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1   /**
2    * Copyright 2009 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.io.hfile;
21  
22  import java.io.IOException;
23  import java.util.List;
24  
25  import org.apache.hadoop.conf.Configuration;
26  
27  /**
28   * Block cache interface. Anything that implements the {@link Cacheable}
29   * interface can be put in the cache.
30   */
31  public interface BlockCache {
32    /**
33     * Add block to cache.
34     * @param cacheKey The block's cache key.
35     * @param buf The block contents wrapped in a ByteBuffer.
36     * @param inMemory Whether block should be treated as in-memory
37     */
38    public void cacheBlock(BlockCacheKey cacheKey, Cacheable buf, boolean inMemory);
39  
40    /**
41     * Add block to cache (defaults to not in-memory).
42     * @param cacheKey The block's cache key.
43     * @param buf The object to cache.
44     */
45    public void cacheBlock(BlockCacheKey cacheKey, Cacheable buf);
46  
47    /**
48     * Fetch block from cache.
49     * @param cacheKey Block to fetch.
50     * @param caching Whether this request has caching enabled (used for stats)
51     * @param repeat Whether this is a repeat lookup for the same block
52     *        (used to avoid double counting cache misses when doing double-check locking)
53     *        {@see HFileReaderV2#readBlock(long, long, boolean, boolean, boolean, BlockType)}
54     * @return Block or null if block is not in 2 cache.
55     */
56    public Cacheable getBlock(BlockCacheKey cacheKey, boolean caching, boolean repeat);
57  
58    /**
59     * Evict block from cache.
60     * @param cacheKey Block to evict
61     * @return true if block existed and was evicted, false if not
62     */
63    public boolean evictBlock(BlockCacheKey cacheKey);
64  
65    /**
66     * Evicts all blocks for the given HFile.
67     *
68     * @return the number of blocks evicted
69     */
70    public int evictBlocksByHfileName(String hfileName);
71  
72    /**
73     * Get the statistics for this block cache.
74     * @return Stats
75     */
76    public CacheStats getStats();
77  
78    /**
79     * Shutdown the cache.
80     */
81    public void shutdown();
82  
83    /**
84     * Returns the total size of the block cache, in bytes.
85     * @return size of cache, in bytes
86     */
87    public long size();
88  
89    /**
90     * Returns the free size of the block cache, in bytes.
91     * @return free space in cache, in bytes
92     */
93    public long getFreeSize();
94  
95    /**
96     * Returns the occupied size of the block cache, in bytes.
97     * @return occupied space in cache, in bytes
98     */
99    public long getCurrentSize();
100 
101   /**
102    * Returns the number of evictions that have occurred.
103    * @return number of evictions
104    */
105   public long getEvictedCount();
106 
107   /**
108    * Returns the number of blocks currently cached in the block cache.
109    * @return number of blocks in the cache
110    */
111   public long getBlockCount();
112 
113   /**
114    * Performs a BlockCache summary and returns a List of BlockCacheColumnFamilySummary objects.
115    * This method could be fairly heavyweight in that it evaluates the entire HBase file-system
116    * against what is in the RegionServer BlockCache.
117    * <br><br>
118    * The contract of this interface is to return the List in sorted order by Table name, then
119    * ColumnFamily.
120    *
121    * @param conf HBaseConfiguration
122    * @return List of BlockCacheColumnFamilySummary
123    * @throws IOException exception
124    */
125   public List<BlockCacheColumnFamilySummary> getBlockCacheColumnFamilySummaries(Configuration conf) throws IOException;
126 }