org.apache.hadoop.hbase.util.PoolMap 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.hadoop.hbase.util;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import org.apache.yetus.audience.InterfaceAudience;
/**
* The PoolMap maps a key to a collection of values, the elements of which are managed
* by a pool. In effect, that collection acts as a shared pool of resources, access to which is
* closely controlled as per the semantics of the pool.
*
* In case the size of the pool is set to a non-zero positive number, that is used to cap the number
* of resources that a pool may contain for any given key. A size of {@link Integer#MAX_VALUE} is
* interpreted as an unbounded pool.
*
*
* PoolMap is thread-safe. It does not remove elements automatically. Unused resources must be
* closed and removed explicitly.
*
* @param the type of the key to the resource
* @param the type of the resource being pooled
*/
@InterfaceAudience.Private
public class PoolMap {
private final Map> pools;
private final PoolType poolType;
private final int poolMaxSize;
public PoolMap(PoolType poolType, int poolMaxSize) {
pools = new HashMap<>();
this.poolType = poolType;
this.poolMaxSize = poolMaxSize;
}
public V getOrCreate(K key, PoolResourceSupplier supplier) throws IOException {
synchronized (pools) {
Pool pool = pools.get(key);
if (pool == null) {
pool = createPool();
pools.put(key, pool);
}
try {
return pool.getOrCreate(supplier);
} catch (IOException | RuntimeException | Error e) {
if (pool.size() == 0) {
pools.remove(key);
}
throw e;
}
}
}
public boolean remove(K key, V value) {
synchronized (pools) {
Pool pool = pools.get(key);
if (pool == null) {
return false;
}
boolean removed = pool.remove(value);
if (removed && pool.size() == 0) {
pools.remove(key);
}
return removed;
}
}
public List values() {
List values = new ArrayList<>();
synchronized (pools) {
for (Pool pool : pools.values()) {
Collection poolValues = pool.values();
if (poolValues != null) {
values.addAll(poolValues);
}
}
}
return values;
}
public void clear() {
synchronized (pools) {
for (Pool pool : pools.values()) {
pool.clear();
}
pools.clear();
}
}
public interface PoolResourceSupplier {
R get() throws IOException;
}
protected static V createResource(PoolResourceSupplier supplier) throws IOException {
V resource = supplier.get();
return Objects.requireNonNull(resource, "resource cannot be null.");
}
protected interface Pool {
R getOrCreate(PoolResourceSupplier supplier) throws IOException;
boolean remove(R resource);
void clear();
Collection values();
int size();
}
public enum PoolType {
ThreadLocal,
RoundRobin;
public static PoolType valueOf(String poolTypeName, PoolType defaultPoolType) {
PoolType poolType = PoolType.fuzzyMatch(poolTypeName);
return (poolType != null) ? poolType : defaultPoolType;
}
public static String fuzzyNormalize(String name) {
return name != null ? name.replaceAll("-", "").trim().toLowerCase(Locale.ROOT) : "";
}
public static PoolType fuzzyMatch(String name) {
for (PoolType poolType : values()) {
if (fuzzyNormalize(name).equals(fuzzyNormalize(poolType.name()))) {
return poolType;
}
}
return null;
}
}
protected Pool createPool() {
switch (poolType) {
case RoundRobin:
return new RoundRobinPool<>(poolMaxSize);
case ThreadLocal:
return new ThreadLocalPool<>();
default:
return new RoundRobinPool<>(poolMaxSize);
}
}
/**
* The RoundRobinPool represents a {@link PoolMap.Pool}, which stores its resources
* in an {@link ArrayList}. It load-balances access to its resources by returning a different
* resource every time a given key is looked up.
*
* If {@link #maxSize} is set to {@link Integer#MAX_VALUE}, then the size of the pool is
* unbounded. Otherwise, it caps the number of resources in this pool to the (non-zero positive)
* value specified in {@link #maxSize}.
*
* @param the type of the resource
*/
@SuppressWarnings("serial")
static class RoundRobinPool implements Pool {
private final List resources;
private final int maxSize;
private int nextIndex;
public RoundRobinPool(int maxSize) {
if (maxSize <= 0) {
throw new IllegalArgumentException("maxSize must be positive");
}
resources = new ArrayList<>(maxSize);
this.maxSize = maxSize;
}
@Override
public R getOrCreate(PoolResourceSupplier supplier) throws IOException {
int size = resources.size();
R resource;
/* letting pool to grow */
if (size < maxSize) {
resource = createResource(supplier);
resources.add(resource);
} else {
resource = resources.get(nextIndex);
/* at this point size cannot be 0 */
nextIndex = (nextIndex + 1) % size;
}
return resource;
}
@Override
public boolean remove(R resource) {
return resources.remove(resource);
}
@Override
public void clear() {
resources.clear();
}
@Override
public Collection values() {
return resources;
}
@Override
public int size() {
return resources.size();
}
}
/**
* The ThreadLocalPool represents a {@link PoolMap.Pool} that works similarly to
* {@link ThreadLocal} class. It essentially binds the resource to the thread from which it is
* accessed. It doesn't remove resources when a thread exits, those resources must be closed
* manually.
*
* Note that the size of the pool is essentially bounded by the number of threads that add
* resources to this pool.
*
* @param the type of the resource
*/
static class ThreadLocalPool implements Pool {
private final Map resources;
public ThreadLocalPool() {
resources = new HashMap<>();
}
@Override
public R getOrCreate(PoolResourceSupplier supplier) throws IOException {
Thread myself = Thread.currentThread();
R resource = resources.get(myself);
if (resource == null) {
resource = createResource(supplier);
resources.put(myself, resource);
}
return resource;
}
@Override
public boolean remove(R resource) {
/* remove can be called from any thread */
return resources.values().remove(resource);
}
@Override
public int size() {
return resources.size();
}
@Override
public void clear() {
resources.clear();
}
@Override
public Collection values() {
return resources.values();
}
}
}