Merge "High precision rate of change timedelta" into stable/ocata8.1.0

16 files changed, 151 insertions, 27 deletions

diff --git a/ceilometer/compute/pollsters/__init__.py b/ceilometer/compute/pollsters/__init__.py
index f3360270..c3ef015b 100644
--- a/ceilometer/compute/pollsters/__init__.py
+++ b/ceilometer/compute/pollsters/__init__.py
@@ -73,7 +73,7 @@ class BaseComputePollster(plugin_base.PollsterBase):
         return duration
 
     def _get_samples_per_devices(self, attribute, instance, _name, _type,
-                                 _unit):
+                                 _unit, monotonic_time=None):
         samples = []
         for disk, value in six.iteritems(attribute):
             samples.append(util.make_sample_from_instance(
@@ -85,5 +85,6 @@ class BaseComputePollster(plugin_base.PollsterBase):
                 volume=value,
                 resource_id="%s-%s" % (instance.id, disk),
                 additional_metadata={'disk_name': disk},
+                monotonic_time=monotonic_time,
             ))
         return samples
diff --git a/ceilometer/compute/pollsters/cpu.py b/ceilometer/compute/pollsters/cpu.py
index b8287d3b..167e194d 100644
--- a/ceilometer/compute/pollsters/cpu.py
+++ b/ceilometer/compute/pollsters/cpu.py
@@ -14,6 +14,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+
+import monotonic
 from oslo_log import log
 
 import ceilometer
@@ -46,6 +48,7 @@ class CPUPollster(pollsters.BaseComputePollster):
                     unit='ns',
                     volume=cpu_info.time,
                     additional_metadata=cpu_num,
+                    monotonic_time=monotonic.monotonic()
                 )
             except virt_inspector.InstanceNotFoundException as err:
                 # Instance was deleted while getting samples. Ignore it.
diff --git a/ceilometer/compute/pollsters/disk.py b/ceilometer/compute/pollsters/disk.py
index 9b35fdc1..82ecf40a 100644
--- a/ceilometer/compute/pollsters/disk.py
+++ b/ceilometer/compute/pollsters/disk.py
@@ -17,6 +17,7 @@
 import abc
 import collections
 
+import monotonic
 from oslo_log import log
 import six
 
@@ -33,7 +34,7 @@ LOG = log.getLogger(__name__)
 
 DiskIOData = collections.namedtuple(
     'DiskIOData',
-    'r_bytes r_requests w_bytes w_requests per_disk_requests',
+    'r_bytes r_requests w_bytes w_requests per_disk_requests polled_time',
 )
 
 DiskRateData = collections.namedtuple('DiskRateData',
@@ -103,12 +104,14 @@ class _Base(pollsters.BaseComputePollster):
                 'write_bytes': per_device_write_bytes,
                 'write_requests': per_device_write_requests,
             }
+            polled_time = monotonic.monotonic()
             i_cache[instance.id] = DiskIOData(
                 r_bytes=r_bytes,
                 r_requests=r_requests,
                 w_bytes=w_bytes,
                 w_requests=w_requests,
                 per_disk_requests=per_device_requests,
+                polled_time=polled_time
             )
         return i_cache[instance.id]
 
@@ -128,13 +131,15 @@ class _Base(pollsters.BaseComputePollster):
             volume=getattr(c_data, _volume),
             additional_metadata={
                 'device': c_data.per_disk_requests[_metadata].keys()},
+            monotonic_time=c_data.polled_time,
         )]
 
     def _get_samples_per_device(self, c_data, _attr, instance, _name, _unit):
         """Return one or more Samples for meter 'disk.device.*'"""
         return self._get_samples_per_devices(c_data.per_disk_requests[_attr],
                                              instance, _name,
-                                             sample.TYPE_CUMULATIVE, _unit)
+                                             sample.TYPE_CUMULATIVE, _unit,
+                                             c_data.polled_time)
 
     def get_samples(self, manager, cache, resources):
         for instance in resources:
diff --git a/ceilometer/compute/pollsters/net.py b/ceilometer/compute/pollsters/net.py
index 933d6577..54ae7f7a 100644
--- a/ceilometer/compute/pollsters/net.py
+++ b/ceilometer/compute/pollsters/net.py
@@ -16,6 +16,7 @@
 
 import copy
 
+import monotonic
 from oslo_log import log
 
 import ceilometer
@@ -34,7 +35,8 @@ class _Base(pollsters.BaseComputePollster):
     NET_USAGE_MESSAGE = ' '.join(["NETWORK USAGE:", "%s %s:", "read-bytes=%d",
                                   "write-bytes=%d"])
 
