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https://issues.apache.org/jira/browse/HADOOP-6605?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13035659#comment-13035659
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Eli Collins commented on HADOOP-6605:
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bq. a) we're getting into platform specific code without a good reason
The motivation is that users don't shouldn't have to manually set an
environment variable that we can detect automatically. Multiple users have
requested this. Why is this not a good reason? We make improvements both for
new users (who want an easier out of the box experience) and experienced admins
(who will manually configure HADOOP_HOME).
bq. b) this could have significant performance ramifications as we add more and
more paths to support more and more OSes
How so? The new code *only* executes if HADOOP_HOME is not already set, and
the code just checks for the existence of bin/java in a set of directories, it
bails as soon as it finds one. This is not an expensive operation.
bq. c) there is a config option to specifically eliminate the need to do this
The existence of a configuration parameter does not mean we're not allowed to
try to detect a reasonable default if it's not set. We also automatically set a
default MAX_HEAP_SIZE and let users override it, this is not different.
> Add JAVA_HOME detection to hadoop-config
> ----------------------------------------
>
> Key: HADOOP-6605
> URL: https://issues.apache.org/jira/browse/HADOOP-6605
> Project: Hadoop Common
> Issue Type: Improvement
> Reporter: Chad Metcalf
> Assignee: Eli Collins
> Priority: Minor
> Fix For: 0.22.0
>
> Attachments: HADOOP-6605.patch, hadoop-6605-1.patch
>
>
> The commands that source hadoop-config.sh currently bail with an error if
> JAVA_HOME is not set. Let's detect JAVA_HOME (from a list of locations on
> various OS types) if JAVA_HOME is not already set by hadoop-env.sh or the
> environment. This way users don't have to manually configure it.
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