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Align DeltaHistogram in SignalFx registry with count and total (#3799)
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Count and total for Step Meters have been made to roll over at the start of the step. SignalFx's DeltaHistogram however did not align to this, resulting in a histogram that does not match with the count/total values as it should. This makes those align and generally updates the implementation to align better with the behavior provided to StepMeterRegistry implementations.

Closes gh-3774
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@lenin-jaganathan
lenin-jaganathan authored Jun 12, 2023
1 parent 693ffa8 commit 03a227a
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Showing 10 changed files with 260 additions and 196 deletions.
25 changes: 17 additions & 8 deletions ...registry-signalfx/src/main/java/io/micrometer/signalfx/CumulativeHistogramConfigUtil.java
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*/
final class CumulativeHistogramConfigUtil {

static DistributionStatisticConfig updateConfig(DistributionStatisticConfig distributionStatisticConfig) {
private static final double[] EMPTY_SLO = new double[0];

static DistributionStatisticConfig updateConfig(DistributionStatisticConfig distributionStatisticConfig,
boolean isDelta) {
double[] sloBoundaries = distributionStatisticConfig.getServiceLevelObjectiveBoundaries();
if (sloBoundaries == null || sloBoundaries.length == 0) {
return distributionStatisticConfig;
}
double[] newSloBoundaries = sloBoundaries;
// Add the +Inf bucket since the "count" resets every export.
if (!isPositiveInf(sloBoundaries[sloBoundaries.length - 1])) {
newSloBoundaries = Arrays.copyOf(sloBoundaries, sloBoundaries.length + 1);
newSloBoundaries[newSloBoundaries.length - 1] = Double.MAX_VALUE;
}

return DistributionStatisticConfig.builder()
// Set the expiration duration for the histogram counts to be effectively
// infinite.
// Without this, the counts are reset every expiry duration.
.expiry(Duration.ofNanos(Long.MAX_VALUE)) // effectively infinite
.bufferLength(1)
.serviceLevelObjectives(newSloBoundaries)
// If delta Histograms are enabled, empty the slo's and use
// StepBucketHistogram.
.serviceLevelObjectives(isDelta ? EMPTY_SLO : addPositiveInfBucket(sloBoundaries))
.build()
.merge(distributionStatisticConfig);
}

static double[] addPositiveInfBucket(double[] sloBoundaries) {
double[] newSloBoundaries = sloBoundaries;
// Add the +Inf bucket since the "count" resets every export.
if (!isPositiveInf(sloBoundaries[sloBoundaries.length - 1])) {
newSloBoundaries = Arrays.copyOf(sloBoundaries, sloBoundaries.length + 1);
newSloBoundaries[newSloBoundaries.length - 1] = Double.MAX_VALUE;
}
return newSloBoundaries;
}

private static boolean isPositiveInf(double bucket) {
return bucket == Double.POSITIVE_INFINITY || bucket == Double.MAX_VALUE || (long) bucket == Long.MAX_VALUE;
}
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41 changes: 0 additions & 41 deletions ...crometer-registry-signalfx/src/main/java/io/micrometer/signalfx/DeltaHistogramCounts.java
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84 changes: 34 additions & 50 deletions ...r-registry-signalfx/src/main/java/io/micrometer/signalfx/SignalfxDistributionSummary.java
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package io.micrometer.signalfx;

import io.micrometer.common.lang.Nullable;
import io.micrometer.core.instrument.AbstractDistributionSummary;
import io.micrometer.core.instrument.Clock;
import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
import io.micrometer.core.instrument.distribution.HistogramSnapshot;
import io.micrometer.core.instrument.distribution.TimeWindowMax;
import io.micrometer.core.instrument.step.StepTuple2;

import java.util.concurrent.atomic.DoubleAdder;
import java.util.concurrent.atomic.LongAdder;
import io.micrometer.core.instrument.distribution.StepBucketHistogram;
import io.micrometer.core.instrument.step.StepDistributionSummary;

/**
* This class is mostly the same as
* {@link io.micrometer.core.instrument.step.StepDistributionSummary}, with one notable
* difference: the {@link DistributionStatisticConfig} is modified before being passed to
* the super class constructor - that forces the histogram generated by this meter to be
* cumulative.
* A StepDistributionSummary which provides support for multiple flavours of Histograms to
* be recorded based on {@link SignalFxConfig#publishCumulativeHistogram()} and
* {@link SignalFxConfig#publishDeltaHistogram()}.
*
* @author Bogdan Drutu
* @author Mateusz Rzeszutek
* @author Lenin Jaganathan
*/
final class SignalfxDistributionSummary extends AbstractDistributionSummary {

private final LongAdder count = new LongAdder();

private final DoubleAdder total = new DoubleAdder();

private final StepTuple2<Long, Double> countTotal;

private final TimeWindowMax max;
final class SignalfxDistributionSummary extends StepDistributionSummary {

