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Diffstat (limited to 'keystone/openstack/common/local.py')
-rw-r--r-- | keystone/openstack/common/local.py | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/keystone/openstack/common/local.py b/keystone/openstack/common/local.py new file mode 100644 index 00000000..e82f17d0 --- /dev/null +++ b/keystone/openstack/common/local.py @@ -0,0 +1,47 @@ +# vim: tabstop=4 shiftwidth=4 softtabstop=4 + +# Copyright 2011 OpenStack Foundation. +# 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. + +"""Local storage of variables using weak references""" + +import threading +import weakref + + +class WeakLocal(threading.local): + def __getattribute__(self, attr): + rval = super(WeakLocal, self).__getattribute__(attr) + if rval: + # NOTE(mikal): this bit is confusing. What is stored is a weak + # reference, not the value itself. We therefore need to lookup + # the weak reference and return the inner value here. + rval = rval() + return rval + + def __setattr__(self, attr, value): + value = weakref.ref(value) + return super(WeakLocal, self).__setattr__(attr, value) + + +# NOTE(mikal): the name "store" should be deprecated in the future +store = WeakLocal() + +# A "weak" store uses weak references and allows an object to fall out of scope +# when it falls out of scope in the code that uses the thread local storage. A +# "strong" store will hold a reference to the object so that it never falls out +# of scope. +weak_store = WeakLocal() +strong_store = threading.local() |