我目前有一个 mapReduce 程序,可以将数据发送到具有不同文件名的 hdfs。所以在我的 reducer 中,我使用 MultipleOutputs 写入 HDFS 中的不同文件(下面的完整 reducer 代码)。
我想使用 mrunit 测试我的代码,下面是我的测试方法。
@Test
public void reducerMRUnit() throws IOException{
String output="";
ArrayList<Text> list = new ArrayList<Text>(0);
list.add(new Text(""));
reduceDriver.withInput(new Text(""), list);
reduceDriver.withPathOutput(new Text(output),NullWritable.get(),"");
reduceDriver.runTest();
}
但是,当我运行这个测试时,它给了我 NPE。
java.lang.NullPointerException
at org.apache.hadoop.fs.Path.<init>(Path.java:104)
at org.apache.hadoop.fs.Path.<init>(Path.java:93)
at org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.getDefaultWorkFile(FileOutputFormat.java:286)
at org.apache.hadoop.mapreduce.lib.output.TextOutputFormat.getRecordWriter(TextOutputFormat.java:129)
at org.apache.hadoop.mapreduce.lib.output.MultipleOutputs.getRecordWriter(MultipleOutputs.java:476)
at org.apache.hadoop.mapreduce.lib.output.MultipleOutputs.write(MultipleOutputs.java:456)
at org.clinical3PO.learn.fasta.ArffToFastAReducer.reduce(ArffToFastAReducer.java:127)
at org.clinical3PO.learn.fasta.ArffToFastAReducer.reduce(ArffToFastAReducer.java:1)
at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:171)
at org.apache.hadoop.mrunit.mapreduce.ReduceDriver.run(ReduceDriver.java:265)
at org.apache.hadoop.mrunit.TestDriver.runTest(TestDriver.java:640)
at org.apache.hadoop.mrunit.TestDriver.runTest(TestDriver.java:627)
at org.clinical3PO.learn.fasta.MRUnitTest.ArffToFastAReducerMRUnitTest.reducerMRUnit(ArffToFastAReducerMRUnitTest.java:63)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
reducer 代码:
import java.io.IOException;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;
public class AReducer extends Reducer<Text, Text, Text, NullWritable>{
private MultipleOutputs<Text, NullWritable> mos = null;
@Override
public void setup(Context context) throws IOException {
mos = new MultipleOutputs<Text, NullWritable>(context);
}
@Override
public void reduce(Text key, Iterable<Text> values, Context context)
throws IOException, InterruptedException {
mos = new MultipleOutputs<Text, NullWritable>(context);
mos.write(key, value, "filename");
}
@Override
public void cleanup(Context context) throws IOException, InterruptedException {
mos.close();
}
}
有什么建议吗?
最佳答案
MRUnit 目前有一个已知问题,该问题没有得到很好的记录,即测试 MultipleOutputs
需要使用 PowerMockRunner
和 PrepareForTest
注释运行测试应用于模拟 reducer 类。 JIRA 问题 MRUNIT-13和 MRUNIT-213包含对此的详细讨论。 MRUNIT-213 仍未解决/未修复。
然后,将 PowerMock 添加到项目中会引发一些进一步的挑战,以排列 Mockito 和 PowerMock 的正确兼容版本。关于 Using PowerMock with Mockito 的文档涵盖哪些版本兼容。
我尝试对您的示例进行这些更改。这通过了 NullPointerException
,但随后我遇到了最后一个问题。测试中声明的预期路径输出与 reducer 代码使用的 "filename"
路径不匹配。我更改了预期的路径输出以使测试完全通过。
这是我的最终结果:一个完整的项目与您的示例测试。享受吧!
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>test</groupId>
<artifactId>test-mrunit</artifactId>
<packaging>jar</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>Test MRUnit</name>
<description>Test MRUnit</description>
<properties>
<hadoop.version>2.7.1</hadoop.version>
<powermock.version>1.6.4</powermock.version>
</properties>
<dependencies>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>${hadoop.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-mapreduce-client-core</artifactId>
<version>${hadoop.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-all</artifactId>
<version>1.10.19</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-core</artifactId>
<version>${powermock.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-module-junit4</artifactId>
<version>${powermock.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-api-mockito</artifactId>
<version>${powermock.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.mrunit</groupId>
<artifactId>mrunit</artifactId>
<version>1.1.0</version>
<classifier>hadoop2</classifier>
<scope>test</scope>
</dependency>
</dependencies>
</project>
src/main/java/AReducer.java
import java.io.IOException;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;
public class AReducer extends Reducer<Text, Text, Text, NullWritable>{
private MultipleOutputs<Text, NullWritable> mos = null;
@Override
public void setup(Context context) throws IOException {
mos = new MultipleOutputs<Text, NullWritable>(context);
}
@Override
public void reduce(Text key, Iterable<Text> values, Context context)
throws IOException, InterruptedException {
mos.write(key, NullWritable.get(), "filename");
}
@Override
public void cleanup(Context context) throws IOException, InterruptedException {
mos.close();
}
}
src/test/java/TestAReducer.java
import java.io.IOException;
import java.util.ArrayList;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mrunit.mapreduce.ReduceDriver;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
@RunWith(PowerMockRunner.class)
@PrepareForTest(AReducer.class)
public class TestAReducer {
@Test
public void reducerMRUnit() throws IOException{
ReduceDriver reduceDriver = new ReduceDriver(new AReducer());
String output = "";
ArrayList<Text> list = new ArrayList<Text>(0);
list.add(new Text(""));
reduceDriver.withInput(new Text(""), list);
reduceDriver.withPathOutput(new Text(output), NullWritable.get(), "filename");
reduceDriver.runTest();
}
}
关于java - MRUnit 测试在使用 MULTIPLEOUTPUTS 写入 HDFS 时给出 NULLPOINTER 异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34604769/