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Lib/site-packages/django/core/cache/__init__.py

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+"""
+Caching framework.
+
+This package defines set of cache backends that all conform to a simple API.
+In a nutshell, a cache is a set of values -- which can be any object that
+may be pickled -- identified by string keys.  For the complete API, see
+the abstract BaseCache class in django.core.cache.backends.base.
+
+Client code should use the `cache` variable defined here to access the default
+cache backend and look up non-default cache backends in the `caches` dict-like
+object.
+
+See docs/topics/cache.txt for information on the public API.
+"""
+from asgiref.local import Local
+
+from django.conf import settings
+from django.core import signals
+from django.core.cache.backends.base import (
+    BaseCache, CacheKeyWarning, InvalidCacheBackendError, InvalidCacheKey,
+)
+from django.utils.module_loading import import_string
+
+__all__ = [
+    'cache', 'caches', 'DEFAULT_CACHE_ALIAS', 'InvalidCacheBackendError',
+    'CacheKeyWarning', 'BaseCache', 'InvalidCacheKey',
+]
+
+DEFAULT_CACHE_ALIAS = 'default'
+
+
+def _create_cache(backend, **kwargs):
+    try:
+        # Try to get the CACHES entry for the given backend name first
+        try:
+            conf = settings.CACHES[backend]
+        except KeyError:
+            try:
+                # Trying to import the given backend, in case it's a dotted path
+                import_string(backend)
+            except ImportError as e:
+                raise InvalidCacheBackendError("Could not find backend '%s': %s" % (
+                    backend, e))
+            location = kwargs.pop('LOCATION', '')
+            params = kwargs
+        else:
+            params = {**conf, **kwargs}
+            backend = params.pop('BACKEND')
+            location = params.pop('LOCATION', '')
+        backend_cls = import_string(backend)
+    except ImportError as e:
+        raise InvalidCacheBackendError(
+            "Could not find backend '%s': %s" % (backend, e))
+    return backend_cls(location, params)
+
+
+class CacheHandler:
+    """
+    A Cache Handler to manage access to Cache instances.
+
+    Ensure only one instance of each alias exists per thread.
+    """
+    def __init__(self):
+        self._caches = Local()
+
+    def __getitem__(self, alias):
+        try:
+            return self._caches.caches[alias]
+        except AttributeError:
+            self._caches.caches = {}
+        except KeyError:
+            pass
+
+        if alias not in settings.CACHES:
+            raise InvalidCacheBackendError(
+                "Could not find config for '%s' in settings.CACHES" % alias
+            )
+
+        cache = _create_cache(alias)
+        self._caches.caches[alias] = cache
+        return cache
+
+    def all(self):
+        return getattr(self._caches, 'caches', {}).values()
+
+
+caches = CacheHandler()
+
+
+class DefaultCacheProxy:
+    """
+    Proxy access to the default Cache object's attributes.
+
+    This allows the legacy `cache` object to be thread-safe using the new
+    ``caches`` API.
+    """
+    def __getattr__(self, name):
+        return getattr(caches[DEFAULT_CACHE_ALIAS], name)
+
+    def __setattr__(self, name, value):
+        return setattr(caches[DEFAULT_CACHE_ALIAS], name, value)
+
+    def __delattr__(self, name):
+        return delattr(caches[DEFAULT_CACHE_ALIAS], name)
+
+    def __contains__(self, key):
+        return key in caches[DEFAULT_CACHE_ALIAS]
+
+    def __eq__(self, other):
+        return caches[DEFAULT_CACHE_ALIAS] == other
+
+
+cache = DefaultCacheProxy()
+
+
+def close_caches(**kwargs):
+    # Some caches -- python-memcached in particular -- need to do a cleanup at the
+    # end of a request cycle. If not implemented in a particular backend
+    # cache.close is a no-op
+    for cache in caches.all():
+        cache.close()
+
+
+signals.request_finished.connect(close_caches)

