Add Sample priority

With the routing notifier we can now issue high-frequency notifications
and not worry about clogging up the queue. The Sample priority will
be used for this situation.

Change-Id: Ia4aa77b7aa4ca9458e97ca3ed81101d92934b691

oslo/messaging/notify/_impl_log.py

@@ -30,4 +30,6 @@ class LogDriver(notifier._Driver):
     def notify(self, ctxt, message, priority):
         logger = logging.getLogger('%s.%s' % (self.LOGGER_BASE,
                                               message['event_type']))
-        getattr(logger, priority.lower())(jsonutils.dumps(message))
+        method = getattr(logger, priority.lower(), None)
+        if method:
+            method(jsonutils.dumps(message))

oslo/messaging/notify/notifier.py

@@ -243,6 +243,24 @@ class Notifier(object):
         """
         self._notify(ctxt, event_type, payload, 'CRITICAL')
 
+    def sample(self, ctxt, event_type, payload):
+        """Send a notification at sample level.
+
+        Sample notifications are for high-frequency events
+        that typically contain small payloads. eg: "CPU = 70%"
+
+        Not all drivers support the sample level
+        (log, for example) so these could be dropped.
+
+        :param ctxt: a request context dict
+        :type ctxt: dict
+        :param event_type: describes the event, e.g. 'compute.create_instance'
+        :type event_type: str
+        :param payload: the notification payload
+        :type payload: dict
+        """
+        self._notify(ctxt, event_type, payload, 'SAMPLE')
+
 
 class _SubNotifier(Notifier):
 

tests/test_notifier.py

@@ -21,6 +21,7 @@ import fixtures
 import testscenarios
 
 from oslo import messaging
+from oslo.messaging.notify import _impl_log
 from oslo.messaging.notify import _impl_messaging
 from oslo.messaging.notify import _impl_test
 from oslo.messaging.notify import notifier as msg_notifier
@@ -104,6 +105,7 @@ class TestMessagingNotifier(test_utils.BaseTestCase):
         ('info', dict(priority='info')),
         ('warn', dict(priority='warn')),
         ('error', dict(priority='error')),
+        ('sample', dict(priority='sample')),
         ('critical', dict(priority='critical')),
     ]
 
@@ -283,3 +285,19 @@ class TestLogNotifier(test_utils.BaseTestCase):
         self.mox.ReplayAll()
 
         notifier.info({}, 'test.notify', 'bar')
+
+    def test_sample_priority(self):
+        # Ensure logger drops sample-level notifications.
+        driver = _impl_log.LogDriver(None, None, None)
+
+        logger = self.mox.CreateMock(
+            logging.getLogger('oslo.messaging.notification.foo'))
+        logger.sample = None
+        self.mox.StubOutWithMock(logging, 'getLogger')
+        logging.getLogger('oslo.messaging.notification.foo').\
+            AndReturn(logger)
+
+        self.mox.ReplayAll()
+
+        msg = {'event_type': 'foo'}
+        driver.notify(None, msg, "sample")