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Core module of Micrometer containing instrumentation API and implementation
/*
* Copyright 2017 VMware, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.micrometer.core.instrument.distribution;
import io.micrometer.core.instrument.Clock;
import io.micrometer.core.instrument.config.InvalidConfigurationException;
import io.micrometer.core.lang.Nullable;
import java.io.PrintStream;
import java.lang.reflect.Array;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
/**
* An abstract base class for histogram implementations who maintain samples in a ring
* buffer to decay older samples and give greater weight to recent samples.
*
* @param the type of the buckets in a ring buffer
* @param the type of accumulated histogram
* @author Jon Schneider
* @author Trustin Heuiseung Lee
*/
@SuppressWarnings("ConstantConditions")
abstract class AbstractTimeWindowHistogram implements Histogram {
@SuppressWarnings("rawtypes")
private static final AtomicIntegerFieldUpdater rotatingUpdater = AtomicIntegerFieldUpdater
.newUpdater(AbstractTimeWindowHistogram.class, "rotating");
final DistributionStatisticConfig distributionStatisticConfig;
private final Clock clock;
private final boolean supportsAggregablePercentiles;
private final T[] ringBuffer;
private short currentBucket;
private final long durationBetweenRotatesMillis;
private volatile boolean accumulatedHistogramStale;
private volatile long lastRotateTimestampMillis;
@SuppressWarnings({ "unused", "FieldCanBeLocal" })
private volatile int rotating; // 0 - not rotating, 1 - rotating
@Nullable
private U accumulatedHistogram;
@SuppressWarnings("unchecked")
AbstractTimeWindowHistogram(Clock clock, DistributionStatisticConfig distributionStatisticConfig,
Class bucketType, boolean supportsAggregablePercentiles) {
this.clock = clock;
this.distributionStatisticConfig = validateDistributionConfig(distributionStatisticConfig);
this.supportsAggregablePercentiles = supportsAggregablePercentiles;
final int ageBuckets = distributionStatisticConfig.getBufferLength();
if (ageBuckets <= 0) {
rejectHistogramConfig("bufferLength (" + ageBuckets + ") must be greater than 0.");
}
ringBuffer = (T[]) Array.newInstance(bucketType, ageBuckets);
durationBetweenRotatesMillis = distributionStatisticConfig.getExpiry().toMillis() / ageBuckets;
if (durationBetweenRotatesMillis <= 0) {
rejectHistogramConfig("expiry (" + distributionStatisticConfig.getExpiry().toMillis()
+ "ms) / bufferLength (" + ageBuckets + ") must be greater than 0.");
}
currentBucket = 0;
lastRotateTimestampMillis = clock.wallTime();
}
private static DistributionStatisticConfig validateDistributionConfig(
DistributionStatisticConfig distributionStatisticConfig) {
if (distributionStatisticConfig.getPercentiles() != null) {
for (double p : distributionStatisticConfig.getPercentiles()) {
if (p < 0 || p > 1) {
rejectHistogramConfig(
"percentiles must contain only the values between 0.0 and 1.0. " + "Found " + p);
}
}
if (distributionStatisticConfig.getPercentilePrecision() == null) {
rejectHistogramConfig("when publishing percentiles a precision must be specified.");
}
}
final Double minimumExpectedValue = distributionStatisticConfig.getMinimumExpectedValueAsDouble();
final Double maximumExpectedValue = distributionStatisticConfig.getMaximumExpectedValueAsDouble();
if (minimumExpectedValue == null || minimumExpectedValue <= 0) {
rejectHistogramConfig("minimumExpectedValue (" + minimumExpectedValue + ") must be greater than 0.");
}
if (maximumExpectedValue == null || maximumExpectedValue < minimumExpectedValue) {
rejectHistogramConfig("maximumExpectedValue (" + maximumExpectedValue
+ ") must be equal to or greater than minimumExpectedValue (" + minimumExpectedValue + ").");
}
if (distributionStatisticConfig.getServiceLevelObjectiveBoundaries() != null) {
for (double slo : distributionStatisticConfig.getServiceLevelObjectiveBoundaries()) {
if (slo <= 0) {
rejectHistogramConfig(
"serviceLevelObjectiveBoundaries must contain only the values greater than 0. " + "Found "
