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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4461) DirectoryScanner: volume path prefix takes up memory for every block that is scanned
Date Fri, 01 Feb 2013 01:02:35 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4461?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13568320#comment-13568320

Hadoop QA commented on HDFS-4461:

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  against trunk revision .

    {color:red}-1 patch{color}.  The patch command could not apply the patch.

Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/3927//console

This message is automatically generated.
> DirectoryScanner: volume path prefix takes up memory for every block that is scanned

> -------------------------------------------------------------------------------------
>                 Key: HDFS-4461
>                 URL: https://issues.apache.org/jira/browse/HDFS-4461
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 2.0.3-alpha
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>            Priority: Minor
>         Attachments: 002.patch, memory-analysis.png
> In the {{DirectoryScanner}}, we create a class {{ScanInfo}} for every block.  This object
contains two File objects-- one for the metadata file, and one for the block file.  Since
those File objects contain full paths, users who pick a lengthly path for their volume roots
will end up using an extra N_blocks * path_prefix bytes per block scanned.  We also don't
really need to store File objects-- storing strings and then creating File objects as needed
would be cheaper.  This has been causing out-of-memory conditions for users who pick such
long volume paths.

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