diff --git a/ceilometer/tests/pipeline_base.py b/ceilometer/tests/pipeline_base.py
index 4ff335ab..adcc9695 100644
--- a/ceilometer/tests/pipeline_base.py
+++ b/ceilometer/tests/pipeline_base.py
@@ -1742,12 +1742,11 @@ class BasePipelineTestCase(base.BaseTestCase):
         pipeline_manager = pipeline.PipelineManager(self.pipeline_cfg,
                                                     self.transformer_manager)
         pipe = pipeline_manager.pipelines[0]
-
-        pipe.publish_data(None, counters)
+        for s in counters:
+            pipe.publish_data(None, s)
+            pipe.flush(None)
         publisher = pipeline_manager.pipelines[0].publishers[0]
         expected_len = len(test_resources) * len(expected)
-        self.assertEqual(0, len(publisher.samples))
-        pipe.flush(None)
         self.assertEqual(expected_len, len(publisher.samples))
 
         # bucket samples by resource first
@@ -1817,7 +1816,7 @@ class BasePipelineTestCase(base.BaseTestCase):
             dict(name='memory.usage', volume=512.0),
             dict(name='memory', volume=1024.0),
         ]
-        expected = [50.0]
+        expected = [25.0]
         self._do_test_arithmetic(expression, scenario, expected)
 
     def test_arithmetic_transformer_missing(self):
diff --git a/ceilometer/transformer/arithmetic.py b/ceilometer/transformer/arithmetic.py
index 365c7848..63a844cb 100644
--- a/ceilometer/transformer/arithmetic.py
+++ b/ceilometer/transformer/arithmetic.py
@@ -101,15 +101,14 @@ class ArithmeticTransformer(transformer.TransformerBase):
 
     def flush(self, context):
         new_samples = []
+        cache_clean_list = []
         if not self.misconfigured:
             for resource_id in self.cache:
                 if self._check_requirements(resource_id):
                     new_samples.append(self._calculate(resource_id))
-                else:
-                    LOG.warn(_('Unable to perform calculation, not all of '
-                               '{%s} are present'),
-                             ', '.join(self.required_meters))
-            self.cache.clear()
+                    cache_clean_list.append(resource_id)
+            for res_id in cache_clean_list:
+                self.cache.pop(res_id)
         return new_samples
 
     @classmethod