migrate moon code from github to opnfv

Change-Id: Ice53e368fd1114d56a75271aa9f2e598e3eba604
Signed-off-by: WuKong <rebirthmonkey@gmail.com>

4 files changed, 667 insertions, 0 deletions

diff --git a/keystone-moon/keystone/common/cache/backends/__init__.py b/keystone-moon/keystone/common/cache/backends/__init__.py
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/keystone-moon/keystone/common/cache/backends/__init__.py
diff --git a/keystone-moon/keystone/common/cache/backends/memcache_pool.py b/keystone-moon/keystone/common/cache/backends/memcache_pool.py
new file mode 100644
index 00000000..f3990b12
--- /dev/null
+++ b/keystone-moon/keystone/common/cache/backends/memcache_pool.py
@@ -0,0 +1,61 @@
+# Copyright 2014 Mirantis Inc
+# All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+"""dogpile.cache backend that uses Memcached connection pool"""
+
+import functools
+import logging
+
+from dogpile.cache.backends import memcached as memcached_backend
+
+from keystone.common.cache import _memcache_pool
+
+
+LOG = logging.getLogger(__name__)
+
+
+# Helper to ease backend refactoring
+class ClientProxy(object):
+    def __init__(self, client_pool):
+        self.client_pool = client_pool
+
+    def _run_method(self, __name, *args, **kwargs):
+        with self.client_pool.acquire() as client:
+            return getattr(client, __name)(*args, **kwargs)
+
+    def __getattr__(self, name):
+        return functools.partial(self._run_method, name)
+
+
+class PooledMemcachedBackend(memcached_backend.MemcachedBackend):
+    # Composed from GenericMemcachedBackend's and MemcacheArgs's __init__
+    def __init__(self, arguments):
+        super(PooledMemcachedBackend, self).__init__(arguments)
+        self.client_pool = _memcache_pool.MemcacheClientPool(
+            self.url,
+            arguments={
+                'dead_retry': arguments.get('dead_retry', 5 * 60),
+                'socket_timeout': arguments.get('socket_timeout', 3),
+            },
+            maxsize=arguments.get('pool_maxsize', 10),
+            unused_timeout=arguments.get('pool_unused_timeout', 60),
+            conn_get_timeout=arguments.get('pool_connection_get_timeout', 10),
+        )
+
+    # Since all methods in backend just call one of methods of client, this
+    # lets us avoid need to hack it too much
+    @property
+    def client(self):
+        return ClientProxy(self.client_pool)
diff --git a/keystone-moon/keystone/common/cache/backends/mongo.py b/keystone-moon/keystone/common/cache/backends/mongo.py
new file mode 100644
index 00000000..b5de9bc4
--- /dev/null
+++ b/keystone-moon/keystone/common/cache/backends/mongo.py
@@ -0,0 +1,557 @@
+# Copyright 2014 Hewlett-Packard Development Company, L.P.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import abc
+import datetime
+
+from dogpile.cache import api
+from dogpile.cache import util as dp_util
+from oslo_log import log
+from oslo_utils import importutils
+from oslo_utils import timeutils
+import six
+
+from keystone import exception
+from keystone.i18n import _, _LW
+
+
+NO_VALUE = api.NO_VALUE
+LOG = log.getLogger(__name__)
+
+
+class MongoCacheBackend(api.CacheBackend):
+    """A MongoDB based caching backend implementing dogpile backend APIs.
+
+    Arguments accepted in the arguments dictionary:
+
+    :param db_hosts: string (required), hostname or IP address of the
+        MongoDB server instance. This can be a single MongoDB connection URI,
+        or a list of MongoDB connection URIs.
+
+    :param db_name: string (required), the name of the database to be used.
+
+    :param cache_collection: string (required), the name of collection to store
+        cached data.
+        *Note:* Different collection name can be provided if there is need to
+        create separate container (i.e. collection) for cache data. So region
+        configuration is done per collection.
+
+    Following are optional parameters for MongoDB backend configuration,
+
+    :param username: string, the name of the user to authenticate.
+
+    :param password: string, the password of the user to authenticate.
+
+    :param max_pool_size: integer, the maximum number of connections that the
+        pool will open simultaneously. By default the pool size is 10.