@Nullable
private final DeltaHistogramCounts deltaHistogramCounts;
private final StepBucketHistogram stepBucketHistogram;

SignalfxDistributionSummary(Id id, Clock clock, DistributionStatisticConfig distributionStatisticConfig,
double scale, long stepMillis, boolean isDelta) {
super(id, clock, CumulativeHistogramConfigUtil.updateConfig(distributionStatisticConfig), scale, false);
this.countTotal = new StepTuple2<>(clock, stepMillis, 0L, 0.0, count::sumThenReset, total::sumThenReset);
max = new TimeWindowMax(clock, distributionStatisticConfig);
if (distributionStatisticConfig.isPublishingHistogram() && isDelta) {
deltaHistogramCounts = new DeltaHistogramCounts();
super(id, clock, distributionStatisticConfig, scale, stepMillis, defaultHistogram(clock,
CumulativeHistogramConfigUtil.updateConfig(distributionStatisticConfig, isDelta), false));

double[] slo = distributionStatisticConfig.getServiceLevelObjectiveBoundaries();
if (slo != null && slo.length > 0 && isDelta) {
stepBucketHistogram = new StepBucketHistogram(clock, stepMillis,
DistributionStatisticConfig.builder()
.serviceLevelObjectives(CumulativeHistogramConfigUtil.addPositiveInfBucket(slo))
.build()
.merge(distributionStatisticConfig),
false, true);
}
else {
deltaHistogramCounts = null;
stepBucketHistogram = null;
}
}

@Override
protected void recordNonNegative(double amount) {
count.increment();
total.add(amount);
max.record(amount);
if (stepBucketHistogram != null) {
stepBucketHistogram.recordDouble(amount);
}
super.recordNonNegative(amount);
}

@Override
public long count() {
return countTotal.poll1();
}

@Override
public double totalAmount() {
return countTotal.poll2();
}

@Override
public double max() {
return max.poll();
if (stepBucketHistogram != null) {
// Force the stepBucketHistogram to be aligned to step by calling count. This
// ensures that all
// values exported by the Timer are measured for the same step.
stepBucketHistogram.poll();
}
return super.count();
}

@Override
public HistogramSnapshot takeSnapshot() {
HistogramSnapshot currentSnapshot = super.takeSnapshot();
if (deltaHistogramCounts == null) {
if (stepBucketHistogram == null) {
return currentSnapshot;
}
return new HistogramSnapshot(currentSnapshot.count(), // Already delta in sfx
// implementation.
currentSnapshot.total(), // Already delta in sfx implementation.
currentSnapshot.max(), // Max cannot be calculated as delta, keep the
// current.
currentSnapshot.percentileValues(), // No changes to the percentile
// values.
deltaHistogramCounts.calculate(currentSnapshot.histogramCounts()), currentSnapshot::outputSummary);
return new HistogramSnapshot(currentSnapshot.count(), currentSnapshot.total(), currentSnapshot.max(),
currentSnapshot.percentileValues(), stepBucketHistogram.poll(), currentSnapshot::outputSummary);
}

}
84 changes: 34 additions & 50 deletions ...ions/micrometer-registry-signalfx/src/main/java/io/micrometer/signalfx/SignalfxTimer.java
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package io.micrometer.signalfx;

import io.micrometer.common.lang.Nullable;
import io.micrometer.core.instrument.AbstractTimer;
import io.micrometer.core.instrument.Clock;
import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
import io.micrometer.core.instrument.distribution.HistogramSnapshot;
import io.micrometer.core.instrument.distribution.TimeWindowMax;
import io.micrometer.core.instrument.distribution.StepBucketHistogram;
import io.micrometer.core.instrument.distribution.pause.PauseDetector;
import io.micrometer.core.instrument.step.StepTuple2;
import io.micrometer.core.instrument.util.TimeUtils;
import io.micrometer.core.instrument.step.StepTimer;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.LongAdder;