-    def make_vnic_sample(self, instance, name, type, unit, volume, vnic_data):
+    def make_vnic_sample(self, instance, name, type, unit, volume, vnic_data,
+                         monotonic_time):
         metadata = copy.copy(vnic_data)
         additional_metadata = dict(zip(metadata._fields, metadata))
         if vnic_data.fref is not None:
@@ -53,7 +55,8 @@ class _Base(pollsters.BaseComputePollster):
             unit=unit,
             volume=volume,
             resource_id=rid,
-            additional_metadata=additional_metadata
+            additional_metadata=additional_metadata,
+            monotonic_time=monotonic_time,
         )
 
     CACHE_KEY_VNIC = 'vnics'
@@ -72,9 +75,10 @@ class _Base(pollsters.BaseComputePollster):
     def _get_vnics_for_instance(self, cache, inspector, instance):
         i_cache = cache.setdefault(self.CACHE_KEY_VNIC, {})
         if instance.id not in i_cache:
-            i_cache[instance.id] = list(
-                self._get_vnic_info(inspector, instance)
-            )
+            data = list(self._get_vnic_info(inspector, instance))
+            polled_time = monotonic.monotonic()
+            i_cache[instance.id] = [(vnic, info, polled_time)
+                                    for vnic, info in data]
         return i_cache[instance.id]
 
     def get_samples(self, manager, cache, resources):
@@ -88,11 +92,11 @@ class _Base(pollsters.BaseComputePollster):
                     self.inspector,
                     instance,
                 )
-                for vnic, info in vnics:
+                for vnic, info, polled_time in vnics:
                     LOG.debug(self.NET_USAGE_MESSAGE, instance_name,
                               vnic.name, self._get_rx_info(info),
                               self._get_tx_info(info))
-                    yield self._get_sample(instance, vnic, info)
+                    yield self._get_sample(instance, vnic, info, polled_time)
             except virt_inspector.InstanceNotFoundException as err:
                 # Instance was deleted while getting samples. Ignore it.
                 LOG.debug('Exception while getting samples %s', err)
@@ -179,7 +183,7 @@ class _ErrorsBase(_Base):
 
 class IncomingBytesPollster(_Base):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.incoming.bytes',
@@ -187,12 +191,13 @@ class IncomingBytesPollster(_Base):
             unit='B',
             volume=info.rx_bytes,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
 
 
 class IncomingPacketsPollster(_PacketsBase):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.incoming.packets',
@@ -200,12 +205,13 @@ class IncomingPacketsPollster(_PacketsBase):
             unit='packet',
             volume=info.rx_packets,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
 
 
 class OutgoingBytesPollster(_Base):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.outgoing.bytes',
@@ -213,12 +219,13 @@ class OutgoingBytesPollster(_Base):
             unit='B',
             volume=info.tx_bytes,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
 
 
 class OutgoingPacketsPollster(_PacketsBase):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.outgoing.packets',
@@ -226,12 +233,13 @@ class OutgoingPacketsPollster(_PacketsBase):
             unit='packet',
             volume=info.tx_packets,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
 
 
 class IncomingBytesRatePollster(_RateBase):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.incoming.bytes.rate',
@@ -239,12 +247,13 @@ class IncomingBytesRatePollster(_RateBase):
             unit='B/s',
             volume=info.rx_bytes_rate,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
 
 
 class OutgoingBytesRatePollster(_RateBase):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.outgoing.bytes.rate',
@@ -252,12 +261,13 @@ class OutgoingBytesRatePollster(_RateBase):
             unit='B/s',
             volume=info.tx_bytes_rate,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
 
 
 class IncomingDropPollster(_DropBase):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.incoming.packets.drop',
@@ -265,12 +275,13 @@ class IncomingDropPollster(_DropBase):
             unit='packet',
             volume=info.rx_drop,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
 
 
 class OutgoingDropPollster(_DropBase):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.outgoing.packets.drop',
@@ -278,12 +289,13 @@ class OutgoingDropPollster(_DropBase):
             unit='packet',
             volume=info.tx_drop,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
 
 
 class IncomingErrorsPollster(_ErrorsBase):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.incoming.packets.error',
@@ -291,12 +303,13 @@ class IncomingErrorsPollster(_ErrorsBase):
             unit='packet',
             volume=info.rx_errors,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
 
 
 class OutgoingErrorsPollster(_ErrorsBase):
 