Lib/site-packages/django/core/cache/backends/base.py

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+"Base Cache class."
+import time
+import warnings
+
+from django.core.exceptions import ImproperlyConfigured
+from django.utils.module_loading import import_string
+
+
+class InvalidCacheBackendError(ImproperlyConfigured):
+    pass
+
+
+class CacheKeyWarning(RuntimeWarning):
+    pass
+
+
+class InvalidCacheKey(ValueError):
+    pass
+
+
+# Stub class to ensure not passing in a `timeout` argument results in
+# the default timeout
+DEFAULT_TIMEOUT = object()
+
+# Memcached does not accept keys longer than this.
+MEMCACHE_MAX_KEY_LENGTH = 250
+
+
+def default_key_func(key, key_prefix, version):
+    """
+    Default function to generate keys.
+
+    Construct the key used by all other methods. By default, prepend
+    the `key_prefix'. KEY_FUNCTION can be used to specify an alternate
+    function with custom key making behavior.
+    """
+    return '%s:%s:%s' % (key_prefix, version, key)
+
+
+def get_key_func(key_func):
+    """
+    Function to decide which key function to use.
+
+    Default to ``default_key_func``.
+    """
+    if key_func is not None:
+        if callable(key_func):
+            return key_func
+        else:
+            return import_string(key_func)
+    return default_key_func
+
+
+class BaseCache:
+    def __init__(self, params):
+        timeout = params.get('timeout', params.get('TIMEOUT', 300))
+        if timeout is not None:
+            try:
+                timeout = int(timeout)
+            except (ValueError, TypeError):
+                timeout = 300
+        self.default_timeout = timeout
+
+        options = params.get('OPTIONS', {})
+        max_entries = params.get('max_entries', options.get('MAX_ENTRIES', 300))
+        try:
+            self._max_entries = int(max_entries)
+        except (ValueError, TypeError):
+            self._max_entries = 300
+
+        cull_frequency = params.get('cull_frequency', options.get('CULL_FREQUENCY', 3))
+        try:
+            self._cull_frequency = int(cull_frequency)
+        except (ValueError, TypeError):
+            self._cull_frequency = 3
+
+        self.key_prefix = params.get('KEY_PREFIX', '')
+        self.version = params.get('VERSION', 1)
+        self.key_func = get_key_func(params.get('KEY_FUNCTION'))
+
+    def get_backend_timeout(self, timeout=DEFAULT_TIMEOUT):
+        """
+        Return 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):
+        """
+        Construct the key used by all other methods. By default, use the
+        key_func to generate a key (which, by default, prepends the
+        `key_prefix' and 'version'). A different key function can be provided
+        at the time of cache construction; alternatively, you can subclass the
+        cache backend to provide custom key making behavior.
+        """
+        if version is None:
+            version = self.version
+
+        return self.key_func(key, self.key_prefix, version)
+
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        """
+        Set a value in the cache if the key does not already exist. If
+        timeout is given, use that timeout for the key; otherwise use the
+        default cache timeout.
+
+        Return True if the value was stored, False otherwise.
+        """
+        raise NotImplementedError('subclasses of BaseCache must provide an add() method')
+
+    def get(self, key, default=None, version=None):
+        """
+        Fetch a given key from the cache. If the key does not exist, return
+        default, which itself defaults to None.
+        """
+        raise NotImplementedError('subclasses of BaseCache must provide a get() method')
+
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        """
+        Set a value in the cache. If timeout is given, use that timeout for the
+        key; otherwise use the default cache timeout.
+        """
+        raise NotImplementedError('subclasses of BaseCache must provide a set() method')
+
+    def touch(self, key, timeout=DEFAULT_TIMEOUT, version=None):
+        """
+        Update the key's expiry time using timeout. Return True if successful
+        or False if the key does not exist.
+        """
+        raise NotImplementedError('subclasses of BaseCache must provide a touch() method')
+
+    def delete(self, key, version=None):
+        """
+        Delete a key from the cache and return whether it succeeded, failing
+        silently.
+        """
+        raise NotImplementedError('subclasses of BaseCache must provide a delete() method')
+
+    def get_many(self, keys, version=None):
+        """
+        Fetch a bunch of keys from the cache. For certain backends (memcached,
+        pgsql) this can be *much* faster when fetching multiple values.
+
+        Return a dict mapping each key in keys to its value. If the given
+        key is missing, it will be missing from the response dict.
+        """
+        d = {}
+        for k in keys:
+            val = self.get(k, version=version)
+            if val is not None:
