collector: use an intermediate proxy class for event dispatcher

This makes sure that the base class EventDispatcherBase does not owns
any code itself. This makes external plugin easier to implement as they
don't _have_ to inherit from EventDispatcherBase, they just need to
implement a `record_events(events)' method and that's it.

This will allow Panko to provide the database dispatcher without having
a hard dependency on Ceilometer.

Change-Id: I094aed1e7e081fe1de130d987035a6c9d977d25e

ceilometer/collector.py

@@ -24,7 +24,7 @@ from oslo_utils import netutils
 from oslo_utils import units
 
 from ceilometer import dispatcher
-from ceilometer.i18n import _, _LE
+from ceilometer.i18n import _, _LE, _LW
 from ceilometer import messaging
 from ceilometer import service_base
 from ceilometer import utils
@@ -94,7 +94,8 @@ class CollectorService(service_base.ServiceBase):
                 self.event_listener = (
                     messaging.get_batch_notification_listener(
                         transport, [event_target],
-                        [EventEndpoint(self.event_manager)],
+                        [EventEndpoint(
+                            EventDispatcherVerificator(self.event_manager))],
                         allow_requeue=True,
                         batch_size=cfg.CONF.collector.batch_size,
                         batch_timeout=cfg.CONF.collector.batch_timeout))
@@ -161,6 +162,23 @@ class SampleEndpoint(CollectorEndpoint):
     ep_type = 'sample'
 
 
+class EventDispatcherVerificator(object):
+    def __init__(self, dispatcher):
+        self.dispatcher = dispatcher
+
+    def verify_and_record_events(self, events):
+        """Verify event signature and record them."""
+        goods = []
+        for event in events:
+            if utils.verify_signature(
+                    event, self.conf.publisher.telemetry_secret):
+                goods.append(event)
+            else:
+                LOG.warning(_LW(
+                    'event signature invalid, discarding event: %s'), event)
+        return self.dispatcher.record_events(goods)
+
+
 class EventEndpoint(CollectorEndpoint):
     method = 'verify_and_record_events'
     ep_type = 'event'

ceilometer/dispatcher/__init__.py

@@ -21,7 +21,6 @@ import six
 from stevedore import named
 
 from ceilometer.i18n import _LW
-from ceilometer.publisher import utils
 
 
 LOG = log.getLogger(__name__)
@@ -108,15 +107,3 @@ class EventDispatcherBase(Base):
     @abc.abstractmethod
     def record_events(self, events):
         """Record events."""
-
-    def verify_and_record_events(self, events):
-        """Verify event signature and record them."""
-        goods = []
-        for event in events:
-            if utils.verify_signature(
-                    event, self.conf.publisher.telemetry_secret):
-                goods.append(event)
-            else:
-                LOG.warning(_LW(
-                    'event signature invalid, discarding event: %s'), event)
-        return self.record_events(goods)

ceilometer/tests/unit/dispatcher/test_db.py

@@ -44,28 +44,6 @@ class TestDispatcherDB(base.BaseTestCase):
             self.dispatcher.record_events(event)
         self.assertEqual(1, len(record_events.call_args_list[0][0][0]))
 
-    @mock.patch('ceilometer.publisher.utils.verify_signature')
-    def test_event_with_bad_signature(self, mocked_verify):
-        event = event_models.Event(uuid.uuid4(), 'test',
-                                   datetime.datetime(2012, 7, 2, 13, 53, 40),
-                                   [], {}).serialize()
-
-        def _fake_verify(ev, secret):
-            if ev.get('message_signature') == 'bad_signature':
-                return False
-            return True
-        mocked_verify.side_effect = _fake_verify
-        with mock.patch.object(self.dispatcher.event_conn,
-                               'record_events') as record_events:
-            event['message_signature'] = 'bad_signature'
-            self.dispatcher.verify_and_record_events([event])
-            self.assertEqual([], record_events.call_args_list[0][0][0])
-            del event['message_signature']
-            event['message_signature'] = utils.compute_signature(
-                event, self.CONF.publisher.telemetry_secret)
-            self.dispatcher.verify_and_record_events([event])
-            self.assertEqual(1, len(record_events.call_args_list[1][0][0]))
-
     def test_valid_message(self):
         msg = {'counter_name': 'test',
                'resource_id': self.id(),