1 /**
2 * Copyright 2008 The Apache Software Foundation
3 *
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20 package org.apache.hadoop.hbase.mapreduce;
21
22 import java.io.IOException;
23
24 import org.apache.commons.logging.Log;
25 import org.apache.commons.logging.LogFactory;
26 import org.apache.hadoop.conf.Configurable;
27 import org.apache.hadoop.conf.Configuration;
28 import org.apache.hadoop.hbase.HBaseConfiguration;
29 import org.apache.hadoop.hbase.client.HTable;
30 import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
31 import org.apache.hadoop.hbase.util.Bytes;
32 import org.apache.hadoop.mapreduce.Partitioner;
33
34 /**
35 * This is used to partition the output keys into groups of keys.
36 * Keys are grouped according to the regions that currently exist
37 * so that each reducer fills a single region so load is distributed.
38 *
39 * <p>This class is not suitable as partitioner creating hfiles
40 * for incremental bulk loads as region spread will likely change between time of
41 * hfile creation and load time. See {@link LoadIncrementalHFiles}
42 * and <a href="http://hbase.apache.org/docs/current/bulk-loads.html">Bulk Load</a>.
43 *
44 * @param <KEY> The type of the key.
45 * @param <VALUE> The type of the value.
46 */
47 public class HRegionPartitioner<KEY, VALUE>
48 extends Partitioner<ImmutableBytesWritable, VALUE>
49 implements Configurable {
50
51 private final Log LOG = LogFactory.getLog(TableInputFormat.class);
52 private Configuration conf = null;
53 private HTable table;
54 private byte[][] startKeys;
55
56 /**
57 * Gets the partition number for a given key (hence record) given the total
58 * number of partitions i.e. number of reduce-tasks for the job.
59 *
60 * <p>Typically a hash function on a all or a subset of the key.</p>
61 *
62 * @param key The key to be partitioned.
63 * @param value The entry value.
64 * @param numPartitions The total number of partitions.
65 * @return The partition number for the <code>key</code>.
66 * @see org.apache.hadoop.mapreduce.Partitioner#getPartition(
67 * java.lang.Object, java.lang.Object, int)
68 */
69 @Override
70 public int getPartition(ImmutableBytesWritable key,
71 VALUE value, int numPartitions) {
72 byte[] region = null;
73 // Only one region return 0
74 if (this.startKeys.length == 1){
75 return 0;
76 }
77 try {
78 // Not sure if this is cached after a split so we could have problems
79 // here if a region splits while mapping
80 region = table.getRegionLocation(key.get()).getRegionInfo().getStartKey();
81 } catch (IOException e) {
82 LOG.error(e);
83 }
84 for (int i = 0; i < this.startKeys.length; i++){
85 if (Bytes.compareTo(region, this.startKeys[i]) == 0 ){
86 if (i >= numPartitions-1){
87 // cover if we have less reduces then regions.
88 return (Integer.toString(i).hashCode()
89 & Integer.MAX_VALUE) % numPartitions;
90 }
91 return i;
92 }
93 }
94 // if above fails to find start key that match we need to return something
95 return 0;
96 }
97
98 /**
99 * Returns the current configuration.
100 *
101 * @return The current configuration.
102 * @see org.apache.hadoop.conf.Configurable#getConf()
103 */
104 @Override
105 public Configuration getConf() {
106 return conf;
107 }
108
109 /**
110 * Sets the configuration. This is used to determine the start keys for the
111 * given table.
112 *
113 * @param configuration The configuration to set.
114 * @see org.apache.hadoop.conf.Configurable#setConf(
115 * org.apache.hadoop.conf.Configuration)
116 */
117 @Override
118 public void setConf(Configuration configuration) {
119 this.conf = configuration;
120 try {
121 HBaseConfiguration.addHbaseResources(conf);
122 this.table = new HTable(this.conf,
123 configuration.get(TableOutputFormat.OUTPUT_TABLE));
124 } catch (IOException e) {
125 LOG.error(e);
126 }
127 try {
128 this.startKeys = this.table.getStartKeys();
129 } catch (IOException e) {
130 LOG.error(e);
131 }
132 }
133 }