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https://issues.apache.org/jira/browse/HADOOP-16018?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Kai Xie updated HADOOP-16018:
-----------------------------
Status: Patch Available (was: Open)
> 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: 2.9.2, 3.2.0
> 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-2-003.patch, HADOOP-16018-branch-2-004.patch,
> HADOOP-16018-branch-2-004.patch, HADOOP-16018-branch-2-004.patch,
> HADOOP-16018-branch-2-004.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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