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
25 /**
26 * Block cache interface. Anything that implements the {@link Cacheable}
27 * interface can be put in the cache.
28 */
29 @InterfaceAudience.Private
30 public interface BlockCache extends Iterable<CachedBlock> {
31 /**
32 * Add block to cache.
33 * @param cacheKey The block's cache key.
34 * @param buf The block contents wrapped in a ByteBuffer.
35 * @param inMemory Whether block should be treated as in-memory
36 */
37 void cacheBlock(BlockCacheKey cacheKey, Cacheable buf, boolean inMemory);
38
39 /**
40 * Add block to cache (defaults to not in-memory).
41 * @param cacheKey The block's cache key.
42 * @param buf The object to cache.
43 */
44 void cacheBlock(BlockCacheKey cacheKey, Cacheable buf);
45
46 /**
47 * Fetch block from cache.
48 * @param cacheKey Block to fetch.
49 * @param caching Whether this request has caching enabled (used for stats)
50 * @param repeat Whether this is a repeat lookup for the same block
51 * (used to avoid double counting cache misses when doing double-check locking)
52 * @param updateCacheMetrics Whether to update cache metrics or not
53 * @return Block or null if block is not in 2 cache.
54 */
55 Cacheable getBlock(BlockCacheKey cacheKey, boolean caching, boolean repeat,
56 boolean updateCacheMetrics);
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 boolean evictBlock(BlockCacheKey cacheKey);
64
65 /**
66 * Evicts all blocks for the given HFile.
67 *
68 * @return the number of blocks evicted
69 */
70 int evictBlocksByHfileName(String hfileName);
71
72 /**
73 * Get the statistics for this block cache.
74 * @return Stats
75 */
76 CacheStats getStats();
77
78 /**
79 * Shutdown the cache.
80 */
81 void shutdown();
82
83 /**
84 * Returns the total size of the block cache, in bytes.
85 * @return size of cache, in bytes
86 */
87 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 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 long getCurrentSize();
100
101 /**
102 * Returns the number of blocks currently cached in the block cache.
103 * @return number of blocks in the cache
104 */
105 long getBlockCount();
106
107 /**
108 * @return Iterator over the blocks in the cache.
109 */
110 Iterator<CachedBlock> iterator();
111
112 /**
113 * @return The list of sub blockcaches that make up this one; returns null if no sub caches.
114 */
115 BlockCache [] getBlockCaches();
116 }