Promote exponential histogram data interfaces to stable package (#5120)

* Promote exponential histogram data interfaces to stable package * Spotless
open-telemetry · Jan 21, 2023 · c427bf2 · c427bf2
1 parent f28e0ad
commit c427bf2
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diff --git a/docs/apidiffs/current_vs_latest/opentelemetry-sdk-metrics.txt b/docs/apidiffs/current_vs_latest/opentelemetry-sdk-metrics.txt
@@ -1,4 +1,35 @@
 Comparing source compatibility of  against 
++++  NEW INTERFACE: PUBLIC(+) ABSTRACT(+) io.opentelemetry.sdk.metrics.data.ExponentialHistogramBuckets  (not serializable)
+	+++  CLASS FILE FORMAT VERSION: 52.0 <- n.a.
+	+++  NEW SUPERCLASS: java.lang.Object
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) java.util.List getBucketCounts()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) int getOffset()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) int getScale()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) long getTotalCount()
++++  NEW INTERFACE: PUBLIC(+) ABSTRACT(+) io.opentelemetry.sdk.metrics.data.ExponentialHistogramData  (not serializable)
+	+++  CLASS FILE FORMAT VERSION: 52.0 <- n.a.
+	+++  NEW INTERFACE: io.opentelemetry.sdk.metrics.data.Data
+	+++  NEW SUPERCLASS: java.lang.Object
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) io.opentelemetry.sdk.metrics.data.AggregationTemporality getAggregationTemporality()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) java.util.Collection getPoints()
++++  NEW INTERFACE: PUBLIC(+) ABSTRACT(+) io.opentelemetry.sdk.metrics.data.ExponentialHistogramPointData  (not serializable)
+	+++  CLASS FILE FORMAT VERSION: 52.0 <- n.a.
+	+++  NEW INTERFACE: io.opentelemetry.sdk.metrics.data.PointData
+	+++  NEW SUPERCLASS: java.lang.Object
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) long getCount()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) java.util.List getExemplars()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) double getMax()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) double getMin()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) io.opentelemetry.sdk.metrics.data.ExponentialHistogramBuckets getNegativeBuckets()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) io.opentelemetry.sdk.metrics.data.ExponentialHistogramBuckets getPositiveBuckets()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) int getScale()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) double getSum()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) long getZeroCount()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) boolean hasMax()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) boolean hasMin()
+***  MODIFIED INTERFACE: PUBLIC ABSTRACT io.opentelemetry.sdk.metrics.data.MetricData  (not serializable)
+	===  CLASS FILE FORMAT VERSION: 52.0 <- 52.0
+	+++  NEW METHOD: PUBLIC(+) io.opentelemetry.sdk.metrics.data.ExponentialHistogramData getExponentialHistogramData()
 ***  MODIFIED INTERFACE: PUBLIC ABSTRACT io.opentelemetry.sdk.metrics.export.MetricReader  (not serializable)
 	===  CLASS FILE FORMAT VERSION: 52.0 <- 52.0
 	+++  NEW INTERFACE: java.io.Closeable

diff --git a/...io/opentelemetry/exporter/internal/otlp/metrics/ExponentialHistogramBucketsMarshaler.java b/...io/opentelemetry/exporter/internal/otlp/metrics/ExponentialHistogramBucketsMarshaler.java
@@ -10,7 +10,7 @@
 import io.opentelemetry.exporter.internal.marshal.Serializer;
 import io.opentelemetry.proto.metrics.v1.internal.ExponentialHistogramDataPoint;
 import io.opentelemetry.sdk.internal.PrimitiveLongList;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramBuckets;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramBuckets;
 import java.io.IOException;
 import java.util.List;
 

diff --git a/.../opentelemetry/exporter/internal/otlp/metrics/ExponentialHistogramDataPointMarshaler.java b/.../opentelemetry/exporter/internal/otlp/metrics/ExponentialHistogramDataPointMarshaler.java
@@ -10,7 +10,7 @@
 import io.opentelemetry.exporter.internal.marshal.Serializer;
 import io.opentelemetry.exporter.internal.otlp.KeyValueMarshaler;
 import io.opentelemetry.proto.metrics.v1.internal.ExponentialHistogramDataPoint;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramPointData;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramPointData;
 import java.io.IOException;
 import java.util.Collection;
 

