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.lang.ref.Reference;
  22 import java.util.concurrent.locks.ReentrantReadWriteLock;
  23
  24 import org.apache.yetus.audience.InterfaceAudience;
  25
  26 import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
  27
  28 /**
  29  * Allows multiple concurrent clients to lock on a numeric id with ReentrantReadWriteLock. The
  30  * intended usage for read lock is as follows:
  31  *
  32  * <pre>
  33  * ReentrantReadWriteLock lock = idReadWriteLock.getLock(id);
  34  * try {
  35  *   lock.readLock().lock();
  36  *   // User code.
  37  * } finally {
  38  *   lock.readLock().unlock();
  39  * }
  40  * </pre>
  41  *
  42  * For write lock, use lock.writeLock()
  43  */
  44 @InterfaceAudience.Private
  45 public class IdReadWriteLock<T> {
  46   // The number of lock we want to easily support. It's not a maximum.
  47   private static final int NB_CONCURRENT_LOCKS = 1000;
  48   /**
  49    * The pool to get entry from, entries are mapped by {@link Reference} and will be automatically
  50    * garbage-collected by JVM
  51    */
  52   private final ObjectPool<T, ReentrantReadWriteLock> lockPool;
  53   private final ReferenceType refType;
  54
  55   public IdReadWriteLock() {
  56     this(ReferenceType.WEAK);
  57   }
  58
  59   /**
  60    * Constructor of IdReadWriteLock
  61    * @param referenceType type of the reference used in lock pool, {@link ReferenceType#WEAK} by
  62    *          default. Use {@link ReferenceType#SOFT} if the key set is limited and the locks will
  63    *          be reused with a high frequency
  64    */
  65   public IdReadWriteLock(ReferenceType referenceType) {
  66     this.refType = referenceType;
  67     switch (referenceType) {
  68       case SOFT:
  69         lockPool = new SoftObjectPool<>(new ObjectPool.ObjectFactory<T, ReentrantReadWriteLock>() {
  70           @Override
  71           public ReentrantReadWriteLock createObject(T id) {
  72             return new ReentrantReadWriteLock();
  73           }
  74         }, NB_CONCURRENT_LOCKS);
  75         break;
  76       case WEAK:
  77       default:
  78         lockPool = new WeakObjectPool<>(new ObjectPool.ObjectFactory<T, ReentrantReadWriteLock>() {
  79           @Override
  80           public ReentrantReadWriteLock createObject(T id) {
  81             return new ReentrantReadWriteLock();
  82           }
  83         }, NB_CONCURRENT_LOCKS);
  84     }
  85   }
  86
  87   public static enum ReferenceType {
  88     WEAK, SOFT
  89   }
  90
  91   /**
  92    * Get the ReentrantReadWriteLock corresponding to the given id
  93    * @param id an arbitrary number to identify the lock
  94    */
  95   public ReentrantReadWriteLock getLock(T id) {
  96     lockPool.purge();
  97     ReentrantReadWriteLock readWriteLock = lockPool.get(id);
  98     return readWriteLock;
  99   }
 100
 101   /** For testing */
 102   @VisibleForTesting
 103   int purgeAndGetEntryPoolSize() {
 104     gc();
 105     Threads.sleep(200);
 106     lockPool.purge();
 107     return lockPool.size();
 108   }
 109
 110   @edu.umd.cs.findbugs.annotations.SuppressWarnings(value="DM_GC", justification="Intentional")
 111   private void gc() {
 112     System.gc();
 113   }
 114
 115   @VisibleForTesting
 116   public void waitForWaiters(T id, int numWaiters) throws InterruptedException {
 117     for (ReentrantReadWriteLock readWriteLock;;) {
 118       readWriteLock = lockPool.get(id);
 119       if (readWriteLock != null) {
 120         synchronized (readWriteLock) {
 121           if (readWriteLock.getQueueLength() >= numWaiters) {
 122             return;
 123           }
 124         }
 125       }
 126       Thread.sleep(50);
 127     }
 128   }
 129
 130   @VisibleForTesting
 131   public ReferenceType getReferenceType() {
 132     return this.refType;
 133   }
 134 }