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From "Chris Nauroth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-12990) lz4 incompatibility between OS and Hadoop
Date Fri, 01 Apr 2016 16:54:25 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15221965#comment-15221965
] 

Chris Nauroth commented on HADOOP-12990:
----------------------------------------

Is this actually expected to work?  Hadoop logic puts some framing around raw LZ4 so that
the data is a sequence of length-prefixed compressed chunks.  I don't know the internals of
the Linux lz4 tool, but unless it matches that framing strategy exactly (which I wouldn't
expect it to), then I don't expect this would work.

I know this is true of Snappy.  There are various Snappy CLIs out there, and they don't work
well with our Snappy codec, because they don't implement the same framing.

Of course, it would be nice if there was a more graceful failure mode than trying to do a
huge allocation and hitting {{OutOfMemoryError}}.

> lz4 incompatibility between OS and Hadoop
> -----------------------------------------
>
>                 Key: HADOOP-12990
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12990
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: io, native
>    Affects Versions: 2.6.0
>            Reporter: John Zhuge
>            Priority: Minor
>
> {{hdfs dfs -text}} hit exception when trying to view the compression file created by
Linux lz4 tool.
> The Hadoop version has HADOOP-11184 "update lz4 to r123", thus it is using LZ4 library
in release r123.
> Linux lz4 version:
> {code}
> $ /tmp/lz4 -h 2>&1 | head -1
> *** LZ4 Compression CLI 64-bits r123, by Yann Collet (Apr  1 2016) ***
> {code}
> Test steps:
> {code}
> $ cat 10rows.txt
> 001|c1|c2|c3|c4|c5|c6|c7|c8|c9
> 002|c1|c2|c3|c4|c5|c6|c7|c8|c9
> 003|c1|c2|c3|c4|c5|c6|c7|c8|c9
> 004|c1|c2|c3|c4|c5|c6|c7|c8|c9
> 005|c1|c2|c3|c4|c5|c6|c7|c8|c9
> 006|c1|c2|c3|c4|c5|c6|c7|c8|c9
> 007|c1|c2|c3|c4|c5|c6|c7|c8|c9
> 008|c1|c2|c3|c4|c5|c6|c7|c8|c9
> 009|c1|c2|c3|c4|c5|c6|c7|c8|c9
> 010|c1|c2|c3|c4|c5|c6|c7|c8|c9
> $ /tmp/lz4 10rows.txt 10rows.txt.r123.lz4
> Compressed 310 bytes into 105 bytes ==> 33.87%
> $ hdfs dfs -put 10rows.txt.r123.lz4 /tmp
> $ hdfs dfs -text /tmp/10rows.txt.r123.lz4
> 16/04/01 08:19:07 INFO compress.CodecPool: Got brand-new decompressor [.lz4]
> Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
>     at org.apache.hadoop.io.compress.BlockDecompressorStream.getCompressedData(BlockDecompressorStream.java:123)
>     at org.apache.hadoop.io.compress.BlockDecompressorStream.decompress(BlockDecompressorStream.java:98)
>     at org.apache.hadoop.io.compress.DecompressorStream.read(DecompressorStream.java:85)
>     at java.io.InputStream.read(InputStream.java:101)
>     at org.apache.hadoop.io.IOUtils.copyBytes(IOUtils.java:85)
>     at org.apache.hadoop.io.IOUtils.copyBytes(IOUtils.java:59)
>     at org.apache.hadoop.io.IOUtils.copyBytes(IOUtils.java:119)
>     at org.apache.hadoop.fs.shell.Display$Cat.printToStdout(Display.java:106)
>     at org.apache.hadoop.fs.shell.Display$Cat.processPath(Display.java:101)
>     at org.apache.hadoop.fs.shell.Command.processPaths(Command.java:317)
>     at org.apache.hadoop.fs.shell.Command.processPathArgument(Command.java:289)
>     at org.apache.hadoop.fs.shell.Command.processArgument(Command.java:271)
>     at org.apache.hadoop.fs.shell.Command.processArguments(Command.java:255)
>     at org.apache.hadoop.fs.shell.FsCommand.processRawArguments(FsCommand.java:118)
>     at org.apache.hadoop.fs.shell.Command.run(Command.java:165)
>     at org.apache.hadoop.fs.FsShell.run(FsShell.java:315)
>     at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
>     at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:84)
>     at org.apache.hadoop.fs.FsShell.main(FsShell.java:372)
> {code}



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