Useful decorators.
"""
import collections
+import datetime
import functools
import logging
If called later with the same arguments, the cached value is returned
(not reevaluated).
"""
- def __init__(self, func, ignore_kwargs=None, is_method=False):
+
+ # 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.
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):
"""
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:
return self.func(*args, **kwargs)
if key in self.cache:
- logger.debug("Got value from cache...")
- value = self.cache[key]
- return ret_or_raise(value)
- else:
- try:
- value = self.func(*args, **kwargs)
- except Exception as exc:
- logger.error("Exception while calling function: %r" % (exc,))
- value = exc
- self.cache[key] = value
- return ret_or_raise(value)
+ 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):
"""
--- /dev/null
+# -*- 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()