Make ironic-api compatible with WSGI containers other than mod_wsgi

Using ironic-api-wsgi implies mod_wsgi, some other containers require
an importable module. This patch modifies ironic.api.wsgi to be usable
this way and documents it.

Change-Id: I8493eb36293a0214081e0adb59c3a267c9688819

doc/source/install/include/configure-ironic-api-mod_wsgi.inc

@@ -74,3 +74,20 @@ Bare Metal service comes with an example file for configuring the
 .. note::
    The file ``ironic-api-wsgi`` is automatically generated by pbr and is
    available in `IRONIC_BIN` directory. It should not be modified.
+
+Configure another WSGI container
+--------------------------------
+
+A slightly different approach has to be used for WSGI containers that cannot
+use ``ironic-api-wsgi``. For example, for *gunicorn*:
+
+.. code-block:: console
+
+    gunicorn -b 0.0.0.0:6385 'ironic.api.wsgi:initialize_wsgi_app(argv=[])'
+
+If you want to pass a configuration file, use:
+
+.. code-block:: console
+
+    gunicorn -b 0.0.0.0:6385 \
+        'ironic.api.wsgi:initialize_wsgi_app(argv=["ironic-api", "--config-file=/path/to/_ironic.conf"])'

ironic/api/wsgi.py

@@ -25,10 +25,11 @@ CONF = cfg.CONF
 LOG = log.getLogger(__name__)
 
 
-def initialize_wsgi_app():
+# NOTE(dtantsur): WSGI containers may need to override the passed argv.
+def initialize_wsgi_app(argv=sys.argv):
     i18n.install('ironic')
 
-    service.prepare_service(sys.argv)
+    service.prepare_service(argv)
 
     LOG.debug("Configuration:")
     CONF.log_opt_values(LOG, log.DEBUG)

releasenotes/notes/any-wsgi-8d6ccb0590104146.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Makes ``ironic.api.wsgi`` compatible with WSGI containers that cannot use
+    an executable WSGI entry point. For example, with gunicorn::
+
+        gunicorn -b 0.0.0.0:6385 'ironic.api.wsgi:initialize_wsgi_app(argv=[])'