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diff --git a/keystone-moon/keystone/common/manager.py b/keystone-moon/keystone/common/manager.py
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+++ b/keystone-moon/keystone/common/manager.py
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+# Copyright 2012 OpenStack Foundation
+#
+# 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 functools
+
+from oslo_utils import importutils
+
+
+def response_truncated(f):
+    """Truncate the list returned by the wrapped function.
+
+    This is designed to wrap Manager list_{entity} methods to ensure that
+    any list limits that are defined are passed to the driver layer.  If a
+    hints list is provided, the wrapper will insert the relevant limit into
+    the hints so that the underlying driver call can try and honor it. If the
+    driver does truncate the response, it will update the 'truncated' attribute
+    in the 'limit' entry in the hints list, which enables the caller of this
+    function to know if truncation has taken place.  If, however, the driver
+    layer is unable to perform truncation, the 'limit' entry is simply left in
+    the hints list for the caller to handle.
+
+    A _get_list_limit() method is required to be present in the object class
+    hierarchy, which returns the limit for this backend to which we will
+    truncate.
+
+    If a hints list is not provided in the arguments of the wrapped call then
+    any limits set in the config file are ignored.  This allows internal use
+    of such wrapped methods where the entire data set is needed as input for
+    the calculations of some other API (e.g. get role assignments for a given
+    project).
+
+    """
+    @functools.wraps(f)
+    def wrapper(self, *args, **kwargs):
+        if kwargs.get('hints') is None:
+            return f(self, *args, **kwargs)
+
+        list_limit = self.driver._get_list_limit()
+        if list_limit:
+            kwargs['hints'].set_limit(list_limit)
+        return f(self, *args, **kwargs)
+    return wrapper
+
+
+class Manager(object):
+    """Base class for intermediary request layer.
+
+    The Manager layer exists to support additional logic that applies to all
+    or some of the methods exposed by a service that are not specific to the
+    HTTP interface.
+
+    It also provides a stable entry point to dynamic backends.
+
+    An example of a probable use case is logging all the calls.
+
+    """
+
+    def __init__(self, driver_name):
+        self.driver = importutils.import_object(driver_name)
+
+    def __getattr__(self, name):
+        """Forward calls to the underlying driver."""
+        f = getattr(self.driver, name)
+        setattr(self, name, f)
+        return f