Add greenthread local storage model from nova

Thread local storage is obviously a very useful facility to have
available.

Nova has a very simple API for this which uses eventlet's corolocal
module and weakrefs. This looks to be generally useful and complete,
so let's pull it into openstack-common.

Change-Id: I52a08124297c9cb79def447436859bd8d2c0b622

1 files changed, 37 insertions, 0 deletions

diff --git a/openstack/common/local.py b/openstack/common/local.py
new file mode 100644
index 0000000..19d9627
--- /dev/null
+++ b/openstack/common/local.py
@@ -0,0 +1,37 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2011 OpenStack LLC.
+# 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.
+
+"""Greenthread local storage of variables using weak references"""
+
+import weakref
+
+from eventlet import corolocal
+
+
+class WeakLocal(corolocal.local):
+    def __getattribute__(self, attr):
+        rval = corolocal.local.__getattribute__(self, attr)
+        if rval:
+            rval = rval()
+        return rval
+
+    def __setattr__(self, attr, value):
+        value = weakref.ref(value)
+        return corolocal.local.__setattr__(self, attr, value)
+
+
+store = WeakLocal()