diff --git a/ceilometer/notification.py b/ceilometer/notification.py
index 1207bd58b6..7383907e8a 100644
--- a/ceilometer/notification.py
+++ b/ceilometer/notification.py
@@ -73,10 +73,12 @@ OPTS = [
                          "notifications go to rabbit-nova:5672, while all "
                          "cinder notifications go to rabbit-cinder:5672."),
     cfg.IntOpt('batch_size',
-               default=1,
+               default=100, min=1,
                help='Number of notification messages to wait before '
-               'publishing them'),
+               'publishing them. Batching is advised when transformations are'
+               'applied in pipeline.'),
     cfg.IntOpt('batch_timeout',
+               default=5,
                help='Number of seconds to wait before publishing samples'
                'when batch_size is not reached (None means indefinitely)'),
 ]
@@ -258,10 +260,10 @@ class NotificationService(service_base.PipelineBasedService):
         urls = cfg.CONF.notification.messaging_urls or [None]
         for url in urls:
             transport = messaging.get_transport(url)
+            # NOTE(gordc): ignore batching as we want pull
+            # to maintain sequencing as much as possible.
             listener = messaging.get_batch_notification_listener(
-                transport, targets, endpoints,
-                batch_size=cfg.CONF.notification.batch_size,
-                batch_timeout=cfg.CONF.notification.batch_timeout)
+                transport, targets, endpoints)
             listener.start()
             self.listeners.append(listener)
 
@@ -309,7 +311,10 @@ class NotificationService(service_base.PipelineBasedService):
             endpoints,
             batch_size=cfg.CONF.notification.batch_size,
             batch_timeout=cfg.CONF.notification.batch_timeout)
-        self.pipeline_listener.start()
+        # NOTE(gordc): set single thread to process data sequentially
+        # if batching enabled.
+        batch = (1 if cfg.CONF.notification.batch_size > 1 else None)
+        self.pipeline_listener.start(override_pool_size=batch)
 
     def terminate(self):
         self.shutdown = True
diff --git a/ceilometer/pipeline.py b/ceilometer/pipeline.py
index e174608ab7..5067c4656c 100644
--- a/ceilometer/pipeline.py
+++ b/ceilometer/pipeline.py
@@ -17,6 +17,7 @@
 import abc
 import hashlib
 from itertools import chain
+from operator import methodcaller
 import os
 
 from oslo_config import cfg
@@ -105,7 +106,7 @@ class SamplePipelineEndpoint(PipelineEndpoint):
                 s, cfg.CONF.publisher.telemetry_secret)
         ]
         with self.publish_context as p:
-            p(samples)
+            p(sorted(samples, key=methodcaller('get_iso_timestamp')))
 
 
 class EventPipelineEndpoint(PipelineEndpoint):
diff --git a/ceilometer/sample.py b/ceilometer/sample.py
index 933bc94880..0f8e54e37f 100644
--- a/ceilometer/sample.py
+++ b/ceilometer/sample.py
@@ -24,7 +24,7 @@ import copy
 import uuid
 
 from oslo_config import cfg
-
+from oslo_utils import timeutils
 
 OPTS = [
     cfg.StrOpt('sample_source',
@@ -99,6 +99,10 @@ class Sample(object):
     def set_timestamp(self, timestamp):
         self.timestamp = timestamp
 
+    def get_iso_timestamp(self):
+        return timeutils.parse_isotime(self.timestamp)
+
+
 TYPE_GAUGE = 'gauge'
 TYPE_DELTA = 'delta'
 TYPE_CUMULATIVE = 'cumulative'
diff --git a/ceilometer/tests/functional/test_notification.py b/ceilometer/tests/functional/test_notification.py
index 02452d1a90..8b482ba625 100644
--- a/ceilometer/tests/functional/test_notification.py
+++ b/ceilometer/tests/functional/test_notification.py
@@ -379,6 +379,16 @@ class TestRealNotificationHA(BaseRealNotification):
         fake_publisher_cls.return_value = self.publisher
         self._check_notification_service()
 
+    @mock.patch.object(oslo_messaging.MessageHandlingServer, 'start')
+    def test_notification_threads(self, m_listener):
+        self.CONF.set_override('batch_size', 1, group='notification')
+        self.srv.run()
+        m_listener.assert_called_with(override_pool_size=None)
+        m_listener.reset_mock()
+        self.CONF.set_override('batch_size', 2, group='notification')
+        self.srv.run()
+        m_listener.assert_called_with(override_pool_size=1)
+
     @mock.patch('oslo_messaging.get_batch_notification_listener')
     def test_reset_listener_on_refresh(self, mock_listener):
         mock_listener.side_effect = [
diff --git a/releasenotes/notes/single-thread-pipelines-f9e6ac4b062747fe.yaml b/releasenotes/notes/single-thread-pipelines-f9e6ac4b062747fe.yaml
new file mode 100644
index 0000000000..c041e90101
--- /dev/null
+++ b/releasenotes/notes/single-thread-pipelines-f9e6ac4b062747fe.yaml
@@ -0,0 +1,11 @@
+---
+upgrade:
+  - Batching is enabled by default now when coordinated workers are enabled.
+    Depending on load, it is recommended to scale out the number of
+    `pipeline_processing_queues` to improve distribution. `batch_size` should
+    also be configured accordingly.
+fixes:
+  - Fix to improve handling messages in environments heavily backed up.
+    Previously, notification handlers greedily grabbed messages from queues
+    which could cause ordering issues. A fix was applied to sequentially
+    process messages in a single thread to prevent ordering issues.