/** * Copyright 2008 The Apache Software Foundation * * 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.conf.Configurable; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hbase.HBaseConfiguration; import org.apache.hadoop.hbase.client.HTable; import org.apache.hadoop.hbase.io.ImmutableBytesWritable; 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. * * <p>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 <a href="http://hbase.apache.org/docs/current/bulk-loads.html">Bulk Load</a>. * * @param <KEY> The type of the key. * @param <VALUE> The type of the value. */ public class HRegionPartitioner<KEY, VALUE> extends Partitioner<ImmutableBytesWritable, VALUE> implements Configurable { private final Log LOG = LogFactory.getLog(TableInputFormat.class); private Configuration conf = null; private HTable table; 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. * * <p>Typically a hash function on a all or a subset of the key.</p> * * @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 <code>key</code>. * @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 = table.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 = configuration; try { HBaseConfiguration.addHbaseResources(conf); this.table = new HTable(this.conf, configuration.get(TableOutputFormat.OUTPUT_TABLE)); } catch (IOException e) { LOG.error(e); } try { this.startKeys = this.table.getStartKeys(); } catch (IOException e) { LOG.error(e); } } }