Hadoop执行Job时报DiskChecker$DiskErrorException异常原因

q29191

　　版本：

$ hadoop version
Hadoop 0.20.2-cdh3u4
Subversion git://ubuntu-slave01/var/lib/jenkins/workspace/CDH3u4-Full-RC/build/cdh3/hadoop20/0.20.2-cdh3u4/source -r 214dd731e3bdb687cb55988d3f47dd9e248c5690
Compiled by jenkins on Mon May  7 13:01:39 PDT 2012
From source with checksum a60c9795e41a3248b212344fb131c12c
　　问题描述：
　　Hadoop执行MR的时候抛org.apache.hadoop.util.DiskChecker$DiskErrorException异常，详情如下：

org.apache.hadoop.util.DiskChecker$DiskErrorException: Could not find any valid local directory for output/map_4.out
at org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.getLocalPathForWrite(LocalDirAllocator.java:376)
at org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:146)
at org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:127)
at org.apache.hadoop.mapred.MapOutputFile.getInputFileForWrite(MapOutputFile.java:176)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier.createKVIterator(ReduceTask.java:2374)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier.access$400(ReduceTask.java:582)
　　问题原因：
　　执行org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.getLocalPathForWrite(...)磁盘空间不足抛异常了
　　解决方式：
　　1.查找用户log看看那个job占的空间大

du -m --max-depth=1 /yourpath/mapred/local/userlogs | sort -n
　　2.此job如果已经执行完成了那么直接rm -rf即可
　　最终解决方案：
　　修改hadoop保留用户日志的时间，修改mapred-site.xml 的mapred.userlog.retain.hours

  <property>
<name>mapred.userlog.retain.hours</name>
<value>10</value>
</property>