+                d[k] = val
+        return d
+
+    def get_or_set(self, key, default, timeout=DEFAULT_TIMEOUT, version=None):
+        """
+        Fetch a given key from the cache. If the key does not exist,
+        add the key and set it to the default value. The default value can
+        also be any callable. If timeout is given, use that timeout for the
+        key; otherwise use the default cache timeout.
+
+        Return the value of the key stored or retrieved.
+        """
+        val = self.get(key, version=version)
+        if val is None:
+            if callable(default):
+                default = default()
+            if default is not None:
+                self.add(key, default, timeout=timeout, version=version)
+                # Fetch the value again to avoid a race condition if another
+                # caller added a value between the first get() and the add()
+                # above.
+                return self.get(key, default, version=version)
+        return val
+
+    def has_key(self, key, version=None):
+        """
+        Return True if the key is in the cache and has not expired.
+        """
+        return self.get(key, version=version) is not None
+
+    def incr(self, key, delta=1, version=None):
+        """
+        Add delta to value in the cache. If the key does not exist, raise a
+        ValueError exception.
+        """
+        value = self.get(key, version=version)
+        if value is None:
+            raise ValueError("Key '%s' not found" % key)
+        new_value = value + delta
+        self.set(key, new_value, version=version)
+        return new_value
+
+    def decr(self, key, delta=1, version=None):
+        """
+        Subtract delta from value in the cache. If the key does not exist, raise
+        a ValueError exception.
+        """
+        return self.incr(key, -delta, version=version)
+
+    def __contains__(self, key):
+        """
+        Return True if the key is in the cache and has not expired.
+        """
+        # This is a separate method, rather than just a copy of has_key(),
+        # so that it always has the same functionality as has_key(), even
+        # if a subclass overrides it.
+        return self.has_key(key)
+
+    def set_many(self, data, timeout=DEFAULT_TIMEOUT, version=None):
+        """
+        Set a bunch of values in the cache at once from a dict of key/value
+        pairs.  For certain backends (memcached), this is much more efficient
+        than calling set() multiple times.
+
+        If timeout is given, use that timeout for the key; otherwise use the
+        default cache timeout.
+
+        On backends that support it, return a list of keys that failed
+        insertion, or an empty list if all keys were inserted successfully.
+        """
+        for key, value in data.items():
+            self.set(key, value, timeout=timeout, version=version)
+        return []
+
+    def delete_many(self, keys, version=None):
+        """
+        Delete a bunch of values in the cache at once. For certain backends
+        (memcached), this is much more efficient than calling delete() multiple
+        times.
+        """
+        for key in keys:
+            self.delete(key, version=version)
+
+    def clear(self):
+        """Remove *all* values from the cache at once."""
+        raise NotImplementedError('subclasses of BaseCache must provide a clear() method')
+
+    def validate_key(self, key):
+        """
+        Warn about keys that would not be portable to the memcached
+        backend. This encourages (but does not force) writing backend-portable
+        cache code.
+        """
+        for warning in memcache_key_warnings(key):
+            warnings.warn(warning, CacheKeyWarning)
+
+    def incr_version(self, key, delta=1, version=None):
+        """
+        Add delta to the cache version for the supplied key. Return the new
+        version.
+        """
+        if version is None:
+            version = self.version
+
+        value = self.get(key, version=version)
+        if value is None:
+            raise ValueError("Key '%s' not found" % key)
+
+        self.set(key, value, version=version + delta)
+        self.delete(key, version=version)
+        return version + delta
+
+    def decr_version(self, key, delta=1, version=None):
+        """
+        Subtract delta from the cache version for the supplied key. Return the
+        new version.
+        """
+        return self.incr_version(key, -delta, version)
+
+    def close(self, **kwargs):
+        """Close the cache connection"""
+        pass
+
+
+def memcache_key_warnings(key):
+    if len(key) > MEMCACHE_MAX_KEY_LENGTH:
+        yield (
+            'Cache key will cause errors if used with memcached: %r '
+            '(longer than %s)' % (key, MEMCACHE_MAX_KEY_LENGTH)
+        )
+    for char in key:
+        if ord(char) < 33 or ord(char) == 127:
+            yield (
+                'Cache key contains characters that will cause errors if '
+                'used with memcached: %r' % key
+            )
+            break