+
+    :param w: integer, write acknowledgement for MongoDB client
+
+        If not provided, then no default is set on MongoDB and then write
+        acknowledgement behavior occurs as per MongoDB default. This parameter
+        name is same as what is used in MongoDB docs. This value is specified
+        at collection level so its applicable to `cache_collection` db write
+        operations.
+
+        If this is a replica set, write operations will block until they have
+        been replicated to the specified number or tagged set  of servers.
+        Setting w=0 disables write acknowledgement and all other write concern
+        options.
+
+    :param read_preference: string, the read preference mode for MongoDB client
+        Expected value is ``primary``, ``primaryPreferred``, ``secondary``,
+        ``secondaryPreferred``, or ``nearest``. This read_preference is
+        specified at collection level so its applicable to `cache_collection`
+        db read operations.
+
+    :param use_replica: boolean, flag to indicate if replica client to be
+        used. Default is `False`. `replicaset_name` value is required if
+        `True`.
+
+    :param replicaset_name: string, name of replica set.
+        Becomes required if `use_replica` is `True`
+
+    :param son_manipulator: string, name of class with module name which
+        implements MongoDB SONManipulator.
+        Default manipulator used is :class:`.BaseTransform`.
+
+        This manipulator is added per database. In multiple cache
+        configurations, the manipulator name should be same if same
+        database name ``db_name`` is used in those configurations.
+
+        SONManipulator is used to manipulate custom data types as they are
+        saved or retrieved from MongoDB. Custom impl is only needed if cached
+        data is custom class and needs transformations when saving or reading
+        from db. If dogpile cached value contains built-in data types, then
+        BaseTransform class is sufficient as it already handles dogpile
+        CachedValue class transformation.
+
+    :param mongo_ttl_seconds: integer, interval in seconds to indicate maximum
+        time-to-live value.
+        If value is greater than 0, then its assumed that cache_collection
+        needs to be TTL type (has index at 'doc_date' field).
+        By default, the value is -1 and its disabled.
+        Reference: <http://docs.mongodb.org/manual/tutorial/expire-data/>
+
+        .. NOTE::
+
+            This parameter is different from Dogpile own
+            expiration_time, which is the number of seconds after which Dogpile
+            will consider the value to be expired. When Dogpile considers a
+            value to be expired, it continues to use the value until generation
+            of a new value is complete, when using CacheRegion.get_or_create().
+            Therefore, if you are setting `mongo_ttl_seconds`, you will want to
+            make sure it is greater than expiration_time by at least enough
+            seconds for new values to be generated, else the value would not
+            be available during a regeneration, forcing all threads to wait for
+            a regeneration each time a value expires.
+
+    :param ssl: boolean, If True, create the connection to the server
+        using SSL. Default is `False`. Client SSL connection parameters depends
+        on server side SSL setup. For further reference on SSL configuration:
+        <http://docs.mongodb.org/manual/tutorial/configure-ssl/>
+
+    :param ssl_keyfile: string, the private keyfile used to identify the
+        local connection against mongod. If included with the certfile then
+        only the `ssl_certfile` is needed. Used only when `ssl` is `True`.
+
+    :param ssl_certfile: string, the certificate file used to identify the
+        local connection against mongod. Used only when `ssl` is `True`.
+
+    :param ssl_ca_certs: string, the ca_certs file contains a set of
+        concatenated 'certification authority' certificates, which are used to
+        validate certificates passed from the other end of the connection.
+        Used only when `ssl` is `True`.
+
+    :param ssl_cert_reqs: string, the parameter cert_reqs specifies whether
+        a certificate is required from the other side of the connection, and
+        whether it will be validated if provided. It must be one of the three
+        values ``ssl.CERT_NONE`` (certificates ignored), ``ssl.CERT_OPTIONAL``
+        (not required, but validated if provided), or
+        ``ssl.CERT_REQUIRED`` (required and validated). If the value of this
+        parameter is not ``ssl.CERT_NONE``, then the ssl_ca_certs parameter
+        must point to a file of CA certificates. Used only when `ssl`
+        is `True`.
+
+    Rest of arguments are passed to mongo calls for read, write and remove.
