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Date: Fri, 21 Apr 2006 01:22:05 +0000 (GMT+00:00)
From: "Runping Qi (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-153) skip records that throw exceptions
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    [ http://issues.apache.org/jira/browse/HADOOP-153?page=comments#action_12375457 ] 

Runping Qi commented on HADOOP-153:
-----------------------------------


+1

Exceptions in the map and reduce functions that are implemented by the user should be handled by the user within the functions.
In the current implementation of sequencial file record reader, it is hard to skip to the next record if exception happens during record reading.


> skip records that throw exceptions
> ----------------------------------
>
>          Key: HADOOP-153
>          URL: http://issues.apache.org/jira/browse/HADOOP-153
>      Project: Hadoop
>         Type: New Feature

>   Components: mapred
>     Versions: 0.2
>     Reporter: Doug Cutting
>     Assignee: Doug Cutting
>      Fix For: 0.2

>
> MapReduce should skip records that throw exceptions.
> If the exception is thrown under RecordReader.next() then RecordReader implementations should automatically skip to the start of a subsequent record.
> Exceptions in map and reduce implementations can simply be logged, unless they happen under RecordWriter.write().  Cancelling partial output could be hard.  So such output errors will still result in task failure.
> This behaviour should be optional, but enabled by default.  A count of errors per task and job should be maintained and displayed in the web ui.  Perhaps if some percentage of records (>50%?) result in exceptions then the task should fail.  This would stop jobs early that are misconfigured or have buggy code.
> Thoughts?

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