org.glowroot.collector.LazyHistogram Maven / Gradle / Ivy
/*
* Copyright 2015 the original author or authors.
*
* 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
*
* http://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 org.glowroot.collector;
import java.lang.reflect.Field;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.zip.DataFormatException;
import javax.annotation.Nullable;
import org.glowroot.shaded.google.common.annotations.VisibleForTesting;
import org.glowroot.shaded.HdrHistogram.Histogram;
import org.checkerframework.checker.nullness.qual.EnsuresNonNull;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
import org.glowroot.shaded.slf4j.Logger;
import org.glowroot.shaded.slf4j.LoggerFactory;
public class LazyHistogram {
private static final Logger logger = LoggerFactory.getLogger(LazyHistogram.class);
private static final int HISTOGRAM_SIGNIFICANT_DIGITS = 2;
private static final int MAX_VALUES = 1024;
// this is temporary workaround until next HdrHistogram release
// see https://github.com/HdrHistogram/HdrHistogram/pull/59
private static final @Nullable Field hdrHistogramInternalField;
static {
Field field = null;
try {
Class clazz = Class.forName("org.glowroot.shaded.HdrHistogram.AbstractHistogramBase");
field = clazz.getDeclaredField("intermediateUncompressedByteBuffer");
field.setAccessible(true);
} catch (Exception e) {
logger.error(e.getMessage(), e);
}
hdrHistogramInternalField = field;
}
private long[] values = new long[8];
private int size;
private boolean sorted;
private @MonotonicNonNull Histogram histogram;
public void decodeFromByteBuffer(ByteBuffer buffer) throws DataFormatException {
if (buffer.getInt() == 0) {
// 0 means list of (already sorted) longs
// read size and use it to pre-allocate correctly sized array
int numNewValues = buffer.getInt();
ensureCapacity(size + numNewValues);
if (histogram == null) {
// only will be sorted afterwards if starting out empty
sorted = size == 0;
while (buffer.remaining() > 0) {
values[size++] = buffer.getLong();
}
} else {
while (buffer.remaining() > 0) {
histogram.recordValue(buffer.getLong());
}
}
} else {
// 1 means compressed histogram
if (histogram == null) {
convertValuesToHistogram();
}
histogram.add(Histogram.decodeFromCompressedByteBuffer(buffer, 0));
}
}
public long getValueAtPercentile(double percentile) {
if (histogram == null) {
if (size == 0) {
// this is consisten with HdrHistogram behavior
return 0;
}
if (!sorted) {
sortValues();
}
return values[(int) Math.ceil(size * percentile / 100) - 1];
}
return histogram.getValueAtPercentile(percentile);
}
public int getNeededByteBufferCapacity() {
if (histogram == null) {
return 8 + size * 8;
} else {
return 4 + histogram.getNeededByteBufferCapacity();
}
}
public byte[] encodeUsingTempByteBuffer(ByteBuffer tempBuffer) {
if (histogram == null) {
tempBuffer.putInt(0);
// write the size so can pre-allocate correctly sized array when reading
tempBuffer.putInt(size);
if (!sorted) {
// sort values before storing so don't have to sort each time later when calculating
// percentiles
sortValues();
}
for (int i = 0; i < size; i++) {
tempBuffer.putLong(values[i]);
}
} else {
tempBuffer.putInt(1);
if (hdrHistogramInternalField != null) {
// this is temporary workaround until next HdrHistogram release
// see https://github.com/HdrHistogram/HdrHistogram/pull/59
try {
hdrHistogramInternalField.set(histogram, null);
} catch (IllegalArgumentException e) {
logger.error(e.getMessage(), e);
} catch (IllegalAccessException e) {
logger.error(e.getMessage(), e);
}
}
histogram.encodeIntoCompressedByteBuffer(tempBuffer);
}
int size = tempBuffer.position();
tempBuffer.flip();
byte[] histogramBytes = new byte[size];
tempBuffer.get(histogramBytes, 0, size);
return histogramBytes;
}
@VisibleForTesting
public void add(long value) {
ensureCapacity(size + 1);
if (histogram != null) {
histogram.recordValue(value);
} else {
values[size++] = value;
sorted = false;
}
}
private void ensureCapacity(int capacity) {
if (histogram != null) {
return;
}
if (capacity > MAX_VALUES) {
convertValuesToHistogram();
return;
}
if (capacity > values.length) {
// at least double in size
long[] temp = new long[Math.max(size * 2, capacity)];
System.arraycopy(values, 0, temp, 0, size);
values = temp;
}
}
@EnsuresNonNull("histogram")
private void convertValuesToHistogram() {
histogram = new Histogram(HISTOGRAM_SIGNIFICANT_DIGITS);
for (int i = 0; i < size; i++) {
histogram.recordValue(values[i]);
}
values = new long[0];
}
private void sortValues() {
Arrays.sort(values, 0, size);
sorted = true;
}
}