Expose neutron api application as a wsgi script

This can then be loaded into a wsgi compatible web server like
apache2/httpd or nginx.

DocImpact A new neutron-api script is installed, and can be used to
start either a standalone wsgi server (calling the script directly),
or as a wsgi script loaded by a web server (e.g. by httpd/mod_wsgi).

Change-Id: Ie9bb8b33f6e1335219e574d832ac264b043d90e6
Partial-Bug: #1666779
Co-Authored-By: Brandon Logan <brandon.logan@rackspace.com>
Co-Authored-By: Ihar Hrachyshka <ihrachys@redhat.com>

neutron/server/__init__.py

@@ -22,9 +22,10 @@ from oslo_config import cfg
 
 from neutron._i18n import _
 from neutron.common import config
+from neutron.common import profiler
 
 
-def boot_server(server_func):
+def _init_configuration():
     # the configuration will be read into the cfg.CONF global data structure
     config.init(sys.argv[1:])
     config.setup_logging()
@@ -33,9 +34,19 @@ def boot_server(server_func):
         sys.exit(_("ERROR: Unable to find configuration file via the default"
                    " search paths (~/.neutron/, ~/, /etc/neutron/, /etc/) and"
                    " the '--config-file' option!"))
+
+
+def boot_server(server_func):
+    _init_configuration()
     try:
         server_func()
     except KeyboardInterrupt:
         pass
     except RuntimeError as e:
         sys.exit(_("ERROR: %s") % e)
+
+
+def get_application():
+    _init_configuration()
+    profiler.setup('neutron-server', cfg.CONF.host)
+    return config.load_paste_app('neutron')

releasenotes/notes/add-wsgi-script-support-e611fa5b5c2043a5.yaml

@@ -0,0 +1,7 @@
+---
+prelude: >
+    This release adds support for running Neutron API component with a ``mod_wsgi``
+    compatible web server.
+features:
+  - Neutron API can now be managed by a ``mod_wsgi`` compatible web server (e.g.
+    ``apache2`` (``httpd``), ``nginx``, etc.)

setup.cfg

@@ -41,6 +41,8 @@ scripts =
     bin/neutron-rootwrap-xen-dom0
 
 [entry_points]
+wsgi_scripts =
+    neutron-api = neutron.server:get_application
 console_scripts =
     neutron-db-manage = neutron.db.migration.cli:main
     neutron-debug = neutron.debug.shell:main