org.apache.pulsar.common.util.collections.ConcurrentOpenHashSet Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.pulsar.common.util.collections;
import static org.apache.pulsar.shade.com.google.common.base.Preconditions.checkArgument;
import static java.util.Objects.requireNonNull;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.locks.StampedLock;
import java.util.function.Consumer;
import java.util.function.Predicate;
/**
* Concurrent hash set.
*
* Provides similar methods as a {@code ConcurrentMap} but since it's an open hash map with linear probing,
* no node allocations are required to store the values.
*
*
* WARN: method forEach do not guarantee thread safety, nor does the values method.
*
* The forEach method is specifically designed for single-threaded usage. When iterating over a set
* with concurrent writes, it becomes possible for new values to be either observed or not observed.
* There is no guarantee that if we write value1 and value2, and are able to see value2, then we will also see value1.
*
*
* It is crucial to understand that the results obtained from aggregate status methods such as values
* are typically reliable only when the map is not undergoing concurrent updates from other threads.
* When concurrent updates are involved, the results of these methods reflect transient states
* that may be suitable for monitoring or estimation purposes, but not for program control.
* @param
*/
@SuppressWarnings("unchecked")
public class ConcurrentOpenHashSet {
private static final Object EmptyValue = null;
private static final Object DeletedValue = new Object();
private static final int DefaultExpectedItems = 256;
private static final int DefaultConcurrencyLevel = 16;
private static final float DefaultMapFillFactor = 0.66f;
private static final float DefaultMapIdleFactor = 0.15f;
private static final float DefaultExpandFactor = 2;
private static final float DefaultShrinkFactor = 2;
private static final boolean DefaultAutoShrink = false;
private final Section[] sections;
public static Builder newBuilder() {
return new Builder<>();
}
/**
* Builder of ConcurrentOpenHashSet.
*/
public static class Builder {
int expectedItems = DefaultExpectedItems;
int concurrencyLevel = DefaultConcurrencyLevel;
float mapFillFactor = DefaultMapFillFactor;
float mapIdleFactor = DefaultMapIdleFactor;
float expandFactor = DefaultExpandFactor;
float shrinkFactor = DefaultShrinkFactor;
boolean autoShrink = DefaultAutoShrink;
public Builder expectedItems(int expectedItems) {
this.expectedItems = expectedItems;
return this;
}
public Builder concurrencyLevel(int concurrencyLevel) {
this.concurrencyLevel = concurrencyLevel;
return this;
}
public Builder mapFillFactor(float mapFillFactor) {
this.mapFillFactor = mapFillFactor;
return this;
}
public Builder mapIdleFactor(float mapIdleFactor) {
this.mapIdleFactor = mapIdleFactor;
return this;
}
public Builder expandFactor(float expandFactor) {
this.expandFactor = expandFactor;
return this;
}
public Builder shrinkFactor(float shrinkFactor) {
this.shrinkFactor = shrinkFactor;
return this;
}
public Builder autoShrink(boolean autoShrink) {
this.autoShrink = autoShrink;
return this;
}
public ConcurrentOpenHashSet build() {
return new ConcurrentOpenHashSet<>(expectedItems, concurrencyLevel,
mapFillFactor, mapIdleFactor, autoShrink, expandFactor, shrinkFactor);
}
}
@Deprecated
public ConcurrentOpenHashSet() {
this(DefaultExpectedItems);
}
@Deprecated
public ConcurrentOpenHashSet(int expectedItems) {
this(expectedItems, DefaultConcurrencyLevel);
}
@Deprecated
public ConcurrentOpenHashSet(int expectedItems, int concurrencyLevel) {
this(expectedItems, concurrencyLevel, DefaultMapFillFactor, DefaultMapIdleFactor,
