hadoop PipesPartitioner 源码
haddop PipesPartitioner 代码
文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/pipes/PipesPartitioner.java
/**
* 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.mapred.pipes;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.Partitioner;
import org.apache.hadoop.util.ReflectionUtils;
/**
* This partitioner is one that can either be set manually per a record or it
* can fall back onto a Java partitioner that was set by the user.
*/
class PipesPartitioner<K extends WritableComparable,
V extends Writable>
implements Partitioner<K, V> {
private static final ThreadLocal<Integer> CACHE = new ThreadLocal<Integer>();
private Partitioner<K, V> part = null;
@SuppressWarnings("unchecked")
public void configure(JobConf conf) {
part =
ReflectionUtils.newInstance(Submitter.getJavaPartitioner(conf), conf);
}
/**
* Set the next key to have the given partition.
* @param newValue the next partition value
*/
static void setNextPartition(int newValue) {
CACHE.set(newValue);
}
/**
* If a partition result was set manually, return it. Otherwise, we call
* the Java partitioner.
* @param key the key to partition
* @param value the value to partition
* @param numPartitions the number of reduces
*/
public int getPartition(K key, V value,
int numPartitions) {
Integer result = CACHE.get();
if (result == null) {
return part.getPartition(key, value, numPartitions);
} else {
return result;
}
}
}
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