/**
* This class is mostly the same as {@link io.micrometer.core.instrument.step.StepTimer},
* with one notable difference: the {@link DistributionStatisticConfig} is modified before
* being passed to the super class constructor - that forces the histogram generated by
* this meter to be cumulative.
* A StepTimer which provides support for multiple flavours of Histograms to be recorded
* based on {@link SignalFxConfig#publishCumulativeHistogram()} and
* {@link SignalFxConfig#publishDeltaHistogram()}.
*
* @author Bogdan Drutu
* @author Mateusz Rzeszutek
* @author Lenin Jaganathan
*/
final class SignalfxTimer extends AbstractTimer {

private final LongAdder count = new LongAdder();

private final LongAdder total = new LongAdder();

private final StepTuple2<Long, Long> countTotal;

private final TimeWindowMax max;
final class SignalfxTimer extends StepTimer {

@Nullable
private final DeltaHistogramCounts deltaHistogramCounts;
private final StepBucketHistogram stepBucketHistogram;

SignalfxTimer(Id id, Clock clock, DistributionStatisticConfig distributionStatisticConfig,
PauseDetector pauseDetector, TimeUnit baseTimeUnit, long stepMillis, boolean isDelta) {
super(id, clock, CumulativeHistogramConfigUtil.updateConfig(distributionStatisticConfig), pauseDetector,
baseTimeUnit, false);
countTotal = new StepTuple2<>(clock, stepMillis, 0L, 0L, count::sumThenReset, total::sumThenReset);
max = new TimeWindowMax(clock, distributionStatisticConfig);
if (distributionStatisticConfig.isPublishingHistogram() && isDelta) {
deltaHistogramCounts = new DeltaHistogramCounts();
super(id, clock, distributionStatisticConfig, pauseDetector, baseTimeUnit, stepMillis, defaultHistogram(clock,
CumulativeHistogramConfigUtil.updateConfig(distributionStatisticConfig, isDelta), false));

double[] slo = distributionStatisticConfig.getServiceLevelObjectiveBoundaries();
if (slo != null && slo.length > 0 && isDelta) {
stepBucketHistogram = new StepBucketHistogram(clock, stepMillis,
DistributionStatisticConfig.builder()
.serviceLevelObjectives(CumulativeHistogramConfigUtil.addPositiveInfBucket(slo))
.build()
.merge(distributionStatisticConfig),
false, true);
}
else {
deltaHistogramCounts = null;
stepBucketHistogram = null;
}
}

@Override
protected void recordNonNegative(long amount, TimeUnit unit) {
final long nanoAmount = (long) TimeUtils.convert(amount, unit, TimeUnit.NANOSECONDS);
count.increment();
total.add(nanoAmount);
max.record(amount, unit);
if (stepBucketHistogram != null) {
stepBucketHistogram.recordLong(TimeUnit.NANOSECONDS.convert(amount, unit));
}
super.recordNonNegative(amount, unit);
}

@Override
public long count() {
return countTotal.poll1();
}

@Override
public double totalTime(TimeUnit unit) {
return TimeUtils.nanosToUnit(countTotal.poll2(), unit);
}

@Override
public double max(TimeUnit unit) {
return max.poll(unit);
if (stepBucketHistogram != null) {
// Force the stepBucketHistogram to be aligned to step by calling count. This
// ensures that all
// values exported by the Timer are measured for the same step.
stepBucketHistogram.poll();
}
return super.count();
}

@Override
public HistogramSnapshot takeSnapshot() {
HistogramSnapshot currentSnapshot = super.takeSnapshot();
if (deltaHistogramCounts == null) {
if (stepBucketHistogram == null) {
return currentSnapshot;
}
return new HistogramSnapshot(currentSnapshot.count(), // Already delta in sfx
// implementation
currentSnapshot.total(), // Already delta in sfx implementation
currentSnapshot.max(), // Max cannot be calculated as delta, keep the
// current.
currentSnapshot.percentileValues(), // No changes to the percentile
// values.
deltaHistogramCounts.calculate(currentSnapshot.histogramCounts()), currentSnapshot::outputSummary);
return new HistogramSnapshot(currentSnapshot.count(), currentSnapshot.total(), currentSnapshot.max(),
currentSnapshot.percentileValues(), stepBucketHistogram.poll(), currentSnapshot::outputSummary);
}

}
45 changes: 0 additions & 45 deletions ...eter-registry-signalfx/src/test/java/io/micrometer/signalfx/DeltaHistogramCountsTest.java
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