[
https://issues.apache.org/jira/browse/MAPREDUCE-6216?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Jens Rabe updated MAPREDUCE-6216:
---------------------------------
Description:
In some occasions, when reading MapFiles which were generated by
MapFileOutputFormat with BZIP2 BLOCK compression, using getClosest(key, value,
true) on the MapFile reader causes an IOException to be thrown with the message
"File is corrupt!" When doing "hdfs fsck", it shows that everything is OK, and
the underlying data and index files can also be read correctly if read with a
SequenceFile.Reader.
The exception happens in the readBlock() method of the SequenceFile.Reader
class.
My guess is that, since MapFile.Reader's seekInternal() method does "seek()"
instead of "sync()", it is not correctly checked if the cursor is really
positioned at a valid location.
was:
In some occasions, when reading MapFiles which were generated by
MapFileOutputFormat with BZIP2 BLOCK compression, using getClosest(key, value,
true) on the MapFile reader causes an IOException to be thrown with the message
"File is corrupt!" When doing "hdfs fsck", it shows that everything is OK, and
the underlying data and index files can also be read correctly if read with a
SequenceFile.Reader.
The exception happens in the readBlock() method of the SequenceFile.Reader
class.
My guess is that, since MapFile.Reader's seekInternal() method does "seek()"
instead of "sync()", the indices in the index file must point to "synced"
positions. When the exception occurrs, the position the cursor is to be
positioned at is not valid.
So I think the culprit is the generation of the index files when MapFiles are
output.
> Seeking backwards in MapFiles does not always correctly sync the underlying
> SequenceFile, resulting in "File is corrupt" exceptions
> -----------------------------------------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-6216
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6216
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 2.4.1
> Reporter: Jens Rabe
> Priority: Critical
> Labels: mapfile, sequencefile
>
> In some occasions, when reading MapFiles which were generated by
> MapFileOutputFormat with BZIP2 BLOCK compression, using getClosest(key,
> value, true) on the MapFile reader causes an IOException to be thrown with
> the message "File is corrupt!" When doing "hdfs fsck", it shows that
> everything is OK, and the underlying data and index files can also be read
> correctly if read with a SequenceFile.Reader.
> The exception happens in the readBlock() method of the SequenceFile.Reader
> class.
> My guess is that, since MapFile.Reader's seekInternal() method does "seek()"
> instead of "sync()", it is not correctly checked if the cursor is really
> positioned at a valid location.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
