Polish "Improve Otlp Delta Aggregation with support for max and Histogram" (#3876)

See gh-3749

Author: izeye

implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpMeterRegistry.java

@@ -22,6 +22,7 @@
 import io.micrometer.core.instrument.*;
 import io.micrometer.core.instrument.config.NamingConvention;
 import io.micrometer.core.instrument.distribution.*;
+import io.micrometer.core.instrument.distribution.Histogram;
 import io.micrometer.core.instrument.distribution.pause.PauseDetector;
 import io.micrometer.core.instrument.internal.DefaultGauge;
 import io.micrometer.core.instrument.internal.DefaultLongTaskTimer;
@@ -39,7 +40,6 @@
 import io.opentelemetry.proto.collector.metrics.v1.ExportMetricsServiceRequest;
 import io.opentelemetry.proto.common.v1.AnyValue;
 import io.opentelemetry.proto.common.v1.KeyValue;
-import io.opentelemetry.proto.metrics.v1.Histogram;
 import io.opentelemetry.proto.metrics.v1.*;
 import io.opentelemetry.proto.resource.v1.Resource;
 
@@ -372,14 +372,14 @@ Metric writeHistogramSupport(HistogramSupport histogramSupport) {
                     .addExplicitBounds(isTimeBased ? countAtBucket.bucket(getBaseTimeUnit()) : countAtBucket.bucket());
                 histogramDataPoint.addBucketCounts((long) countAtBucket.count());
             }
-            metricBuilder.setHistogram(Histogram.newBuilder()
+            metricBuilder.setHistogram(io.opentelemetry.proto.metrics.v1.Histogram.newBuilder()
                 .setAggregationTemporality(otlpAggregationTemporality)
                 .addDataPoints(histogramDataPoint));
             return metricBuilder.build();
         }
 
         return metricBuilder
-            .setHistogram(Histogram.newBuilder()
+            .setHistogram(io.opentelemetry.proto.metrics.v1.Histogram.newBuilder()
                 .setAggregationTemporality(otlpAggregationTemporality)
                 .addDataPoints(histogramDataPoint))
             .build();
@@ -388,7 +388,7 @@ Metric writeHistogramSupport(HistogramSupport histogramSupport) {
     // VisibleForTesting
     Metric writeFunctionTimer(FunctionTimer functionTimer) {
         return getMetricBuilder(functionTimer.getId())
-            .setHistogram(Histogram.newBuilder()
+            .setHistogram(io.opentelemetry.proto.metrics.v1.Histogram.newBuilder()
                 .addDataPoints(HistogramDataPoint.newBuilder()
                     .addAllAttributes(getTagsForId(functionTimer.getId()))
                     .setStartTimeUnixNano(getStartTimeNanos((functionTimer)))
@@ -466,14 +466,13 @@ Iterable<KeyValue> getResourceAttributes() {
         return attributes;
     }
 
-    static io.micrometer.core.instrument.distribution.Histogram getHistogram(Clock clock,
-            DistributionStatisticConfig distributionStatisticConfig, AggregationTemporality aggregationTemporality) {
+    static Histogram getHistogram(Clock clock, DistributionStatisticConfig distributionStatisticConfig,
+            AggregationTemporality aggregationTemporality) {
         return getHistogram(clock, distributionStatisticConfig, aggregationTemporality, 0);
     }
 
-    static io.micrometer.core.instrument.distribution.Histogram getHistogram(Clock clock,
-            DistributionStatisticConfig distributionStatisticConfig, AggregationTemporality aggregationTemporality,
-            long stepMillis) {
+    static Histogram getHistogram(Clock clock, DistributionStatisticConfig distributionStatisticConfig,
+            AggregationTemporality aggregationTemporality, long stepMillis) {
         // While publishing to OTLP, we export either Histogram datapoint / Summary
         // datapoint. So, we will make the histogram either of them and not both.
         // Though AbstractTimer/Distribution Summary prefers publishing percentiles,
@@ -488,7 +487,7 @@ static io.micrometer.core.instrument.distribution.Histogram getHistogram(Clock c
                     .build()
                     .merge(distributionStatisticConfig), true, false);
             }
-            else if (AggregationTemporality.isDelta(aggregationTemporality) && stepMillis > 0) {
+            if (AggregationTemporality.isDelta(aggregationTemporality) && stepMillis > 0) {
                 return new OtlpStepBucketHistogram(clock, stepMillis, distributionStatisticConfig, true, false);
             }
         }

implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpStepDistributionSummary.java

