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.yetus.audience.InterfaceAudience;
021
022/**
023 * Allows for defining different compression rate predicates on its implementing classes. Useful
024 * when compression is in place, and we want to define block size based on the compressed size,
025 * rather than the default behaviour that considers the uncompressed size only. Since we don't
026 * actually know the compressed size until we actual apply compression in the block byte buffer, we
027 * need to "predicate" this compression rate and minimize compression execution to avoid excessive
028 * resources usage. Different approaches for predicating the compressed block size can be defined by
029 * implementing classes. The <code>updateLatestBlockSizes</code> allows for updating uncompressed
030 * and compressed size values, and is called during block finishing (when we finally apply
031 * compression on the block data). Final block size predicate logic is implemented in
032 * <code>shouldFinishBlock</code>, which is called by the block writer once uncompressed size has
033 * reached the configured BLOCK size, and additional checks should be applied to decide if the block
034 * can be finished.
035 */
036@InterfaceAudience.Private
037public interface BlockCompressedSizePredicator {
038
039  String BLOCK_COMPRESSED_SIZE_PREDICATOR = "hbase.block.compressed.size.predicator";
040
041  String MAX_BLOCK_SIZE_UNCOMPRESSED = "hbase.block.max.size.uncompressed";
042
043  /**
044   * Updates the predicator with both compressed and uncompressed sizes of latest block written. To
045   * be called once the block is finshed and flushed to disk after compression.
046   * @param context      the HFileContext containg the configured max block size.
047   * @param uncompressed the uncompressed size of last block written.
048   * @param compressed   the compressed size of last block written.
049   */
050  void updateLatestBlockSizes(HFileContext context, int uncompressed, int compressed);
051
052  /**
053   * Decides if the block should be finished based on the comparison of its uncompressed size
054   * against an adjusted size based on a predicated compression factor.
055   * @param uncompressed true if the block should be finished.
056   */
057  boolean shouldFinishBlock(int uncompressed);
058
059}