-    def _get_sample(self, instance, vnic, info):
+    def _get_sample(self, instance, vnic, info, polled_time):
         return self.make_vnic_sample(
             instance,
             name='network.outgoing.packets.error',
@@ -304,4 +317,5 @@ class OutgoingErrorsPollster(_ErrorsBase):
             unit='packet',
             volume=info.tx_errors,
             vnic_data=vnic,
+            monotonic_time=polled_time,
         )
diff --git a/ceilometer/compute/pollsters/util.py b/ceilometer/compute/pollsters/util.py
index 11f39ffe..a0ac83b7 100644
--- a/ceilometer/compute/pollsters/util.py
+++ b/ceilometer/compute/pollsters/util.py
@@ -76,7 +76,8 @@ def _get_metadata_from_object(conf, instance):
 
 
 def make_sample_from_instance(conf, instance, name, type, unit, volume,
-                              resource_id=None, additional_metadata=None):
+                              resource_id=None, additional_metadata=None,
+                              monotonic_time=None):
     additional_metadata = additional_metadata or {}
     resource_metadata = _get_metadata_from_object(conf, instance)
     resource_metadata.update(additional_metadata)
@@ -89,6 +90,7 @@ def make_sample_from_instance(conf, instance, name, type, unit, volume,
         project_id=instance.tenant_id,
         resource_id=resource_id or instance.id,
         resource_metadata=resource_metadata,
+        monotonic_time=monotonic_time,
     )
 
 
diff --git a/ceilometer/pipeline.py b/ceilometer/pipeline.py
index d39afc82..8db7bc09 100644
--- a/ceilometer/pipeline.py
+++ b/ceilometer/pipeline.py
@@ -110,7 +110,10 @@ class SamplePipelineEndpoint(PipelineEndpoint):
                                resource_id=s['resource_id'],
                                timestamp=s['timestamp'],
                                resource_metadata=s['resource_metadata'],
-                               source=s.get('source'))
+                               source=s.get('source'),
+                               # NOTE(sileht): May come from an older node,
+                               # Put None in this case.
+                               monotonic_time=s.get('monotonic_time'))
             for s in samples if publisher_utils.verify_signature(
                 s, self.conf.publisher.telemetry_secret)
         ]
diff --git a/ceilometer/publisher/utils.py b/ceilometer/publisher/utils.py
index 6db55a4f..b49f0220 100644
--- a/ceilometer/publisher/utils.py
+++ b/ceilometer/publisher/utils.py
@@ -98,6 +98,7 @@ def meter_message_from_counter(sample, secret):
            'timestamp': sample.timestamp,
            'resource_metadata': sample.resource_metadata,
            'message_id': sample.id,
+           'monotonic_time': sample.monotonic_time,
            }
     msg['message_signature'] = compute_signature(msg, secret)
     return msg
diff --git a/ceilometer/sample.py b/ceilometer/sample.py
index d5318822..ed780127 100644
--- a/ceilometer/sample.py
+++ b/ceilometer/sample.py
@@ -95,7 +95,7 @@ class Sample(object):
 
     def __init__(self, name, type, unit, volume, user_id, project_id,
                  resource_id, timestamp=None, resource_metadata=None,
-                 source=None, id=None):
+                 source=None, id=None, monotonic_time=None):
         self.name = name
         self.type = type
         self.unit = unit
@@ -107,6 +107,7 @@ class Sample(object):
         self.resource_metadata = resource_metadata or {}
         self.source = source or self.SOURCE_DEFAULT
         self.id = id or str(uuid.uuid1())
+        self.monotonic_time = monotonic_time
 