@@ -50,7 +50,7 @@ class OtlpStepDistributionSummary extends AbstractDistributionSummary {
 
     @Override
     protected void recordNonNegative(double amount) {
-        count.add(1);
+        count.add(1L);
         total.add(amount);
         max.record(amount);
     }

implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpStepTimer.java

@@ -54,7 +54,7 @@ class OtlpStepTimer extends AbstractTimer {
     @Override
     protected void recordNonNegative(final long amount, final TimeUnit unit) {
         final long nanoAmount = (long) TimeUtils.convert(amount, unit, TimeUnit.NANOSECONDS);
-        count.add(1);
+        count.add(1L);
         total.add(nanoAmount);
         max.record(nanoAmount);
     }

implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/StepMax.java

@@ -22,16 +22,15 @@
 import java.util.function.Supplier;
 
 /**
- * A {@link StepValue} implementation that tracks max over a Step Interval.
+ * A {@link StepValue} implementation that tracks max over a step interval.
  *
  * @author Lenin Jaganathan
- * @since 1.11.0
  */
 class StepMax extends StepValue<Double> {
 
-    private final DoubleAccumulator current = new DoubleAccumulator(Double::max, 0);
+    private final DoubleAccumulator current = new DoubleAccumulator(Double::max, 0d);
 
-    public StepMax(Clock clock, long stepMillis) {
+    StepMax(Clock clock, long stepMillis) {
         super(clock, stepMillis);
     }
 
@@ -45,7 +44,7 @@ protected Double noValue() {
         return 0.0;
     }
 
-    public void record(double value) {
+    void record(double value) {
         current.accumulate(value);
     }
 

implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OtlpCumulativeMeterRegistryTest.java

@@ -16,6 +16,7 @@
 package io.micrometer.registry.otlp;
 
 import io.micrometer.core.instrument.*;
+import io.micrometer.core.instrument.binder.BaseUnits;
 import io.opentelemetry.proto.metrics.v1.NumberDataPoint;
 import org.junit.jupiter.api.Test;
 
@@ -201,7 +202,7 @@ void functionTimer() {
     @Test
     void distributionSummary() {
         DistributionSummary size = DistributionSummary.builder("http.response.size")
-            .baseUnit("bytes")
+            .baseUnit(BaseUnits.BYTES)
             .register(registry);
         size.record(100);
         size.record(15);
@@ -218,7 +219,7 @@ void distributionSummary() {
     @Test
     void distributionSummaryWithHistogramBuckets() {
         DistributionSummary size = DistributionSummary.builder("http.request.size")
-            .baseUnit("bytes")
+            .baseUnit(BaseUnits.BYTES)
             .publishPercentileHistogram()
             .register(registry);
         size.record(100);

implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OtlpDeltaMeterRegistryCompatibilityTest.java

@@ -21,7 +21,7 @@
 
 import java.time.Duration;
 
-public class OtlpDeltaMeterRegistryCompatibilityTest extends MeterRegistryCompatibilityKit {
+class OtlpDeltaMeterRegistryCompatibilityTest extends MeterRegistryCompatibilityKit {
 
     @Override
     public MeterRegistry registry() {

implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OtlpDeltaMeterRegistryTest.java

@@ -65,7 +65,7 @@ public String get(String key) {
                 return null;
             }
         };
-    };
+    }
 
