[jira] [Resolved] (HADOOP-17531) DistCp: Reduce memory usage on copying huge directories

["Ayush Saxena (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-17531?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ayush Saxena resolved HADOOP-17531.
-----------------------------------
    Fix Version/s: 3.3.1
     Hadoop Flags: Reviewed
     Release Note: Added a -useiterator option in distcp which uses listStatusIterator for building the listing. Primarily to reduce memory usage at client for building listing.
       Resolution: Fixed

> DistCp: Reduce memory usage on copying huge directories
> -------------------------------------------------------
>
>                 Key: HADOOP-17531
>                 URL: https://issues.apache.org/jira/browse/HADOOP-17531
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Ayush Saxena
>            Assignee: Ayush Saxena
>            Priority: Critical
>              Labels: pull-request-available
>             Fix For: 3.3.1, 3.4.0
>
>         Attachments: MoveToStackIterator.patch, gc-NewD-512M-3.8ML.log
>
>          Time Spent: 10h 10m
>  Remaining Estimate: 0h
>
> Presently distCp, uses the producer-consumer kind of setup while building the listing, the input queue and output queue are both unbounded, thus the listStatus grows quite huge.
> Rel Code Part :
> https://github.com/apache/hadoop/blob/trunk/hadoop-tools/hadoop-distcp/src/main/java/org/apache/hadoop/tools/SimpleCopyListing.java#L635
> This goes on bredth-first traversal kind of stuff(uses queue instead of earlier stack), so if you have files at lower depth, it will like open up the entire tree and the start processing....



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