Add config to enable Default Exponential Histogram for Prometheus Exporter

exporters/prometheus/src/test/java/io/opentelemetry/exporter/prometheus/CollectorIntegrationTest.java

@@ -17,18 +17,24 @@
 import com.linecorp.armeria.server.grpc.protocol.AbstractUnaryGrpcService;
 import com.linecorp.armeria.testing.junit5.server.ServerExtension;
 import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.metrics.DoubleHistogram;
 import io.opentelemetry.api.metrics.Meter;
 import io.opentelemetry.proto.collector.metrics.v1.ExportMetricsServiceRequest;
 import io.opentelemetry.proto.collector.metrics.v1.ExportMetricsServiceResponse;
 import io.opentelemetry.proto.common.v1.AnyValue;
 import io.opentelemetry.proto.common.v1.KeyValue;
 import io.opentelemetry.proto.metrics.v1.AggregationTemporality;
+import io.opentelemetry.proto.metrics.v1.Histogram;
+import io.opentelemetry.proto.metrics.v1.HistogramDataPoint;
 import io.opentelemetry.proto.metrics.v1.Metric;
 import io.opentelemetry.proto.metrics.v1.NumberDataPoint;
 import io.opentelemetry.proto.metrics.v1.ResourceMetrics;
 import io.opentelemetry.proto.metrics.v1.ScopeMetrics;
 import io.opentelemetry.proto.metrics.v1.Sum;
+import io.opentelemetry.sdk.metrics.Aggregation;
+import io.opentelemetry.sdk.metrics.InstrumentType;
 import io.opentelemetry.sdk.metrics.SdkMeterProvider;
+import io.opentelemetry.sdk.metrics.export.DefaultAggregationSelector;
 import io.opentelemetry.sdk.resources.Resource;
 import java.io.UncheckedIOException;
 import java.time.Duration;
@@ -71,7 +77,14 @@ class CollectorIntegrationTest {
 
  @BeforeAll
  static void beforeAll() {
- PrometheusHttpServer prometheusHttpServer = PrometheusHttpServer.builder().setPort(0).build();
+ PrometheusHttpServer prometheusHttpServer =
+ PrometheusHttpServer.builder()
+ .setPort(0)
+ .setDefaultAggregationSelector(
+ DefaultAggregationSelector.getDefault()
+ .with(InstrumentType.HISTOGRAM, Aggregation.base2ExponentialBucketHistogram()))
+ .build();
+
  prometheusPort = prometheusHttpServer.getAddress().getPort();
  resource = Resource.getDefault();
  meterProvider =
@@ -115,12 +128,16 @@ void afterEach() {
  @Test
  void endToEnd() {
  Meter meter = meterProvider.meterBuilder("test").setInstrumentationVersion("1.0.0").build();
-
  meter
  .counterBuilder("requests")
  .build()
  .add(3, Attributes.builder().put("animal", "bear").build());
 
+ DoubleHistogram histogram = meter.histogramBuilder("latency").build();
+
+ histogram.record(3, Attributes.builder().put("animal", "bear").build());
+ histogram.record(5, Attributes.builder().put("animal", "bear").build());
+
  await()
  .atMost(Duration.ofSeconds(30))
  .untilAsserted(() -> assertThat(grpcServer.metricRequests.size()).isGreaterThan(0));
@@ -169,6 +186,11 @@ void endToEnd() {
  .orElseThrow(() -> new IllegalStateException("missing scope with name \"test\""));
  assertThat(testScopeMetrics.getScope().getVersion()).isEqualTo("1.0.0");
 
+ verifyCounterMetric(testScopeMetrics);
+ verifyHistogramMetric(testScopeMetrics);
+ }
+
+ private static void verifyCounterMetric(ScopeMetrics testScopeMetrics) {
  Optional<Metric> optRequestTotal =
  testScopeMetrics.getMetricsList().stream()
  .filter(metric -> metric.getName().equals("requests_total"))
@@ -194,6 +216,32 @@ void endToEnd() {
  stringKeyValue("otel_scope_version", "1.0.0"));
  }
 
+ private static void verifyHistogramMetric(ScopeMetrics testScopeMetrics) {
+ Optional<Metric> optRequestTotal =
+ testScopeMetrics.getMetricsList().stream()
+ .filter(metric -> metric.getName().equals("latency"))
+ .findFirst();
+ assertThat(optRequestTotal).isPresent();
+ Metric requestTotal = optRequestTotal.get();
+ assertThat(requestTotal.getDataCase()).isEqualTo(Metric.DataCase.HISTOGRAM);
+
+ Histogram requestHistogram = requestTotal.getHistogram();
+ assertThat(requestHistogram.getAggregationTemporality())
+ .isEqualTo(AggregationTemporality.AGGREGATION_TEMPORALITY_CUMULATIVE);
+ assertThat(requestHistogram.getDataPointsCount()).isEqualTo(1);
+
+ HistogramDataPoint requestHistogramDataPoints = requestHistogram.getDataPoints(0);
+ assertThat(requestHistogramDataPoints.getCount()).isEqualTo(2);
+ assertThat(requestHistogramDataPoints.getBucketCountsCount()).isEqualTo(1);
+ assertThat(requestHistogramDataPoints.getAttributesList())
+ .containsExactlyInAnyOrder(
+ stringKeyValue("animal", "bear"),
+ // Scope name and version are serialized as attributes to disambiguate metrics with the
+ // same name in different scopes
+ stringKeyValue("otel_scope_name", "test"),
+ stringKeyValue("otel_scope_version", "1.0.0"));
+ }
+
  private static KeyValue stringKeyValue(String key, String value) {
  return KeyValue.newBuilder()
  .setKey(key)