     @Test
     void gauge() {
@@ -321,7 +321,7 @@ void testMetricsStartAndEndTime() {
         Function<Meter, NumberDataPoint> getDataPoint = (meter) -> writeToMetric(meter).getSum().getDataPoints(0);
         assertThat(getDataPoint.apply(counter).getStartTimeUnixNano()).isEqualTo(0);
         assertThat(getDataPoint.apply(counter).getTimeUnixNano()).isEqualTo(60000000000L);
-        clock.addSeconds(59);
+        clock.addSeconds(otlpConfig().step().getSeconds() - 1);
         assertThat(getDataPoint.apply(counter).getStartTimeUnixNano()).isEqualTo(0);
         assertThat(getDataPoint.apply(counter).getTimeUnixNano()).isEqualTo(60000000000L);
         clock.addSeconds(1);

micrometer-core/src/main/java/io/micrometer/core/instrument/AbstractDistributionSummary.java

@@ -29,19 +29,34 @@ protected AbstractDistributionSummary(Id id, Clock clock, DistributionStatisticC
         this(id, scale, defaultHistogram(clock, distributionStatisticConfig, supportsAggregablePercentiles));
     }
 
+    /**
+     * Creates an {@code AbstractDistributionSummary} instance.
+     * @param id meter ID
+     * @param scale scale
+     * @param histogram histogram
+     * @since 1.11.0
+     */
     protected AbstractDistributionSummary(Id id, double scale, @Nullable Histogram histogram) {
         super(id);
         this.scale = scale;
         this.histogram = histogram == null ? NoopHistogram.INSTANCE : histogram;
     }
 
+    /**
+     * Creates a default histogram.
+     * @param clock clock
+     * @param distributionStatisticConfig distribution statistic configuration
+     * @param supportsAggregablePercentiles whether to support aggregable percentiles
+     * @return a default histogram
+     * @since 1.11.0
+     */
     protected static Histogram defaultHistogram(Clock clock, DistributionStatisticConfig distributionStatisticConfig,
             boolean supportsAggregablePercentiles) {
         if (distributionStatisticConfig.isPublishingPercentiles()) {
             // hdr-based histogram
             return new TimeWindowPercentileHistogram(clock, distributionStatisticConfig, supportsAggregablePercentiles);
         }
-        else if (distributionStatisticConfig.isPublishingHistogram()) {
+        if (distributionStatisticConfig.isPublishingHistogram()) {
             // fixed boundary histograms, which have a slightly better memory footprint
             // when we don't need Micrometer-computed percentiles
             return new TimeWindowFixedBoundaryHistogram(clock, distributionStatisticConfig,

micrometer-core/src/main/java/io/micrometer/core/instrument/AbstractTimer.java

@@ -86,6 +86,15 @@ protected AbstractTimer(Id id, Clock clock, DistributionStatisticConfig distribu
                 defaultHistogram(clock, distributionStatisticConfig, supportsAggregablePercentiles));
     }
 
+    /**
+     * Creates a new timer.
+     * @param id The timer's name and tags.
+     * @param clock The clock used to measure latency.
+     * @param pauseDetector Compensation for coordinated omission.
+     * @param baseTimeUnit The time scale of this timer.
+     * @param histogram Histogram.
+     * @since 1.11.0
+     */
     protected AbstractTimer(Id id, Clock clock, PauseDetector pauseDetector, TimeUnit baseTimeUnit,
             Histogram histogram) {
         super(id);
@@ -95,13 +104,23 @@ protected AbstractTimer(Id id, Clock clock, PauseDetector pauseDetector, TimeUni
         this.histogram = histogram;
     }
 
+    /**
+     * Creates a default histogram.
+     * @param clock The clock used to measure latency.
+     * @param distributionStatisticConfig Configuration determining which distribution
+     * statistics are sent.
+     * @param supportsAggregablePercentiles Indicates whether the registry supports
+     * percentile approximations from histograms.
+     * @return a default histogram
+     * @since 1.11.0
+     */
     protected static Histogram defaultHistogram(Clock clock, DistributionStatisticConfig distributionStatisticConfig,
             boolean supportsAggregablePercentiles) {
         if (distributionStatisticConfig.isPublishingPercentiles()) {
             // hdr-based histogram
             return new TimeWindowPercentileHistogram(clock, distributionStatisticConfig, supportsAggregablePercentiles);
         }
-        else if (distributionStatisticConfig.isPublishingHistogram()) {
+        if (distributionStatisticConfig.isPublishingHistogram()) {
             // fixed boundary histograms, which have a slightly better memory footprint
             // when we don't need Micrometer-computed percentiles
             return new TimeWindowFixedBoundaryHistogram(clock, distributionStatisticConfig,

micrometer-core/src/main/java/io/micrometer/core/instrument/cumulative/CumulativeDistributionSummary.java