+    So related options can be specified to pass to these operations.
+
+    Further details of various supported arguments can be referred from
+    <http://api.mongodb.org/python/current/api/pymongo/>
+
+    """
+
+    def __init__(self, arguments):
+        self.api = MongoApi(arguments)
+
+    @dp_util.memoized_property
+    def client(self):
+        """Initializes MongoDB connection and collection defaults.
+
+        This initialization is done only once and performed as part of lazy
+        inclusion of MongoDB dependency i.e. add imports only if related
+        backend is used.
+
+        :return: :class:`.MongoApi` instance
+        """
+        self.api.get_cache_collection()
+        return self.api
+
+    def get(self, key):
+        value = self.client.get(key)
+        if value is None:
+            return NO_VALUE
+        else:
+            return value
+
+    def get_multi(self, keys):
+        values = self.client.get_multi(keys)
+        return [
+            NO_VALUE if key not in values
+            else values[key] for key in keys
+        ]
+
+    def set(self, key, value):
+        self.client.set(key, value)
+
+    def set_multi(self, mapping):
+        self.client.set_multi(mapping)
+
+    def delete(self, key):
+        self.client.delete(key)
+
+    def delete_multi(self, keys):
+        self.client.delete_multi(keys)
+
+
+class MongoApi(object):
+    """Class handling MongoDB specific functionality.
+
+    This class uses PyMongo APIs internally to create database connection
+    with configured pool size, ensures unique index on key, does database
+    authentication and ensure TTL collection index if configured so.
+    This class also serves as handle to cache collection for dogpile cache
+    APIs.
+
+    In a single deployment, multiple cache configuration can be defined. In
+    that case of multiple cache collections usage, db client connection pool
+    is shared when cache collections are within same database.
+    """
+
+    # class level attributes for re-use of db client connection and collection
+    _DB = {}  # dict of db_name: db connection reference
+    _MONGO_COLLS = {}  # dict of cache_collection : db collection reference
+
+    def __init__(self, arguments):
+        self._init_args(arguments)
+        self._data_manipulator = None
+
+    def _init_args(self, arguments):
+        """Helper logic for collecting and parsing MongoDB specific arguments.
+
+        The arguments passed in are separated out in connection specific
+        setting and rest of arguments are passed to create/update/delete
+        db operations.
+        """
+        self.conn_kwargs = {}  # connection specific arguments
+
+        self.hosts = arguments.pop('db_hosts', None)
+        if self.hosts is None:
+            msg = _('db_hosts value is required')
+            raise exception.ValidationError(message=msg)
+
+        self.db_name = arguments.pop('db_name', None)
+        if self.db_name is None:
+            msg = _('database db_name is required')
+            raise exception.ValidationError(message=msg)
+
+        self.cache_collection = arguments.pop('cache_collection', None)
+        if self.cache_collection is None:
+            msg = _('cache_collection name is required')
+            raise exception.ValidationError(message=msg)
+
+        self.username = arguments.pop('username', None)
+        self.password = arguments.pop('password', None)
+        self.max_pool_size = arguments.pop('max_pool_size', 10)
+
+        self.w = arguments.pop('w', -1)
+        try:
+            self.w = int(self.w)
+        except ValueError:
+            msg = _('integer value expected for w (write concern attribute)')
+            raise exception.ValidationError(message=msg)
+
+        self.read_preference = arguments.pop('read_preference', None)
+
+        self.use_replica = arguments.pop('use_replica', False)
+        if self.use_replica:
+            if arguments.get('replicaset_name') is None:
+                msg = _('replicaset_name required when use_replica is True')
+                raise exception.ValidationError(message=msg)
+            self.replicaset_name = arguments.get('replicaset_name')
+
+        self.son_manipulator = arguments.pop('son_manipulator', None)
+
+        # set if mongo collection needs to be TTL type.
+        # This needs to be max ttl for any cache entry.
+        # By default, -1 means don't use TTL collection.
