Add new neutron.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: I5350dff6be0daf1d4e5e5dfa4aab745b765436f7
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

neutron/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 Neutron API."""
+
+import threading
+
+from neutron import server
+from neutron.server import api_eventlet
+
+application = None
+lock = threading.Lock()
+with lock:
+    if application is None:
+        application = server.boot_server(api_eventlet.eventlet_api_server)

releasenotes/notes/add-neutron-wsgi-module-68e2418a0f9124e5.yaml

@@ -0,0 +1,22 @@
+---
+features:
+  - |
+    A new module, ``neutron.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/neutron-api
+
+    You can now use:
+
+    .. code-block:: ini
+
+        [uwsgi]
+        module = neutron.wsgi.api:application
+
+    This also simplifies deployment with other WSGI servers that expect module
+    paths such as gunicorn.