From 56ecbc1a2c43d7f1304b9707f9e971460406280b Mon Sep 17 00:00:00 2001 From: Nicolas Liochon Date: Tue, 13 Oct 2015 11:22:28 +0200 Subject: [PATCH] HBASE-14268 Improve KeyLocker - add missing files --- .../hadoop/hbase/util/WeakObjectPool.java | 195 ++++++++++++++++++ .../hadoop/hbase/util/TestWeakObjectPool.java | 133 ++++++++++++ 2 files changed, 328 insertions(+) create mode 100644 hbase-common/src/main/java/org/apache/hadoop/hbase/util/WeakObjectPool.java create mode 100644 hbase-common/src/test/java/org/apache/hadoop/hbase/util/TestWeakObjectPool.java diff --git a/hbase-common/src/main/java/org/apache/hadoop/hbase/util/WeakObjectPool.java b/hbase-common/src/main/java/org/apache/hadoop/hbase/util/WeakObjectPool.java new file mode 100644 index 00000000000..7757c6caf4d --- /dev/null +++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/util/WeakObjectPool.java @@ -0,0 +1,195 @@ +/* + * 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.lang.ref.ReferenceQueue; +import java.lang.ref.WeakReference; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; + +import org.apache.hadoop.hbase.classification.InterfaceAudience; + +/** + * A {@code WeakReference} based shared object pool. + * The objects are kept in weak references and + * associated with keys which are identified by the {@code equals} method. + * The objects are created by {@link ObjectFactory} on demand. + * The object creation is expected to be lightweight, + * and the objects may be excessively created and discarded. + * Thread safe. + */ +@InterfaceAudience.Private +public class WeakObjectPool { + /** + * An {@code ObjectFactory} object is used to create + * new shared objects on demand. + */ + public interface ObjectFactory { + /** + * Creates a new shared object associated with the given {@code key}, + * identified by the {@code equals} method. + * This method may be simultaneously called by multiple threads + * with the same key, and the excessive objects are just discarded. + */ + V createObject(K key); + } + + private final ReferenceQueue staleRefQueue = new ReferenceQueue(); + + private class ObjectReference extends WeakReference { + final K key; + + ObjectReference(K key, V obj) { + super(obj, staleRefQueue); + this.key = key; + } + } + + private final ObjectFactory objectFactory; + + /** Does not permit null keys. */ + private final ConcurrentMap referenceCache; + + /** + * The default initial capacity, + * used when not otherwise specified in a constructor. + */ + public static final int DEFAULT_INITIAL_CAPACITY = 16; + + /** + * The default concurrency level, + * used when not otherwise specified in a constructor. + */ + public static final int DEFAULT_CONCURRENCY_LEVEL = 16; + + /** + * Creates a new pool with the default initial capacity (16) + * and the default concurrency level (16). + * + * @param objectFactory the factory to supply new objects on demand + * + * @throws NullPointerException if {@code objectFactory} is null + */ + public WeakObjectPool(ObjectFactory objectFactory) { + this(objectFactory, DEFAULT_INITIAL_CAPACITY, DEFAULT_CONCURRENCY_LEVEL); + } + + /** + * Creates a new pool with the given initial capacity + * and the default concurrency level (16). + * + * @param objectFactory the factory to supply new objects on demand + * @param initialCapacity the initial capacity to keep objects in the pool + * + * @throws NullPointerException if {@code objectFactory} is null + * @throws IllegalArgumentException if {@code initialCapacity} is negative + */ + public WeakObjectPool(ObjectFactory objectFactory, int initialCapacity) { + this(objectFactory, initialCapacity, DEFAULT_CONCURRENCY_LEVEL); + } + + /** + * Creates a new pool with the given initial capacity + * and the given concurrency level. + * + * @param objectFactory the factory to supply new objects on demand + * @param initialCapacity the initial capacity to keep objects in the pool + * @param concurrencyLevel the estimated count of concurrently accessing threads + * + * @throws NullPointerException if {@code objectFactory} is null + * @throws IllegalArgumentException if {@code initialCapacity} is negative or + * {@code concurrencyLevel} is non-positive + */ + public WeakObjectPool( + ObjectFactory objectFactory, + int initialCapacity, + int concurrencyLevel) { + + if (objectFactory == null) { + throw new