Fix delta histogram sum not being reset on collection (#2533)

Author: pichlermarc

CHANGELOG.md

@@ -12,6 +12,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#2525](https://github.com/open-telemetry/opentelemetry-python/pull/2525))
 - Change OTLPHandler to LoggingHandler
   ([#2528](https://github.com/open-telemetry/opentelemetry-python/pull/2528))
+- Fix delta histogram sum not being reset on collection
+  ([#2533](https://github.com/open-telemetry/opentelemetry-python/pull/2533))
 
 ## [1.10.0-0.29b0](https://github.com/open-telemetry/opentelemetry-python/releases/tag/v1.10.0-0.29b0) - 2022-03-10
 

opentelemetry-sdk/src/opentelemetry/sdk/_metrics/aggregation.py

@@ -191,17 +191,19 @@ def collect(self) -> Histogram:
         with self._lock:
             value = self._bucket_counts
             start_time_unix_nano = self._start_time_unix_nano
+            histogram_sum = self._sum
 
             self._bucket_counts = self._get_empty_bucket_counts()
             self._start_time_unix_nano = now + 1
+            self._sum = 0
 
         return Histogram(
             start_time_unix_nano=start_time_unix_nano,
             time_unix_nano=now,
             bucket_counts=tuple(value),
             explicit_bounds=self._boundaries,
             aggregation_temporality=AggregationTemporality.DELTA,
-            sum=self._sum,
+            sum=histogram_sum,
         )
 
 

opentelemetry-sdk/tests/metrics/test_aggregation.py

@@ -286,6 +286,7 @@ def test_collect(self):
         first_histogram = explicit_bucket_histogram_aggregation.collect()
 
         self.assertEqual(first_histogram.bucket_counts, (0, 1, 0, 0))
+        self.assertEqual(first_histogram.sum, 1)
 
         # CI fails the last assertion without this
         sleep(0.1)
@@ -294,6 +295,7 @@ def test_collect(self):
         second_histogram = explicit_bucket_histogram_aggregation.collect()
 
         self.assertEqual(second_histogram.bucket_counts, (0, 1, 0, 0))
+        self.assertEqual(second_histogram.sum, 1)
 
         self.assertGreater(
             second_histogram.time_unix_nano, first_histogram.time_unix_nano