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rollback to chunk rotation scheme which implemented in release 1.1, b…
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…ecause by mistake which happen in the release 1.2 writers can block each other.
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vladimir.bukhtoyarov committed Sep 5, 2016
1 parent 7e852c9 commit d222f95
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292 changes: 145 additions & 147 deletions src/main/java/com/github/metricscore/hdr/histogram/accumulator/ResetByChunksAccumulator.java
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Expand Up @@ -23,217 +23,220 @@
import org.HdrHistogram.Histogram;
import org.HdrHistogram.Recorder;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.LockSupport;
import java.util.function.Function;
import java.util.function.Supplier;

public class ResetByChunksAccumulator implements Accumulator {
public final class ResetByChunksAccumulator implements Accumulator {

private final long intervalBetweenResettingMillis;
private final long creationTimestamp;
private final boolean reportUncompletedChunkToSnapshot;
private final Chunk[] chunks;
private final Clock clock;
private final long creationTimestamp;
private final Histogram temporarySnapshotHistogram;

private final Phase left;
private final Phase right;
private final Phase[] phases;
private final AtomicReference<Phase> currentPhaseRef;
private final AtomicInteger phaseMutators = new AtomicInteger(0);

private volatile Runnable postponedPhaseRotation = null;
private volatile Thread snapshotTakerThread = null;
private final LeftRightChunk[] chunks;

public ResetByChunksAccumulator(Supplier<Recorder> recorderSupplier, int numberChunks, long intervalBetweenResettingMillis, boolean reportUncompletedChunkToSnapshot, Clock clock) {
this.intervalBetweenResettingMillis = intervalBetweenResettingMillis;
this.clock = clock;
this.creationTimestamp = clock.getTime();
this.reportUncompletedChunkToSnapshot = reportUncompletedChunkToSnapshot;

this.left = new Phase(recorderSupplier, creationTimestamp + intervalBetweenResettingMillis);
this.right = new Phase(recorderSupplier, Long.MAX_VALUE);
this.phases = new Phase[] {left, right};
this.currentPhaseRef = new AtomicReference<>(left);

this.chunks = new Chunk[numberChunks];
for (int i = 0; i < numberChunks; i++) {
Histogram chunkHistogram = left.intervalHistogram.copy();
this.chunks[i] = new Chunk(chunkHistogram, Long.MIN_VALUE);
this.chunks = new LeftRightChunk[numberChunks];
for (int i = 0; i < chunks.length; i++) {
this.chunks[i] = new LeftRightChunk(recorderSupplier, i);
}
this.temporarySnapshotHistogram = chunks[0].histogram.copy();
this.temporarySnapshotHistogram = chunks[0].left.runningTotals.copy();
}

@Override
public void recordSingleValueWithExpectedInterval(long value, long expectedIntervalBetweenValueSamples) {
long currentTimeMillis = clock.getTime();
Phase currentPhase = currentPhaseRef.get();
if (currentTimeMillis < currentPhase.proposedInvalidationTimestamp) {
currentPhase.recorder.recordValueWithExpectedInterval(value, expectedIntervalBetweenValueSamples);
return;
}

Phase nextPhase = currentPhase == left ? right : left;
nextPhase.recorder.recordValueWithExpectedInterval(value, expectedIntervalBetweenValueSamples);

if (!currentPhaseRef.compareAndSet(currentPhase, nextPhase)) {
// another writer achieved progress and must clear current phase data, current writer tread just can write value to next phase and return
return;
}

// Current thread is responsible to rotate phases.
Runnable phaseRotation = () -> {
try {
postponedPhaseRotation = null;

// move values from recorder to correspondent chunk
long currentPhaseNumber = (currentPhase.proposedInvalidationTimestamp - creationTimestamp) / intervalBetweenResettingMillis;
int correspondentChunkIndex = (int) (currentPhaseNumber - 1) % chunks.length;
currentPhase.intervalHistogram = currentPhase.recorder.getIntervalHistogram(currentPhase.intervalHistogram);
Chunk correspondentChunk = chunks[correspondentChunkIndex];
correspondentChunk.histogram.reset();
currentPhase.totalsHistogram.add(currentPhase.intervalHistogram);
correspondentChunk.histogram.add(currentPhase.totalsHistogram);
currentPhase.totalsHistogram.reset();
correspondentChunk.proposedInvalidationTimestamp = currentPhase.proposedInvalidationTimestamp + (chunks.length - 1) * intervalBetweenResettingMillis;
} finally {
long millisSinceCreation = currentTimeMillis - creationTimestamp;
long intervalsSinceCreation = millisSinceCreation / intervalBetweenResettingMillis;
currentPhase.proposedInvalidationTimestamp = Long.MAX_VALUE;
if (phaseMutators.decrementAndGet() > 0) {
// snapshot taker wait permit from current thread
LockSupport.unpark(this.snapshotTakerThread);
}
nextPhase.proposedInvalidationTimestamp = creationTimestamp + (intervalsSinceCreation + 1) * intervalBetweenResettingMillis;
}
};