NullPointerException(); + } + this.objectFactory = objectFactory; + + this.referenceCache = new ConcurrentHashMap( + initialCapacity, 0.75f, concurrencyLevel); + // 0.75f is the default load factor threshold of ConcurrentHashMap. + } + + /** + * Removes stale references of shared objects from the pool. + * References newly becoming stale may still remain. + * The implementation of this method is expected to be lightweight + * when there is no stale reference. + */ + public void purge() { + // This method is lightweight while there is no stale reference + // with the Oracle (Sun) implementation of {@code ReferenceQueue}, + // because {@code ReferenceQueue.poll} just checks a volatile instance + // variable in {@code ReferenceQueue}. + + while (true) { + @SuppressWarnings("unchecked") + ObjectReference ref = (ObjectReference)staleRefQueue.poll(); + if (ref == null) { + break; + } + referenceCache.remove(ref.key, ref); + } + } + + /** + * Returns a shared object associated with the given {@code key}, + * which is identified by the {@code equals} method. + * @throws NullPointerException if {@code key} is null + */ + public V get(K key) { + ObjectReference ref = referenceCache.get(key); + if (ref != null) { + V obj = ref.get(); + if (obj != null) { + return obj; + } + referenceCache.remove(key, ref); + } + + V newObj = objectFactory.createObject(key); + ObjectReference newRef = new ObjectReference(key, newObj); + while (true) { + ObjectReference existingRef = referenceCache.putIfAbsent(key, newRef); + if (existingRef == null) { + return newObj; + } + + V existingObject = existingRef.get(); + if (existingObject != null) { + return existingObject; + } + referenceCache.remove(key, existingRef); + } + } + + /** + * Returns an estimated count of objects kept in the pool. + * This also counts stale references, + * and you might want to call {@link #purge()} beforehand. + */ + public int size() { + return referenceCache.size(); + } +} diff --git a/hbase-common/src/test/java/org/apache/hadoop/hbase/util/TestWeakObjectPool.java b/hbase-common/src/test/java/org/apache/hadoop/hbase/util/TestWeakObjectPool.java new file mode 100644 index 00000000000..ae322067a73 --- /dev/null +++ b/hbase-common/src/test/java/org/apache/hadoop/hbase/util/TestWeakObjectPool.java @@ -0,0 +1,133 @@ +/* + * 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.util.concurrent.CountDownLatch; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.concurrent.atomic.AtomicReference; + +import org.apache.hadoop.hbase.testclassification.SmallTests; +import org.junit.Assert; +import org.junit.Before; +import org.junit.Test; +import org.junit.experimental.categories.Category; + +@Category({SmallTests.class}) +public class TestWeakObjectPool { + WeakObjectPool pool; + + @Before + public void setUp() { + pool = new WeakObjectPool( + new WeakObjectPool.ObjectFactory() { + @Override + public Object createObject(String key) { + return new Object(); + } + }); + } + + @Test + public void testKeys() { + Object obj1 = pool.get("a"); + Object obj2 = pool.get(new String("a")); + + Assert.assertSame(obj1, obj2); + + Object obj3 = pool.get("b"); + + Assert.assertNotSame(obj1, obj3); + } + + @Test + public void testWeakReference() throws Exception { + Object obj1 = pool.get("a"); + int hash1 = System.identityHashCode(obj1); + + System.gc(); + System.gc(); + System.gc(); + + Thread.sleep(10); + // Sleep a while because references newly becoming stale + // may still remain when calling the {@code purge} method. + pool.purge(); + Assert.assertEquals(1, pool.size()); + + Object obj2 = pool.get("a"); + Assert.assertSame(obj1, obj2); + + obj1 = null; + obj2 = null; + + System.gc(); + System.gc(); + System.gc(); + + Thread.sleep(10); + pool.purge(); + Assert.assertEquals(0, pool.size()); + + Object obj3 = pool.get("a"); + Assert.assertNotEquals(hash1, System.identityHashCode(obj3)); + } + + @Test(timeout=1000) + public void testCongestion() throws Exception { + final int THREAD_COUNT = 100; + + final AtomicBoolean assertionFailed = new AtomicBoolean(); + final AtomicReference expectedObjRef = new AtomicReference(); + final CountDownLatch prepareLatch = new CountDownLatch(THREAD_COUNT); + final CountDownLatch startLatch = new CountDownLatch(1); + final CountDownLatch endLatch = new CountDownLatch(THREAD_COUNT); + + for (int i=0; i