Readds plugins code and respective tests

[osm/MON.git] / osm_mon / plugins / OpenStack / singleton.py

diff --git a/osm_mon/plugins/OpenStack/singleton.py b/osm_mon/plugins/OpenStack/singleton.py
new file mode 100644 (file)
index 0000000..59c5ee5
--- /dev/null
+++ b/osm_mon/plugins/OpenStack/singleton.py
@@ -0,0 +1,40 @@
+# Copyright 2017 Intel Research and Development Ireland Limited
+# *************************************************************
+
+# This file is part of OSM Monitoring module
+# All Rights Reserved to Intel Corporation
+
+# 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.
+
+# For those usages not covered by the Apache License, Version 2.0 please
+# contact: helena.mcgough@intel.com or adrian.hoban@intel.com
+##
+"""Simple singleton class."""
+
+from __future__ import unicode_literals
+
+
+class Singleton(object):
+    """Simple singleton class."""
+
+    def __init__(self, decorated):
+        """Initialize singleton instance."""
+        self._decorated = decorated
+
+    def instance(self):
+        """Return singleton instance."""
+        try:
+            return self._instance
+        except AttributeError:
+            self._instance = self._decorated()
+            return self._instance