diff --git a/...n/java/io/opentelemetry/exporter/internal/otlp/metrics/ExponentialHistogramMarshaler.java b/...n/java/io/opentelemetry/exporter/internal/otlp/metrics/ExponentialHistogramMarshaler.java
@@ -10,7 +10,7 @@
 import io.opentelemetry.exporter.internal.marshal.ProtoEnumInfo;
 import io.opentelemetry.exporter.internal.marshal.Serializer;
 import io.opentelemetry.proto.metrics.v1.internal.ExponentialHistogram;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramData;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramData;
 import java.io.IOException;
 
 /**

diff --git a/...common/src/main/java/io/opentelemetry/exporter/internal/otlp/metrics/MetricMarshaler.java b/...common/src/main/java/io/opentelemetry/exporter/internal/otlp/metrics/MetricMarshaler.java
@@ -12,7 +12,6 @@
 import io.opentelemetry.exporter.internal.marshal.Serializer;
 import io.opentelemetry.proto.metrics.v1.internal.Metric;
 import io.opentelemetry.sdk.metrics.data.MetricData;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramData;
 import java.io.IOException;
 
 final class MetricMarshaler extends MarshalerWithSize {
@@ -57,8 +56,7 @@ static Marshaler create(MetricData metric) {
         dataField = Metric.HISTOGRAM;
         break;
       case EXPONENTIAL_HISTOGRAM:
-        dataMarshaler =
-            ExponentialHistogramMarshaler.create(ExponentialHistogramData.fromMetricData(metric));
+        dataMarshaler = ExponentialHistogramMarshaler.create(metric.getExponentialHistogramData());
         dataField = Metric.EXPONENTIAL_HISTOGRAM;
     }
 

diff --git a/...est/java/io/opentelemetry/exporter/internal/otlp/metrics/MetricsRequestMarshalerTest.java b/...est/java/io/opentelemetry/exporter/internal/otlp/metrics/MetricsRequestMarshalerTest.java
@@ -41,12 +41,16 @@
 import io.opentelemetry.proto.metrics.v1.SummaryDataPoint;
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
 import io.opentelemetry.sdk.metrics.data.AggregationTemporality;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramBuckets;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramPointData;
 import io.opentelemetry.sdk.metrics.data.HistogramPointData;
 import io.opentelemetry.sdk.metrics.data.MetricData;
 import io.opentelemetry.sdk.metrics.data.PointData;
 import io.opentelemetry.sdk.metrics.data.SummaryPointData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableDoubleExemplarData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableDoublePointData;
+import io.opentelemetry.sdk.metrics.internal.data.ImmutableExponentialHistogramData;
+import io.opentelemetry.sdk.metrics.internal.data.ImmutableExponentialHistogramPointData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableGaugeData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableHistogramData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableHistogramPointData;
@@ -57,9 +61,6 @@
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableSummaryData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableSummaryPointData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableValueAtQuantile;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramBuckets;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramData;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramPointData;
 import io.opentelemetry.sdk.resources.Resource;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -415,7 +416,7 @@ void exponentialHistogramDataPoints() {
     assertThat(
             toExponentialHistogramDataPoints(
                 ImmutableList.of(
-                    ExponentialHistogramPointData.create(
+                    ImmutableExponentialHistogramPointData.create(
                         0,
                         123.4,
                         1,
@@ -427,7 +428,7 @@ void exponentialHistogramDataPoints() {
                         456,
                         Attributes.empty(),
                         Collections.emptyList()),
-                    ExponentialHistogramPointData.create(
+                    ImmutableExponentialHistogramPointData.create(
                         0,
                         123.4,
                         1,
@@ -827,10 +828,10 @@ void toProtoMetric_exponentialHistogram() {
                     "name",
                     "description",
                     "1",
-                    ExponentialHistogramData.create(
+                    ImmutableExponentialHistogramData.create(
                         AggregationTemporality.CUMULATIVE,
                         singletonList(
-                            ExponentialHistogramPointData.create(
+                            ImmutableExponentialHistogramPointData.create(
                                 20,
                                 123.4,
                                 257,