Lib/site-packages/django/core/cache/backends/db.py

@@ -0,0 +1,282 @@
+"Database cache backend."
+import base64
+import pickle
+from datetime import datetime
+
+from django.conf import settings
+from django.core.cache.backends.base import DEFAULT_TIMEOUT, BaseCache
+from django.db import DatabaseError, connections, models, router, transaction
+from django.utils import timezone
+
+
+class Options:
+    """A class that will quack like a Django model _meta class.
+
+    This allows cache operations to be controlled by the router
+    """
+    def __init__(self, table):
+        self.db_table = table
+        self.app_label = 'django_cache'
+        self.model_name = 'cacheentry'
+        self.verbose_name = 'cache entry'
+        self.verbose_name_plural = 'cache entries'
+        self.object_name = 'CacheEntry'
+        self.abstract = False
+        self.managed = True
+        self.proxy = False
+        self.swapped = False
+
+
+class BaseDatabaseCache(BaseCache):
+    def __init__(self, table, params):
+        super().__init__(params)
+        self._table = table
+
+        class CacheEntry:
+            _meta = Options(table)
+        self.cache_model_class = CacheEntry
+
+
+class DatabaseCache(BaseDatabaseCache):
+
+    # This class uses cursors provided by the database connection. This means
+    # it reads expiration values as aware or naive datetimes, depending on the
+    # value of USE_TZ and whether the database supports time zones. The ORM's
+    # conversion and adaptation infrastructure is then used to avoid comparing
+    # aware and naive datetimes accidentally.
+
+    pickle_protocol = pickle.HIGHEST_PROTOCOL
+
+    def get(self, key, default=None, version=None):
+        return self.get_many([key], version).get(key, default)
+
+    def get_many(self, keys, version=None):
+        if not keys:
+            return {}
+
+        key_map = {}
+        for key in keys:
+            self.validate_key(key)
+            key_map[self.make_key(key, version)] = key
+
+        db = router.db_for_read(self.cache_model_class)
+        connection = connections[db]
+        quote_name = connection.ops.quote_name
+        table = quote_name(self._table)
+
+        with connection.cursor() as cursor:
+            cursor.execute(
+                'SELECT %s, %s, %s FROM %s WHERE %s IN (%s)' % (
+                    quote_name('cache_key'),
+                    quote_name('value'),
+                    quote_name('expires'),
+                    table,
+                    quote_name('cache_key'),
+                    ', '.join(['%s'] * len(key_map)),
+                ),
+                list(key_map),
+            )
+            rows = cursor.fetchall()
+
+        result = {}
+        expired_keys = []
+        expression = models.Expression(output_field=models.DateTimeField())
+        converters = (connection.ops.get_db_converters(expression) + expression.get_db_converters(connection))
+        for key, value, expires in rows:
+            for converter in converters:
+                expires = converter(expires, expression, connection)
+            if expires < timezone.now():
+                expired_keys.append(key)
+            else:
+                value = connection.ops.process_clob(value)
+                value = pickle.loads(base64.b64decode(value.encode()))
+                result[key_map.get(key)] = value
+        self._base_delete_many(expired_keys)
+        return result
+
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        self._base_set('set', key, value, timeout)
+
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        return self._base_set('add', key, value, timeout)
+
+    def touch(self, key, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        return self._base_set('touch', key, None, timeout)
+
+    def _base_set(self, mode, key, value, timeout=DEFAULT_TIMEOUT):
+        timeout = self.get_backend_timeout(timeout)
+        db = router.db_for_write(self.cache_model_class)
+        connection = connections[db]
+        quote_name = connection.ops.quote_name
+        table = quote_name(self._table)
+
+        with connection.cursor() as cursor:
+            cursor.execute("SELECT COUNT(*) FROM %s" % table)
+            num = cursor.fetchone()[0]
+            now = timezone.now()
+            now = now.replace(microsecond=0)
+            if timeout is None:
+                exp = datetime.max
+            elif settings.USE_TZ:
+                exp = datetime.utcfromtimestamp(timeout)
+            else:
+                exp = datetime.fromtimestamp(timeout)
+            exp = exp.replace(microsecond=0)
+            if num > self._max_entries:
+                self._cull(db, cursor, now)
+            pickled = pickle.dumps(value, self.pickle_protocol)
+            # The DB column is expecting a string, so make sure the value is a
+            # string, not bytes. Refs #19274.
+            b64encoded = base64.b64encode(pickled).decode('latin1')
+            try:
+                # Note: typecasting for datetimes is needed by some 3rd party
+                # database backends. All core backends work without typecasting,
+                # so be careful about changes here - test suite will NOT pick
+                # regressions.
+                with transaction.atomic(using=db):
+                    cursor.execute(
+                        'SELECT %s, %s FROM %s WHERE %s = %%s' % (
+                            quote_name('cache_key'),
+                            quote_name('expires'),
+                            table,
