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https://issues.apache.org/jira/browse/HADOOP-2404?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12557369#action_12557369
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Doug Cutting commented on HADOOP-2404:
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> I thought and still think it is more fair not to provide any backward
> compatibility at all [ ... ]
Huh? That's a change from what you stated in [#action_12550831]. No one is
asking for 100% back-compatibility here, but rather for a reasonable
interpretation where possible of configuration parameters that have changed.
At the very least, if we can easily detect that someone is using a feature that
has been incompatibly changed, we should attempt to emit a warning, and not
just let things mysteriously fail, no?
> I understand your irritation on the configuration issues, but I don't
> understand why blame my or equally any other patch for not dealing with them.
You imply that I am asking this issue to fix a few instances of a widespread
problem unrelated to the issue. That is not the case. The issue is both
specific and related.
If a config parameter is only read in a single place, then no accessor method
is needed. If it is simply read in multiple places, then an accessor method is
nice, since it helps prevent misspellings and makes things easier if the
parameter ever requires more processing, but not mandatory. Once some
processing is needed for every access to a parameter then an accessor method is
required, since otherwise we'd replicate non-trivial program logic.
HADOOP-2185 pushed several parameters past this threshold, since
back-compatibility processing is now required when these parameters are
accessed, and thus accessor methods must be added.
> HADOOP-2185 breaks compatibility with hadoop-0.15.0
> ---------------------------------------------------
>
> Key: HADOOP-2404
> URL: https://issues.apache.org/jira/browse/HADOOP-2404
> Project: Hadoop
> Issue Type: Bug
> Components: conf
> Affects Versions: 0.16.0
> Reporter: Arun C Murthy
> Assignee: Konstantin Shvachko
> Priority: Blocker
> Fix For: 0.16.0
>
> Attachments: ConfigConvert.patch, ConfigConvert2.patch,
> ConfigurationConverter.patch
>
>
> HADOOP-2185 removed the following configuration parameters:
> {noformat}
> dfs.secondary.info.port
> dfs.datanode.port
> dfs.info.port
> mapred.job.tracker.info.port
> tasktracker.http.port
> {noformat}
> and changed the following configuration parameters:
> {noformat}
> dfs.secondary.info.bindAddress
> dfs.datanode.bindAddress
> dfs.info.bindAddress
> mapred.job.tracker.info.bindAddress
> mapred.task.tracker.report.bindAddress
> tasktracker.http.bindAddress
> {noformat}
> without a backward-compatibility story.
> Lots are applications/cluster-configurations are prone to fail hence, we need
> a way to keep things working as-is for 0.16.0 and remove them for 0.17.0.
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