Generate doc for versioned notifications

This commit adds a new sphinx extension that inspects the nova code
and adds information about the existing versioned notifications to
the nofitications devref. This way the devref is automatically kept
up to date with relevant information.

Partially-Implements: bp versioned-notification-api
Change-Id: If65d5d81e26cb2b4a9f57a8c7d37d3de310ebe00

doc/ext/versioned_notifications.py

@@ -0,0 +1,112 @@
+# 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.
+
+"""
+This provides a sphinx extension able to list the implemented versioned
+notifications into the developer documentation.
+
+It is used via a single directive in the .rst file
+
+  .. versioned_notifications::
+
+"""
+
+from sphinx.util.compat import Directive
+from docutils import nodes
+
+from nova.objects import base
+from nova.objects import notification
+
+
+def full_name(cls):
+    return cls.__module__ + '.' + cls.__name__
+
+
+class VersionedNotificationDirective(Directive):
+
+    LINK_PREFIX = 'https://git.openstack.org/cgit/openstack/nova/plain/'
+    SAMPLE_ROOT = 'doc/notification_samples/'
+
+    def run(self):
+        notifications = self._collect_notifications()
+        return self._build_markup(notifications)
+
+    def _collect_notifications(self):
+        notifications = []
+        ovos = base.NovaObjectRegistry.obj_classes()
+        for name, cls in ovos.items():
+            cls = cls[0]
+            if (issubclass(cls, notification.NotificationBase) and
+                    cls != notification.NotificationBase):
+
+                payload_name = cls.fields['payload'].objname
+                payload_cls = ovos[payload_name][0]
+
+                notifications.append((full_name(cls), full_name(payload_cls),
+                                      cls.sample))
+        return notifications
+
+    def _build_markup(self, notifications):
+        content = []
+        cols = ['Notification class', 'Payload class', 'Sample file link']
+        table = nodes.table()
+        content.append(table)
+        group = nodes.tgroup(cols=len(cols))
+        table.append(group)
+
+        head = nodes.thead()
+        group.append(head)
+
+        for i in range(len(cols)):
+            group.append(nodes.colspec(colwidth=1))
+
+        body = nodes.tbody()
+        group.append(body)
+
+        # fill the table header
+        row = nodes.row()
+        body.append(row)
+        for col_name in cols:
+            col = nodes.entry()
+            row.append(col)
+            text = nodes.strong(text=col_name)
+            col.append(text)
+
+        # fill the table content, one notification per row
+        for name, payload, sample in notifications:
+            row = nodes.row()
+            body.append(row)
+            col = nodes.entry()
+            row.append(col)
+            text = nodes.literal(text=name)
+            col.append(text)
+
+            col = nodes.entry()
+            row.append(col)
+            text = nodes.literal(text=payload)
+            col.append(text)
+
+            col = nodes.entry()
+            row.append(col)
+            ref = nodes.reference(refuri=self.LINK_PREFIX +
+                                  self.SAMPLE_ROOT + sample)
+            txt = nodes.inline()
+            col.append(txt)
+            txt.append(ref)
+            ref.append(nodes.literal(text=sample))
+
+        return content
+
+
+def setup(app):
+    app.add_directive('versioned_notifications',
+                      VersionedNotificationDirective)

doc/source/conf.py

@@ -35,6 +35,7 @@
               'oslosphinx',
               "ext.support_matrix",
               'oslo_config.sphinxconfiggen',
+              'ext.versioned_notifications'
               ]
 
 config_generator_config_file = '../../etc/nova/nova-config-generator.conf'

doc/source/notifications.rst

@@ -98,6 +98,10 @@ notification payload:
 * a major version bump indicates a backward incompatible change of the payload
   which can mean removed fields, type change, etc in the payload.
 
+There is a Nova configuration parameter `notification_format` that can be used
+to specify which notifications are emitted by Nova. The possible values are
+`unversioned`, `versioned`, `both` and the default value is `both`.
+
 How to add a new versioned notification
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -115,6 +119,7 @@ in [3]_.
 The following code example defines the necessary model classes for a new
 notification `myobject.update`::
 
+    @notification.notification_sample('myobject-update.json')
     @base.NovaObjectRegistry.register
     class MyObjectNotification(notification.NotificationBase):
         # Version 1.0: Initial version
@@ -172,6 +177,7 @@ between the fields of existing objects and the fields of the new payload
 object. For example the service.status notification reuses the existing
 `nova.objects.service.Service` object when defines the notification's payload::
 
+    @notification.notification_sample('service-update.json')
     @base.NovaObjectRegistry.register
     class ServiceStatusNotification(notification.NotificationBase):
         # Version 1.0: Initial version
@@ -181,7 +187,6 @@ object. For example the service.status notification reuses the existing
             'payload': fields.ObjectField('ServiceStatusPayload')
         }
 
-
     @base.NovaObjectRegistry.register
     class ServiceStatusPayload(notification.NotificationPayloadBase):
         SCHEMA = {
@@ -254,9 +259,18 @@ with a `host` and a `binary` string parameter or it can be generated from a
 `Service` object by calling `NotificationPublisher.from_service_obj` function.
 
 Versioned notifications shall have a sample file stored under
-`doc/sample_notifications` directory. For example the `service.update`
-notification has a sample file stored in
-`doc/sample_notifications/service-update.json`.
+`doc/sample_notifications` directory and the notification object shall be
+decorated with the `notification_sample` decorator. For example the
+`service.update` notification has a sample file stored in
+`doc/sample_notifications/service-update.json` and the
+ServiceUpdateNotification class is decorated accordingly.
+
+Existing versioned notifications
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. versioned_notifications::
+
+
 
 .. [1] http://docs.openstack.org/developer/oslo.messaging/notifier.html
 .. [2] http://docs.openstack.org/developer/oslo.versionedobjects

nova/objects/notification.py

@@ -134,3 +134,17 @@ def emit(self, context):
                                 (self.publisher.binary,
                                  self.publisher.host),
                    payload=self.payload.obj_to_primitive())
+
+
+def notification_sample(sample):
+    """Class decorator to attach the notification sample information
+    to the notification object for documentation generation purposes.
+
+    :param sample: the path of the sample json file relative to the
+                   doc/notification_samples/ directory in the nova repository
+                   root.
+    """
+    def wrap(cls):
+        cls.sample = sample
+        return cls
+    return wrap

nova/objects/service.py

@@ -393,6 +393,7 @@ def get_all(cls, context, disabled=None, set_zones=False):
                                   db_services)
 
 
+@notification.notification_sample('service-update.json')
 @base.NovaObjectRegistry.register
 class ServiceStatusNotification(notification.NotificationBase):
     # Version 1.0: Initial version

releasenotes/notes/service-status-notification-e137297f5d5aa45d.yaml

@@ -4,4 +4,6 @@ features:
     When the status of the Service object is changed nova will
     send a new service.update notification with versioned payload
     according to bp versioned-notification-api.
+    The new notification is documented in
+    http://docs.openstack.org/developer/nova/notifications.html
 

releasenotes/notes/versioned-notifications-423f4d8d2a3992c6.yaml

@@ -5,3 +5,5 @@ features:
     which notification format shall be used by nova. The possible values
     are 'unversioned' (e.g. legacy), 'versioned', 'both'. The default
     value is 'both'.
+    The new versioned notifications are documented in
+    http://docs.openstack.org/developer/nova/notifications.html