     def as_dict(self):
         return copy.copy(self.__dict__)
diff --git a/ceilometer/storage/impl_hbase.py b/ceilometer/storage/impl_hbase.py
index 494db884..aafaff6c 100644
--- a/ceilometer/storage/impl_hbase.py
+++ b/ceilometer/storage/impl_hbase.py
@@ -143,6 +143,10 @@ class Connection(hbase_base.Connection, base.Connection):
         :param data: a dictionary such as returned by
           ceilometer.publisher.utils.meter_message_from_counter
         """
+
+        # We must not record thing.
+        data.pop("monotonic_time", None)
+
         with self.conn_pool.connection() as conn:
             resource_table = conn.table(self.RESOURCE_TABLE)
             meter_table = conn.table(self.METER_TABLE)
diff --git a/ceilometer/storage/impl_mongodb.py b/ceilometer/storage/impl_mongodb.py
index 82ed679c..afe2e527 100644
--- a/ceilometer/storage/impl_mongodb.py
+++ b/ceilometer/storage/impl_mongodb.py
@@ -259,6 +259,13 @@ class Connection(pymongo_base.Connection):
         # unconditionally insert sample timestamps and resource metadata
         # (in the update case, this must be conditional on the sample not
         # being out-of-order)
+
+        # We must not store this
+        samples = copy.deepcopy(samples)
+
+        for sample in samples:
+            sample.pop("monotonic_time", None)
+
         sorted_samples = sorted(
             copy.deepcopy(samples),
             key=lambda s: (s['resource_id'], s['timestamp']))
diff --git a/ceilometer/tests/functional/api/v2/test_post_samples_scenarios.py b/ceilometer/tests/functional/api/v2/test_post_samples_scenarios.py
index 033f2925..ca787ded 100644
--- a/ceilometer/tests/functional/api/v2/test_post_samples_scenarios.py
+++ b/ceilometer/tests/functional/api/v2/test_post_samples_scenarios.py
@@ -80,6 +80,7 @@ class TestPostSamples(v2.FunctionalTest):
         s1[0]['source'] = '%s:openstack' % s1[0]['project_id']
 
         self.assertEqual(s1, data.json)
+        s1[0]["monotonic_time"] = None
         self.assertEqual(s1[0], self.published[0][0])
 
     def test_nested_metadata(self):
@@ -107,6 +108,7 @@ class TestPostSamples(v2.FunctionalTest):
         unwound['resource_metadata'] = {'nest': {'name1': 'value1',
                                                  'name2': 'value3'},
                                         'name2': 'value2'}
+        unwound["monotonic_time"] = None
         # only the published sample should be unwound, not the representation
         # in the API response
         self.assertEqual(s1[0], data.json[0])
@@ -218,6 +220,7 @@ class TestPostSamples(v2.FunctionalTest):
             msg['timestamp'] = timestamp.replace(tzinfo=None).isoformat()
 
             self.assertEqual(s, c)
+            s["monotonic_time"] = None
             self.assertEqual(s, self.published[0][x])
 
     def test_missing_mandatory_fields(self):
@@ -278,6 +281,7 @@ class TestPostSamples(v2.FunctionalTest):
             s['timestamp'] = data.json[x]['timestamp']
             s.setdefault('resource_metadata', dict())
             self.assertEqual(s, data.json[x])
+            s['monotonic_time'] = None
             self.assertEqual(s, self.published[0][x])
 
     def test_multiple_samples_multiple_sources(self):
@@ -328,6 +332,7 @@ class TestPostSamples(v2.FunctionalTest):
             s['timestamp'] = data.json[x]['timestamp']
             s.setdefault('resource_metadata', dict())
             self.assertEqual(s, data.json[x])
+            s['monotonic_time'] = None
             self.assertEqual(s, self.published[0][x])
 
     def test_missing_project_user_id(self):
@@ -364,4 +369,6 @@ class TestPostSamples(v2.FunctionalTest):
             s['project_id'] = project_id
 
