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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-713) dfs list operation is too expensive
Date Tue, 20 Nov 2007 12:53:43 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-713?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12543884
] 

Hudson commented on HADOOP-713:
-------------------------------

Integrated in Hadoop-Nightly #309 (See [http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Nightly/309/])

> dfs list operation is too expensive
> -----------------------------------
>
>                 Key: HADOOP-713
>                 URL: https://issues.apache.org/jira/browse/HADOOP-713
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.8.0
>            Reporter: Hairong Kuang
>            Assignee: dhruba borthakur
>            Priority: Blocker
>             Fix For: 0.15.1
>
>         Attachments: optimizeComputeContentLen.patch, optimizeComputeContentLen2.patch,
optimizeComputeContentLen3.patch
>
>
> A list request to dfs returns an array of DFSFileInfo. A DFSFileInfo of a directory contains
a field called contentsLen, indicating its size  which gets computed at the namenode side
by resursively going through its subdirs. At the same time, the whole dfs directory tree is
locked.
> The list operation is used a lot by DFSClient for listing a directory, getting a file's
size and # of replicas, and getting the size of dfs. Only the last operation needs the field
contentsLen to be computed.
> To reduce its cost, we can add a flag to the list request. ContentsLen is computed If
the flag is set. By default, the flag is false.

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