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OpenStack Study: manager.py**** CubicPower OpenStack Study ****
# 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 keystone.openstack.common import importutils
**** CubicPower OpenStack Study **** 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
**** CubicPower OpenStack Study **** 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
**** CubicPower OpenStack Study **** 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. """
**** CubicPower OpenStack Study **** def __init__(self, driver_name): self.driver = importutils.import_object(driver_name)
**** CubicPower OpenStack Study **** def __getattr__(self, name): """Forward calls to the underlying driver.""" f = getattr(self.driver, name) @functools.wraps(f) def _wrapper(*args, **kw): return f(*args, **kw) setattr(self, name, _wrapper) return _wrapper
**** CubicPower OpenStack Study **** def _wrapper(*args, **kw): return f(*args, **kw) setattr(self, name, _wrapper) return _wrapper
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