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https://issues.apache.org/jira/browse/HADOOP-4927?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12669812#action_12669812
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Chris Douglas commented on HADOOP-4927:
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bq. this feature is a sort of generic across the different output formats and
having the framework support this would be useful.
True. Still, while it is generic functionality, it's neither difficult nor
inefficient in user-space. Absent either of the latter criteria, putting it
into the framework seems premature, at least. If this should be abstracted,
wouldn't it make sense as an OutputFormat in lib? That seems no less brittle
than using a framework configuration variable and I've difficulty seeing this
setting scoped to the whole cluster...
bq. I am okay with the current patch in terms of the behavior and the framework
support it adds for lazy creation of the destination output "something" (where
"something" is easy to explain when interpreted as a file).
Unless there's a non-FileOutputFormat use case that's also easy to explain, it
remains unclear that this is the correct abstraction. Creating a setting on
FileOutputFormat seems like a good idea. Whether that's implemented in
FileOutputFormat only or via an OuputFormat wrapper class depends on how
generally applicable the abstraction is. Since its motivation is expensive
clutter in HDFS, it's not obvious to me that the latter is justified, let alone
tight integration with the framework.
> Part files on the output filesystem are created irrespective of whether the
> corresponding task has anything to write there
> --------------------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-4927
> URL: https://issues.apache.org/jira/browse/HADOOP-4927
> Project: Hadoop Core
> Issue Type: New Feature
> Components: mapred
> Reporter: Devaraj Das
> Assignee: Jothi Padmanabhan
> Fix For: 0.21.0
>
> Attachments: hadoop-4927-v1.patch, hadoop-4927-v2.patch,
> hadoop-4927.patch
>
>
> When OutputFormat.getRecordWriter is invoked, a part file is created on the
> output filesystem. But the created RecordWriter is not used until the
> OutputCollector.collect call is made by the task (user's code). This results
> in empty part files even if the OutputCollector.collect is never invoked by
> the corresponding tasks.
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