001/*
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *     http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 */
019package org.apache.hadoop.hbase.util;
020
021import java.util.concurrent.locks.ReentrantReadWriteLock;
022
023import org.apache.yetus.audience.InterfaceAudience;
024import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
025
026/**
027 * Allows multiple concurrent clients to lock on a numeric id with ReentrantReadWriteLock. The
028 * intended usage for read lock is as follows:
029 *
030 * <pre>
031 * ReentrantReadWriteLock lock = idReadWriteLock.getLock(id);
032 * try {
033 *   lock.readLock().lock();
034 *   // User code.
035 * } finally {
036 *   lock.readLock().unlock();
037 * }
038 * </pre>
039 *
040 * For write lock, use lock.writeLock()
041 */
042@InterfaceAudience.Private
043public abstract class IdReadWriteLock<T> {
044  public abstract ReentrantReadWriteLock getLock(T id);
045
046  @VisibleForTesting
047  public void waitForWaiters(T id, int numWaiters) throws InterruptedException {
048    for (ReentrantReadWriteLock readWriteLock;;) {
049      readWriteLock = getLock(id);
050      if (readWriteLock != null) {
051        synchronized (readWriteLock) {
052          if (readWriteLock.getQueueLength() >= numWaiters) {
053            return;
054          }
055        }
056      }
057      Thread.sleep(50);
058    }
059  }
060}