Commit bf757a2f authored by Michael Manfre's avatar Michael Manfre Committed by Tim Graham
Browse files

Fixed #21147 -- Avoided time.time precision issue with cache backends. 

The precision of time.time() is OS specific and it is possible for the
resolution to be low enough to allow reading a cache key previously set
with a timeout of 0.
parent 8c272473

django/core/cache/backends/base.py

+13 −0
Original line number Diff line number Diff line 
"Base Cache class."

from __future__ import unicode_literals



import time

import warnings



from django.core.exceptions import ImproperlyConfigured, DjangoRuntimeWarning
@@ -74,6 +75,18 @@ class BaseCache(object): 
        self.version = params.get('VERSION', 1)

        self.key_func = get_key_func(params.get('KEY_FUNCTION', None))



    def get_backend_timeout(self, timeout=DEFAULT_TIMEOUT):

        """

        Returns the timeout value usable by this backend based upon the provided

        timeout.

        """

        if timeout == DEFAULT_TIMEOUT:

            timeout = self.default_timeout

        elif timeout == 0:

            # ticket 21147 - avoid time.time() related precision issues

            timeout = -1

        return None if timeout is None else time.time() + timeout



    def make_key(self, key, version=None):

        """Constructs the key used by all other methods. By default it

        uses the key_func to generate a key (which, by default,

django/core/cache/backends/db.py

+3 −4
Original line number Diff line number Diff line
@@ -92,8 +92,7 @@ class DatabaseCache(BaseDatabaseCache): 
        return self._base_set('add', key, value, timeout)



    def _base_set(self, mode, key, value, timeout=DEFAULT_TIMEOUT):

        if timeout == DEFAULT_TIMEOUT:

            timeout = self.default_timeout

        timeout = self.get_backend_timeout(timeout)

        db = router.db_for_write(self.cache_model_class)

        table = connections[db].ops.quote_name(self._table)

        cursor = connections[db].cursor()
@@ -105,9 +104,9 @@ class DatabaseCache(BaseDatabaseCache): 
        if timeout is None:

            exp = datetime.max

        elif settings.USE_TZ:

            exp = datetime.utcfromtimestamp(time.time() + timeout)

            exp = datetime.utcfromtimestamp(timeout)

        else:

            exp = datetime.fromtimestamp(time.time() + timeout)

            exp = datetime.fromtimestamp(timeout)

        exp = exp.replace(microsecond=0)

        if num > self._max_entries:

            self._cull(db, cursor, now)

django/core/cache/backends/filebased.py

+1 −4
Original line number Diff line number Diff line
@@ -51,9 +51,6 @@ class FileBasedCache(BaseCache): 
        fname = self._key_to_file(key)

        dirname = os.path.dirname(fname)



        if timeout == DEFAULT_TIMEOUT:

            timeout = self.default_timeout



        self._cull()



        try:
@@ -61,7 +58,7 @@ class FileBasedCache(BaseCache): 
                os.makedirs(dirname)



            with open(fname, 'wb') as f:

                expiry = None if timeout is None else time.time() + timeout

                expiry = self.get_backend_timeout(timeout)

                pickle.dump(expiry, f, pickle.HIGHEST_PROTOCOL)

                pickle.dump(value, f, pickle.HIGHEST_PROTOCOL)

        except (IOError, OSError):

django/core/cache/backends/locmem.py

+1 −4
Original line number Diff line number Diff line
@@ -63,11 +63,8 @@ class LocMemCache(BaseCache): 
    def _set(self, key, value, timeout=DEFAULT_TIMEOUT):

        if len(self._cache) >= self._max_entries:

            self._cull()

        if timeout == DEFAULT_TIMEOUT:

            timeout = self.default_timeout

        expiry = None if timeout is None else time.time() + timeout

        self._cache[key] = value

        self._expire_info[key] = expiry

        self._expire_info[key] = self.get_backend_timeout(timeout)



    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):

        key = self.make_key(key, version=version)

django/core/cache/backends/memcached.py

+13 −5
Original line number Diff line number Diff line
@@ -7,9 +7,17 @@ from threading import local 
from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT



from django.utils import six

from django.utils.deprecation import RenameMethodsBase

from django.utils.encoding import force_str



class BaseMemcachedCache(BaseCache):



class BaseMemcachedCacheMethods(RenameMethodsBase):

    renamed_methods = (

        ('_get_memcache_timeout', 'get_backend_timeout', PendingDeprecationWarning),

    )





class BaseMemcachedCache(six.with_metaclass(BaseMemcachedCacheMethods, BaseCache)):

    def __init__(self, server, params, library, value_not_found_exception):

        super(BaseMemcachedCache, self).__init__(params)

        if isinstance(server, six.string_types):
@@ -36,7 +44,7 @@ class BaseMemcachedCache(BaseCache): 


        return self._client



    def _get_memcache_timeout(self, timeout=DEFAULT_TIMEOUT):

    def get_backend_timeout(self, timeout=DEFAULT_TIMEOUT):

        """

        Memcached deals with long (> 30 days) timeouts in a special

        way. Call this function to obtain a safe value for your timeout.
@@ -68,7 +76,7 @@ class BaseMemcachedCache(BaseCache): 


    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):

        key = self.make_key(key, version=version)

        return self._cache.add(key, value, self._get_memcache_timeout(timeout))

        return self._cache.add(key, value, self.get_backend_timeout(timeout))



    def get(self, key, default=None, version=None):

        key = self.make_key(key, version=version)
@@ -79,7 +87,7 @@ class BaseMemcachedCache(BaseCache): 


    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):

        key = self.make_key(key, version=version)

        self._cache.set(key, value, self._get_memcache_timeout(timeout))

        self._cache.set(key, value, self.get_backend_timeout(timeout))



    def delete(self, key, version=None):

        key = self.make_key(key, version=version)
@@ -140,7 +148,7 @@ class BaseMemcachedCache(BaseCache): 
        for key, value in data.items():

            key = self.make_key(key, version=version)

            safe_data[key] = value

        self._cache.set_multi(safe_data, self._get_memcache_timeout(timeout))

        self._cache.set_multi(safe_data, self.get_backend_timeout(timeout))



    def delete_many(self, keys, version=None):

        l = lambda x: self.make_key(x, version=version)