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.io.hfile;
20
21 import java.util.Iterator;
22
23 import org.apache.hadoop.hbase.classification.InterfaceAudience;
24 import org.apache.hadoop.hbase.io.hfile.Cacheable.MemoryType;
25
26 /**
27 * Block cache interface. Anything that implements the {@link Cacheable}
28 * interface can be put in the cache.
29 */
30 @InterfaceAudience.Private
31 public interface BlockCache extends Iterable<CachedBlock> {
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 * @param cacheDataInL1 If multi-tier block cache deploy -- i.e. has an L1 and L2 tier -- then
38 * if this flag is true, cache data blocks up in the L1 tier (meta blocks are probably being
39 * cached in L1 already).
40 */
41 void cacheBlock(BlockCacheKey cacheKey, Cacheable buf, boolean inMemory, boolean cacheDataInL1);
42
43 /**
44 * Add block to cache (defaults to not in-memory).
45 * @param cacheKey The block's cache key.
46 * @param buf The object to cache.
47 */
48 void cacheBlock(BlockCacheKey cacheKey, Cacheable buf);
49
50 /**
51 * Fetch block from cache.
52 * @param cacheKey Block to fetch.
53 * @param caching Whether this request has caching enabled (used for stats)
54 * @param repeat Whether this is a repeat lookup for the same block
55 * (used to avoid double counting cache misses when doing double-check locking)
56 * @param updateCacheMetrics Whether to update cache metrics or not
57 * @return Block or null if block is not in 2 cache.
58 */
59 Cacheable getBlock(BlockCacheKey cacheKey, boolean caching, boolean repeat,
60 boolean updateCacheMetrics);
61
62 /**
63 * Evict block from cache.
64 * @param cacheKey Block to evict
65 * @return true if block existed and was evicted, false if not
66 */
67 boolean evictBlock(BlockCacheKey cacheKey);
68
69 /**
70 * Evicts all blocks for the given HFile.
71 *
72 * @return the number of blocks evicted
73 */
74 int evictBlocksByHfileName(String hfileName);
75
76 /**
77 * Get the statistics for this block cache.
78 * @return Stats
79 */
80 CacheStats getStats();
81
82 /**
83 * Shutdown the cache.
84 */
85 void shutdown();
86
87 /**
88 * Returns the total size of the block cache, in bytes.
89 * @return size of cache, in bytes
90 */
91 long size();
92
93 /**
94 * Returns the free size of the block cache, in bytes.
95 * @return free space in cache, in bytes
96 */
97 long getFreeSize();
98
99 /**
100 * Returns the occupied size of the block cache, in bytes.
101 * @return occupied space in cache, in bytes
102 */
103 long getCurrentSize();
104
105 /**
106 * Returns the number of blocks currently cached in the block cache.
107 * @return number of blocks in the cache
108 */
109 long getBlockCount();
110
111 /**
112 * @return Iterator over the blocks in the cache.
113 */
114 Iterator<CachedBlock> iterator();
115
116 /**
117 * @return The list of sub blockcaches that make up this one; returns null if no sub caches.
118 */
119 BlockCache [] getBlockCaches();
120
121 /**
122 * Called when the scanner using the block decides to return the block once its usage
123 * is over.
124 * This API should be called after the block is used, failing to do so may have adverse effects
125 * by preventing the blocks from being evicted because of which it will prevent new hot blocks
126 * from getting added to the block cache. The implementation of the BlockCache will decide
127 * on what to be done with the block based on the memory type of the block's {@link MemoryType}.
128 * @param cacheKey the cache key of the block
129 * @param block the hfileblock to be returned
130 */
131 void returnBlock(BlockCacheKey cacheKey, Cacheable block);
132 }