Add min/max fields to HistogramDataPoint (#279)

* Add min/max fields to HistogramDataPoint

* Typos

* 10 minutes

* make min/max optional but strictly refer to (start_time, end_time]

* --experimental_allow_proto3_optional

* remove gogo

* Changelog

* revert accidental makefile

CHANGELOG.md

@@ -10,7 +10,8 @@ Full list of differences found in [this compare](https://github.com/open-telemet
 
 ### Changed
 
-* Remove if no changes for this section before release.
+* Introduce optional `min` and `max` fields to the Histogram and ExponentialHistogram data points.
+  [(#279)](https://github.com/open-telemetry/opentelemetry-proto/pull/279)
 
 ### Added
 

opentelemetry/proto/metrics/v1/metrics.proto

@@ -492,6 +492,12 @@ message HistogramDataPoint {
   // Flags that apply to this specific data point.  See DataPointFlags
   // for the available flags and their meaning.
   uint32 flags = 10;
+
+  // min is the minimum value over (start_time, end_time].
+  optional double min = 11;
+
+  // max is the maximum value over (start_time, end_time].
+  optional double max = 12;
 }
 
 // ExponentialHistogramDataPoint is a single data point in a timeseries that describes the
@@ -594,6 +600,12 @@ message ExponentialHistogramDataPoint {
   // (Optional) List of exemplars collected from
   // measurements that were used to form the data point
   repeated Exemplar exemplars = 11;
+
+  // min is the minimum value over (start_time, end_time].
+  optional double min = 12;
+
+  // max is the maximum value over (start_time, end_time].
+  optional double max = 13;
 }
 
 // SummaryDataPoint is a single data point in a timeseries that describes the