+                            quote_name('cache_key'),
+                        ),
+                        [key]
+                    )
+                    result = cursor.fetchone()
+
+                    if result:
+                        current_expires = result[1]
+                        expression = models.Expression(output_field=models.DateTimeField())
+                        for converter in (connection.ops.get_db_converters(expression) +
+                                          expression.get_db_converters(connection)):
+                            current_expires = converter(current_expires, expression, connection)
+
+                    exp = connection.ops.adapt_datetimefield_value(exp)
+                    if result and mode == 'touch':
+                        cursor.execute(
+                            'UPDATE %s SET %s = %%s WHERE %s = %%s' % (
+                                table,
+                                quote_name('expires'),
+                                quote_name('cache_key')
+                            ),
+                            [exp, key]
+                        )
+                    elif result and (mode == 'set' or (mode == 'add' and current_expires < now)):
+                        cursor.execute(
+                            'UPDATE %s SET %s = %%s, %s = %%s WHERE %s = %%s' % (
+                                table,
+                                quote_name('value'),
+                                quote_name('expires'),
+                                quote_name('cache_key'),
+                            ),
+                            [b64encoded, exp, key]
+                        )
+                    elif mode != 'touch':
+                        cursor.execute(
+                            'INSERT INTO %s (%s, %s, %s) VALUES (%%s, %%s, %%s)' % (
+                                table,
+                                quote_name('cache_key'),
+                                quote_name('value'),
+                                quote_name('expires'),
+                            ),
+                            [key, b64encoded, exp]
+                        )
+                    else:
+                        return False  # touch failed.
+            except DatabaseError:
+                # To be threadsafe, updates/inserts are allowed to fail silently
+                return False
+            else:
+                return True
+
+    def delete(self, key, version=None):
+        self.validate_key(key)
+        return self._base_delete_many([self.make_key(key, version)])
+
+    def delete_many(self, keys, version=None):
+        key_list = []
+        for key in keys:
+            self.validate_key(key)
+            key_list.append(self.make_key(key, version))
+        self._base_delete_many(key_list)
+
+    def _base_delete_many(self, keys):
+        if not keys:
+            return False
+
+        db = router.db_for_write(self.cache_model_class)
+        connection = connections[db]
+        quote_name = connection.ops.quote_name
+        table = quote_name(self._table)
+
+        with connection.cursor() as cursor:
+            cursor.execute(
+                'DELETE FROM %s WHERE %s IN (%s)' % (
+                    table,
+                    quote_name('cache_key'),
+                    ', '.join(['%s'] * len(keys)),
+                ),
+                keys,
+            )
+        return bool(cursor.rowcount)
+
+    def has_key(self, key, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+
+        db = router.db_for_read(self.cache_model_class)
+        connection = connections[db]
+        quote_name = connection.ops.quote_name
+
+        if settings.USE_TZ:
+            now = datetime.utcnow()
+        else:
+            now = datetime.now()
+        now = now.replace(microsecond=0)
+
+        with connection.cursor() as cursor:
+            cursor.execute(
+                'SELECT %s FROM %s WHERE %s = %%s and expires > %%s' % (
+                    quote_name('cache_key'),
+                    quote_name(self._table),
+                    quote_name('cache_key'),
+                ),
+                [key, connection.ops.adapt_datetimefield_value(now)]
+            )
+            return cursor.fetchone() is not None
+
+    def _cull(self, db, cursor, now):
+        if self._cull_frequency == 0:
+            self.clear()
+        else:
+            connection = connections[db]
+            table = connection.ops.quote_name(self._table)
+            cursor.execute("DELETE FROM %s WHERE expires < %%s" % table,
+                           [connection.ops.adapt_datetimefield_value(now)])
+            cursor.execute("SELECT COUNT(*) FROM %s" % table)
+            num = cursor.fetchone()[0]
+            if num > self._max_entries:
+                cull_num = num // self._cull_frequency
+                cursor.execute(
+                    connection.ops.cache_key_culling_sql() % table,
+                    [cull_num])
+                last_cache_key = cursor.fetchone()
+                if last_cache_key:
+                    cursor.execute(
+                        'DELETE FROM %s WHERE cache_key < %%s' % table,
+                        [last_cache_key[0]],
+                    )
+
+    def clear(self):
+        db = router.db_for_write(self.cache_model_class)
+        connection = connections[db]
+        table = connection.ops.quote_name(self._table)
+        with connection.cursor() as cursor:
+            cursor.execute('DELETE FROM %s' % table)

