org.apache.bookkeeper.util.collections.ConcurrentOpenHashMap 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.bookkeeper.util.collections;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.collect.Lists;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.locks.StampedLock;
import java.util.function.BiConsumer;
import java.util.function.BiPredicate;
import java.util.function.Function;
/**
* Concurrent hash map.
*
* 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
*
* @param
*/
@SuppressWarnings("unchecked")
public class ConcurrentOpenHashMap {
private static final Object EmptyKey = null;
private static final Object DeletedKey = 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 ConcurrentOpenHashMap.
*/
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 ConcurrentOpenHashMap build() {
return new ConcurrentOpenHashMap<>(expectedItems, concurrencyLevel,
mapFillFactor, mapIdleFactor, autoShrink, expandFactor, shrinkFactor);
}
}
@Deprecated
public ConcurrentOpenHashMap() {
this(DefaultExpectedItems);
}
@Deprecated
public ConcurrentOpenHashMap(int expectedItems) {
this(expectedItems, DefaultConcurrencyLevel);
}
@Deprecated
public ConcurrentOpenHashMap(int expectedItems, int concurrencyLevel) {
this(expectedItems, concurrencyLevel, DefaultMapFillFactor, DefaultMapIdleFactor,
DefaultAutoShrink, DefaultExpandFactor, DefaultShrinkFactor);
}
public ConcurrentOpenHashMap(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 (Section s : sections) {
size += s.size;
}
return size;
}
public long capacity() {
long capacity = 0;
for (Section s : sections) {
capacity += s.capacity;
}
return capacity;
}
public boolean isEmpty() {
for (Section s : sections) {
if (s.size != 0) {
return false;
}
}
return true;
}
public V get(K key) {
checkNotNull(key);
long h = hash(key);
return getSection(h).get(key, (int) h);
}
public boolean containsKey(K key) {
return get(key) != null;
}
public V put(K key, V value) {
checkNotNull(key);
checkNotNull(value);
long h = hash(key);
return getSection(h).put(key, value, (int) h, false, null);
}
public V putIfAbsent(K key, V value) {
checkNotNull(key);
checkNotNull(value);
long h = hash(key);
return getSection(h).put(key, value, (int) h, true, null);
}
public V computeIfAbsent(K key, Function provider) {
checkNotNull(key);
checkNotNull(provider);
long h = hash(key);
return getSection(h).put(key, null, (int) h, true, provider);
}
public V remove(K key) {
checkNotNull(key);
long h = hash(key);
return getSection(h).remove(key, null, (int) h);
}
public boolean remove(K key, Object value) {
checkNotNull(key);
checkNotNull(value);
long h = hash(key);
return getSection(h).remove(key, value, (int) h) != null;
}
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 (Section s : sections) {
s.clear();
}
}
public void forEach(BiConsumer processor) {
for (Section s : sections) {
s.forEach(processor);
}
}
public int removeIf(BiPredicate filter) {
checkNotNull(filter);
int removedCount = 0;
for (Section s : sections) {
removedCount += s.removeIf(filter);
}
return removedCount;
}
/**
* @return a new list of all keys (makes a copy)
*/
public List keys() {
List keys = Lists.newArrayList();
forEach((key, value) -> keys.add(key));
return keys;
}
public List values() {
List values = Lists.newArrayList();
forEach((key, value) -> values.add(value));
return values;
}
// A section is a portion of the hash map that is covered by a single
@SuppressWarnings("serial")
private static final class Section extends StampedLock {
// Each item take up 2 continuous array space.
private static final int ITEM_SIZE = 2;
// Keys and values are stored interleaved in the table array
private volatile Object[] table;
private volatile int capacity;
private final int initCapacity;
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.table = new Object[ITEM_SIZE * 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);
}
V get(K key, int keyHash) {
long stamp = tryOptimisticRead();
boolean acquiredLock = false;
// add local variable here, so OutOfBound won't happen
Object[] table = this.table;
// calculate table.length / 2 as capacity to avoid rehash changing capacity
int bucket = signSafeMod(keyHash, table.length / ITEM_SIZE);
try {
while (true) {
// First try optimistic locking
K storedKey = (K) table[bucket];
V storedValue = (V) table[bucket + 1];
if (!acquiredLock && validate(stamp)) {
// The values we have read are consistent
if (key.equals(storedKey)) {
return storedValue;
} else if (storedKey == EmptyKey) {
// Not found
return null;
}
} else {
// Fallback to acquiring read lock
if (!acquiredLock) {
stamp = readLock();
acquiredLock = true;
// update local variable
table = this.table;
bucket = signSafeMod(keyHash, table.length / ITEM_SIZE);
storedKey = (K) table[bucket];
storedValue = (V) table[bucket + 1];
}
if (key.equals(storedKey)) {
return storedValue;
} else if (storedKey == EmptyKey) {
// Not found
return null;
}
}
bucket = (bucket + ITEM_SIZE) & (table.length - 1);
}
} finally {
if (acquiredLock) {
unlockRead(stamp);
}
}
}
V put(K key, V value, int keyHash, boolean onlyIfAbsent, Function valueProvider) {
long stamp = writeLock();
int bucket = signSafeMod(keyHash, capacity);
// Remember where we find the first available spot
int firstDeletedKey = -1;
