org.apache.hadoop.hbase.mapreduce.HRegionPartitioner Maven / Gradle / Ivy
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*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.mapreduce;
import java.io.IOException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceStability;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.Connection;
import org.apache.hadoop.hbase.client.ConnectionFactory;
import org.apache.hadoop.hbase.client.RegionLocator;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapred.TableOutputFormat;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.mapreduce.Partitioner;
/**
* This is used to partition the output keys into groups of keys.
* Keys are grouped according to the regions that currently exist
* so that each reducer fills a single region so load is distributed.
*
* This class is not suitable as partitioner creating hfiles
* for incremental bulk loads as region spread will likely change between time of
* hfile creation and load time. See {@link LoadIncrementalHFiles}
* and Bulk Load.
*
* @param The type of the key.
* @param The type of the value.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class HRegionPartitioner
extends Partitioner
implements Configurable {
private static final Log LOG = LogFactory.getLog(HRegionPartitioner.class);
private Configuration conf = null;
// Connection and locator are not cleaned up; they just die when partitioner is done.
private Connection connection;
private RegionLocator locator;
private byte[][] startKeys;
/**
* Gets the partition number for a given key (hence record) given the total
* number of partitions i.e. number of reduce-tasks for the job.
*
* Typically a hash function on a all or a subset of the key.
*
* @param key The key to be partitioned.
* @param value The entry value.
* @param numPartitions The total number of partitions.
* @return The partition number for the key.
* @see org.apache.hadoop.mapreduce.Partitioner#getPartition(
* java.lang.Object, java.lang.Object, int)
*/
@Override
public int getPartition(ImmutableBytesWritable key,
VALUE value, int numPartitions) {
byte[] region = null;
// Only one region return 0
if (this.startKeys.length == 1){
return 0;
}
try {
// Not sure if this is cached after a split so we could have problems
// here if a region splits while mapping
region = this.locator.getRegionLocation(key.get()).getRegionInfo().getStartKey();
} catch (IOException e) {
LOG.error(e);
}
for (int i = 0; i < this.startKeys.length; i++){
if (Bytes.compareTo(region, this.startKeys[i]) == 0 ){
if (i >= numPartitions-1){
// cover if we have less reduces then regions.
return (Integer.toString(i).hashCode()
& Integer.MAX_VALUE) % numPartitions;
}
return i;
}
}
// if above fails to find start key that match we need to return something
return 0;
}
/**
* Returns the current configuration.
*
* @return The current configuration.
* @see org.apache.hadoop.conf.Configurable#getConf()
*/
@Override
public Configuration getConf() {
return conf;
}
/**
* Sets the configuration. This is used to determine the start keys for the
* given table.
*
* @param configuration The configuration to set.
* @see org.apache.hadoop.conf.Configurable#setConf(
* org.apache.hadoop.conf.Configuration)
*/
@Override
public void setConf(Configuration configuration) {
this.conf = HBaseConfiguration.create(configuration);
try {
this.connection = ConnectionFactory.createConnection(HBaseConfiguration.create(conf));
TableName tableName = TableName.valueOf(conf.get(TableOutputFormat.OUTPUT_TABLE));
this.locator = this.connection.getRegionLocator(tableName);
} catch (IOException e) {
LOG.error(e);
}
try {
this.startKeys = this.locator.getStartKeys();
} catch (IOException e) {
LOG.error(e);
}
}
}