| /* |
| * |
| * 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.locks.ReentrantReadWriteLock; |
| |
| import org.apache.hadoop.hbase.classification.InterfaceAudience; |
| |
| import com.google.common.annotations.VisibleForTesting; |
| |
| /** |
| * Allows multiple concurrent clients to lock on a numeric id with ReentrantReadWriteLock. The |
| * intended usage for read lock is as follows: |
| * |
| * <pre> |
| * ReentrantReadWriteLock lock = idReadWriteLock.getLock(id); |
| * try { |
| * lock.readLock().lock(); |
| * // User code. |
| * } finally { |
| * lock.readLock().unlock(); |
| * } |
| * </pre> |
| * |
| * For write lock, use lock.writeLock() |
| */ |
| @InterfaceAudience.Private |
| public class IdReadWriteLock { |
| // The number of lock we want to easily support. It's not a maximum. |
| private static final int NB_CONCURRENT_LOCKS = 1000; |
| // The pool to get entry from, entries are mapped by weak reference to make it able to be |
| // garbage-collected asap |
| private final WeakObjectPool<Long, ReentrantReadWriteLock> lockPool = |
| new WeakObjectPool<Long, ReentrantReadWriteLock>( |
| new WeakObjectPool.ObjectFactory<Long, ReentrantReadWriteLock>() { |
| @Override |
| public ReentrantReadWriteLock createObject(Long id) { |
| return new ReentrantReadWriteLock(); |
| } |
| }, NB_CONCURRENT_LOCKS); |
| |
| /** |
| * Get the ReentrantReadWriteLock corresponding to the given id |
| * @param id an arbitrary number to identify the lock |
| */ |
| public ReentrantReadWriteLock getLock(long id) { |
| lockPool.purge(); |
| ReentrantReadWriteLock readWriteLock = lockPool.get(id); |
| return readWriteLock; |
| } |
| |
| /** For testing */ |
| @VisibleForTesting |
| int purgeAndGetEntryPoolSize() { |
| gc(); |
| Threads.sleep(200); |
| lockPool.purge(); |
| return lockPool.size(); |
| } |
| |
| @edu.umd.cs.findbugs.annotations.SuppressWarnings(value="DM_GC", justification="Intentional") |
| private void gc() { |
| System.gc(); |
| } |
| |
| @VisibleForTesting |
| public void waitForWaiters(long id, int numWaiters) throws InterruptedException { |
| for (ReentrantReadWriteLock readWriteLock;;) { |
| readWriteLock = lockPool.get(id); |
| if (readWriteLock != null) { |
| synchronized (readWriteLock) { |
| if (readWriteLock.getQueueLength() >= numWaiters) { |
| return; |
| } |
| } |
| } |
| Thread.sleep(50); |
| } |
| } |
| } |