hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/KeyPrefixRegionSplitPolicy.java

   1 /**
   2  * Licensed to the Apache Software Foundation (ASF) under one
   3  * or more contributor license agreements.  See the NOTICE file
   4  * distributed with this work for additional information
   5  * regarding copyright ownership.  The ASF licenses this file
   6  * to you under the Apache License, Version 2.0 (the
   7  * "License"); you may not use this file except in compliance
   8  * with the License.  You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18 package org.apache.hadoop.hbase.regionserver;
  19
  20 import java.util.Arrays;
  21
  22 import org.apache.yetus.audience.InterfaceAudience;
  23 import org.slf4j.Logger;
  24 import org.slf4j.LoggerFactory;
  25
  26 /**
  27  * A custom RegionSplitPolicy implementing a SplitPolicy that groups
  28  * rows by a prefix of the row-key
  29  *
  30  * This ensures that a region is not split "inside" a prefix of a row key.
  31  * I.e. rows can be co-located in a region by their prefix.
  32  */
  33 @InterfaceAudience.Private
  34 public class KeyPrefixRegionSplitPolicy extends IncreasingToUpperBoundRegionSplitPolicy {
  35   private static final Logger LOG = LoggerFactory
  36       .getLogger(KeyPrefixRegionSplitPolicy.class);
  37   @Deprecated
  38   public static final String PREFIX_LENGTH_KEY_DEPRECATED = "prefix_split_key_policy.prefix_length";
  39   public static final String PREFIX_LENGTH_KEY = "KeyPrefixRegionSplitPolicy.prefix_length";
  40
  41   private int prefixLength = 0;
  42
  43   @Override
  44   public String toString() {
  45     return "KeyPrefixRegionSplitPolicy{" + "prefixLength=" + prefixLength + ", " +
  46       super.toString() + '}';
  47   }
  48
  49   @Override
  50   protected void configureForRegion(HRegion region) {
  51     super.configureForRegion(region);
  52     prefixLength = 0;
  53
  54     // read the prefix length from the table descriptor
  55     String prefixLengthString = region.getTableDescriptor().getValue(
  56         PREFIX_LENGTH_KEY);
  57     if (prefixLengthString == null) {
  58       //read the deprecated value
  59       prefixLengthString = region.getTableDescriptor().getValue(PREFIX_LENGTH_KEY_DEPRECATED);
  60       if (prefixLengthString == null) {
  61         LOG.error(PREFIX_LENGTH_KEY + " not specified for table "
  62             + region.getTableDescriptor().getTableName()
  63             + ". Using default RegionSplitPolicy");
  64         return;
  65       }
  66     }
  67     try {
  68       prefixLength = Integer.parseInt(prefixLengthString);
  69     } catch (NumberFormatException nfe) {
  70       /* Differentiate NumberFormatException from an invalid value range reported below. */
  71       LOG.error("Number format exception when parsing " + PREFIX_LENGTH_KEY + " for table "
  72           + region.getTableDescriptor().getTableName() + ":"
  73           + prefixLengthString + ". " + nfe);
  74       return;
  75     }
  76     if (prefixLength <= 0) {
  77       LOG.error("Invalid value for " + PREFIX_LENGTH_KEY + " for table "
  78           + region.getTableDescriptor().getTableName() + ":"
  79           + prefixLengthString + ". Using default RegionSplitPolicy");
  80     }
  81   }
  82
  83   @Override
  84   protected byte[] getSplitPoint() {
  85     byte[] splitPoint = super.getSplitPoint();
  86     if (prefixLength > 0 && splitPoint != null && splitPoint.length > 0) {
  87       // group split keys by a prefix
  88       return Arrays.copyOf(splitPoint,
  89           Math.min(prefixLength, splitPoint.length));
  90     } else {
  91       return splitPoint;
  92     }
  93   }
  94 }