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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.hadoop.hbase.codec.prefixtree.decode;
20  
21  import java.util.Queue;
22  import java.util.concurrent.LinkedBlockingQueue;
23  
24  import org.apache.hadoop.hbase.classification.InterfaceAudience;
25  import org.apache.hadoop.hbase.nio.ByteBuff;
26  
27  /**
28   * <p>
29   * Pools PrefixTreeArraySearcher objects. Each Searcher can consist of hundreds or thousands of
30   * objects and 1 is needed for each HFile during a Get operation. With tens of thousands of
31   * Gets/second, reusing these searchers may save a lot of young gen collections.
32   * </p>
33   * Alternative implementation would be a ByteBufferSearcherPool (not implemented yet).
34   */
35  @InterfaceAudience.Private
36  public class ArraySearcherPool {
37  
38    /**
39     * One decoder is needed for each storefile for each Get operation so we may need hundreds at the
40     * same time, however, decoding is a CPU bound activity so should limit this to something in the
41     * realm of maximum reasonable active threads.
42     */
43    private static final Integer MAX_POOL_SIZE = 1000;
44  
45    protected Queue<PrefixTreeArraySearcher> pool
46      = new LinkedBlockingQueue<PrefixTreeArraySearcher>(MAX_POOL_SIZE);
47  
48    public PrefixTreeArraySearcher checkOut(ByteBuff buffer, boolean includesMvccVersion) {
49      PrefixTreeArraySearcher searcher = pool.poll();//will return null if pool is empty
50      searcher = DecoderFactory.ensureArraySearcherValid(buffer, searcher, includesMvccVersion);
51      return searcher;
52    }
53  
54    public void checkIn(PrefixTreeArraySearcher searcher) {
55      searcher.releaseBlockReference();
56      pool.offer(searcher);
57    }
58  
59    @Override
60    public String toString() {
61      return ("poolSize:" + pool.size());
62    }
63  
64  }