diff --git a/exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/Serializer.java b/exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/Serializer.java
@@ -37,7 +37,6 @@
 import io.opentelemetry.sdk.metrics.data.PointData;
 import io.opentelemetry.sdk.metrics.data.SummaryPointData;
 import io.opentelemetry.sdk.metrics.data.ValueAtQuantile;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramData;
 import io.opentelemetry.sdk.resources.Resource;
 import java.io.BufferedWriter;
 import java.io.IOException;
@@ -646,7 +645,7 @@ static Collection<? extends PointData> getPoints(MetricData metricData) {
       case HISTOGRAM:
         return metricData.getHistogramData().getPoints();
       case EXPONENTIAL_HISTOGRAM:
-        return ExponentialHistogramData.fromMetricData(metricData).getPoints();
+        return metricData.getExponentialHistogramData().getPoints();
     }
     return Collections.emptyList();
   }

diff --git a/...esting/src/main/java/io/opentelemetry/sdk/testing/assertj/ExponentialHistogramAssert.java b/...esting/src/main/java/io/opentelemetry/sdk/testing/assertj/ExponentialHistogramAssert.java
@@ -6,8 +6,8 @@
 package io.opentelemetry.sdk.testing.assertj;
 
 import io.opentelemetry.sdk.metrics.data.AggregationTemporality;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramData;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramPointData;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramData;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramPointData;
 import org.assertj.core.api.AbstractAssert;
 import org.assertj.core.api.AbstractIterableAssert;
 import org.assertj.core.api.Assertions;

diff --git a/...src/main/java/io/opentelemetry/sdk/testing/assertj/ExponentialHistogramBucketsAssert.java b/...src/main/java/io/opentelemetry/sdk/testing/assertj/ExponentialHistogramBucketsAssert.java
@@ -5,7 +5,7 @@
 
 package io.opentelemetry.sdk.testing.assertj;
 
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramBuckets;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramBuckets;
 import java.util.List;
 import org.assertj.core.api.AbstractAssert;
 import org.assertj.core.api.Assertions;

diff --git a/...c/main/java/io/opentelemetry/sdk/testing/assertj/ExponentialHistogramPointDataAssert.java b/...c/main/java/io/opentelemetry/sdk/testing/assertj/ExponentialHistogramPointDataAssert.java
@@ -5,7 +5,7 @@
 
 package io.opentelemetry.sdk.testing.assertj;
 
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramPointData;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramPointData;
 import org.assertj.core.api.Assertions;
 
 /** Test assertions for {@link ExponentialHistogramPointData}. */

diff --git a/sdk/metrics-testing/src/main/java/io/opentelemetry/sdk/testing/assertj/MetricAssertions.java b/sdk/metrics-testing/src/main/java/io/opentelemetry/sdk/testing/assertj/MetricAssertions.java
@@ -6,9 +6,9 @@
 package io.opentelemetry.sdk.testing.assertj;
 
 import io.opentelemetry.sdk.metrics.data.ExemplarData;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramBuckets;
+import io.opentelemetry.sdk.metrics.data.ExponentialHistogramPointData;
 import io.opentelemetry.sdk.metrics.data.MetricData;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramBuckets;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramPointData;
 import org.assertj.core.api.Assertions;
 
 /** Test assertions for data heading to exporters within the Metrics SDK. */

diff --git a/sdk/metrics-testing/src/main/java/io/opentelemetry/sdk/testing/assertj/MetricDataAssert.java b/sdk/metrics-testing/src/main/java/io/opentelemetry/sdk/testing/assertj/MetricDataAssert.java
@@ -8,7 +8,6 @@
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
 import io.opentelemetry.sdk.metrics.data.MetricData;
 import io.opentelemetry.sdk.metrics.data.MetricDataType;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramData;
 import io.opentelemetry.sdk.resources.Resource;
 import org.assertj.core.api.AbstractAssert;
 
