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https://issues.apache.org/jira/browse/HADOOP-4868?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12661213#action_12661213
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Doug Cutting commented on HADOOP-4868:
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> Option 3 looks to be simpler.
I agree. That's the sort of thing I had in mind. Nutch does something similar
to include Hadoop in its builds.
> One way could be by some variable CMD_DISPATCHER_CLASS which gets overridden
> in the mapred and hdfs.
I was thinking this would be done based on the name of the primary sub-command
(fs, job, pipes, etc.). We're already proposing to break back-compatibility,
changing 'bin/hadoop job' to 'bin/hadoop-mapred job'. Under my proposal this
might instead become 'bin/hadoop mapred job' (effectively just removing the
dash). Note that 'bin/hadoop fs' could remain unchanged, since we have a
package named 'fs'.
We could preserve 100% compatibilty by placing all command dispatchers under
org.apache.hadoop.command. So the 'job' command dispatcher could be
org.apache.hadoop.command.job.Command or somesuch.
> Just having this won't be sufficient as we need to print help messages
> listing all the available commands.
To list all available commands we can scan the classpath (java.class.path),
and, for each file or directory, scan it for org.apache.hadoop.command
sub-packages.
> Split the hadoop script into 3 parts
> ------------------------------------
>
> Key: HADOOP-4868
> URL: https://issues.apache.org/jira/browse/HADOOP-4868
> Project: Hadoop Core
> Issue Type: Improvement
> Components: scripts
> Reporter: Sharad Agarwal
> Assignee: Sharad Agarwal
> Attachments: 4868_v1.patch, 4868_v2.patch
>
>
> We need to split the bin/hadoop into 3 parts for core, mapred and hdfs. This
> will enable us to distribute the individual scripts with each component.
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