+ slo);
}
}
}
return distributionStatisticConfig;
}
private static void rejectHistogramConfig(String msg) {
throw new InvalidConfigurationException("Invalid distribution configuration: " + msg);
}
void initRingBuffer() {
for (int i = 0; i < ringBuffer.length; i++) {
ringBuffer[i] = newBucket();
}
accumulatedHistogram = newAccumulatedHistogram(ringBuffer);
}
abstract T newBucket();
abstract void recordLong(T bucket, long value);
abstract void recordDouble(T bucket, double value);
abstract void resetBucket(T bucket);
abstract U newAccumulatedHistogram(T[] ringBuffer);
abstract void accumulate();
abstract void resetAccumulatedHistogram();
abstract double valueAtPercentile(double percentile);
abstract double countAtValue(double value);
double countAtValue(long value) {
return countAtValue((double) value);
}
void outputSummary(PrintStream out, double bucketScaling) {
}
@Override
public final HistogramSnapshot takeSnapshot(long count, double total, double max) {
rotate();
final ValueAtPercentile[] values;
final CountAtBucket[] counts;
synchronized (this) {
accumulateIfStale();
values = takeValueSnapshot();
counts = takeCountSnapshot();
}
return new HistogramSnapshot(count, total, max, values, counts, this::outputSummary);
}
private void accumulateIfStale() {
if (accumulatedHistogramStale) {
accumulate();
accumulatedHistogramStale = false;
}
}
private ValueAtPercentile[] takeValueSnapshot() {
double[] monitoredPercentiles = distributionStatisticConfig.getPercentiles();
if (monitoredPercentiles == null || monitoredPercentiles.length == 0) {
return null;
}
final ValueAtPercentile[] values = new ValueAtPercentile[monitoredPercentiles.length];
for (int i = 0; i < monitoredPercentiles.length; i++) {
final double p = monitoredPercentiles[i];
values[i] = new ValueAtPercentile(p, valueAtPercentile(p * 100));
}
return values;
}
private CountAtBucket[] takeCountSnapshot() {
if (!distributionStatisticConfig.isPublishingHistogram()) {
return null;
}
final Set monitoredValues = distributionStatisticConfig
.getHistogramBuckets(supportsAggregablePercentiles);
if (monitoredValues.isEmpty()) {
return null;
}
final CountAtBucket[] counts = new CountAtBucket[monitoredValues.size()];
final Iterator iterator = monitoredValues.iterator();
for (int i = 0; i < counts.length; i++) {
final double v = iterator.next();
counts[i] = new CountAtBucket(v, countAtValue(v));
}
return counts;
}
public void recordLong(long value) {
rotate();
try {
for (T bucket : ringBuffer) {
recordLong(bucket, value);
}
}
catch (IndexOutOfBoundsException ignored) {
// the value is so large (or small) that the dynamic range of the histogram
// cannot be extended to include it
}
finally {
accumulatedHistogramStale = true;
}
}
public void recordDouble(double value) {
rotate();
try {
for (T bucket : ringBuffer) {
recordDouble(bucket, value);
}
}
catch (IndexOutOfBoundsException ignored) {
// the value is so large (or small) that the dynamic range of the histogram
// cannot be extended to include it
}
finally {
accumulatedHistogramStale = true;
}
}
private void rotate() {
long timeSinceLastRotateMillis = clock.wallTime() - lastRotateTimestampMillis;
if (timeSinceLastRotateMillis < durationBetweenRotatesMillis) {
// Need to wait more for next rotation.
return;
}
if (!rotatingUpdater.compareAndSet(this, 0, 1)) {
// Being rotated by other thread already.
return;
}
try {
int iterations = 0;
synchronized (this) {
do {
resetBucket(ringBuffer[currentBucket]);
if (++currentBucket >= ringBuffer.length) {
currentBucket = 0;
}
timeSinceLastRotateMillis -= durationBetweenRotatesMillis;
lastRotateTimestampMillis += durationBetweenRotatesMillis;
}
while (timeSinceLastRotateMillis >= durationBetweenRotatesMillis && ++iterations < ringBuffer.length);
resetAccumulatedHistogram();
accumulatedHistogramStale = true;
}
}
finally {
rotating = 0;
}
}
protected U accumulatedHistogram() {
return accumulatedHistogram;
}
protected T currentHistogram() {
return ringBuffer[currentBucket];
}
}