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 * @param <KEY> The type of the key.
40 * @param <VALUE> The type of the value.
41 */
42 public class HRegionPartitioner<KEY, VALUE>
43 extends Partitioner<ImmutableBytesWritable, VALUE>
44 implements Configurable {
45
46 private final Log LOG = LogFactory.getLog(TableInputFormat.class);
47 private Configuration conf = null;
48 private HTable table;
49 private byte[][] startKeys;
50
51 /**
52 * Gets the partition number for a given key (hence record) given the total
53 * number of partitions i.e. number of reduce-tasks for the job.
54 *
55 * <p>Typically a hash function on a all or a subset of the key.</p>
56 *
57 * @param key The key to be partitioned.
58 * @param value The entry value.
59 * @param numPartitions The total number of partitions.
60 * @return The partition number for the <code>key</code>.
61 * @see org.apache.hadoop.mapreduce.Partitioner#getPartition(
62 * java.lang.Object, java.lang.Object, int)
63 */
64 @Override
65 public int getPartition(ImmutableBytesWritable key,
66 VALUE value, int numPartitions) {
67 byte[] region = null;
68 // Only one region return 0
69 if (this.startKeys.length == 1){
70 return 0;
71 }
72 try {
73 // Not sure if this is cached after a split so we could have problems
74 // here if a region splits while mapping
75 region = table.getRegionLocation(key.get()).getRegionInfo().getStartKey();
76 } catch (IOException e) {
77 LOG.error(e);
78 }
79 for (int i = 0; i < this.startKeys.length; i++){
80 if (Bytes.compareTo(region, this.startKeys[i]) == 0 ){
81 if (i >= numPartitions-1){
82 // cover if we have less reduces then regions.
83 return (Integer.toString(i).hashCode()
84 & Integer.MAX_VALUE) % numPartitions;
85 }
86 return i;
87 }
88 }
89 // if above fails to find start key that match we need to return something
90 return 0;
91 }
92
93 /**
94 * Returns the current configuration.
95 *
96 * @return The current configuration.
97 * @see org.apache.hadoop.conf.Configurable#getConf()
98 */
99 @Override
100 public Configuration getConf() {
101 return conf;
102 }
103
104 /**
105 * Sets the configuration. This is used to determine the start keys for the
106 * given table.
107 *
108 * @param configuration The configuration to set.
109 * @see org.apache.hadoop.conf.Configurable#setConf(
110 * org.apache.hadoop.conf.Configuration)
111 */
112 @Override
113 public void setConf(Configuration configuration) {
114 this.conf = configuration;
115 try {
116 HBaseConfiguration.addHbaseResources(conf);
117 this.table = new HTable(this.conf,
118 configuration.get(TableOutputFormat.OUTPUT_TABLE));
119 } catch (IOException e) {
120 LOG.error(e);
121 }
122 try {
123 this.startKeys = this.table.getStartKeys();
124 } catch (IOException e) {
125 LOG.error(e);
126 }
127 }
128 }