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https://issues.apache.org/jira/browse/HADOOP-7611?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13098027#comment-13098027
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M. C. Srivas commented on HADOOP-7611:
--------------------------------------
On MapR, this is the intended affect ... the shuffle files should be placed in
the DFS and not on local drives. So if you are planning to make changes, please
do so in a HDFS-only manner.
> SequenceFile.Sorter creates local temp files on HDFS
> ----------------------------------------------------
>
> Key: HADOOP-7611
> URL: https://issues.apache.org/jira/browse/HADOOP-7611
> Project: Hadoop Common
> Issue Type: Bug
> Components: io
> Affects Versions: 0.20.2
> Environment: CentOS 5.6 64-bit, Oracle JDK 1.6.0_26 64-bit
> Reporter: Bryan Keller
>
> When using SequenceFile.Sorter to sort or merge sequence files that exist in
> HDFS, it attempts to create temp files in a directory structure specified by
> mapred.local.dir but on HDFS, not in the local file system. The problem code
> is in MergeQueue.merge(). Starting at line 2953:
> {code}
> Path outputFile = lDirAlloc.getLocalPathForWrite(
> tmpFilename.toString(),
> approxOutputSize, conf);
> LOG.debug("writing intermediate results to " + outputFile);
> Writer writer = cloneFileAttributes(
>
> fs.makeQualified(segmentsToMerge.get(0).segmentPathName),
> fs.makeQualified(outputFile),
> null);
> {code}
> The outputFile here is a local path without a scheme, e.g.
> "/mnt/mnt1/mapred/local", specified by the mapred.local.dir property. If we
> are sorting files on HDFS, the fs object is a DistributedFileSystem. The call
> to fs.makeQualified(outputFile) appends the fs object's scheme to the local
> temp path returned by lDirAlloc, e.g. hdfs://mnt/mnt1/mapred/local. This
> directory is then created (if the proper permissions are available) on HDFS.
> If the HDFS permissions are not available, the sort/merge fails even though
> the directories exist locally.
> The code should instead always use the local file system if retrieving a path
> from the mapred.local.dir property. The unit tests do not test this
> condition, they only test using the local file system for sort and merge.
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