Add wsgi module

This allows deployment tooling to easily switch from passing a binary
path to passing a Python module path. We'll use it shortly.

Change-Id: I7a50ba8ce16184dce3b8a3dec7801155c7a605cd
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

cinder/wsgi/api.py

@@ -0,0 +1,24 @@
+# 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.
+
+"""WSGI application entry-point for Cinder Volume API."""
+
+import threading
+
+from cinder.wsgi import wsgi
+
+application = None
+
+lock = threading.Lock()
+with lock:
+    if application is None:
+        application = wsgi.initialize_application()

doc/source/conf.py

@@ -64,7 +64,9 @@ apidoc_excluded_paths = [
     'zonemanager/drivers/*',
     'zonemanager/drivers',
     'backup/drivers/*',
-    'backup/drivers']
+    'backup/drivers',
+    'wsgi/api.py',
+]
 apidoc_separate_modules = True
 
 config_generator_config_file = (

releasenotes/notes/add-cinder-wsgi-module-ae72ad42bfebbea8.yaml

@@ -0,0 +1,22 @@
+---
+features:
+  - |
+    A new module, ``cinder.wsgi``, has been added as a place to gather WSGI
+    ``application`` objects. This is intended to ease deployment by providing
+    a consistent location for these objects. For example, if using uWSGI then
+    instead of:
+
+    .. code-block:: ini
+
+        [uwsgi]
+        wsgi-file = /bin/cinder-wsgi
+
+    You can now use:
+
+    .. code-block:: ini
+
+        [uwsgi]
+        module = cinder.wsgi.api:application
+
+    This also simplifies deployment with other WSGI servers that expect module
+    paths such as gunicorn.