Lib/site-packages/django/core/cache/backends/dummy.py

@@ -0,0 +1,39 @@
+"Dummy cache backend"
+
+from django.core.cache.backends.base import DEFAULT_TIMEOUT, BaseCache
+
+
+class DummyCache(BaseCache):
+    def __init__(self, host, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        return True
+
+    def get(self, key, default=None, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        return default
+
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+
+    def touch(self, key, timeout=DEFAULT_TIMEOUT, version=None):
+        self.validate_key(key)
+        return False
+
+    def delete(self, key, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        return False
+
+    def has_key(self, key, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        return False
+
+    def clear(self):
+        pass

Lib/site-packages/django/core/cache/backends/filebased.py

@@ -0,0 +1,164 @@
+"File-based cache backend"
+import glob
+import hashlib
+import os
+import pickle
+import random
+import tempfile
+import time
+import zlib
+
+from django.core.cache.backends.base import DEFAULT_TIMEOUT, BaseCache
+from django.core.files import locks
+from django.core.files.move import file_move_safe
+
+
+class FileBasedCache(BaseCache):
+    cache_suffix = '.djcache'
+    pickle_protocol = pickle.HIGHEST_PROTOCOL
+
+    def __init__(self, dir, params):
+        super().__init__(params)
+        self._dir = os.path.abspath(dir)
+        self._createdir()
+
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        if self.has_key(key, version):
+            return False
+        self.set(key, value, timeout, version)
+        return True
+
+    def get(self, key, default=None, version=None):
+        fname = self._key_to_file(key, version)
+        try:
+            with open(fname, 'rb') as f:
+                if not self._is_expired(f):
+                    return pickle.loads(zlib.decompress(f.read()))
+        except FileNotFoundError:
+            pass
+        return default
+
+    def _write_content(self, file, timeout, value):
+        expiry = self.get_backend_timeout(timeout)
+        file.write(pickle.dumps(expiry, self.pickle_protocol))
+        file.write(zlib.compress(pickle.dumps(value, self.pickle_protocol)))
+
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        self._createdir()  # Cache dir can be deleted at any time.
+        fname = self._key_to_file(key, version)
+        self._cull()  # make some room if necessary
+        fd, tmp_path = tempfile.mkstemp(dir=self._dir)
+        renamed = False
+        try:
+            with open(fd, 'wb') as f:
+                self._write_content(f, timeout, value)
+            file_move_safe(tmp_path, fname, allow_overwrite=True)
+            renamed = True
+        finally:
+            if not renamed:
+                os.remove(tmp_path)
+
+    def touch(self, key, timeout=DEFAULT_TIMEOUT, version=None):
+        try:
+            with open(self._key_to_file(key, version), 'r+b') as f:
+                try:
+                    locks.lock(f, locks.LOCK_EX)
+                    if self._is_expired(f):
+                        return False
+                    else:
+                        previous_value = pickle.loads(zlib.decompress(f.read()))
+                        f.seek(0)
+                        self._write_content(f, timeout, previous_value)
+                        return True
+                finally:
+                    locks.unlock(f)
+        except FileNotFoundError:
+            return False
+
+    def delete(self, key, version=None):
+        return self._delete(self._key_to_file(key, version))
+
+    def _delete(self, fname):
+        if not fname.startswith(self._dir) or not os.path.exists(fname):
+            return False
+        try:
+            os.remove(fname)
+        except FileNotFoundError:
+            # The file may have been removed by another process.
+            return False
+        return True
+
+    def has_key(self, key, version=None):
+        fname = self._key_to_file(key, version)
+        if os.path.exists(fname):
+            with open(fname, 'rb') as f:
+                return not self._is_expired(f)
+        return False
+
+    def _cull(self):
+        """
+        Remove random cache entries if max_entries is reached at a ratio
+        of num_entries / cull_frequency. A value of 0 for CULL_FREQUENCY means
+        that the entire cache will be purged.
+        """
+        filelist = self._list_cache_files()
+        num_entries = len(filelist)
+        if num_entries < self._max_entries:
+            return  # return early if no culling is required
+        if self._cull_frequency == 0:
+            return self.clear()  # Clear the cache when CULL_FREQUENCY = 0
+        # Delete a random selection of entries
+        filelist = random.sample(filelist,
+                                 int(num_entries / self._cull_frequency))
+        for fname in filelist:
+            self._delete(fname)
+
+    def _createdir(self):
+        # Set the umask because os.makedirs() doesn't apply the "mode" argument
+        # to intermediate-level directories.
+        old_umask = os.umask(0o077)
+        try:
+            os.makedirs(self._dir, 0o700, exist_ok=True)
+        finally:
+            os.umask(old_umask)
+
+    def _key_to_file(self, key, version=None):
+        """
+        Convert a key into a cache file path. Basically this is the
+        root cache path joined with the md5sum of the key and a suffix.
+        """
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        return os.path.join(self._dir, ''.join(
+            [hashlib.md5(key.encode()).hexdigest(), self.cache_suffix]))
+
+    def clear(self):
+        """
+        Remove all the cache files.
+        """
+        for fname in self._list_cache_files():
+            self._delete(fname)
+
+    def _is_expired(self, f):
+        """
+        Take an open cache file `f` and delete it if it's expired.
+        """
+        try:
+            exp = pickle.load(f)
+        except EOFError:
+            exp = 0  # An empty file is considered expired.
+        if exp is not None and exp < time.time():
+            f.close()  # On Windows a file has to be closed before deleting
+            self._delete(f.name)
+            return True
+        return False
+
+    def _list_cache_files(self):
+        """
+        Get a list of paths to all the cache files. These are all the files
+        in the root cache dir that end on the cache_suffix.
+        """
+        return [
+            os.path.join(self._dir, fname)
+            for fname in glob.glob1(self._dir, '*%s' % self.cache_suffix)
+        ]

