hadoop job 内存溢出

在进行mapreduce任务性能测试的时候，在Shuffle的时候，老是会报java.lang.OutOfMemoryError内存溢出错误。堆栈信息如下：

2016-01-23 10:34:42,216 INFO  [main] mapreduce.Job: Task Id : attempt_1453272487300_1980_r_000000_0, Status : FAILED
Error: org.apache.hadoop.mapreduce.task.reduce.Shuffle$ShuffleError: error in shuffle in fetcher#4
        at org.apache.hadoop.mapreduce.task.reduce.Shuffle.run(Shuffle.java:134)
        at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:376)
        at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:163)
        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:1628)
        at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
Caused by: java.lang.OutOfMemoryError: Java heap space
        at org.apache.hadoop.io.BoundedByteArrayOutputStream.<init>(BoundedByteArrayOutputStream.java:56)
        at org.apache.hadoop.io.BoundedByteArrayOutputStream.<init>(BoundedByteArrayOutputStream.java:46)
        at org.apache.hadoop.mapreduce.task.reduce.InMemoryMapOutput.<init>(InMemoryMapOutput.java:63)
        at org.apache.hadoop.mapreduce.task.reduce.MergeManagerImpl.unconditionalReserve(MergeManagerImpl.java:304)
        at org.apache.hadoop.mapreduce.task.reduce.MergeManagerImpl.reserve(MergeManagerImpl.java:294)
        at org.apache.hadoop.mapreduce.task.reduce.Fetcher.copyMapOutput(Fetcher.java:511)
        at org.apache.hadoop.mapreduce.task.reduce.Fetcher.copyFromHost(Fetcher.java:329)
        at org.apache.hadoop.mapreduce.task.reduce.Fetcher.run(Fetcher.java:193)

解决办法：

修改配置文件mapred-site.xml，添加如下配置

<property>
 <name>mapreduce.reduce.shuffle.memory.limit.percent</name>
  <value>0.17</value>
</property>

这个配置表示,单个shuffle能够消耗的内存占reduce所有内存的比例，默认值为0.25.