hbase-server/src/main/java/org/apache/hadoop/hbase/util/IdReadWriteLock.java

   1 /*
   2  *
   3  * Licensed to the Apache Software Foundation (ASF) under one
   4  * or more contributor license agreements.  See the NOTICE file
   5  * distributed with this work for additional information
   6  * regarding copyright ownership.  The ASF licenses this file
   7  * to you under the Apache License, Version 2.0 (the
   8  * "License"); you may not use this file except in compliance
   9  * with the License.  You may obtain a copy of the License at
  10  *
  11  *     http://www.apache.org/licenses/LICENSE-2.0
  12  *
  13  * Unless required by applicable law or agreed to in writing, software
  14  * distributed under the License is distributed on an "AS IS" BASIS,
  15  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  16  * See the License for the specific language governing permissions and
  17  * limitations under the License.
  18  */
  19 package org.apache.hadoop.hbase.util;
  20
  21 import java.util.concurrent.locks.ReentrantReadWriteLock;
  22
  23 import org.apache.yetus.audience.InterfaceAudience;
  24
  25 /**
  26  * Allows multiple concurrent clients to lock on a numeric id with ReentrantReadWriteLock. The
  27  * intended usage for read lock is as follows:
  28  *
  29  * <pre>
  30  * ReentrantReadWriteLock lock = idReadWriteLock.getLock(id);
  31  * try {
  32  *   lock.readLock().lock();
  33  *   // User code.
  34  * } finally {
  35  *   lock.readLock().unlock();
  36  * }
  37  * </pre>
  38  *
  39  * For write lock, use lock.writeLock()
  40  */
  41 @InterfaceAudience.Private
  42 public abstract class IdReadWriteLock<T> {
  43   public abstract ReentrantReadWriteLock getLock(T id);
  44
  45   public void waitForWaiters(T id, int numWaiters) throws InterruptedException {
  46     for (ReentrantReadWriteLock readWriteLock;;) {
  47       readWriteLock = getLock(id);
  48       if (readWriteLock != null) {
  49         synchronized (readWriteLock) {
  50           if (readWriteLock.getQueueLength() >= numWaiters) {
  51             return;
  52           }
  53         }
  54       }
  55       Thread.sleep(50);
  56     }
  57   }
  58 }