             self.assertEqual(s, data.json[x])
+
+            s['monotonic_time'] = None
             self.assertEqual(s, self.published[0][x])
diff --git a/ceilometer/tests/functional/storage/test_storage_scenarios.py b/ceilometer/tests/functional/storage/test_storage_scenarios.py
index 1273cc9c..a8e0492d 100644
--- a/ceilometer/tests/functional/storage/test_storage_scenarios.py
+++ b/ceilometer/tests/functional/storage/test_storage_scenarios.py
@@ -430,6 +430,7 @@ class RawSampleTest(DBTestBase):
             d = meter.as_dict()
             self.assertTimestampEqual(timeutils.utcnow(), d['recorded_at'])
             del d['recorded_at']
+            d['monotonic_time'] = None
             self.assertIn(d, self.msgs[:3])
 
     def test_get_samples_by_user_limit(self):
@@ -450,6 +451,7 @@ class RawSampleTest(DBTestBase):
             d = meter.as_dict()
             self.assertTimestampEqual(timeutils.utcnow(), d['recorded_at'])
             del d['recorded_at']
+            d['monotonic_time'] = None
             self.assertIn(d, self.msgs[:4])
 
     def test_get_samples_by_resource(self):
@@ -459,6 +461,7 @@ class RawSampleTest(DBTestBase):
         d = results[1].as_dict()
         self.assertEqual(timeutils.utcnow(), d['recorded_at'])
         del d['recorded_at']
+        d['monotonic_time'] = None
         self.assertEqual(self.msgs[0], d)
 
     def test_get_samples_by_metaquery(self):
@@ -470,6 +473,7 @@ class RawSampleTest(DBTestBase):
             d = meter.as_dict()
             self.assertTimestampEqual(timeutils.utcnow(), d['recorded_at'])
             del d['recorded_at']
+            d['monotonic_time'] = None
             self.assertIn(d, self.msgs)
 
     def test_get_samples_by_metaquery_key_with_dot_in_metadata(self):
@@ -721,6 +725,7 @@ class ComplexSampleQueryTest(DBTestBase):
         for sample_item in results:
             d = sample_item.as_dict()
             del d['recorded_at']
+            d['monotonic_time'] = None
             self.assertIn(d, self.msgs)
 
     def test_query_complex_filter_with_regexp(self):
@@ -2785,6 +2790,7 @@ class TestBatchRecordingMetering(tests_db.TestBase):
         for sample_item in results:
             d = sample_item.as_dict()
             del d['recorded_at']
+            d['monotonic_time'] = None
             self.assertIn(d, self.sample_dicts)
 
         resources = list(self.conn.get_resources())
diff --git a/ceilometer/tests/unit/compute/pollsters/test_net.py b/ceilometer/tests/unit/compute/pollsters/test_net.py
index 047307f2..cdf5fed1 100644
--- a/ceilometer/tests/unit/compute/pollsters/test_net.py
+++ b/ceilometer/tests/unit/compute/pollsters/test_net.py
@@ -234,7 +234,8 @@ class TestNetPollster(base.TestPollsterBase):
                                        type=sample.TYPE_CUMULATIVE,
                                        unit='B',
                                        volume=100,
-                                       vnic_data=self.vnic0)
+                                       vnic_data=self.vnic0,
+                                       monotonic_time=123.123)
 
         user_metadata = sm.resource_metadata['user_metadata']
         expected = self.INSTANCE_PROPERTIES[
@@ -259,7 +260,7 @@ class TestNetPollsterCache(base.TestPollsterBase):
                                                rx_drop=20, rx_errors=21,
                                                tx_bytes=3, tx_packets=4,
                                                tx_drop=22, tx_errors=23)
-        vnics = [(vnic0, stats0)]
+        vnics = [(vnic0, stats0, 123.123)]
 
         mgr = manager.AgentManager(0, self.CONF)
         pollster = factory(self.CONF)
diff --git a/ceilometer/tests/unit/pipeline_base.py b/ceilometer/tests/unit/pipeline_base.py
index 67a6f032..979e594d 100644
--- a/ceilometer/tests/unit/pipeline_base.py
+++ b/ceilometer/tests/unit/pipeline_base.py
@@ -21,6 +21,7 @@ import traceback
 import unittest
 
 import mock
+import monotonic
 from oslo_config import fixture as fixture_config
 from oslo_utils import timeutils
 from oslotest import mockpatch
@@ -1097,6 +1098,67 @@ class BasePipelineTestCase(base.BaseTestCase):
         pipe.flush()
         self.assertEqual(0, len(publisher.samples))
 