+        # With ttl set, it creates related index and have doc_date field with
+        # needed expiration interval
+        self.ttl_seconds = arguments.pop('mongo_ttl_seconds', -1)
+        try:
+            self.ttl_seconds = int(self.ttl_seconds)
+        except ValueError:
+            msg = _('integer value expected for mongo_ttl_seconds')
+            raise exception.ValidationError(message=msg)
+
+        self.conn_kwargs['ssl'] = arguments.pop('ssl', False)
+        if self.conn_kwargs['ssl']:
+            ssl_keyfile = arguments.pop('ssl_keyfile', None)
+            ssl_certfile = arguments.pop('ssl_certfile', None)
+            ssl_ca_certs = arguments.pop('ssl_ca_certs', None)
+            ssl_cert_reqs = arguments.pop('ssl_cert_reqs', None)
+            if ssl_keyfile:
+                self.conn_kwargs['ssl_keyfile'] = ssl_keyfile
+            if ssl_certfile:
+                self.conn_kwargs['ssl_certfile'] = ssl_certfile
+            if ssl_ca_certs:
+                self.conn_kwargs['ssl_ca_certs'] = ssl_ca_certs
+            if ssl_cert_reqs:
+                self.conn_kwargs['ssl_cert_reqs'] = (
+                    self._ssl_cert_req_type(ssl_cert_reqs))
+
+        # rest of arguments are passed to mongo crud calls
+        self.meth_kwargs = arguments
+
+    def _ssl_cert_req_type(self, req_type):
+        try:
+            import ssl
+        except ImportError:
+            raise exception.ValidationError(_('no ssl support available'))
+        req_type = req_type.upper()
+        try:
+            return {
+                'NONE': ssl.CERT_NONE,
+                'OPTIONAL': ssl.CERT_OPTIONAL,
+                'REQUIRED': ssl.CERT_REQUIRED
+            }[req_type]
+        except KeyError:
+            msg = _('Invalid ssl_cert_reqs value of %s, must be one of '
+                    '"NONE", "OPTIONAL", "REQUIRED"') % (req_type)
+            raise exception.ValidationError(message=msg)
+
+    def _get_db(self):
+        # defer imports until backend is used
+        global pymongo
+        import pymongo
+        if self.use_replica:
+            connection = pymongo.MongoReplicaSetClient(
+                host=self.hosts, replicaSet=self.replicaset_name,
+                max_pool_size=self.max_pool_size, **self.conn_kwargs)
+        else:  # used for standalone node or mongos in sharded setup
+            connection = pymongo.MongoClient(
+                host=self.hosts, max_pool_size=self.max_pool_size,
+                **self.conn_kwargs)
+
+        database = getattr(connection, self.db_name)
+
+        self._assign_data_mainpulator()
+        database.add_son_manipulator(self._data_manipulator)
+        if self.username and self.password:
+            database.authenticate(self.username, self.password)
+        return database
+
+    def _assign_data_mainpulator(self):
+        if self._data_manipulator is None:
+            if self.son_manipulator:
+                self._data_manipulator = importutils.import_object(
+                    self.son_manipulator)
+            else:
+                self._data_manipulator = BaseTransform()
+
+    def _get_doc_date(self):
+        if self.ttl_seconds > 0:
+            expire_delta = datetime.timedelta(seconds=self.ttl_seconds)
+            doc_date = timeutils.utcnow() + expire_delta
+        else:
+            doc_date = timeutils.utcnow()
+        return doc_date
+
+    def get_cache_collection(self):
+        if self.cache_collection not in self._MONGO_COLLS:
+            global pymongo
+            import pymongo
+            # re-use db client connection if already defined as part of
+            # earlier dogpile cache configuration
+            if self.db_name not in self._DB:
+                self._DB[self.db_name] = self._get_db()
+            coll = getattr(self._DB[self.db_name], self.cache_collection)
+
+            self._assign_data_mainpulator()
+            if self.read_preference:
+                self.read_preference = pymongo.read_preferences.mongos_enum(
+                    self.read_preference)
+                coll.read_preference = self.read_preference
+            if self.w > -1:
+                coll.write_concern['w'] = self.w
+            if self.ttl_seconds > 0:
+                kwargs = {'expireAfterSeconds': self.ttl_seconds}
+                coll.ensure_index('doc_date', cache_for=5, **kwargs)
+            else:
+                self._validate_ttl_index(coll, self.cache_collection,
+                                         self.ttl_seconds)
+            self._MONGO_COLLS[self.cache_collection] = coll
+
+        return self._MONGO_COLLS[self.cache_collection]
+
+    def _get_cache_entry(self, key, value, meta, doc_date):
+        """MongoDB cache data representation.
