remove unnecessary buckets on exponential histograms

Author: loomis-relativity

exporter/opentelemetry-exporter-otlp-proto-common/src/opentelemetry/exporter/otlp/proto/common/_internal/metrics_encoder/__init__.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 import logging
 from os import environ
-from typing import Dict, List
+from typing import Dict, List, Sequence
 
 from opentelemetry.exporter.otlp.proto.common._internal import (
     _encode_attributes,
@@ -43,7 +43,9 @@
 )
 from opentelemetry.sdk.metrics.export import (
     AggregationTemporality,
+    ExponentialHistogram as ExponentialHistogramType,
     Gauge,
+    Histogram as HistogramType,
     MetricExporter,
     MetricsData,
     Sum,
@@ -167,6 +169,12 @@ def _get_aggregation(
 
         return instrument_class_aggregation
 
+def truncate_trailing_zeros(lst: Sequence[int]) -> Sequence[int]:
+    if lst:
+        for i, value in enumerate(reversed(lst)):
+            if value != 0:
+                return lst[0:len(lst)-i]
+    return []
 
 class EncodingException(Exception):
     """
@@ -207,12 +215,17 @@ def encode_metrics(data: MetricsData) -> ExportMetricsServiceRequest:
 
 
 def _encode_resource_metrics(resource_metrics, resource_metrics_dict):
+
     resource = resource_metrics.resource
+
     # It is safe to assume that each entry in data.resource_metrics is
     # associated with an unique resource.
     scope_metrics_dict = {}
+
     resource_metrics_dict[resource] = scope_metrics_dict
+
     for scope_metrics in resource_metrics.scope_metrics:
+
         instrumentation_scope = scope_metrics.scope
 
         # The SDK groups metrics in instrumentation scopes already so
@@ -299,18 +312,19 @@ def _encode_metric(metric, pb2_metric):
 
     elif isinstance(metric.data, ExponentialHistogramType):
         for data_point in metric.data.data_points:
-            if data_point.positive.bucket_counts:
+
+            if positive_buckets := truncate_trailing_zeros(data_point.positive.bucket_counts):
                 positive = pb2.ExponentialHistogramDataPoint.Buckets(
                     offset=data_point.positive.offset,
-                    bucket_counts=data_point.positive.bucket_counts,
+                    bucket_counts=positive_buckets,
                 )
             else:
                 positive = None
 
-            if data_point.negative.bucket_counts:
+            if negative_buckets := truncate_trailing_zeros(data_point.negative.bucket_counts):
                 negative = pb2.ExponentialHistogramDataPoint.Buckets(
                     offset=data_point.negative.offset,
-                    bucket_counts=data_point.negative.bucket_counts,
+                    bucket_counts=negative_buckets,
                 )
             else:
                 negative = None

exporter/opentelemetry-exporter-otlp-proto-common/tests/test_metrics_encoder.py

@@ -17,6 +17,7 @@
 
 from opentelemetry.exporter.otlp.proto.common._internal.metrics_encoder import (
     EncodingException,
+    truncate_trailing_zeros,
 )
 from opentelemetry.exporter.otlp.proto.common.metrics_encoder import (
     encode_metrics,
@@ -854,6 +855,13 @@ def test_encode_multiple_scope_histogram(self):
         actual = encode_metrics(metrics_data)
         self.assertEqual(expected, actual)
 
+    def test_truncate_trailing_zeros(self):
+        self.assertEqual([], truncate_trailing_zeros([]))
+        self.assertEqual([], truncate_trailing_zeros([0]))
+        self.assertEqual([0, 1], truncate_trailing_zeros([0, 1]))
+        self.assertEqual([0, 1], truncate_trailing_zeros([0, 1, 0]))
+        self.assertEqual([1, -1], truncate_trailing_zeros([1, -1, 0, 0]))
+
     def test_encode_exponential_histogram(self):
         exponential_histogram = Metric(
             name="exponential_histogram",
@@ -869,8 +877,8 @@ def test_encode_exponential_histogram(self):
                         sum=3,
                         scale=4,
                         zero_count=5,
-                        positive=Buckets(offset=6, bucket_counts=[7, 8]),
-                        negative=Buckets(offset=9, bucket_counts=[10, 11]),
+                        positive=Buckets(offset=6, bucket_counts=[7, 8, 0]),
+                        negative=Buckets(offset=9, bucket_counts=[10, 11, 0, 0]),
                         flags=12,
                         min=13.0,
                         max=14.0,