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CloneKeyValueStoreMapReduce.java
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CloneKeyValueStoreMapReduce.java
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/*
* Licensed to the University of California, Berkeley 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 tachyon.examples.keyvalue.hadoop;
import java.io.IOException;
import java.util.Iterator;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import tachyon.client.keyvalue.hadoop.KeyValueInputFormat;
import tachyon.client.keyvalue.hadoop.KeyValueOutputCommitter;
import tachyon.client.keyvalue.hadoop.KeyValueOutputFormat;
/**
* This boring MapReduce job clones a key-value store to a different URI.
*/
public final class CloneKeyValueStoreMapReduce {
/**
* The mapper emits all key-value pairs it receives to reducers.
*/
public static class Map extends MapReduceBase
implements Mapper<BytesWritable, BytesWritable, BytesWritable, BytesWritable> {
@Override
public void map(BytesWritable key, BytesWritable value,
OutputCollector<BytesWritable, BytesWritable> out, Reporter reporter) throws IOException {
out.collect(key, value);
}
}
/**
* The reducer writes all key-value pairs it receives to the new key-value store.
*/
public static class Reduce extends MapReduceBase
implements Reducer<BytesWritable, BytesWritable, BytesWritable, BytesWritable> {
@Override
public void reduce(BytesWritable key, Iterator<BytesWritable> values,
OutputCollector<BytesWritable, BytesWritable> out, Reporter reporter) throws IOException {
while (values.hasNext()) {
out.collect(key, values.next());
}
}
}
/**
* @param args two parameters, the first is the input key-value store path, the second is the
* output key-value store path
* @throws Exception if any exception happens
*/
public static void main(String[] args) throws Exception {
JobConf conf = new JobConf(CloneKeyValueStoreMapReduce.class);
conf.setJobName("clone key-value store");
conf.setOutputKeyClass(BytesWritable.class);
conf.setOutputValueClass(BytesWritable.class);
conf.setMapperClass(Map.class);
conf.setReducerClass(Reduce.class);
conf.setInputFormat(KeyValueInputFormat.class);
conf.setOutputFormat(KeyValueOutputFormat.class);
conf.setOutputCommitter(KeyValueOutputCommitter.class);
FileInputFormat.setInputPaths(conf, new Path(args[0]));
FileOutputFormat.setOutputPath(conf, new Path(args[1]));
JobClient.runJob(conf);
}
}