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https://issues.apache.org/jira/browse/HADOOP-9517?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13660956#comment-13660956
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Doug Cutting commented on HADOOP-9517:
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I vote to strengthen the compatibility requirements for user data file formats.
If we permit any user file-format changes that are not *forward* compatible at
all then they must be rare and very well marked as incompatibilities. It's
generally better to create a new format that programs must opt in to. An
unaltered program, when run against a new version, should ideally continue to
generate data that can still be read by older versions and other potential
implementations of the format. Otherwise we break workflows unless every
element of the flow is updated in lockstep. Rather we'd like to permit both
writers or readers of data files to be upgraded independently. Many folks have
multiple clusters that are not updated simultaneously and might move data files
between them.
> Define Hadoop Compatibility
> ---------------------------
>
> Key: HADOOP-9517
> URL: https://issues.apache.org/jira/browse/HADOOP-9517
> Project: Hadoop Common
> Issue Type: Bug
> Components: documentation
> Reporter: Arun C Murthy
> Assignee: Karthik Kambatla
> Attachments: hadoop-9517.patch, hadoop-9517.patch, hadoop-9517.patch,
> hadoop-9517.patch
>
>
> As we get ready to call hadoop-2 stable we need to better define 'Hadoop
> Compatibility'.
> http://wiki.apache.org/hadoop/Compatibility is a start, let's document
> requirements clearly and completely.
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