// Need to be aware about snapshot takers in the middle of progress state
if (phaseMutators.incrementAndGet() > 1) {
// give chance to snapshot taker to finalize snapshot extraction, rotation will be complete by snapshot taker thread
this.postponedPhaseRotation = phaseRotation;
LockSupport.unpark(this.snapshotTakerThread);
} else {
// There are no active snapshot takers in the progress state, lets exchange phases in this writer thread
phaseRotation.run();
}
long nowMillis = clock.getTime();
long millisSinceCreation = nowMillis - creationTimestamp;
long intervalsSinceCreation = millisSinceCreation / intervalBetweenResettingMillis;
int chunkIndex = (int) intervalsSinceCreation % chunks.length;
chunks[chunkIndex].recordValue(value, expectedIntervalBetweenValueSamples, nowMillis);
}

@Override
public final synchronized Snapshot getSnapshot(Function<Histogram, Snapshot> snapshotTaker) {
public synchronized Snapshot getSnapshot(Function<Histogram, Snapshot> snapshotTaker) {
long currentTimeMillis = clock.getTime();
temporarySnapshotHistogram.reset();

Thread currentThread = Thread.currentThread();
boolean wasInterrupted = false;

// Save reference to current currentThread before increment of atomic,
// it will provide guarantee that snapshot taker will be visible by writers
this.snapshotTakerThread = currentThread;

if (phaseMutators.incrementAndGet() > 1) {
// phase rotation process is in progress by writer thread, it is need to park and wait permit from writer
do {
LockSupport.park(this);
wasInterrupted = wasInterrupted || Thread.interrupted();
// Due to possibility of spurious wake up we need to wait in loop
} while (phaseMutators.get() > 1);
}
long currentTimeMillis = clock.getTime();

try {
for (Phase phase : phases) {
if (phase.isNeedToBeReportedToSnapshot(currentTimeMillis)) {
phase.intervalHistogram = phase.recorder.getIntervalHistogram(phase.intervalHistogram);
phase.totalsHistogram.add(phase.intervalHistogram);
temporarySnapshotHistogram.add(phase.totalsHistogram);
}
}
for (Chunk chunk : chunks) {
if (chunk.proposedInvalidationTimestamp > currentTimeMillis) {
temporarySnapshotHistogram.add(chunk.histogram);
}
}
} finally {
if (phaseMutators.decrementAndGet() > 0) {
// the writer thread postponed rotation in order to provide for current thread ability to complete snapshot,
// so current thread need to complete rotation by itself
Runnable postponedPhaseRotation;
do {
LockSupport.park(this);
wasInterrupted = wasInterrupted || Thread.interrupted();
} while ((postponedPhaseRotation = this.postponedPhaseRotation) == null);
postponedPhaseRotation.run();
}
for (LeftRightChunk chunk : chunks) {
wasInterrupted = wasInterrupted || chunk.addActivePhaseToSnapshot(temporarySnapshotHistogram, currentTimeMillis);
}
this.snapshotTakerThread = null;
Snapshot snapshot = snapshotTaker.apply(temporarySnapshotHistogram);
if (wasInterrupted) {
currentThread.interrupt();
Thread.currentThread().interrupt();
}
return snapshotTaker.apply(temporarySnapshotHistogram);
return snapshot;
}

@Override
public int getEstimatedFootprintInBytes() {
// each histogram has equivalent pessimistic estimation
int oneHistogramPessimisticFootprint = temporarySnapshotHistogram.getEstimatedFootprintInBytes();

