hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/DelimitedKeyPrefixRegionSplitRestriction.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.io.IOException;
  21 import java.util.Arrays;
  22 import org.apache.hadoop.conf.Configuration;
  23 import org.apache.hadoop.hbase.client.TableDescriptor;
  24 import org.apache.hadoop.hbase.util.Bytes;
  25 import org.apache.yetus.audience.InterfaceAudience;
  26 import org.slf4j.Logger;
  27 import org.slf4j.LoggerFactory;
  28
  29 /**
  30  * A {@link RegionSplitRestriction} implementation that groups rows by a prefix of the row-key with
  31  * a delimiter. Only the first delimiter for the row key will define the prefix of the row key that
  32  * is used for grouping.
  33  * <p>
  34  * This ensures that a region is not split "inside" a prefix of a row key.
  35  * I.e. rows can be co-located in a region by their prefix.
  36  *
  37  * As an example, if you have row keys delimited with <code>_</code>, like
  38  * <code>userid_eventtype_eventid</code>, and use prefix delimiter _, this split policy ensures
  39  * that all rows starting with the same userid, belongs to the same region.
  40  */
  41 @InterfaceAudience.Private
  42 public class DelimitedKeyPrefixRegionSplitRestriction extends RegionSplitRestriction {
  43   private static final Logger LOG =
  44     LoggerFactory.getLogger(DelimitedKeyPrefixRegionSplitRestriction.class);
  45
  46   public static final String DELIMITER_KEY =
  47     "hbase.regionserver.region.split_restriction.delimiter";
  48
  49   private byte[] delimiter = null;
  50
  51   @Override
  52   public void initialize(TableDescriptor tableDescriptor, Configuration conf) throws IOException {
  53     String delimiterString = tableDescriptor.getValue(DELIMITER_KEY);
  54     if (delimiterString == null || delimiterString.length() == 0) {
  55       delimiterString = conf.get(DELIMITER_KEY);
  56       if (delimiterString == null || delimiterString.length() == 0) {
  57         LOG.error("{} not specified for table {}. "
  58           + "Using the default RegionSplitRestriction", DELIMITER_KEY,
  59           tableDescriptor.getTableName());
  60         return;
  61       }
  62     }
  63     delimiter = Bytes.toBytes(delimiterString);
  64   }
  65
  66   @Override
  67   public byte[] getRestrictedSplitPoint(byte[] splitPoint) {
  68     if (delimiter != null) {
  69       // find the first occurrence of delimiter in split point
  70       int index = org.apache.hbase.thirdparty.com.google.common.primitives.Bytes.indexOf(
  71         splitPoint, delimiter);
  72       if (index < 0) {
  73         LOG.warn("Delimiter {} not found for split key {}", Bytes.toString(delimiter),
  74           Bytes.toStringBinary(splitPoint));
  75         return splitPoint;
  76       }
  77
  78       // group split keys by a prefix
  79       return Arrays.copyOf(splitPoint, Math.min(index, splitPoint.length));
  80     } else {
  81       return splitPoint;
  82     }
  83   }
  84 }