@@ -107,6 +106,6 @@ public ExponentialHistogramAssert hasExponentialHistogram() {
           MetricDataType.EXPONENTIAL_HISTOGRAM,
           actual.getType());
     }
-    return new ExponentialHistogramAssert(ExponentialHistogramData.fromMetricData(actual));
+    return new ExponentialHistogramAssert(actual.getExponentialHistogramData());
   }
 }
diff --git a/...rics-testing/src/test/java/io/opentelemetry/sdk/testing/assertj/MetricAssertionsTest.java b/...rics-testing/src/test/java/io/opentelemetry/sdk/testing/assertj/MetricAssertionsTest.java
@@ -13,9 +13,9 @@
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
 import io.opentelemetry.sdk.metrics.data.AggregationTemporality;
 import io.opentelemetry.sdk.metrics.data.MetricData;
+import io.opentelemetry.sdk.metrics.internal.data.ImmutableExponentialHistogramData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableGaugeData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableMetricData;
-import io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram.ExponentialHistogramData;
 import io.opentelemetry.sdk.resources.Resource;
 import java.util.Collections;
 import org.junit.jupiter.api.Test;
@@ -33,7 +33,7 @@ public class MetricAssertionsTest {
           /* name= */ "exponential_histogram",
           /* description= */ "description",
           /* unit= */ "unit",
-          ExponentialHistogramData.create(
+          ImmutableExponentialHistogramData.create(
               AggregationTemporality.CUMULATIVE,
               // Points
               Collections.emptyList()));
@@ -45,7 +45,7 @@ public class MetricAssertionsTest {
           /* name= */ "exponential_histogram_delta",
           /* description= */ "description",
           /* unit= */ "unit",
-          ExponentialHistogramData.create(
+          ImmutableExponentialHistogramData.create(
               AggregationTemporality.DELTA,
               // Points
               Collections.emptyList()));

diff --git a/...istogram/ExponentialHistogramBuckets.java → ...ics/data/ExponentialHistogramBuckets.java b/...istogram/ExponentialHistogramBuckets.java → ...ics/data/ExponentialHistogramBuckets.java
@@ -3,7 +3,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-package io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram;
+package io.opentelemetry.sdk.metrics.data;
 
 import java.util.List;
 import javax.annotation.concurrent.Immutable;
@@ -20,8 +20,7 @@
  * <code>offset</code> is -3, the bucket lower bounds would be 0.125, 0.25, 0.5, 1.0, 2,0, etc. If
  * <code>offset</code> is +3, the bucket lower bounds would be 8.0, 16.0, 32.0, etc.
  *
- * <p>This class is internal and is hence not for public use. Its APIs are unstable and can change
- * at any time.
+ * @since 1.23.0
  */
 @Immutable
 public interface ExponentialHistogramBuckets {