+
+        Storing cache key as ``_id`` field as MongoDB by default creates
+        unique index on this field. So no need to create separate field and
+        index for storing cache key. Cache data has additional ``doc_date``
+        field for MongoDB TTL collection support.
+        """
+        return dict(_id=key, value=value, meta=meta, doc_date=doc_date)
+
+    def _validate_ttl_index(self, collection, coll_name, ttl_seconds):
+        """Checks if existing TTL index is removed on a collection.
+
+        This logs warning when existing collection has TTL index defined and
+        new cache configuration tries to disable index with
+        ``mongo_ttl_seconds < 0``. In that case, existing index needs
+        to be addressed first to make new configuration effective.
+        Refer to MongoDB documentation around TTL index for further details.
+        """
+        indexes = collection.index_information()
+        for indx_name, index_data in six.iteritems(indexes):
+            if all(k in index_data for k in ('key', 'expireAfterSeconds')):
+                existing_value = index_data['expireAfterSeconds']
+                fld_present = 'doc_date' in index_data['key'][0]
+                if fld_present and existing_value > -1 and ttl_seconds < 1:
+                    msg = _LW('TTL index already exists on db collection '
+                              '<%(c_name)s>, remove index <%(indx_name)s> '
+                              'first to make updated mongo_ttl_seconds value '
+                              'to be  effective')
+                    LOG.warn(msg, {'c_name': coll_name,
+                                   'indx_name': indx_name})
+
+    def get(self, key):
+        critieria = {'_id': key}
+        result = self.get_cache_collection().find_one(spec_or_id=critieria,
+                                                      **self.meth_kwargs)
+        if result:
+            return result['value']
+        else:
+            return None
+
+    def get_multi(self, keys):
+        db_results = self._get_results_as_dict(keys)
+        return {doc['_id']: doc['value'] for doc in six.itervalues(db_results)}
+
+    def _get_results_as_dict(self, keys):
+        critieria = {'_id': {'$in': keys}}
+        db_results = self.get_cache_collection().find(spec=critieria,
+                                                      **self.meth_kwargs)
+        return {doc['_id']: doc for doc in db_results}
+
+    def set(self, key, value):
+        doc_date = self._get_doc_date()
+        ref = self._get_cache_entry(key, value.payload, value.metadata,
+                                    doc_date)
+        spec = {'_id': key}
+        # find and modify does not have manipulator support
+        # so need to do conversion as part of input document
+        ref = self._data_manipulator.transform_incoming(ref, self)
+        self.get_cache_collection().find_and_modify(spec, ref, upsert=True,
+                                                    **self.meth_kwargs)
+
+    def set_multi(self, mapping):
+        """Insert multiple documents specified as key, value pairs.
+
+        In this case, multiple documents can be added via insert provided they
+        do not exist.
+        Update of multiple existing documents is done one by one
+        """
+        doc_date = self._get_doc_date()
+        insert_refs = []
+        update_refs = []
+        existing_docs = self._get_results_as_dict(mapping.keys())
+        for key, value in mapping.items():
+            ref = self._get_cache_entry(key, value.payload, value.metadata,
+                                        doc_date)
+            if key in existing_docs:
+                ref['_id'] = existing_docs[key]['_id']
+                update_refs.append(ref)
+            else:
+                insert_refs.append(ref)
+        if insert_refs:
+            self.get_cache_collection().insert(insert_refs, manipulate=True,
+                                               **self.meth_kwargs)
+        for upd_doc in update_refs:
+            self.get_cache_collection().save(upd_doc, manipulate=True,
+                                             **self.meth_kwargs)
+
+    def delete(self, key):
+        critieria = {'_id': key}
+        self.get_cache_collection().remove(spec_or_id=critieria,
+                                           **self.meth_kwargs)
+
+    def delete_multi(self, keys):
+        critieria = {'_id': {'$in': keys}}
+        self.get_cache_collection().remove(spec_or_id=critieria,
+                                           **self.meth_kwargs)
+
+
+@six.add_metaclass(abc.ABCMeta)
+class AbstractManipulator(object):
+    """Abstract class with methods which need to be implemented for custom
+    manipulation.
