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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3647) Corner-case in IFile leads to failed tasks
Date Fri, 11 Jul 2008 04:21:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3647?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12612752#action_12612752
] 

Devaraj Das commented on HADOOP-3647:
-------------------------------------

I have two comments:
1) The second seek  in TaskTracker::doGet seems expensive esp because it is only for debugging.
It can be optimized to get the same info.
2) The comment   " // TODO: Remove this after a 'fix' for HADOOP-3647   // WARN: This won't
work for compressed map-outputs!" should be removed from ReduceTask.java.


> Corner-case in IFile leads to failed tasks
> ------------------------------------------
>
>                 Key: HADOOP-3647
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3647
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.18.0
>            Reporter: Arun C Murthy
>            Assignee: Arun C Murthy
>            Priority: Blocker
>             Fix For: 0.18.0
>
>         Attachments: HADOOP-3647_0_20080708.patch
>
>
> A couple of reduce tasks failed at IFile.Reader.next, one with:
> {noformat}
> java.lang.NegativeArraySizeException
>    at org.apache.hadoop.mapred.IFile$Reader.readNextBlock(IFile.java:246)
>    at org.apache.hadoop.mapred.IFile$Reader.next(IFile.java:298)
>    at org.apache.hadoop.mapred.Merger$Segment.next(Merger.java:134)
>    at org.apache.hadoop.mapred.Merger$MergeQueue.adjustPriorityQueue(Merger.java:225)
>    at org.apache.hadoop.mapred.Merger$MergeQueue.next(Merger.java:242)
>    at org.apache.hadoop.mapred.Task$ValuesIterator.readNextKey(Task.java:720)
>    at org.apache.hadoop.mapred.Task$ValuesIterator.next(Task.java:679)
>    at org.apache.hadoop.mapred.ReduceTask$ReduceValuesIterator.next(ReduceTask.java:225)
>    at org.apache.hadoop.mapred.lib.IdentityReducer.reduce(IdentityReducer.java:39)
>    at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:316)
>    at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2157)
> {noformat}
> On a related note, another failed at:
> {code:title=IFile.java:380}
>       // Position for the next record
>       long skipped = dataIn.skip(recordLength);
>       if (skipped != recordLength) {
>         throw new IOException("Failed to skip past record of length: " + 
>                               recordLength);
>       }
> {code}
> where recordLength was *-17*.

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