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Posted to common-issues@hadoop.apache.org by "Steve Loughran (JIRA)" <ji...@apache.org> on 2019/01/02 20:05:00 UTC
[jira] [Assigned] (HADOOP-16018) DistCp won't reassemble chunks
when blocks per chunk > 0
[ https://issues.apache.org/jira/browse/HADOOP-16018?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Steve Loughran reassigned HADOOP-16018:
---------------------------------------
Assignee: Kai X
> 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
> Assignee: 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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