Fix ignored [notification] batch_size

The [notification] batch_size parameter has had no effect since
workload partitioning was removed during Stein cycle[1]. This change
fixes the ignored parameter and ensure the parameter is used to enable
batch processing of notifications.

[1] 9d90ce8d37

Change-Id: Id46679933cf96ecaca864aeae271052386b51815

ceilometer/notification.py

@@ -44,10 +44,13 @@ OPTS = [
                          "notifications go to rabbit-nova:5672, while all "
                          "cinder notifications go to rabbit-cinder:5672."),
     cfg.IntOpt('batch_size',
-               default=100, min=1,
+               default=1, min=1,
                help='Number of notification messages to wait before '
-               'publishing them. Batching is advised when transformations are '
-               'applied in pipeline.'),
+               'publishing them.'),
+    cfg.IntOpt('batch_timeout',
+               help='Number of seconds to wait before dispatching samples '
+                    'when batch_size is not reached (None means indefinitely).'
+               ),
     cfg.IntOpt('workers',
                default=1,
                min=1,
@@ -138,7 +141,9 @@ class NotificationService(cotyledon.Service):
             # NOTE(gordc): ignore batching as we want pull
             # to maintain sequencing as much as possible.
             listener = messaging.get_batch_notification_listener(
-                transport, targets, endpoints, allow_requeue=True)
+                transport, targets, endpoints, allow_requeue=True,
+                batch_size=self.conf.notification.batch_size,
+                batch_timeout=self.conf.notification.batch_timeout)
             listener.start(
                 override_pool_size=self.conf.max_parallel_requests
             )

releasenotes/notes/deprecate-notification-batch_size-b739264a223d279d.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+  - |
+    The ``[notification] batch_size`` parameter has been deprecated.
+    The parameter has not used since the Stein release.

releasenotes/notes/fix-notification-batch-9bb42cbdf817e7f9.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    The ``[notification] batch_size`` parameter now takes effect to enable
+    batch processing of notifications. The ``[notification] batch_timeout``
+    parameter has been restored at the same time to determine how much and
+    how long notifications are kept.