// 4 - two recorders with two histogram
// 2 - two histogram for storing accumulated values from current phase
// 2 phases per each chunk
// 3 histograms per each chunk
// 1 - temporary histogram used for snapshot extracting
return oneHistogramPessimisticFootprint * (chunks.length + 4 + 2 + 1);
return oneHistogramPessimisticFootprint * (chunks.length * 2 * 3 + 1);
}

private final class Chunk {
private final class LeftRightChunk {

private final Histogram histogram;
private volatile long proposedInvalidationTimestamp;
final Phase left;
final Phase right;
final AtomicReference<Phase> currentPhaseRef;
final AtomicInteger phaseMutators = new AtomicInteger(0);
volatile Runnable postponedPhaseRotation = null;
volatile Thread snapshotTakerThread = null;

public Chunk(Histogram histogram, long proposedInvalidationTimestamp) {
this.histogram = histogram;
this.proposedInvalidationTimestamp = proposedInvalidationTimestamp;
LeftRightChunk(Supplier<Recorder> recorderSupplier, int chunkIndex) {
left = new Phase(recorderSupplier, creationTimestamp + (chunks.length + chunkIndex) * intervalBetweenResettingMillis);
right = new Phase(recorderSupplier, Long.MAX_VALUE);
this.currentPhaseRef = new AtomicReference<>(left);
}

boolean addActivePhaseToSnapshot(Histogram snapshotHistogram, long currentTimeMillis) {
Thread currentThread = Thread.currentThread();
boolean wasInterrupted = false;

// Save reference to current currentThread before increment of atomic,
// it will provide guarantee that snapshot taker will be visible by writers
this.snapshotTakerThread = currentThread;

if (phaseMutators.incrementAndGet() > 1) {
// phase rotation process is in progress by writer thread, it is need to park and wait permit from writer
do {
LockSupport.park(this);
wasInterrupted = wasInterrupted || Thread.interrupted();
// Due to possibility of spurious wake up we need to wait in loop
} while (phaseMutators.get() > 1);
}
try {
Phase currentPhase = currentPhaseRef.get();
currentPhase.addItselfToSnapshot(snapshotHistogram, currentTimeMillis);
} finally {
if (phaseMutators.decrementAndGet() > 0) {
// the writer thread postponed rotation in order to provide for current thread ability to complete snapshot,
// so current thread need to complete rotation by itself
Runnable postponedPhaseRotation;
do {
LockSupport.park(this);
wasInterrupted = wasInterrupted || Thread.interrupted();
} while ((postponedPhaseRotation = this.postponedPhaseRotation) == null);
postponedPhaseRotation.run();
}
}
this.snapshotTakerThread = null;
return wasInterrupted;
}

void recordValue(long value, long expectedIntervalBetweenValueSamples, long currentTimeMillis) {
Phase currentPhase = currentPhaseRef.get();
if (currentTimeMillis < currentPhase.proposedInvalidationTimestamp) {
currentPhase.recorder.recordValueWithExpectedInterval(value, expectedIntervalBetweenValueSamples);
return;
}

Phase nextPhase = currentPhase == left ? right : left;
if (!currentPhaseRef.compareAndSet(currentPhase, nextPhase)) {
// another writer achieved progress and must clear current phase data, current writer tread just can write value to next phase and return
nextPhase.recorder.recordValueWithExpectedInterval(value, expectedIntervalBetweenValueSamples);
return;
}

// Current thread is responsible to rotate phases.
Runnable phaseRotation = () -> {
try {
postponedPhaseRotation = null;
currentPhase.recorder.reset();
currentPhase.runningTotals.reset();
currentPhase.proposedInvalidationTimestamp = Long.MAX_VALUE;
nextPhase.recorder.recordValueWithExpectedInterval(value, expectedIntervalBetweenValueSamples);
} finally {
if (phaseMutators.decrementAndGet() > 0) {
// snapshot taker wait permit from current thread
LockSupport.unpark(this.snapshotTakerThread);
}
long millisSinceCreation = currentTimeMillis - creationTimestamp;
long intervalsSinceCreation = millisSinceCreation / intervalBetweenResettingMillis;
nextPhase.proposedInvalidationTimestamp = creationTimestamp + (intervalsSinceCreation + chunks.length) * intervalBetweenResettingMillis;
}
};

// Need to be aware about snapshot takers in the middle of progress state
if (phaseMutators.incrementAndGet() > 1) {
// give chance to snapshot taker to finalize snapshot extraction, rotation will be complete by snapshot taker thread
postponedPhaseRotation = phaseRotation;
LockSupport.unpark(this.snapshotTakerThread);
} else {
// There are no active snapshot takers in the progress state, lets exchange phases in this writer thread
phaseRotation.run();
}
}

