Initial version

'Borrowed' from Heat.

senlin/db/utils.py

@@ -0,0 +1,45 @@
+# 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.
+
+
+class LazyPluggable(object):
+    """A pluggable backend loaded lazily based on some value."""
+
+    def __init__(self, pivot, **backends):
+        self.__backends = backends
+        self.__pivot = pivot
+        self.__backend = None
+
+    def __get_backend(self):
+        if not self.__backend:
+            backend_name = 'sqlalchemy'
+            backend = self.__backends[backend_name]
+            if isinstance(backend, tuple):
+                name = backend[0]
+                fromlist = backend[1]
+            else:
+                name = backend
+                fromlist = backend
+
+            self.__backend = __import__(name, None, None, fromlist)
+        return self.__backend
+
+    def __getattr__(self, key):
+        backend = self.__get_backend()
+        return getattr(backend, key)
+
+
+IMPL = LazyPluggable('backend', sqlalchemy='senlin.db.sqlalchemy.api')
+
+
+def purge_deleted(age, granularity='days'):
+    IMPL.purge_deleted(age, granularity)