Lib/site-packages/django/core/cache/backends/locmem.py

@@ -0,0 +1,123 @@
+"Thread-safe in-memory cache backend."
+import pickle
+import time
+from collections import OrderedDict
+from threading import Lock
+
+from django.core.cache.backends.base import DEFAULT_TIMEOUT, BaseCache
+
+# Global in-memory store of cache data. Keyed by name, to provide
+# multiple named local memory caches.
+_caches = {}
+_expire_info = {}
+_locks = {}
+
+
+class LocMemCache(BaseCache):
+    pickle_protocol = pickle.HIGHEST_PROTOCOL
+
+    def __init__(self, name, params):
+        super().__init__(params)
+        self._cache = _caches.setdefault(name, OrderedDict())
+        self._expire_info = _expire_info.setdefault(name, {})
+        self._lock = _locks.setdefault(name, Lock())
+
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        pickled = pickle.dumps(value, self.pickle_protocol)
+        with self._lock:
+            if self._has_expired(key):
+                self._set(key, pickled, timeout)
+                return True
+            return False
+
+    def get(self, key, default=None, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        with self._lock:
+            if self._has_expired(key):
+                self._delete(key)
+                return default
+            pickled = self._cache[key]
+            self._cache.move_to_end(key, last=False)
+        return pickle.loads(pickled)
+
+    def _set(self, key, value, timeout=DEFAULT_TIMEOUT):
+        if len(self._cache) >= self._max_entries:
+            self._cull()
+        self._cache[key] = value
+        self._cache.move_to_end(key, last=False)
+        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)
+        self.validate_key(key)
+        pickled = pickle.dumps(value, self.pickle_protocol)
+        with self._lock:
+            self._set(key, pickled, timeout)
+
+    def touch(self, key, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        with self._lock:
+            if self._has_expired(key):
+                return False
+            self._expire_info[key] = self.get_backend_timeout(timeout)
+            return True
+
+    def incr(self, key, delta=1, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        with self._lock:
+            if self._has_expired(key):
+                self._delete(key)
+                raise ValueError("Key '%s' not found" % key)
+            pickled = self._cache[key]
+            value = pickle.loads(pickled)
+            new_value = value + delta
+            pickled = pickle.dumps(new_value, self.pickle_protocol)
+            self._cache[key] = pickled
+            self._cache.move_to_end(key, last=False)
+        return new_value
+
+    def has_key(self, key, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        with self._lock:
+            if self._has_expired(key):
+                self._delete(key)
+                return False
+            return True
+
+    def _has_expired(self, key):
+        exp = self._expire_info.get(key, -1)
+        return exp is not None and exp <= time.time()
+
+    def _cull(self):
+        if self._cull_frequency == 0:
+            self._cache.clear()
+            self._expire_info.clear()
+        else:
+            count = len(self._cache) // self._cull_frequency
+            for i in range(count):
+                key, _ = self._cache.popitem()
+                del self._expire_info[key]
+
+    def _delete(self, key):
+        try:
+            del self._cache[key]
+            del self._expire_info[key]
+        except KeyError:
+            return False
+        return True
+
+    def delete(self, key, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        with self._lock:
+            return self._delete(key)
+
+    def clear(self):
+        with self._lock:
+            self._cache.clear()
+            self._expire_info.clear()