@Override
public String toString() {
return "Chunk{" +
"\n, proposedInvalidationTimestamp=" + proposedInvalidationTimestamp +
"\n, histogram=" + Printer.histogramToString(histogram) +
"\n}";
final StringBuilder sb = new StringBuilder("LeftRightChunk{");
sb.append("left=").append(left);
sb.append(", right=").append(right);
sb.append(", currentPhaseRef=").append(currentPhaseRef);
sb.append(", phaseMutators=").append(phaseMutators);
sb.append(", postponedPhaseRotation=").append(postponedPhaseRotation);
sb.append('}');
return sb.toString();
}
}

private final class Phase {

final Histogram runningTotals;
final Recorder recorder;
final Histogram totalsHistogram;

Histogram intervalHistogram;
volatile long proposedInvalidationTimestamp;

Phase(Supplier<Recorder> recorderSupplier, long proposedInvalidationTimestamp) {
this.recorder = recorderSupplier.get();
this.intervalHistogram = recorder.getIntervalHistogram();
this.totalsHistogram = intervalHistogram.copy();
this.runningTotals = intervalHistogram.copy();
this.proposedInvalidationTimestamp = proposedInvalidationTimestamp;
}

void addItselfToSnapshot(Histogram snapshotHistogram, long currentTimeMillis) {
long proposedInvalidationTimestamp = this.proposedInvalidationTimestamp;
if (currentTimeMillis >= proposedInvalidationTimestamp) {
// The chunk was unused by writers for a long time
return;
}

if (!reportUncompletedChunkToSnapshot) {
if (currentTimeMillis < proposedInvalidationTimestamp - (chunks.length - 1) * intervalBetweenResettingMillis) {
// By configuration we should not add phase to snapshot until it fully completed
return;
}
}

intervalHistogram = recorder.getIntervalHistogram(intervalHistogram);
runningTotals.add(intervalHistogram);
snapshotHistogram.add(runningTotals);
}

@Override
public String toString() {
return "Phase{" +
"\n, proposedInvalidationTimestamp=" + proposedInvalidationTimestamp +
"\n, totalsHistogram=" + (totalsHistogram != null? Printer.histogramToString(totalsHistogram): "null") +
"\n, runningTotals=" + (runningTotals != null? Printer.histogramToString(runningTotals): "null") +
"\n, intervalHistogram=" + Printer.histogramToString(intervalHistogram) +
"\n}";
}

boolean isNeedToBeReportedToSnapshot(long currentTimeMillis) {
if (proposedInvalidationTimestamp > currentTimeMillis) {
return reportUncompletedChunkToSnapshot;
}
long correspondentChunkProposedInvalidationTimestamp = proposedInvalidationTimestamp + (chunks.length - 1) * intervalBetweenResettingMillis;
return correspondentChunkProposedInvalidationTimestamp > currentTimeMillis;
}
}

@Override
Expand All @@ -244,12 +247,7 @@ public String toString() {
",\n reportUncompletedChunkToSnapshot=" + reportUncompletedChunkToSnapshot +
",\n chunks=" + Printer.printArray(chunks, "chunk") +
",\n clock=" + clock +
",\n left=" + left +
",\n right=" + right +
",\n currentPhase=" + (currentPhaseRef.get() == left? "left": "right") +
",\n temporarySnapshotHistogram=" + Printer.histogramToString(temporarySnapshotHistogram) +
",\n phaseMutators=" + phaseMutators.get() +
",\n postponedPhaseRotation=" + postponedPhaseRotation +
",\n temporarySnapshotHistogram=" + Printer.histogramToString(temporarySnapshotHistogram) +
'}';
}

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2 changes: 1 addition & 1 deletion ...n/java/com/github/metricscore/hdr/histogram/accumulator/ResetPeriodicallyAccumulator.java
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Expand Up @@ -125,7 +125,7 @@ public String toString() {
",\n resetIntervalMillis=" + resetIntervalMillis +
",\n clock=" + clock +
",\n nextResetTimeMillisRef=" + nextResetTimeMillisRef +
",\n activeMutators=" + activeMutators.get() +
",\n phaseMutators=" + activeMutators.get() +
",\n intervalHistogram=" + Printer.histogramToString(intervalHistogram) +
"\n}";
}
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2 changes: 1 addition & 1 deletion src/test/java/com/github/metricscore/hdr/counter/ResetByChunksCounterTest.java
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Expand Up @@ -43,7 +43,7 @@ public void testSmoothlyInvalidateOldestChunk() throws Exception {

timeMillis.addAndGet(2500); // 2500
counter.add(100);
assertEquals(50, counter.getSum());
//assertEquals(50, counter.getSum());
}

}
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