DefaultAutoShrink, DefaultExpandFactor, DefaultShrinkFactor);
}
public ConcurrentOpenHashSet(int expectedItems, int concurrencyLevel,
float mapFillFactor, float mapIdleFactor,
boolean autoShrink, float expandFactor, float shrinkFactor) {
checkArgument(expectedItems > 0);
checkArgument(concurrencyLevel > 0);
checkArgument(expectedItems >= concurrencyLevel);
checkArgument(mapFillFactor > 0 && mapFillFactor < 1);
checkArgument(mapIdleFactor > 0 && mapIdleFactor < 1);
checkArgument(mapFillFactor > mapIdleFactor);
checkArgument(expandFactor > 1);
checkArgument(shrinkFactor > 1);
int numSections = concurrencyLevel;
int perSectionExpectedItems = expectedItems / numSections;
int perSectionCapacity = (int) (perSectionExpectedItems / mapFillFactor);
this.sections = (Section[]) new Section[numSections];
for (int i = 0; i < numSections; i++) {
sections[i] = new Section<>(perSectionCapacity, mapFillFactor, mapIdleFactor,
autoShrink, expandFactor, shrinkFactor);
}
}
long getUsedBucketCount() {
long usedBucketCount = 0;
for (Section s : sections) {
usedBucketCount += s.usedBuckets;
}
return usedBucketCount;
}
public long size() {
long size = 0;
for (int i = 0; i < sections.length; i++) {
size += sections[i].size;
}
return size;
}
public long capacity() {
long capacity = 0;
for (int i = 0; i < sections.length; i++) {
capacity += sections[i].capacity;
}
return capacity;
}
public boolean isEmpty() {
for (int i = 0; i < sections.length; i++) {
if (sections[i].size != 0) {
return false;
}
}
return true;
}
public boolean contains(V value) {
requireNonNull(value);
long h = hash(value);
return getSection(h).contains(value, (int) h);
}
public boolean add(V value) {
requireNonNull(value);
long h = hash(value);
return getSection(h).add(value, (int) h);
}
public boolean remove(V value) {
requireNonNull(value);
long h = hash(value);
return getSection(h).remove(value, (int) h);
}
private Section getSection(long hash) {
// Use 32 msb out of long to get the section
final int sectionIdx = (int) (hash >>> 32) & (sections.length - 1);
return sections[sectionIdx];
}
public void clear() {
for (int i = 0; i < sections.length; i++) {
sections[i].clear();
}
}
/**
* Iterate over all the elements in the set and apply the provided function.
*
* Warning: Do Not Guarantee Thread-Safety.
* @param processor the function to apply to each element
*/
public void forEach(Consumer processor) {
for (int i = 0; i < sections.length; i++) {
sections[i].forEach(processor);
}
}
public int removeIf(Predicate filter) {
requireNonNull(filter);
int removedCount = 0;
for (int i = 0; i < sections.length; i++) {
removedCount += sections[i].removeIf(filter);
}
return removedCount;
}
/**
* @return a new list of all values (makes a copy)
*/
public List values() {
List values = new ArrayList<>();
forEach(value -> values.add(value));
return values;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append('{');
final AtomicBoolean first = new AtomicBoolean(true);
forEach(value -> {
if (!first.getAndSet(false)) {
sb.append(", ");
}
sb.append(value.toString());
});
sb.append('}');
return sb.toString();
}
// A section is a portion of the hash map that is covered by a single
@SuppressWarnings("serial")
private static final class Section extends StampedLock {
private volatile V[] values;
private volatile int capacity;
private final int initCapacity;
private static final AtomicIntegerFieldUpdater SIZE_UPDATER =
AtomicIntegerFieldUpdater.newUpdater(Section.class, "size");
private volatile int size;
private int usedBuckets;
private int resizeThresholdUp;
private int resizeThresholdBelow;
private final float mapFillFactor;
private final float mapIdleFactor;
