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Core module of Micrometer containing instrumentation API and implementation
/*
* Copyright 2020 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 java.io.PrintStream;
import java.math.BigDecimal;
import java.math.MathContext;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicLongArray;
import java.util.concurrent.atomic.AtomicReferenceArray;
import java.util.concurrent.atomic.DoubleAdder;
/**
* A histogram implementation for non-negative values with automatically created buckets.
* It does not support precomputed percentiles but supports aggregable percentile
* histograms. It's suitable only with VictoriaMetrics storage.
*
* Reference
* implementation written in Go originally by Aliaksandr Valialkin.
*
* @author Aliaksandr Valialkin
* @author Nikolay Ustinov
* @since 1.4.0
*/
public class FixedBoundaryVictoriaMetricsHistogram implements Histogram {
private static final IdxOffset UPPER = new IdxOffset(-1, 2);
private static final IdxOffset LOWER = new IdxOffset(-1, 1);
private static final IdxOffset ZERO = new IdxOffset(-1, 0);
private static final int E10MIN = -9;
private static final int E10MAX = 18;
private static final int DECIMAL_MULTIPLIER = 2;
private static final int BUCKET_SIZE = 9 * DECIMAL_MULTIPLIER;
private static final int BUCKETS_COUNT = E10MAX - E10MIN;
private static final double DECIMAL_PRECISION = 0.01 / DECIMAL_MULTIPLIER;
private static final String[] VMRANGES;
private static final double[] UPPER_BOUNDS;
static {
VMRANGES = new String[3 + BUCKETS_COUNT * BUCKET_SIZE];
VMRANGES[0] = "0...0";
VMRANGES[1] = String.format("0...%.1fe%d", 1.0, E10MIN);
VMRANGES[2] = String.format("%.1fe%d...+Inf", 1.0, E10MAX);
UPPER_BOUNDS = new double[3 + BUCKETS_COUNT * BUCKET_SIZE];
UPPER_BOUNDS[0] = 0.0;
UPPER_BOUNDS[1] = BigDecimal.TEN.pow(E10MIN, MathContext.DECIMAL128).doubleValue();
UPPER_BOUNDS[2] = Double.POSITIVE_INFINITY;
int idx = 3;
String start = String.format("%.1fe%d", 1.0, E10MIN);
for (int bucketIdx = 0; bucketIdx < BUCKETS_COUNT; bucketIdx++) {
for (int offset = 0; offset < BUCKET_SIZE; offset++) {
int e10 = E10MIN + bucketIdx;
double m = 1 + (double) (offset + 1) / DECIMAL_MULTIPLIER;
if (Math.abs(m - 10) < DECIMAL_PRECISION) {
m = 1;
e10++;
}
String end = String.format("%.1fe%d", m, e10);
VMRANGES[idx] = start + "..." + end;
UPPER_BOUNDS[idx] = BigDecimal.valueOf(m).setScale(1, RoundingMode.HALF_UP)
.multiply(BigDecimal.TEN.pow(e10, MathContext.DECIMAL128)).doubleValue();
idx++;
start = end;
}
}
}
final AtomicReferenceArray values;
final AtomicLong zeros;
final AtomicLong lower;
final AtomicLong upper;
final DoubleAdder sum;
public FixedBoundaryVictoriaMetricsHistogram() {
this.zeros = new AtomicLong();
this.lower = new AtomicLong();
this.upper = new AtomicLong();
this.sum = new DoubleAdder();
this.values = new AtomicReferenceArray<>(BUCKETS_COUNT);
}
@Override
public void recordLong(long value) {
recordDouble((double) value);
}
@Override
public void recordDouble(double value) {
if (Double.isNaN(value) || value < 0)
return;
IdxOffset inxs = getBucketIdxAndOffset(value);
sum.add(value);
if (inxs.bucketIdx < 0) {
if (inxs.offset == 0)
zeros.incrementAndGet();
else if (inxs.offset == 1)
lower.incrementAndGet();
else
upper.incrementAndGet();
return;
}
