/**
* 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.mapreduce;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.Arrays;
import java.util.List;
import junit.framework.TestCase;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.FileUtil;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.MiniDFSCluster;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MiniMRCluster;
import org.apache.hadoop.mapred.Utils;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.LazyOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
/**
* A JUnit test to test the Map-Reduce framework's feature to create part
* files only if there is an explicit output.collect. This helps in preventing
* 0 byte files
*/
public class TestMapReduceLazyOutput extends TestCase {
private static final int NUM_HADOOP_SLAVES = 3;
private static final int NUM_MAPS_PER_NODE = 2;
private static final Path INPUT = new Path("/testlazy/input");
private static final List<String> input =
Arrays.asList("All","Roads","Lead","To","Hadoop");
public static class TestMapper
extends Mapper<LongWritable, Text, LongWritable, Text>{
public void map(LongWritable key, Text value, Context context
) throws IOException, InterruptedException {
String id = context.getTaskAttemptID().toString();
// Mapper 0 does not output anything
if (!id.endsWith("0_0")) {
context.write(key, value);
}
}
}
public static class TestReducer
extends Reducer<LongWritable,Text,LongWritable,Text> {
public void reduce(LongWritable key, Iterable<Text> values,
Context context) throws IOException, InterruptedException {
String id = context.getTaskAttemptID().toString();
// Reducer 0 does not output anything
if (!id.endsWith("0_0")) {
for (Text val: values) {
context.write(key, val);
}
}
}
}
private static void runTestLazyOutput(Configuration conf, Path output,
int numReducers, boolean createLazily)
throws Exception {
Job job = new Job(conf, "Test-Lazy-Output");
FileInputFormat.setInputPaths(job, INPUT);
FileOutputFormat.setOutputPath(job, output);
job.setJarByClass(TestMapReduceLazyOutput.class);
job.setInputFormatClass(TextInputFormat.class);
job.setOutputKeyClass(LongWritable.class);
job.setOutputValueClass(Text.class);
job.setNumReduceTasks(numReducers);
job.setMapperClass(TestMapper.class);
job.setReducerClass(TestReducer.class);
if (createLazily) {
LazyOutputFormat.setOutputFormatClass(job, TextOutputFormat.class);
} else {
job.setOutputFormatClass(TextOutputFormat.class);
}
assertTrue(job.waitForCompletion(true));
}
public void createInput(FileSystem fs, int numMappers) throws Exception {
for (int i =0; i < numMappers; i++) {
OutputStream os = fs.create(new Path(INPUT,
"text" + i + ".txt"));
Writer wr = new OutputStreamWriter(os);
for(String inp : input) {
wr.write(inp+"\n");
}
wr.close();
}
}
public void testLazyOutput() throws Exception {
MiniDFSCluster dfs = null;
MiniMRCluster mr = null;
FileSystem fileSys = null;
try {
Configuration conf = new Configuration();
// Start the mini-MR and mini-DFS clusters
dfs = new MiniDFSCluster(conf, NUM_HADOOP_SLAVES, true, null);
fileSys = dfs.getFileSystem();
mr = new MiniMRCluster(NUM_HADOOP_SLAVES, fileSys.getUri().toString(), 1);
int numReducers = 2;
int numMappers = NUM_HADOOP_SLAVES * NUM_MAPS_PER_NODE;
createInput(fileSys, numMappers);
Path output1 = new Path("/testlazy/output1");
// Test 1.
runTestLazyOutput(mr.createJobConf(), output1,
numReducers, true);
Path[] fileList =
FileUtil.stat2Paths(fileSys.listStatus(output1,
new Utils.OutputFileUtils.OutputFilesFilter()));
for(int i=0; i < fileList.length; ++i) {
System.out.println("Test1 File list[" + i + "]" + ": "+ fileList[i]);
}
assertTrue(fileList.length == (numReducers - 1));
// Test 2. 0 Reducers, maps directly write to the output files
Path output2 = new Path("/testlazy/output2");
runTestLazyOutput(mr.createJobConf(), output2, 0, true);
fileList =
FileUtil.stat2Paths(fileSys.listStatus(output2,
new Utils.OutputFileUtils.OutputFilesFilter()));
for(int i=0; i < fileList.length; ++i) {
System.out.println("Test2 File list[" + i + "]" + ": "+ fileList[i]);
}
assertTrue(fileList.length == numMappers - 1);
// Test 3. 0 Reducers, but flag is turned off
Path output3 = new Path("/testlazy/output3");
runTestLazyOutput(mr.createJobConf(), output3, 0, false);
fileList =
FileUtil.stat2Paths(fileSys.listStatus(output3,
new Utils.OutputFileUtils.OutputFilesFilter()));
for(int i=0; i < fileList.length; ++i) {
System.out.println("Test3 File list[" + i + "]" + ": "+ fileList[i]);
}
assertTrue(fileList.length == numMappers);
} finally {
if (dfs != null) { dfs.shutdown(); }
if (mr != null) { mr.shutdown();
}
}
}
}