Console exporter: Display exponential histogram boundaries (#4507)

Author: alanwest

src/OpenTelemetry.Exporter.Console/ConsoleMetricExporter.cs

@@ -146,8 +146,21 @@ public override ExportResult Export(in Batch<Metric> batch)
                         }
                         else
                         {
-                            // TODO: Consider how/if to display buckets for exponential histograms.
-                            bucketsBuilder.AppendLine("Buckets are not displayed for exponential histograms.");
+                            var exponentialHistogramData = metricPoint.GetExponentialHistogramData();
+                            var scale = exponentialHistogramData.Scale;
+
+                            if (exponentialHistogramData.ZeroCount != 0)
+                            {
+                                bucketsBuilder.AppendLine($"Zero Bucket:{exponentialHistogramData.ZeroCount}");
+                            }
+
+                            var offset = exponentialHistogramData.PositiveBuckets.Offset;
+                            foreach (var bucketCount in exponentialHistogramData.PositiveBuckets)
+                            {
+                                var lowerBound = Base2ExponentialBucketHistogram.LowerBoundary(offset, scale).ToString(CultureInfo.InvariantCulture);
+                                var upperBound = Base2ExponentialBucketHistogram.LowerBoundary(++offset, scale).ToString(CultureInfo.InvariantCulture);
+                                bucketsBuilder.AppendLine($"({lowerBound}, {upperBound}]:{bucketCount}");
+                            }
                         }
 
                         valueDisplay = bucketsBuilder.ToString();

src/OpenTelemetry.Exporter.Console/OpenTelemetry.Exporter.Console.csproj

@@ -28,6 +28,7 @@
     <Compile Include="$(RepoRoot)\src\OpenTelemetry\Internal\OpenTelemetrySdkEventSource.cs" Link="Includes\OpenTelemetrySdkEventSource.cs" />
     <Compile Include="$(RepoRoot)\src\OpenTelemetry\Internal\PeriodicExportingMetricReaderHelper.cs" Link="Includes\PeriodicExportingMetricReaderHelper.cs" />
     <Compile Include="$(RepoRoot)\src\OpenTelemetry\Internal\TagTransformer.cs" Link="Includes\TagTransformer.cs" />
+    <Compile Include="$(RepoRoot)\src\OpenTelemetry\Metrics\Base2ExponentialBucketHistogram.LowerBoundary.cs" Link="Includes\Base2ExponentialBucketHistogram.LowerBoundary.cs" />
     <Compile Include="$(RepoRoot)\src\OpenTelemetry.Api\Internal\ExceptionExtensions.cs" Link="Includes\ExceptionExtensions.cs" />
     <Compile Include="$(RepoRoot)\src\OpenTelemetry.Api\Internal\Guard.cs" Link="Includes\Guard.cs" />
     <Compile Include="$(RepoRoot)\src\OpenTelemetry.Api\Internal\SpanAttributeConstants.cs" Link="Includes\SpanAttributeConstants.cs" />