@@ -54,6 +54,15 @@ public CumulativeDistributionSummary(Id id, Clock clock, DistributionStatisticCo
                 distributionStatisticConfig, supportsAggregablePercentiles));
     }
 
+    /**
+     * Creates a {@code CumulativeDistributionSummary} instance.
+     * @param id meter ID
+     * @param clock clock
+     * @param distributionStatisticConfig distribution statistic configuration
+     * @param scale scale
+     * @param histogram histogram
+     * @since 1.11.0
+     */
     protected CumulativeDistributionSummary(Id id, Clock clock, DistributionStatisticConfig distributionStatisticConfig,
             double scale, Histogram histogram) {
         super(id, scale, histogram);

micrometer-core/src/main/java/io/micrometer/core/instrument/cumulative/CumulativeTimer.java

@@ -48,6 +48,16 @@ public CumulativeTimer(Id id, Clock clock, DistributionStatisticConfig distribut
                 AbstractTimer.defaultHistogram(clock, distributionStatisticConfig, supportsAggregablePercentiles));
     }
 
+    /**
+     * Creates a {@code CumulativeTimer} instance.
+     * @param id meter ID
+     * @param clock clock
+     * @param distributionStatisticConfig distribution statistic configuration
+     * @param pauseDetector pause detector
+     * @param baseTimeUnit base time unit
+     * @param histogram histogram
+     * @since 1.11.0
+     */
     protected CumulativeTimer(Id id, Clock clock, DistributionStatisticConfig distributionStatisticConfig,
             PauseDetector pauseDetector, TimeUnit baseTimeUnit, Histogram histogram) {
         super(id, clock, pauseDetector, baseTimeUnit, histogram);

micrometer-core/src/main/java/io/micrometer/core/instrument/distribution/DistributionStatisticConfig.java

@@ -477,7 +477,7 @@ private void validate(DistributionStatisticConfig distributionStatisticConfig) {
             }
 
             if (config.maximumExpectedValue != null && config.maximumExpectedValue <= 0) {
-                rejectConfig("maximumExpectedValue (" + config.minimumExpectedValue + ") must be greater than 0.");
+                rejectConfig("maximumExpectedValue (" + config.maximumExpectedValue + ") must be greater than 0.");
             }
 
             if ((config.minimumExpectedValue != null && config.maximumExpectedValue != null)

micrometer-core/src/main/java/io/micrometer/core/instrument/distribution/FixedBoundaryHistogram.java

@@ -55,15 +55,16 @@ void record(long value) {
     /**
      * The least bucket that is less than or equal to a sample.
      */
-    int leastLessThanOrEqualTo(long key) {
+    int leastLessThanOrEqualTo(double key) {
         int low = 0;
         int high = buckets.length - 1;
 
         while (low <= high) {
             int mid = (low + high) >>> 1;
-            if (buckets[mid] < key)
+            double value = buckets[mid];
+            if (value < key)
                 low = mid + 1;
-            else if (buckets[mid] > key)
+            else if (value > key)
                 high = mid - 1;
             else
                 return mid; // exact match

micrometer-core/src/main/java/io/micrometer/core/instrument/distribution/StepBucketHistogram.java

@@ -26,8 +26,8 @@
 import java.util.function.Supplier;
 
 /**
- * A Histogram implementation which inherits the behaviour of Step Meters i,e this
- * histogram exhibits read and reset behaviour.
+ * A Histogram implementation which inherits the behaviour of step meters, i.e. read and
+ * reset behaviour.
  *
  * @author Lenin Jaganathan
  * @since 1.11.0
@@ -60,7 +60,7 @@ public void recordDouble(double value) {
 
     @Override
     public HistogramSnapshot takeSnapshot(long count, double total, double max) {
-        return new HistogramSnapshot(count, total, max, null, this.poll(), null);
+        return new HistogramSnapshot(count, total, max, null, poll(), null);
     }
 
