Histogram Aggregation - core SDK - aggregator

sdk/metrics/src/jmh/java/io/opentelemetry/sdk/metrics/aggregator/DoubleHistogramBenchmark.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.metrics.aggregator;
+
+import io.opentelemetry.sdk.common.InstrumentationLibraryInfo;
+import io.opentelemetry.sdk.metrics.common.InstrumentDescriptor;
+import io.opentelemetry.sdk.metrics.common.InstrumentType;
+import io.opentelemetry.sdk.metrics.common.InstrumentValueType;
+import io.opentelemetry.sdk.metrics.data.AggregationTemporality;
+import io.opentelemetry.sdk.resources.Resource;
+import java.util.concurrent.TimeUnit;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Threads;
+import org.openjdk.jmh.annotations.Warmup;
+
+@State(Scope.Benchmark)
+public class DoubleHistogramBenchmark {
+  private static final Aggregator<HistogramAccumulation> aggregator =
+      AggregatorFactory.histogram(new double[] {10, 100, 1_000}, AggregationTemporality.DELTA)
+          .create(
+              Resource.getDefault(),
+              InstrumentationLibraryInfo.empty(),
+              InstrumentDescriptor.create(
+                  "name",
+                  "description",
+                  "1",
+                  InstrumentType.VALUE_RECORDER,
+                  InstrumentValueType.DOUBLE));
+  private AggregatorHandle<HistogramAccumulation> aggregatorHandle;
+
+  @Setup(Level.Trial)
+  public final void setup() {
+    aggregatorHandle = aggregator.createHandle();
+  }
+
+  @Benchmark
+  @Fork(1)
+  @Warmup(iterations = 5, time = 1)
+  @Measurement(iterations = 10, time = 1)
+  @OutputTimeUnit(TimeUnit.MILLISECONDS)
+  @Threads(value = 10)
+  public void aggregate_10Threads() {
+    aggregatorHandle.recordDouble(100.0056);
+  }
+
+  @Benchmark
+  @Fork(1)
+  @Warmup(iterations = 5, time = 1)
+  @Measurement(iterations = 10, time = 1)
+  @OutputTimeUnit(TimeUnit.MILLISECONDS)
+  @Threads(value = 5)
+  public void aggregate_5Threads() {
+    aggregatorHandle.recordDouble(100.0056);
+  }
+
+  @Benchmark
+  @Fork(1)
+  @Warmup(iterations = 5, time = 1)
+  @Measurement(iterations = 10, time = 1)
+  @OutputTimeUnit(TimeUnit.MILLISECONDS)
+  @Threads(value = 1)
+  public void aggregate_1Threads() {
+    aggregatorHandle.recordDouble(100.0056);
+  }
+}

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/aggregator/AggregatorFactory.java

@@ -77,6 +77,18 @@ static AggregatorFactory minMaxSumCount() {
     return MinMaxSumCountAggregatorFactory.INSTANCE;
   }
 
+  /**
+   * Returns an {@code AggregatorFactory} that calculates an approximation of the distribution of
+   * the measurements taken.
+   *
+   * @param temporality configures what temporality to be produced for the Histogram metrics.
+   * @param boundaries configures the fixed bucket boundaries.
+   * @return an {@code AggregationFactory} that calculates histogram of recorded measurements.
+   */
+  static AggregatorFactory histogram(double[] boundaries, AggregationTemporality temporality) {
+    return new HistogramAggregatorFactory(boundaries, temporality);
+  }
+
   /**
    * Returns a new {@link Aggregator}.
    *

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/aggregator/DoubleHistogramAggregator.java