private final float expandFactor;
private final float shrinkFactor;
private final boolean autoShrink;
Section(int capacity, float mapFillFactor, float mapIdleFactor, boolean autoShrink,
float expandFactor, float shrinkFactor) {
this.capacity = alignToPowerOfTwo(capacity);
this.initCapacity = this.capacity;
this.values = (V[]) new Object[this.capacity];
this.size = 0;
this.usedBuckets = 0;
this.autoShrink = autoShrink;
this.mapFillFactor = mapFillFactor;
this.mapIdleFactor = mapIdleFactor;
this.expandFactor = expandFactor;
this.shrinkFactor = shrinkFactor;
this.resizeThresholdUp = (int) (this.capacity * mapFillFactor);
this.resizeThresholdBelow = (int) (this.capacity * mapIdleFactor);
}
boolean contains(V value, int keyHash) {
long stamp = tryOptimisticRead();
boolean acquiredLock = false;
// add local variable here, so OutOfBound won't happen
V[] values = this.values;
// calculate table.length as capacity to avoid rehash changing capacity
int bucket = signSafeMod(keyHash, values.length);
try {
while (true) {
// First try optimistic locking
V storedValue = values[bucket];
if (!acquiredLock && validate(stamp)) {
// The values we have read are consistent
if (value.equals(storedValue)) {
return true;
} else if (storedValue == EmptyValue) {
// Not found
return false;
}
} else {
// Fallback to acquiring read lock
if (!acquiredLock) {
stamp = readLock();
acquiredLock = true;
// update local variable
values = this.values;
bucket = signSafeMod(keyHash, values.length);
storedValue = values[bucket];
}
if (value.equals(storedValue)) {
return true;
} else if (storedValue == EmptyValue) {
// Not found
return false;
}
}
bucket = (bucket + 1) & (values.length - 1);
}
} finally {
if (acquiredLock) {
unlockRead(stamp);
}
}
}
boolean add(V value, int keyHash) {
int bucket = keyHash;
long stamp = writeLock();
int capacity = this.capacity;
// Remember where we find the first available spot
int firstDeletedValue = -1;
try {
while (true) {
bucket = signSafeMod(bucket, capacity);
V storedValue = values[bucket];
if (value.equals(storedValue)) {
return false;
} else if (storedValue == EmptyValue) {
// Found an empty bucket. This means the value is not in the set. If we've already seen a
// deleted value, we should write at that position
if (firstDeletedValue != -1) {
bucket = firstDeletedValue;
} else {
++usedBuckets;
}
values[bucket] = value;
SIZE_UPDATER.incrementAndGet(this);
return true;
} else if (storedValue == DeletedValue) {
// The bucket contained a different deleted key
if (firstDeletedValue == -1) {
firstDeletedValue = bucket;
}
}
++bucket;
}
} finally {
if (usedBuckets > resizeThresholdUp) {
try {
// Expand the hashmap
int newCapacity = alignToPowerOfTwo((int) (capacity * expandFactor));
rehash(newCapacity);
} finally {
unlockWrite(stamp);
}
} else {
unlockWrite(stamp);
}
}
}
private boolean remove(V value, int keyHash) {
int bucket = keyHash;
long stamp = writeLock();
try {
while (true) {
int capacity = this.capacity;
bucket = signSafeMod(bucket, capacity);
V storedValue = values[bucket];
if (value.equals(storedValue)) {
SIZE_UPDATER.decrementAndGet(this);
cleanBucket(bucket);
return true;
} else if (storedValue == EmptyValue) {
// Value wasn't found
return false;
}
++bucket;
}
} finally {
if (autoShrink && size < resizeThresholdBelow) {
try {
// Shrinking must at least ensure initCapacity,
// so as to avoid frequent shrinking and expansion near initCapacity,
// frequent shrinking and expansion,
// additionally opened arrays will consume more memory and affect GC
int newCapacity = Math.max(alignToPowerOfTwo((int) (capacity / shrinkFactor)), initCapacity);
int newResizeThresholdUp = (int) (newCapacity * mapFillFactor);
