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From "Dick King (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-153) skip records that throw exceptions
Date Tue, 06 May 2008 01:11:57 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12594432#action_12594432
] 

Dick King commented on HADOOP-153:
----------------------------------

There is a problem with respect to pipes, in that multiple input records can be in the subject
process's stomach when the crash occurs so there's no principled way to say how many of the
records preceding the one that was read just before the exception should be regarded as having
been suspect.  I get that the plan includes that being a configuration variable, but perhaps
there could be a way for the pipes interface to say that a particular record is beyond reproach?

-dk


> skip records that throw exceptions
> ----------------------------------
>
>                 Key: HADOOP-153
>                 URL: https://issues.apache.org/jira/browse/HADOOP-153
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: mapred
>    Affects Versions: 0.2.0
>            Reporter: Doug Cutting
>            Assignee: Devaraj Das
>
> 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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