@@ -0,0 +1,166 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.metrics.aggregator;
+
+import io.opentelemetry.api.metrics.common.Labels;
+import io.opentelemetry.sdk.common.InstrumentationLibraryInfo;
+import io.opentelemetry.sdk.metrics.common.InstrumentDescriptor;
+import io.opentelemetry.sdk.metrics.data.AggregationTemporality;
+import io.opentelemetry.sdk.metrics.data.DoubleHistogramData;
+import io.opentelemetry.sdk.metrics.data.MetricData;
+import io.opentelemetry.sdk.resources.Resource;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.locks.ReentrantLock;
+import javax.annotation.concurrent.GuardedBy;
+
+final class DoubleHistogramAggregator extends AbstractAggregator<HistogramAccumulation> {
+  private static final long[] countsOfOne = new long[] {1};
+
+  private final double[] boundaries;
+
+  DoubleHistogramAggregator(
+      Resource resource,
+      InstrumentationLibraryInfo instrumentationLibraryInfo,
+      InstrumentDescriptor instrumentDescriptor,
+      double[] boundaries,
+      boolean stateful) {
+    super(resource, instrumentationLibraryInfo, instrumentDescriptor, stateful);
+    this.boundaries = boundaries;
+  }
+
+  @Override
+  public AggregatorHandle<HistogramAccumulation> createHandle() {
+    return new Handle(this.boundaries);
+  }
+
+  /**
+   * Return the result of the merge of two histogram accumulations. As long as one Aggregator
+   * instance produces all Accumulations with constant boundaries we don't need to worry about
+   * merging accumulations with different boundaries.
+   */
+  @Override
+  public final HistogramAccumulation merge(HistogramAccumulation x, HistogramAccumulation y) {
+    long[] mergedCounts = new long[x.getCounts().length];
+    for (int i = 0; i < x.getCounts().length; ++i) {
+      mergedCounts[i] = x.getCounts()[i] + y.getCounts()[i];
+    }
+    return HistogramAccumulation.create(x.getSum() + y.getSum(), mergedCounts);
+  }
+
+  @Override
+  public final MetricData toMetricData(
+      Map<Labels, HistogramAccumulation> accumulationByLabels,
+      long startEpochNanos,
+      long lastCollectionEpoch,
+      long epochNanos) {
+    List<Double> boundaries = new ArrayList<>(this.boundaries.length);
+    for (double v : this.boundaries) {
+      boundaries.add(v);
+    }
+    return MetricData.createDoubleHistogram(
+        getResource(),
+        getInstrumentationLibraryInfo(),
+        getInstrumentDescriptor().getName(),
+        getInstrumentDescriptor().getDescription(),
+        getInstrumentDescriptor().getUnit(),
+        DoubleHistogramData.create(
+            isStateful() ? AggregationTemporality.CUMULATIVE : AggregationTemporality.DELTA,
+            MetricDataUtils.toDoubleHistogramPointList(
+                accumulationByLabels,
+                isStateful() ? startEpochNanos : lastCollectionEpoch,
+                epochNanos,
+                boundaries)));
+  }
+
+  @Override
+  public HistogramAccumulation accumulateDouble(double value) {
+    return HistogramAccumulation.create(value, countsOfOne);
+  }
+
+  @Override
+  public HistogramAccumulation accumulateLong(long value) {
+    return HistogramAccumulation.create(value, countsOfOne);
+  }
+
+  static final class Handle extends AggregatorHandle<HistogramAccumulation> {
+    private final double[] boundaries;
+
+    private final ReentrantLock lock = new ReentrantLock();
+
+    @GuardedBy("lock")
+    private final State current;
+
+    Handle(double[] boundaries) {
+      this.boundaries = boundaries;
+      this.current = new State(this.boundaries.length + 1);
+    }
+
+    // Benchmark shows that linear search performs better than binary search with ordinary
+    // buckets.
+    private int findBucketIndex(double value) {
+      for (int i = 0; i < boundaries.length; ++i) {
+        if (Double.compare(value, boundaries[i]) <= 0) {
+          return i;
+        }
+      }
+      return boundaries.length;
+    }
+
+    @Override
+    protected HistogramAccumulation doAccumulateThenReset() {
+      lock.lock();
+      try {
+        HistogramAccumulation acc =
+            HistogramAccumulation.create(
+                current.sum, Arrays.copyOf(current.counts, current.counts.length));
+        current.reset();
+        return acc;
+      } finally {
+        lock.unlock();
+      }
+    }
+
+    @Override
+    protected void doRecordDouble(double value) {
+      int bucketIndex = findBucketIndex(value);
+
+      lock.lock();
+      try {
+        current.record(bucketIndex, value);
+      } finally {
+        lock.unlock();
+      }
+    }
+
+    @Override
+    protected void doRecordLong(long value) {
+      doRecordDouble((double) value);
+    }
+
+    private static final class State {
+      private double sum;
+      private final long[] counts;
+
+      public State(int bucketSize) {
+        this.counts = new long[bucketSize];
+        reset();
+      }
+
+      private void reset() {
+        this.sum = 0;
+        Arrays.fill(this.counts, 0);
+      }
+
+      private void record(int bucketIndex, double value) {
+        this.sum += value;
+        this.counts[bucketIndex]++;
+      }
+    }
+  }
+}

