Support instance methods. + """ + return functools.partial(self.__call__, obj) + + +def memoized_method(function=None, ignore_kwargs=None): + """ + Wrap _memoized to allow for deferred calling + + :type function: callable, or None. + :type ignore_kwargs: None, True or tuple. + """ + if function: + return _memoized(function, is_method=True) + else: + def wrapper(function): + return _memoized( + function, ignore_kwargs=ignore_kwargs, is_method=True) + return wrapper diff --git a/src/leap/common/tests/test_check.py b/src/leap/common/tests/test_check.py index 6ce8493..cd488ff 100644 --- a/src/leap/common/tests/test_check.py +++ b/src/leap/common/tests/test_check.py @@ -27,6 +27,7 @@ import mock from leap.common import check + class CheckTests(unittest.TestCase): def test_raises_on_false_condition(self): with self.assertRaises(AssertionError): diff --git a/src/leap/common/tests/test_memoize.py b/src/leap/common/tests/test_memoize.py new file mode 100644 index 0000000..c923fc5 --- /dev/null +++ b/src/leap/common/tests/test_memoize.py @@ -0,0 +1,76 @@ +# -*- coding: utf-8 -*- +# test_check.py +# Copyright (C) 2013 LEAP +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. +""" +Tests for: + * leap/common/decorators._memoized +""" +try: + import unittest2 as unittest +except ImportError: + import unittest + +from time import sleep + +import mock + +from leap.common.decorators import _memoized + + +class MemoizeTests(unittest.TestCase): + + def test_memoized_call(self): + """ + Test that a memoized function only calls once. + """ + witness = mock.Mock() + + @_memoized + def callmebaby(): + return witness() + + for i in range(10): + callmebaby() + witness.assert_called_once_with() + + def test_cache_invalidation(self): + """ + Test that time makes the cache invalidation expire. + """ + witness = mock.Mock() + + cache_with_alzheimer = _memoized + cache_with_alzheimer.CACHE_INVALIDATION_DELTA = 1 + + @cache_with_alzheimer + def callmebaby(*args): + return witness(*args) + + for i in range(10): + callmebaby() + witness.assert_called_once_with() + + sleep(2) + callmebaby("onemoretime") + + expected = [mock.call(), mock.call("onemoretime")] + self.assertEqual( + witness.call_args_list, + expected) + + +if __name__ == "__main__": + unittest.main() |