diff --git a/sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/data/ExponentialHistogramData.java b/sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/data/ExponentialHistogramData.java
@@ -0,0 +1,44 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.metrics.data;
+
+import java.util.Collection;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * A base-2 exponential histogram metric point, as defined by the OpenTelemetry Exponential
+ * Histogram specification.
+ *
+ * <p><i>Note: This is called "ExponentialHistogramData" to reflect which primitives are used to
+ * record it, however "ExponentialHistogram" is the equivalent OTLP type.</i>
+ *
+ * @see <a
+ *     href="https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/data-model.md#exponentialhistogram">Exponential
+ *     Histogram Data Model</a>
+ * @see ExponentialHistogramPointData
+ * @since 1.23.0
+ */
+@Immutable
+public interface ExponentialHistogramData extends Data<ExponentialHistogramPointData> {
+
+  /**
+   * Returns the {@code AggregationTemporality} of this metric.
+   *
+   * <p>AggregationTemporality describes if the aggregator reports delta changes since last report
+   * time, or cumulative changes since a fixed start time.
+   *
+   * @return the {@code AggregationTemporality} of this metric
+   */
+  AggregationTemporality getAggregationTemporality();
+
+  /**
+   * Returns the collection of {@link ExponentialHistogramPointData} for this histogram.
+   *
+   * @return the collection of data points for this histogram.
+   */
+  @Override
+  Collection<ExponentialHistogramPointData> getPoints();
+}
diff --git a/...togram/ExponentialHistogramPointData.java → ...s/data/ExponentialHistogramPointData.java b/...togram/ExponentialHistogramPointData.java → ...s/data/ExponentialHistogramPointData.java
@@ -3,13 +3,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-package io.opentelemetry.sdk.metrics.internal.data.exponentialhistogram;
+package io.opentelemetry.sdk.metrics.data;
 
-import io.opentelemetry.api.common.Attributes;
-import io.opentelemetry.sdk.metrics.data.DoubleExemplarData;
-import io.opentelemetry.sdk.metrics.data.PointData;
 import java.util.List;
-import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -20,49 +16,14 @@
  * <p>The bucket boundaries are calculated using both the scale {@link #getScale()}, and the offset
  * {@link ExponentialHistogramBuckets#getOffset()}.
  *
- * <p>See <a
- * href="https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/datamodel.md#exponentialhistogram">data
- * model</a>.
- *
- * <p>This class is internal and is hence not for public use. Its APIs are unstable and can change
- * at any time.
+ * @see <a
+ *     href="https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/data-model.md#exponentialhistogram">Exponential
+ *     Histogram Data Model</a>
+ * @since 1.23.0
  */
 @Immutable
 public interface ExponentialHistogramPointData extends PointData {
 
-  /**
-   * Create an ExponentialHistogramPointData.
-   *
-   * @return an ExponentialHistogramPointData.
-   */
-  @SuppressWarnings("TooManyParameters")
-  static ExponentialHistogramPointData create(
-      int scale,
-      double sum,
-      long zeroCount,
-      @Nullable Double min,
-      @Nullable Double max,
-      ExponentialHistogramBuckets positiveBuckets,
-      ExponentialHistogramBuckets negativeBuckets,
-      long startEpochNanos,
-      long epochNanos,
-      Attributes attributes,
-      List<DoubleExemplarData> exemplars) {
-
-    return ImmutableExponentialHistogramPointData.create(
-        scale,
-        sum,
-        zeroCount,
-        min,
-        max,
-        positiveBuckets,
-        negativeBuckets,
-        startEpochNanos,
-        epochNanos,
-        attributes,
-        exemplars);
-  }
-
   /**
    * Scale characterises the resolution of the histogram, with larger values of scale offering
    * greater precision. Bucket boundaries of the histogram are located at integer powers of the

diff --git a/sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/data/MetricData.java b/sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/data/MetricData.java
@@ -10,6 +10,7 @@
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
 import io.opentelemetry.sdk.metrics.SdkMeterProviderBuilder;
 import io.opentelemetry.sdk.metrics.View;
+import io.opentelemetry.sdk.metrics.internal.data.ImmutableExponentialHistogramData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableGaugeData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableHistogramData;
 import io.opentelemetry.sdk.metrics.internal.data.ImmutableSumData;
@@ -159,4 +160,15 @@ default HistogramData getHistogramData() {
     }
     return ImmutableHistogramData.empty();
   }
+
+  /**
+   * Returns the {@link ExponentialHistogramData} if type is {@link
+   * MetricDataType#EXPONENTIAL_HISTOGRAM}, otherwise a default empty data.
+   */
+  default ExponentialHistogramData getExponentialHistogramData() {
+    if (getType() == MetricDataType.EXPONENTIAL_HISTOGRAM) {
+      return (ExponentialHistogramData) getData();
+    }
+    return ImmutableExponentialHistogramData.empty();
+  }
 }