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From "Zsolt Venczel (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-6852) apparent bug in concatenated-bzip2 support (decoding)
Date Mon, 05 Feb 2018 13:45:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16352392#comment-16352392
] 

Zsolt Venczel commented on HADOOP-6852:
---------------------------------------

In the attached patch I have added previously available test files back, re-enabled test-cases
and added a proposed fix:

within BZip2Codec I've changed the default read mode from CONTINUOUS to BYBLOCK at BZip2Codec.createInputStream(InputStream
in, Decompressor decompressor) as BYBLOCK read mode handles concatenated bzip2 correctly and
also this way it is consistent with mapred/LineRecordReader and input/LineRecordReader decompressor
creation logic. As a result of the change the concatenated-bzip2 issue is fixed.

> apparent bug in concatenated-bzip2 support (decoding)
> -----------------------------------------------------
>
>                 Key: HADOOP-6852
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6852
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: io
>    Affects Versions: 0.22.0
>         Environment: Linux x86_64 running 32-bit Hadoop, JDK 1.6.0_15
>            Reporter: Greg Roelofs
>            Assignee: Zsolt Venczel
>            Priority: Major
>         Attachments: HADOOP-6852.01.patch
>
>
> The following simplified code (manually picked out of testMoreBzip2() in https://issues.apache.org/jira/secure/attachment/12448272/HADOOP-6835.v4.trunk-hadoop-mapreduce.patch)
triggers a "java.io.IOException: bad block header" in org.apache.hadoop.io.compress.bzip2.CBZip2InputStream.initBlock(
CBZip2InputStream.java:527):
> {noformat}
>     JobConf jobConf = new JobConf(defaultConf);
>     CompressionCodec bzip2 = new BZip2Codec();
>     ReflectionUtils.setConf(bzip2, jobConf);
>     localFs.delete(workDir, true);
>     // copy multiple-member test file to HDFS
>     String fn2 = "testCompressThenConcat.txt" + bzip2.getDefaultExtension();
>     Path fnLocal2 = new Path(System.getProperty("test.concat.data","/tmp"),fn2);
>     Path fnHDFS2  = new Path(workDir, fn2);
>     localFs.copyFromLocalFile(fnLocal2, fnHDFS2);
>     FileInputFormat.setInputPaths(jobConf, workDir);
>     final FileInputStream in2 = new FileInputStream(fnLocal2.toString());
>     CompressionInputStream cin2 = bzip2.createInputStream(in2);
>     LineReader in = new LineReader(cin2);
>     Text out = new Text();
>     int numBytes, totalBytes=0, lineNum=0;
>     while ((numBytes = in.readLine(out)) > 0) {
>       ++lineNum;
>       totalBytes += numBytes;
>     }
>     in.close();
> {noformat}
> The specified file is also included in the H-6835 patch linked above, and some additional
debug output is included in the commented-out test loop above.  (Only in the linked, "v4"
version of the patch, however--I'm about to remove the debug stuff for checkin.)
> It's possible I've done something completely boneheaded here, but the file, at least,
checks out in a subsequent set of subtests and with stock bzip2 itself.  Only the code above
is problematic; it reads through the first concatenated chunk (17 lines of text) just fine
but chokes on the header of the second one.  Altogether, the test file contains 84 lines of
text and 4 concatenated bzip2 files.
> (It's possible this is a mapreduce issue rather than common, but note that the identical
gzip test works fine.  Possibly it's related to the stream-vs-decompressor dichotomy, though;
intentionally not supported?)



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