     @Override
@@ -95,7 +95,9 @@ private static CountAtBucket[] getEmptyCounts(double[] buckets) {
     private static double[] getBucketsFromDistributionStatisticConfig(
             DistributionStatisticConfig distributionStatisticConfig, boolean supportsAggregablePercentiles) {
         if (distributionStatisticConfig.getMaximumExpectedValueAsDouble() == null
-                || distributionStatisticConfig.getMinimumExpectedValueAsDouble() == null) {
+                || distributionStatisticConfig.getMinimumExpectedValueAsDouble() == null
+                || distributionStatisticConfig.getMaximumExpectedValueAsDouble() <= 0
+                || distributionStatisticConfig.getMinimumExpectedValueAsDouble() <= 0) {
             throw new InvalidConfigurationException(
                     "minimumExpectedValue and maximumExpectedValue should be greater than 0.");
         }

micrometer-core/src/main/java/io/micrometer/core/instrument/distribution/TimeWindowFixedBoundaryHistogram.java

@@ -109,7 +109,7 @@ void resetAccumulatedHistogram() {
     }
 
     /**
-     * For recording efficiency, We turn normal histogram into cumulative count histogram
+     * For recording efficiency, we turn normal histogram into cumulative count histogram
      * only on calls to {@link #countsAtValues(Iterator<Double>)}.
      */
     @Override

micrometer-core/src/main/java/io/micrometer/core/instrument/step/StepValue.java

@@ -43,6 +43,13 @@ public StepValue(final Clock clock, final long stepMillis) {
         this(clock, stepMillis, null);
     }
 
+    /**
+     * Creates a {@code StepValue} instance.
+     * @param clock clock
+     * @param stepMillis step in milliseconds
+     * @param initValue initial value
+     * @since 1.11.0
+     */
     protected StepValue(final Clock clock, final long stepMillis, @Nullable final V initValue) {
         this.clock = clock;
         this.stepMillis = stepMillis;

micrometer-core/src/test/java/io/micrometer/core/instrument/distribution/StepHistogramTest.java

@@ -86,9 +86,10 @@ void sloWithAggregablePercentilesTrue_sloBucketPlusPercentilesHistogramBuckets()
             .merge(distributionStatisticConfig);
         try (StepBucketHistogram histogram = new StepBucketHistogram(clock, step.toMillis(), config,
                 supportsAggregablePercentiles, true)) {
-            assertThat(histogram.takeSnapshot(0, 0, 0).histogramCounts()).contains(new CountAtBucket(slo, 0));
+            CountAtBucket sloBucket = new CountAtBucket(slo, 0);
+            assertThat(histogram.takeSnapshot(0, 0, 0).histogramCounts()).hasSizeGreaterThan(1).contains(sloBucket);
             clock.add(step);
-            assertThat(histogram.takeSnapshot(0, 0, 0).histogramCounts()).contains(new CountAtBucket(slo, 0));
+            assertThat(histogram.takeSnapshot(0, 0, 0).histogramCounts()).hasSizeGreaterThan(1).contains(sloBucket);
         }
     }
 
@@ -103,9 +104,10 @@ void sloWithPercentileHistogramFalse_onlySloBucket() {
             .merge(getConfig(false));
         try (StepBucketHistogram histogram = new StepBucketHistogram(clock, step.toMillis(), config,
                 supportsAggregablePercentiles, true)) {
-            assertThat(histogram.takeSnapshot(0, 0, 0).histogramCounts()).contains(new CountAtBucket(slo, 0));
+            CountAtBucket sloBucket = new CountAtBucket(slo, 0);
+            assertThat(histogram.takeSnapshot(0, 0, 0).histogramCounts()).containsExactly(sloBucket);
             clock.add(step);
-            assertThat(histogram.takeSnapshot(0, 0, 0).histogramCounts()).contains(new CountAtBucket(slo, 0));
+            assertThat(histogram.takeSnapshot(0, 0, 0).histogramCounts()).containsExactly(sloBucket);
         }
     }