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https://issues.apache.org/jira/browse/HADOOP-16018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16726007#comment-16726007
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ASF GitHub Bot commented on HADOOP-16018:
-----------------------------------------
GitHub user kai33 opened a pull request:
https://github.com/apache/hadoop/pull/451
HADOOP-16018: Fix DistCp not reassemble chunks when blocks per chunk > 0
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/kai33/hadoop HADOOP-16018
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/hadoop/pull/451.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #451
----
commit 739a1548261e64d333fc42ae58b0ed3021e4c5b7
Author: Kai33 <gigikie@...>
Date: 2018-12-20T16:19:28Z
Fix DistCp not reassemble chunks when blocks per chunk > 0
----
> 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 X
> Priority: Major
>
> 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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