001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.io.hfile;
019
020import org.apache.hadoop.conf.Configuration;
021import org.apache.yetus.audience.InterfaceAudience;
022
023/**
024 * An on heap block cache implementation extended LruBlockCache and only cache index block. This
025 * block cache should be only used by {@link org.apache.hadoop.hbase.client.ClientSideRegionScanner}
026 * that normally considers to be used by client resides out of the region server, e.g. a container
027 * of a map reduce job.
028 **/
029@InterfaceAudience.Private
030public class IndexOnlyLruBlockCache extends LruBlockCache {
031
032  public IndexOnlyLruBlockCache(long maxSize, long blockSize, boolean evictionThread,
033    Configuration conf) {
034    super(maxSize, blockSize, evictionThread, conf);
035  }
036
037  /**
038   * Cache only index block with the specified name and buffer
039   * @param cacheKey block's cache key
040   * @param buf      block buffer
041   * @param inMemory if block is in-memory
042   */
043  @Override
044  public void cacheBlock(BlockCacheKey cacheKey, Cacheable buf, boolean inMemory) {
045    if (isMetaBlock(buf.getBlockType())) {
046      super.cacheBlock(cacheKey, buf, inMemory);
047    }
048  }
049}