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From "Kai Xie (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-16018) DistCp won't reassemble chunks when blocks per chunk > 0
Date Fri, 18 Jan 2019 02:39:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-16018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16745720#comment-16745720
] 

Kai Xie commented on HADOOP-16018:
----------------------------------

Thanks for resolving the image building issue on branch-2!

Hi [~stevel@apache.org]

I tried to trigger CI with patch branch-2-004 and branch-2-005 (both only introduce a constant
without any usage), and distcp's unit test consistently hangs at TestDistCpSync, TestDistCpSyncReverseFromTarget,
and TestDistCpSyncReverseFromSource.

> DistCp won't reassemble chunks when blocks per chunk > 0
> --------------------------------------------------------
>
>                 Key: HADOOP-16018
>                 URL: https://issues.apache.org/jira/browse/HADOOP-16018
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: tools/distcp
>    Affects Versions: 3.2.0, 2.9.2
>            Reporter: Kai Xie
>            Assignee: Kai Xie
>            Priority: Major
>             Fix For: 3.0.4, 3.2.1, 3.1.3
>
>         Attachments: HADOOP-16018-002.patch, HADOOP-16018-branch-2-002.patch, HADOOP-16018-branch-2-002.patch,
HADOOP-16018-branch-2-003.patch, HADOOP-16018-branch-2-004.patch, HADOOP-16018-branch-2-004.patch,
HADOOP-16018-branch-2-005.patch, HADOOP-16018-branch-2-005.patch, HADOOP-16018.01.patch
>
>
> I was investigating why hadoop-distcp-2.9.2 won't reassemble chunks of the same file
when blocks per chunk has been set > 0.
> In the CopyCommitter::commitJob, this logic can prevent chunks from reassembling if
blocks per chunk is equal to 0:
> {code:java}
> if (blocksPerChunk > 0) {
>   concatFileChunks(conf);
> }
> {code}
> Then in CopyCommitter's ctor, blocksPerChunk is initialised from the config:
> {code:java}
> blocksPerChunk = context.getConfiguration().getInt(
> DistCpOptionSwitch.BLOCKS_PER_CHUNK.getConfigLabel(), 0);
> {code}
>  
> But here the config key DistCpOptionSwitch.BLOCKS_PER_CHUNK.getConfigLabel() will always
returns empty string because it is constructed without config label:
> {code:java}
> BLOCKS_PER_CHUNK("",
> new Option("blocksperchunk", true, "If set to a positive value, files"
> + "with more blocks than this value will be split into chunks of "
> + "<blocksperchunk> blocks to be transferred in parallel, and "
> + "reassembled on the destination. By default, <blocksperchunk> is "
> + "0 and the files will be transmitted in their entirety without "
> + "splitting. This switch is only applicable when the source file "
> + "system implements getBlockLocations method and the target file "
> + "system implements concat method"))
> {code}
> As a result it will fall back to the default value 0 for blocksPerChunk, and prevent
the chunks from reassembling.
>  
>  



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