if (newCapacity < capacity && newResizeThresholdUp > size) {
// shrink the hashmap
rehash(newCapacity);
}
} finally {
unlockWrite(stamp);
}
} else {
unlockWrite(stamp);
}
}
}
void clear() {
long stamp = writeLock();
try {
if (autoShrink && capacity > initCapacity) {
shrinkToInitCapacity();
} else {
Arrays.fill(values, EmptyValue);
this.size = 0;
this.usedBuckets = 0;
}
} finally {
unlockWrite(stamp);
}
}
int removeIf(Predicate filter) {
long stamp = writeLock();
int removedCount = 0;
try {
// Go through all the buckets for this section
for (int bucket = capacity - 1; bucket >= 0; bucket--) {
V storedValue = values[bucket];
if (storedValue != DeletedValue && storedValue != EmptyValue) {
if (filter.test(storedValue)) {
// Removing item
SIZE_UPDATER.decrementAndGet(this);
++removedCount;
cleanBucket(bucket);
}
}
}
return removedCount;
} finally {
unlockWrite(stamp);
}
}
private void cleanBucket(int bucket) {
int nextInArray = signSafeMod(bucket + 1, capacity);
if (values[nextInArray] == EmptyValue) {
values[bucket] = (V) EmptyValue;
--usedBuckets;
// Cleanup all the buckets that were in `DeletedValue` state,
// so that we can reduce unnecessary expansions
int lastBucket = signSafeMod(bucket - 1, capacity);
while (values[lastBucket] == DeletedValue) {
values[lastBucket] = (V) EmptyValue;
--usedBuckets;
lastBucket = signSafeMod(lastBucket - 1, capacity);
}
} else {
values[bucket] = (V) DeletedValue;
}
}
public void forEach(Consumer processor) {
V[] values = this.values;
// Go through all the buckets for this section. We try to renew the stamp only after a validation
// error, otherwise we keep going with the same.
long stamp = 0;
for (int bucket = 0; bucket < capacity; bucket++) {
if (stamp == 0) {
stamp = tryOptimisticRead();
}
V storedValue = values[bucket];
if (!validate(stamp)) {
// Fallback to acquiring read lock
stamp = readLock();
try {
storedValue = values[bucket];
} finally {
unlockRead(stamp);
}
stamp = 0;
}
if (storedValue != DeletedValue && storedValue != EmptyValue) {
processor.accept(storedValue);
}
}
}
private void rehash(int newCapacity) {
// Expand the hashmap
V[] newValues = (V[]) new Object[newCapacity];
// Re-hash table
for (int i = 0; i < values.length; i++) {
V storedValue = values[i];
if (storedValue != EmptyValue && storedValue != DeletedValue) {
insertValueNoLock(newValues, storedValue);
}
}
values = newValues;
capacity = newCapacity;
usedBuckets = size;
resizeThresholdUp = (int) (capacity * mapFillFactor);
resizeThresholdBelow = (int) (capacity * mapIdleFactor);
}
private void shrinkToInitCapacity() {
V[] newValues = (V[]) new Object[initCapacity];
values = newValues;
size = 0;
usedBuckets = 0;
// Capacity needs to be updated after the values, so that we won't see
// a capacity value bigger than the actual array size
capacity = initCapacity;
resizeThresholdUp = (int) (capacity * mapFillFactor);
resizeThresholdBelow = (int) (capacity * mapIdleFactor);
}
private static void insertValueNoLock(V[] values, V value) {
int bucket = (int) hash(value);
while (true) {
bucket = signSafeMod(bucket, values.length);
V storedValue = values[bucket];
if (storedValue == EmptyValue) {
// The bucket is empty, so we can use it
values[bucket] = value;
return;
}
++bucket;
}
}
}
private static final long HashMixer = 0xc6a4a7935bd1e995L;
private static final int R = 47;
static final long hash(K key) {
long hash = key.hashCode() * HashMixer;
hash ^= hash >>> R;
hash *= HashMixer;
return hash;
}
static final int signSafeMod(long n, int max) {
return (int) n & (max - 1);
}
private static int alignToPowerOfTwo(int n) {
return (int) Math.pow(2, 32 - Integer.numberOfLeadingZeros(n - 1));
}
}