Lib/site-packages/django/core/cache/backends/memcached.py

@@ -0,0 +1,215 @@
+"Memcached cache backend"
+
+import pickle
+import re
+import time
+
+from django.core.cache.backends.base import (
+    DEFAULT_TIMEOUT, BaseCache, InvalidCacheKey, memcache_key_warnings,
+)
+from django.utils.functional import cached_property
+
+
+class BaseMemcachedCache(BaseCache):
+    def __init__(self, server, params, library, value_not_found_exception):
+        super().__init__(params)
+        if isinstance(server, str):
+            self._servers = re.split('[;,]', server)
+        else:
+            self._servers = server
+
+        # The exception type to catch from the underlying library for a key
+        # that was not found. This is a ValueError for python-memcache,
+        # pylibmc.NotFound for pylibmc, and cmemcache will return None without
+        # raising an exception.
+        self.LibraryValueNotFoundException = value_not_found_exception
+
+        self._lib = library
+        self._options = params.get('OPTIONS') or {}
+
+    @property
+    def _cache(self):
+        """
+        Implement transparent thread-safe access to a memcached client.
+        """
+        if getattr(self, '_client', None) is None:
+            self._client = self._lib.Client(self._servers, **self._options)
+
+        return self._client
+
+    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.
+        """
+        if timeout == DEFAULT_TIMEOUT:
+            timeout = self.default_timeout
+
+        if timeout is None:
+            # Using 0 in memcache sets a non-expiring timeout.
+            return 0
+        elif int(timeout) == 0:
+            # Other cache backends treat 0 as set-and-expire. To achieve this
+            # in memcache backends, a negative timeout must be passed.
+            timeout = -1
+
+        if timeout > 2592000:  # 60*60*24*30, 30 days
+            # See https://github.com/memcached/memcached/wiki/Programming#expiration
+            # "Expiration times can be set from 0, meaning "never expire", to
+            # 30 days. Any time higher than 30 days is interpreted as a Unix
+            # timestamp date. If you want to expire an object on January 1st of
+            # next year, this is how you do that."
+            #
+            # This means that we have to switch to absolute timestamps.
+            timeout += int(time.time())
+        return int(timeout)
+
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        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)
+        self.validate_key(key)
+        return self._cache.get(key, default)
+
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        if not self._cache.set(key, value, self.get_backend_timeout(timeout)):
+            # make sure the key doesn't keep its old value in case of failure to set (memcached's 1MB limit)
+            self._cache.delete(key)
+
+    def delete(self, key, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        return bool(self._cache.delete(key))
+
+    def get_many(self, keys, version=None):
+        key_map = {self.make_key(key, version=version): key for key in keys}
+        for key in key_map:
+            self.validate_key(key)
+        ret = self._cache.get_multi(key_map.keys())
+        return {key_map[k]: v for k, v in ret.items()}
+
+    def close(self, **kwargs):
+        # Many clients don't clean up connections properly.
+        self._cache.disconnect_all()
+
+    def incr(self, key, delta=1, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        # memcached doesn't support a negative delta
+        if delta < 0:
+            return self._cache.decr(key, -delta)
+        try:
+            val = self._cache.incr(key, delta)
+
+        # python-memcache responds to incr on nonexistent keys by
+        # raising a ValueError, pylibmc by raising a pylibmc.NotFound
+        # and Cmemcache returns None. In all cases,
+        # we should raise a ValueError though.
+        except self.LibraryValueNotFoundException:
+            val = None
+        if val is None:
+            raise ValueError("Key '%s' not found" % key)
+        return val
+
+    def decr(self, key, delta=1, version=None):
+        key = self.make_key(key, version=version)
+        self.validate_key(key)
+        # memcached doesn't support a negative delta
+        if delta < 0:
+            return self._cache.incr(key, -delta)
+        try:
+            val = self._cache.decr(key, delta)
+
+        # python-memcache responds to incr on nonexistent keys by
+        # raising a ValueError, pylibmc by raising a pylibmc.NotFound
+        # and Cmemcache returns None. In all cases,
+        # we should raise a ValueError though.
+        except self.LibraryValueNotFoundException:
+            val = None
+        if val is None:
+            raise ValueError("Key '%s' not found" % key)
+        return val
+
+    def set_many(self, data, timeout=DEFAULT_TIMEOUT, version=None):
+        safe_data = {}
+        original_keys = {}
+        for key, value in data.items():
+            safe_key = self.make_key(key, version=version)
+            self.validate_key(safe_key)
+            safe_data[safe_key] = value
+            original_keys[safe_key] = key
+        failed_keys = self._cache.set_multi(safe_data, self.get_backend_timeout(timeout))
+        return [original_keys[k] for k in failed_keys]
+
+    def delete_many(self, keys, version=None):
+        self._cache.delete_multi(self.make_key(key, version=version) for key in keys)
+
+    def clear(self):
+        self._cache.flush_all()
+
+    def validate_key(self, key):
+        for warning in memcache_key_warnings(key):
+            raise InvalidCacheKey(warning)
+
+
+class MemcachedCache(BaseMemcachedCache):
+    "An implementation of a cache binding using python-memcached"
+    def __init__(self, server, params):
+        import memcache
+        super().__init__(server, params, library=memcache, value_not_found_exception=ValueError)
+
+    @property
+    def _cache(self):
+        if getattr(self, '_client', None) is None:
+            client_kwargs = {'pickleProtocol': pickle.HIGHEST_PROTOCOL}
+            client_kwargs.update(self._options)
+            self._client = self._lib.Client(self._servers, **client_kwargs)
+        return self._client
+
+    def touch(self, key, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        return self._cache.touch(key, self.get_backend_timeout(timeout)) != 0
+
+    def get(self, key, default=None, version=None):
+        key = self.make_key(key, version=version)
+        val = self._cache.get(key)
+        # python-memcached doesn't support default values in get().
+        # https://github.com/linsomniac/python-memcached/issues/159
+        # Remove this method if that issue is fixed.
+        if val is None:
+            return default
+        return val
+
+    def delete(self, key, version=None):
+        # python-memcached's delete() returns True when key doesn't exist.
+        # https://github.com/linsomniac/python-memcached/issues/170
+        # Call _deletetouch() without the NOT_FOUND in expected results.
+        key = self.make_key(key, version=version)
+        return bool(self._cache._deletetouch([b'DELETED'], 'delete', key))
+
+
+class PyLibMCCache(BaseMemcachedCache):
+    "An implementation of a cache binding using pylibmc"
+    def __init__(self, server, params):
+        import pylibmc
+        super().__init__(server, params, library=pylibmc, value_not_found_exception=pylibmc.NotFound)
+
+    @cached_property
+    def _cache(self):
+        return self._lib.Client(self._servers, **self._options)
+
+    def touch(self, key, timeout=DEFAULT_TIMEOUT, version=None):
+        key = self.make_key(key, version=version)
+        if timeout == 0:
+            return self._cache.delete(key)
+        return self._cache.touch(key, self.get_backend_timeout(timeout))
+
+    def close(self, **kwargs):
+        # libmemcached manages its own connections. Don't call disconnect_all()
+        # as it resets the failover state and creates unnecessary reconnects.
+        pass

Lib/site-packages/django/core/cache/utils.py

@@ -0,0 +1,12 @@
+import hashlib
+
+TEMPLATE_FRAGMENT_KEY_TEMPLATE = 'template.cache.%s.%s'
+
+
+def make_template_fragment_key(fragment_name, vary_on=None):
+    hasher = hashlib.md5()
+    if vary_on is not None:
+        for arg in vary_on:
+            hasher.update(str(arg).encode())
+            hasher.update(b':')
+    return TEMPLATE_FRAGMENT_KEY_TEMPLATE % (fragment_name, hasher.hexdigest())