pluggable notification agent

event, meter (and any other custom pipeline) can be enabled/disabled
by setting `pipelines` option under [notification] agent

Change-Id: Ia21256d0308457d077836e27b45d2acb8bb697e4
Closes-Bug: #1720021

ceilometer/notification.py

@@ -24,9 +24,10 @@ from futurist import periodics
 from oslo_config import cfg
 from oslo_log import log
 import oslo_messaging
-from stevedore import extension
+from stevedore import named
 from tooz import coordination
 
+from ceilometer.i18n import _
 from ceilometer import messaging
 from ceilometer import utils
 
@@ -75,7 +76,11 @@ OPTS = [
                deprecated_group='DEFAULT',
                deprecated_name='notification_workers',
                help='Number of workers for notification service, '
-               'default value is 1.')
+               'default value is 1.'),
+    cfg.MultiStrOpt('pipelines',
+                    default=['meter', 'event'],
+                    help="Select which pipeline managers to enable to "
+                    " generate data"),
 ]
 
 
@@ -139,6 +144,9 @@ class NotificationService(cotyledon.Service):
                 for exchange in
                 set(self.conf.notification.notification_control_exchanges)]
 
+    def _log_missing_pipeline(self, names):
+        LOG.error(_('Could not load the following pipelines: %s'), names)
+
     def run(self):
         # Delay startup so workers are jittered
         time.sleep(self.startup_delay)
@@ -146,8 +154,10 @@ class NotificationService(cotyledon.Service):
         super(NotificationService, self).run()
         self.coord_lock = threading.Lock()
 
-        self.managers = [ext.obj for ext in extension.ExtensionManager(
-            namespace='ceilometer.notification.pipeline', invoke_on_load=True,
+        self.managers = [ext.obj for ext in named.NamedExtensionManager(
+            namespace='ceilometer.notification.pipeline',
+            names=self.conf.notification.pipelines, invoke_on_load=True,
+            on_missing_entrypoints_callback=self._log_missing_pipeline,
             invoke_args=(self.conf,
                          self.conf.notification.workload_partitioning))]
 

ceilometer/tests/unit/test_notification.py

@@ -121,6 +121,23 @@ class TestNotification(BaseNotificationTest):
         self.assertEqual(1, len(mock_listener.call_args_list[0][0][1]))
         self.assertEqual(1, len(self.srv.listeners))
 
+    def test_select_pipelines(self):
+        self.CONF.set_override('pipelines', ['event'], group='notification')
+        self.srv.run()
+        self.addCleanup(self.srv.terminate)
+        self.assertEqual(1, len(self.srv.managers))
+        self.assertEqual(1, len(self.srv.listeners[0].dispatcher.endpoints))
+
+    @mock.patch('ceilometer.notification.LOG')
+    def test_select_pipelines_missing(self, logger):
+        self.CONF.set_override('pipelines', ['meter', 'event', 'bad'],
+                               group='notification')
+        self.srv.run()
+        self.addCleanup(self.srv.terminate)
+        self.assertEqual(2, len(self.srv.managers))
+        logger.error.assert_called_with(
+            'Could not load the following pipelines: %s', set(['bad']))
+
 
 class BaseRealNotification(BaseNotificationTest):
     def setup_pipeline(self, counter_names):

doc/source/admin/telemetry-data-collection.rst

@@ -39,6 +39,10 @@ The notification agent is responsible for consuming notifications. This
 component is responsible for consuming from the message bus and transforming
 notifications into events and measurement samples.
 
+By default, the notification agent is configured to build both events and
+samples. To enable selective data models, set the required pipelines using
+`pipelines` option under the `[notification]` section.
+
 Additionally, the notification agent is responsible for all data processing
 such as transformations and publishing. After processing, the data is sent
 to any supported publisher target such as gnocchi or panko. These services

releasenotes/notes/selective-pipeline-notification-47e8a390b1c7dcc4.yaml

@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    The notification-agent can now be configured to either build meters or
+    events. By default, the notification agent will continue to load both
+    pipelines and build both data models. To selectively enable a pipeline,
+    configure the `pipelines` option under the `[notification]` section.
+
+    Addition pipelines can be created following the format used by existing
+    pipelines.