MapReduce二次排序中遇到的問題，及解決方法

遇到的問題

-mapreduce_shuffle does not exist
-EOF Exception

解決方法

mapreduce_shuffle does not exist

Container launch failed for container_1446452318872_0002_01_000002 : org.apache.hadoop.yarn.exceptions.InvalidAuxServiceException: The auxService:mapreduce_shuffle does not exist
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
        at org.apache.hadoop.yarn.api.records.impl.pb.SerializedExceptionPBImpl.instantiateException(SerializedExceptionPBImpl.java:152)
        at org.apache.hadoop.yarn.api.records.impl.pb.SerializedExceptionPBImpl.deSerialize(SerializedExceptionPBImpl.java:106)
        at org.apache.hadoop.mapreduce.v2.app.launcher.ContainerLauncherImpl$Container.launch(ContainerLauncherImpl.java:155)
        at org.apache.hadoop.mapreduce.v2.app.launcher.ContainerLauncherImpl$EventProcessor.run(ContainerLauncherImpl.java:369)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:745)

在yarn-site.xml配置文件中添加如下配置：

<configuration>
<!-- Site specific YARN configuration properties -->
        <property>
            <name>yarn.nodemanager.aux-services</name>
            <value>mapreduce_shuffle</value>
        </property>
        <property>
            <name>yarn.nodemanager.aux-services.mapreduce_shuffle.class</name>
            <value>org.apache.hadoop.mapred.ShuffleHandler</value>
        </property>
</configuration>

EOF Exception

Error: java.lang.RuntimeException: java.io.EOFException
        at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:135)
        at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.compare(MapTask.java:1245)
        at org.apache.hadoop.util.QuickSort.fix(QuickSort.java:35)
        at org.apache.hadoop.util.QuickSort.sortInternal(QuickSort.java:87)
        at org.apache.hadoop.util.QuickSort.sort(QuickSort.java:63)
        at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.sortAndSpill(MapTask.java:1575)
        at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.flush(MapTask.java:1462)
        at org.apache.hadoop.mapred.MapTask$NewOutputCollector.close(MapTask.java:700)
        at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:770)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:340)
        at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:167)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:415)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1556)
        at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:162)
Caused by: java.io.EOFException
        at java.io.DataInputStream.readInt(DataInputStream.java:392)
        at com.wowSpark.secondarySort.NewKey.readFields(NewKey.java:29)
        at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:129)
        ... 14 more

問題原因：

public class NewKey implements WritableComparable<NewKey> {

    ...

    @Override
    public void readFields(DataInput in) throws IOException {
        first = in.readInt();
        second = in.readInt();
    }

    @Override
    public void write(DataOutput out) throws IOException {
        /**原來是這樣寫的
          out.write(first);
          out.write(second);
          因爲上面的readFields方法中用的是
          in.readInt() 讀取四個輸入字節並返回一個 int 值。簡單的說它要讀取4個字節的數據。
          如果這裏使用 out.write() 將指定字節（參數 b 的八個低位）寫入基礎輸出流。它只寫1個字節的數據，因此會導致上面異常
         */
        out.writeInt(first);
        out.writeInt(second);
    }