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/aggregator/HistogramAccumulation.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.metrics.aggregator;
+
+import com.google.auto.value.AutoValue;
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@AutoValue
+abstract class HistogramAccumulation {
+  /**
+   * Creates a new {@link HistogramAccumulation} with the given values. Assume `counts` is read-only
+   * so we don't need a defensive-copy here.
+   *
+   * @return a new {@link HistogramAccumulation} with the given values.
+   */
+  static HistogramAccumulation create(double sum, long[] counts) {
+    return new AutoValue_HistogramAccumulation(sum, counts);
+  }
+
+  HistogramAccumulation() {}
+
+  /**
+   * The sum of all measurements recorded.
+   *
+   * @return the sum of recorded measurements.
+   */
+  abstract double getSum();
+
+  /**
+   * The counts in each bucket. The returned type is a mutable object, but it should be fine because
+   * the class is only used internally.
+   *
+   * @return the counts in each bucket. <b>do not mutate</b> the returned object.
+   */
+  @SuppressWarnings("mutable")
+  abstract long[] getCounts();
+}

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/aggregator/HistogramAggregatorFactory.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.metrics.aggregator;
+
+import io.opentelemetry.sdk.common.InstrumentationLibraryInfo;
+import io.opentelemetry.sdk.metrics.common.InstrumentDescriptor;
+import io.opentelemetry.sdk.metrics.data.AggregationTemporality;
+import io.opentelemetry.sdk.resources.Resource;
+
+final class HistogramAggregatorFactory implements AggregatorFactory {
+  private final double[] boundaries;
+  private final AggregationTemporality temporality;
+
+  HistogramAggregatorFactory(double[] boundaries, AggregationTemporality temporality) {
+    this.boundaries = boundaries;
+    this.temporality = temporality;
+
+    for (int i = 1; i < this.boundaries.length; ++i) {
+      if (Double.compare(this.boundaries[i - 1], this.boundaries[i]) >= 0) {
+        throw new IllegalArgumentException(
+            "invalid bucket boundary: " + this.boundaries[i - 1] + " >= " + this.boundaries[i]);
+      }
+    }
+    if (this.boundaries.length > 0) {
+      if (this.boundaries[0] == Double.NEGATIVE_INFINITY) {
+        throw new IllegalArgumentException("invalid bucket boundary: -Inf");
+      }
+      if (this.boundaries[this.boundaries.length - 1] == Double.POSITIVE_INFINITY) {
+        throw new IllegalArgumentException("invalid bucket boundary: +Inf");
+      }
+    }
+  }
+
+  @Override
+  @SuppressWarnings("unchecked")
+  public <T> Aggregator<T> create(
+      Resource resource,
+      InstrumentationLibraryInfo instrumentationLibraryInfo,
+      InstrumentDescriptor descriptor) {
+    final boolean stateful = this.temporality == AggregationTemporality.CUMULATIVE;
+    switch (descriptor.getValueType()) {
+      case LONG:
+      case DOUBLE:
+        return (Aggregator<T>)
+            new DoubleHistogramAggregator(
+                resource, instrumentationLibraryInfo, descriptor, this.boundaries, stateful);
+    }
+    throw new IllegalArgumentException("Invalid instrument value type");
+  }
+}

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/aggregator/MetricDataUtils.java

@@ -6,6 +6,7 @@
 package io.opentelemetry.sdk.metrics.aggregator;
 
 import io.opentelemetry.api.metrics.common.Labels;
+import io.opentelemetry.sdk.metrics.data.DoubleHistogramPointData;
 import io.opentelemetry.sdk.metrics.data.DoublePointData;
 import io.opentelemetry.sdk.metrics.data.DoubleSummaryPointData;
 import io.opentelemetry.sdk.metrics.data.LongPointData;
@@ -44,4 +45,23 @@ static List<DoubleSummaryPointData> toDoubleSummaryPointList(
             points.add(aggregator.toPoint(startEpochNanos, epochNanos, labels)));
     return points;
   }
+
+  static List<DoubleHistogramPointData> toDoubleHistogramPointList(
+      Map<Labels, HistogramAccumulation> accumulationMap,
+      long startEpochNanos,
+      long epochNanos,
+      List<Double> boundaries) {
+    List<DoubleHistogramPointData> points = new ArrayList<>(accumulationMap.size());
+    accumulationMap.forEach(
+        (labels, aggregator) -> {
+          List<Long> counts = new ArrayList<>(aggregator.getCounts().length);
+          for (long v : aggregator.getCounts()) {
+            counts.add(v);
+          }
+          points.add(
+              DoubleHistogramPointData.create(
+                  startEpochNanos, epochNanos, labels, aggregator.getSum(), boundaries, counts));
+        });
+    return points;
+  }
 }