Register osapi_compute when nova-api is wsgi

When the nova-api services starts from its own standalone binary it
registers itself in the services table. The original wsgi script in
nova/wsgi/nova-api.py did not, leading to the bug referenced below.

The new wsgi script at nova.api.openstack.compute.wsgi, modelled on
a similar thing used for the placement API, provides the necessary
service registration.

If a ServiceTooOld exception happens while trying to register the
service then a very simple (currently very stubby) application is
loaded instead of the compute api. This application returns a 500
and a message.

Some caveats/todos:

* wsgi apps managed under mod-wsgi (and presumably other containers)
  are not imported/compiled/run until the first request is made. In
  this case that means the service handling does not happen until
  that first request, somewhat defeating the purpose if the api is a
  bit idle.

Change-Id: I7c4acfaa6c50ac0e4d6de69eb62ec5bbad72ff85
Closes-Bug: #1661360

nova/api/openstack/compute/wsgi.py

@@ -0,0 +1,86 @@
+#    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 script for Nova API, installed by pbr."""
+
+import os
+
+from oslo_config import cfg
+from oslo_log import log as logging
+from paste import deploy
+
+from nova import config
+from nova import context
+from nova import exception
+from nova import objects
+from nova import service
+from nova import utils
+
+CONF = cfg.CONF
+
+CONFIG_FILES = ['api-paste.ini', 'nova.conf']
+NAME = "osapi_compute"
+
+utils.monkey_patch()
+objects.register_all()
+
+
+def _get_config_files(env=None):
+    if env is None:
+        env = os.environ
+    dirname = env.get('OS_NOVA_CONFIG_DIR', '/etc/nova').strip()
+    return [os.path.join(dirname, config_file)
+            for config_file in CONFIG_FILES]
+
+
+def _setup_service(host, name):
+    ctxt = context.get_admin_context()
+    service_ref = objects.Service.get_by_host_and_binary(
+        ctxt, host, name)
+    if service_ref:
+        service._update_service_ref(service_ref)
+    else:
+        try:
+            service_obj = objects.Service(ctxt)
+            service_obj.host = host
+            service_obj.binary = 'nova-%s' % name
+            service_obj.topic = None
+            service_obj.report_count = 0
+            service_obj.create()
+        except (exception.ServiceTopicExists,
+                exception.ServiceBinaryExists):
+            # If we race to create a record with a sibling, don't
+            # fail here.
+            pass
+
+
+def error_application(exc):
+    # TODO(cdent): make this something other than a stub
+    def application(environ, start_response):
+        start_response('500 Internal Server Error', [
+            ('Content-Type', 'text/plain; charset=UTF-8')])
+        return ['Out of date API service %s\n' % exc]
+    return application
+
+
+def init_application():
+    conf_files = _get_config_files()
+    config.parse_args([], default_config_files=conf_files)
+
+    logging.setup(CONF, "nova")
+    try:
+        _setup_service(CONF.host, NAME)
+    except exception.ServiceTooOld as exc:
+        return error_application(exc)
+
+    conf = conf_files[0]
+
+    return deploy.loadapp('config:%s' % conf, name=NAME)

setup.cfg

@@ -69,6 +69,7 @@ console_scripts =
     nova-xvpvncproxy = nova.cmd.xvpvncproxy:main
 wsgi_scripts =
     nova-placement-api = nova.api.openstack.placement.wsgi:init_application
+    nova-api-wsgi = nova.api.openstack.compute.wsgi:init_application
 
 nova.api.v21.extensions =
     admin_actions = nova.api.openstack.compute.admin_actions:AdminActions