Add __repr__ method for sample.Sample

sample.Sample has no string format method, which will cause useless
message when print log.

Change-Id: I8b9863a4ac6ee3373e18d36681fbfc4c89732111
Closes-Bug: #1386187

ceilometer/sample.py

@@ -73,6 +73,10 @@ class Sample(object):
     def as_dict(self):
         return copy.copy(self.__dict__)
 
+    def __repr__(self):
+        return '<name: %s, volume: %s, resource_id: %s, timestamp: %s>' % (
+            self.name, self.volume, self.resource_id, self.timestamp)
+
     @classmethod
     def from_notification(cls, name, type, volume, unit,
                           user_id, project_id, resource_id,

ceilometer/tests/test_sample.py

@@ -0,0 +1,38 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+"""Tests for ceilometer/sample.py"""
+
+import datetime
+
+from ceilometer import sample
+from ceilometer.tests import base
+
+
+class TestSample(base.BaseTestCase):
+    SAMPLE = sample.Sample(
+        name='cpu',
+        type=sample.TYPE_CUMULATIVE,
+        unit='ns',
+        volume='1234567',
+        user_id='56c5692032f34041900342503fecab30',
+        project_id='ac9494df2d9d4e709bac378cceabaf23',
+        resource_id='1ca738a1-c49c-4401-8346-5c60ebdb03f4',
+        timestamp=datetime.datetime(2014, 10, 29, 14, 12, 15, 485877),
+        resource_metadata={}
+    )
+
+    def test_sample_string_format(self):
+        expected = ('<name: cpu, volume: 1234567, '
+                    'resource_id: 1ca738a1-c49c-4401-8346-5c60ebdb03f4, '
+                    'timestamp: 2014-10-29 14:12:15.485877>')
+        self.assertEqual(expected, str(self.SAMPLE))