+
+    Adding this as a base class for :class:`.BaseTransform` instead of adding
+    import dependency of pymongo specific class i.e.
+    `pymongo.son_manipulator.SONManipulator` and using that as base class.
+    This is done to avoid pymongo dependency if MongoDB backend is not used.
+    """
+    @abc.abstractmethod
+    def transform_incoming(self, son, collection):
+        """Used while saving data to MongoDB.
+
+        :param son: the SON object to be inserted into the database
+        :param collection: the collection the object is being inserted into
+
+        :returns: transformed SON object
+
+        """
+        raise exception.NotImplemented()  # pragma: no cover
+
+    @abc.abstractmethod
+    def transform_outgoing(self, son, collection):
+        """Used while reading data from MongoDB.
+
+        :param son: the SON object being retrieved from the database
+        :param collection: the collection this object was stored in
+
+        :returns: transformed SON object
+        """
+        raise exception.NotImplemented()  # pragma: no cover
+
+    def will_copy(self):
+        """Will this SON manipulator make a copy of the incoming document?
+
+        Derived classes that do need to make a copy should override this
+        method, returning `True` instead of `False`.
+
+        :returns: boolean
+        """
+        return False
+
+
+class BaseTransform(AbstractManipulator):
+    """Base transformation class to store and read dogpile cached data
+    from MongoDB.
+
+    This is needed as dogpile internally stores data as a custom class
+    i.e. dogpile.cache.api.CachedValue
+
+    Note: Custom manipulator needs to always override ``transform_incoming``
+    and ``transform_outgoing`` methods. MongoDB manipulator logic specifically
+    checks that overridden method in instance and its super are different.
+    """
+
+    def transform_incoming(self, son, collection):
+        """Used while saving data to MongoDB."""
+        for (key, value) in son.items():
+            if isinstance(value, api.CachedValue):
+                son[key] = value.payload  # key is 'value' field here
+                son['meta'] = value.metadata
+            elif isinstance(value, dict):  # Make sure we recurse into sub-docs
+                son[key] = self.transform_incoming(value, collection)
+        return son
+
+    def transform_outgoing(self, son, collection):
+        """Used while reading data from MongoDB."""
+        metadata = None
+        # make sure its top level dictionary with all expected fields names
+        # present
+        if isinstance(son, dict) and all(k in son for k in
+                                         ('_id', 'value', 'meta', 'doc_date')):
+            payload = son.pop('value', None)
+            metadata = son.pop('meta', None)
+        for (key, value) in son.items():
+            if isinstance(value, dict):
+                son[key] = self.transform_outgoing(value, collection)
+        if metadata is not None:
+            son['value'] = api.CachedValue(payload, metadata)
+        return son
diff --git a/keystone-moon/keystone/common/cache/backends/noop.py b/keystone-moon/keystone/common/cache/backends/noop.py
new file mode 100644
index 00000000..38329c94
--- /dev/null
+++ b/keystone-moon/keystone/common/cache/backends/noop.py
@@ -0,0 +1,49 @@
+# Copyright 2013 Metacloud
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from dogpile.cache import api
+
+
+NO_VALUE = api.NO_VALUE
+
+
+class NoopCacheBackend(api.CacheBackend):
+    """A no op backend as a default caching backend.
+
+    The no op backend is provided as the default caching backend for keystone
+    to ensure that ``dogpile.cache.memory`` is not used in any real-world
+    circumstances unintentionally.  ``dogpile.cache.memory`` does not have a
+    mechanism to cleanup it's internal dict and therefore could cause run-away
+    memory utilization.
+    """
+    def __init__(self, *args):
+        return
+
+    def get(self, key):
+        return NO_VALUE
+
+    def get_multi(self, keys):
+        return [NO_VALUE for x in keys]
+
+    def set(self, key, value):
+        return
+
+    def set_multi(self, mapping):
+        return
+
+    def delete(self, key):
+        return
+
+    def delete_multi(self, keys):
+        return