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From "Bryan Keller (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-7611) SequenceFile.Sorter creates local temp files on HDFS
Date Mon, 05 Sep 2011 17:46:09 GMT
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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