AtomicLongArray hb = values.get(inxs.bucketIdx);
if (hb == null) {
hb = new AtomicLongArray(BUCKET_SIZE);
if (!values.compareAndSet(inxs.bucketIdx, null, hb))
hb = values.get(inxs.bucketIdx);
}
hb.incrementAndGet(inxs.offset);
}
private static IdxOffset getBucketIdxAndOffset(double value) {
if (value < 0)
throw new RuntimeException(String.format("BUG: v must be positive; got %f", value));
if (value == 0)
return ZERO;
if (Double.POSITIVE_INFINITY == value)
return UPPER;
int e10 = (int) Math.floor(Math.log10(value));
int bucketIdx = e10 - E10MIN;
if (bucketIdx < 0)
return LOWER;
double pow = Math.pow(10, e10);
if (bucketIdx >= BUCKETS_COUNT) {
if ((bucketIdx == BUCKETS_COUNT) && (Math.abs(pow - value) < DECIMAL_PRECISION)) {
// Adjust m to be on par with Prometheus 'le' buckets (aka 'less or
// equal')
return new IdxOffset(BUCKETS_COUNT - 1, BUCKET_SIZE - 1);
}
return UPPER;
}
double m = ((value / pow) - 1) * DECIMAL_MULTIPLIER;
int offset = (int) m;
if (offset < 0)
offset = 0;
else if (offset >= BUCKET_SIZE)
offset = BUCKET_SIZE - 1;
if (Math.abs((double) offset - m) < DECIMAL_PRECISION) {
// Adjust offset to be on par with Prometheus 'le' buckets (aka 'less or
// equal')
offset--;
if (offset < 0) {
bucketIdx--;
if (bucketIdx < 0)
return LOWER;
offset = BUCKET_SIZE - 1;
}
}
return new IdxOffset(bucketIdx, offset);
}
private static int getRangeIndex(int index, int offset) {
if (index < 0) {
if (offset > 2)
throw new RuntimeException(
String.format("BUG: offset must be in range [0...2] for negative bucketIdx; got %d", offset));
return offset;
}
return 3 + index * BUCKET_SIZE + offset;
}
public static String getRangeTagValue(double value) {
IdxOffset idxOffset = getBucketIdxAndOffset(value);
return VMRANGES[getRangeIndex(idxOffset.bucketIdx, idxOffset.offset)];
}
private List nonZeroBuckets() {
List buckets = new ArrayList<>();
long zeroSnap = zeros.get();
if (zeroSnap > 0) {
buckets.add(new CountAtBucket(UPPER_BOUNDS[getRangeIndex(ZERO.bucketIdx, ZERO.offset)], zeroSnap));
}
long lowerSnap = lower.get();
if (lowerSnap > 0) {
buckets.add(new CountAtBucket(UPPER_BOUNDS[getRangeIndex(LOWER.bucketIdx, LOWER.offset)], lowerSnap));
}
long upperSnap = upper.get();
if (upperSnap > 0) {
buckets.add(new CountAtBucket(UPPER_BOUNDS[getRangeIndex(UPPER.bucketIdx, UPPER.offset)], upperSnap));
}
for (int i = 0; i < values.length(); i++) {
AtomicLongArray bucket = values.get(i);
if (bucket != null) {
for (int j = 0; j < bucket.length(); j++) {
long cnt = bucket.get(j);
if (cnt > 0) {
buckets.add(new CountAtBucket(UPPER_BOUNDS[getRangeIndex(i, j)], cnt));
}
}
}
}
return buckets;
}
@Override
public HistogramSnapshot takeSnapshot(long count, double total, double max) {
return new HistogramSnapshot(count, total, max, null, nonZeroBuckets().toArray(new CountAtBucket[0]),
this::outputSummary);
}
private void outputSummary(PrintStream printStream, double bucketScaling) {
printStream.format("%14s %10s\n\n", "Bucket", "TotalCount");
for (CountAtBucket bucket : nonZeroBuckets()) {
printStream.format(Locale.US, "%14.1f %10d\n", bucket.bucket() / bucketScaling, bucket.count());
}
printStream.write('\n');
}
private static class IdxOffset {
final int bucketIdx;
final int offset;
IdxOffset(int bucketIdx, int offset) {
this.bucketIdx = bucketIdx;
this.offset = offset;
}
}
}