+    def test_rate_of_change_precision(self):
+        s = "100.0 / (10**9 * (resource_metadata.cpu_number or 1))"
+        transformer_cfg = [
+            {
+                'name': 'rate_of_change',
+                'parameters': {
+                    'source': {},
+                    'target': {'name': 'cpu_util',
+                               'unit': '%',
+                               'type': sample.TYPE_GAUGE,
+                               'scale': s}
+                }
+            },
+        ]
+        self._set_pipeline_cfg('transformers', transformer_cfg)
+        self._set_pipeline_cfg('meters', ['cpu'])
+        pipeline_manager = pipeline.PipelineManager(
+            self.CONF,
+            self.cfg2file(self.pipeline_cfg), self.transformer_manager)
+        pipe = pipeline_manager.pipelines[0]
+
+        now = timeutils.utcnow()
+        now_time = monotonic.monotonic()
+        # Simulate a laggy poller
+        later = now + datetime.timedelta(seconds=12345)
+        later_time = now_time + 10
+
+        counters = [
+            sample.Sample(
+                name='cpu',
+                type=sample.TYPE_CUMULATIVE,
+                volume=125000000000,
+                unit='ns',
+                user_id='test_user',
+                project_id='test_proj',
+                resource_id='test_resource',
+                timestamp=now.isoformat(),
+                monotonic_time=now_time,
+                resource_metadata={'cpu_number': 4}
+            ),
+            sample.Sample(
+                name='cpu',
+                type=sample.TYPE_CUMULATIVE,
+                volume=165000000000,
+                unit='ns',
+                user_id='test_user',
+                project_id='test_proj',
+                resource_id='test_resource',
+                timestamp=later.isoformat(),
+                monotonic_time=later_time,
+                resource_metadata={'cpu_number': 4}
+            ),
+        ]
+
+        pipe.publish_data(counters)
+        publisher = pipe.publishers[0]
+        self.assertEqual(1, len(publisher.samples))
+
+        cpu_util_sample = publisher.samples[0]
+        self.assertEqual(100, cpu_util_sample.volume)
+
     def test_rate_of_change_max(self):
         s = "100.0 / (10**9 * (resource_metadata.cpu_number or 1))"
         transformer_cfg = [
diff --git a/ceilometer/transformer/conversions.py b/ceilometer/transformer/conversions.py
index 3690bacc..44ac8607 100644
--- a/ceilometer/transformer/conversions.py
+++ b/ceilometer/transformer/conversions.py
@@ -187,12 +187,18 @@ class RateOfChangeTransformer(ScalingTransformer):
         key = s.name + s.resource_id
         prev = self.cache.get(key)
         timestamp = timeutils.parse_isotime(s.timestamp)
-        self.cache[key] = (s.volume, timestamp)
+        self.cache[key] = (s.volume, timestamp, s.monotonic_time)
 
         if prev:
             prev_volume = prev[0]
             prev_timestamp = prev[1]
-            time_delta = timeutils.delta_seconds(prev_timestamp, timestamp)
+            prev_monotonic_time = prev[2]
+            if (prev_monotonic_time is not None and
+                    s.monotonic_time is not None):
+                # NOTE(sileht): Prefer high precision timer
+                time_delta = s.monotonic_time - prev_monotonic_time
+            else:
+                time_delta = timeutils.delta_seconds(prev_timestamp, timestamp)
             # disallow violations of the arrow of time
             if time_delta < 0:
                 LOG.warning(_('dropping out of time order sample: %s'), (s,))
diff --git a/requirements.txt b/requirements.txt
index 21c8c636..fad0c0ee 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -13,6 +13,7 @@ jsonschema!=2.5.0,<3.0.0,>=2.0.0 # MIT
 kafka-python>=1.3.1 # Apache-2.0
 keystonemiddleware!=4.1.0,>=4.0.0 # Apache-2.0
 lxml>=2.3 # BSD
+monotonic
 msgpack-python>=0.4.0 # Apache-2.0
 oslo.concurrency>=3.5.0 # Apache-2.0
 oslo.config>=3.9.0 # Apache-2.0