try {
while (true) {
K storedKey = (K) table[bucket];
V storedValue = (V) table[bucket + 1];
if (key.equals(storedKey)) {
if (!onlyIfAbsent) {
// Over written an old value for same key
table[bucket + 1] = value;
return storedValue;
} else {
return storedValue;
}
} else if (storedKey == EmptyKey) {
// Found an empty bucket. This means the key is not in the map. If we've already seen a deleted
// key, we should write at that position
if (firstDeletedKey != -1) {
bucket = firstDeletedKey;
} else {
++usedBuckets;
}
if (value == null) {
value = valueProvider.apply(key);
}
table[bucket] = key;
table[bucket + 1] = value;
++size;
return valueProvider != null ? value : null;
} else if (storedKey == DeletedKey) {
// The bucket contained a different deleted key
if (firstDeletedKey == -1) {
firstDeletedKey = bucket;
}
}
bucket = (bucket + ITEM_SIZE) & (table.length - 1);
}
} finally {
if (usedBuckets > resizeThresholdUp) {
try {
// Expand the hashmap
int newCapacity = alignToPowerOfTwo((int) (capacity * expandFactor));
rehash(newCapacity);
} finally {
unlockWrite(stamp);
}
} else {
unlockWrite(stamp);
}
}
}
private V remove(K key, Object value, int keyHash) {
long stamp = writeLock();
int bucket = signSafeMod(keyHash, capacity);
try {
while (true) {
K storedKey = (K) table[bucket];
V storedValue = (V) table[bucket + 1];
if (key.equals(storedKey)) {
if (value == null || value.equals(storedValue)) {
--size;
cleanBucket(bucket);
return storedValue;
} else {
return null;
}
} else if (storedKey == EmptyKey) {
// Key wasn't found
return null;
}
bucket = (bucket + ITEM_SIZE) & (table.length - 1);
}
} 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(table, EmptyKey);
this.size = 0;
this.usedBuckets = 0;
}
} finally {
unlockWrite(stamp);
}
}
public void forEach(BiConsumer processor) {
long stamp = tryOptimisticRead();
Object[] table = this.table;
boolean acquiredReadLock = false;
try {
// Validate no rehashing
if (!validate(stamp)) {
// Fallback to read lock
stamp = readLock();
acquiredReadLock = true;
table = this.table;
}
// Go through all the buckets for this section
for (int bucket = 0; bucket < table.length; bucket += ITEM_SIZE) {
K storedKey = (K) table[bucket];
V storedValue = (V) table[bucket + 1];
if (!acquiredReadLock && !validate(stamp)) {
// Fallback to acquiring read lock
stamp = readLock();
acquiredReadLock = true;
storedKey = (K) table[bucket];
storedValue = (V) table[bucket + 1];
}
if (storedKey != DeletedKey && storedKey != EmptyKey) {
processor.accept(storedKey, storedValue);
}
}
} finally {
if (acquiredReadLock) {
unlockRead(stamp);
}
}
}
int removeIf(BiPredicate filter) {
long stamp = writeLock();
int removedCount = 0;
try {
// Go through all the buckets for this section
for (int bucket = 0; size > 0 && bucket < table.length; bucket += ITEM_SIZE) {
K storedKey = (K) table[bucket];
V storedValue = (V) table[bucket + 1];
if (storedKey != DeletedKey && storedKey != EmptyKey) {
if (filter.test(storedKey, storedValue)) {
// Removing item
--size;
++removedCount;
cleanBucket(bucket);
}
}
}
return removedCount;
} 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);
}
}
}
private void cleanBucket(int bucket) {
int nextInArray = (bucket + ITEM_SIZE) & (table.length - 1);
if (table[nextInArray] == EmptyKey) {
table[bucket] = EmptyKey;
table[bucket + 1] = null;
--usedBuckets;
// Cleanup all the buckets that were in `DeletedKey` state,
// so that we can reduce unnecessary expansions
bucket = (bucket - ITEM_SIZE) & (table.length - 1);
while (table[bucket] == DeletedKey) {
table[bucket] = EmptyKey;
table[bucket + 1] = null;
--usedBuckets;
bucket = (bucket - ITEM_SIZE) & (table.length - 1);
}
} else {
table[bucket] = DeletedKey;
table[bucket + 1] = null;
}
}
private void rehash(int newCapacity) {
// Expand the hashmap
Object[] newTable = new Object[ITEM_SIZE * newCapacity];
// Re-hash table
for (int i = 0; i < table.length; i += ITEM_SIZE) {
K storedKey = (K) table[i];
V storedValue = (V) table[i + 1];
if (storedKey != EmptyKey && storedKey != DeletedKey) {
insertKeyValueNoLock(newTable, newCapacity, storedKey, storedValue);
}
}
table = newTable;
usedBuckets = size;
// Capacity needs to be updated after the values, so that we won't see
// a capacity value bigger than the actual array size
capacity = newCapacity;
resizeThresholdUp = (int) (capacity * mapFillFactor);
resizeThresholdBelow = (int) (capacity * mapIdleFactor);
}
private void shrinkToInitCapacity() {
Object[] newTable = new Object[ITEM_SIZE * initCapacity];
table = newTable;
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 insertKeyValueNoLock(Object[] table, int capacity, K key, V value) {
int bucket = signSafeMod(hash(key), capacity);
while (true) {
K storedKey = (K) table[bucket];
if (storedKey == EmptyKey) {
// The bucket is empty, so we can use it
table[bucket] = key;
table[bucket + 1] = value;
return;
}
bucket = (bucket + ITEM_SIZE) & (table.length - 1);
}
}
}
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) {
// as the ITEM_SIZE of Section is 2, so the index is the multiple of 2
// that is to left shift 1 bit
return (int) (n & (max - 1)) << 1;
}
private static int alignToPowerOfTwo(int n) {
return (int) Math.pow(2, 32 - Integer.numberOfLeadingZeros(n - 1));
}
}