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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-987) Exposing MiniDFS and MiniMR clusters as a single process command-line
Date Tue, 15 Sep 2009 22:59:57 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-987?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12755777#action_12755777
] 

Tsz Wo (Nicholas), SZE commented on MAPREDUCE-987:
--------------------------------------------------

> Agreed that circular dependencies are to be avoided. I've moved this issue into MAPREDUCE,
and spun up a new patch.
Thanks, Philip.

> Do we anticipate a world where MR doesn't depend statically on HDFS (i.e., it only depends
on the FileSystem interfaces)?
Theoretically, mapreduce does not depend on hdfs.  However, the performance of mapreduce would
be bad without hdfs.  I guess there is no serious applications using mapreduce without hdfs,
except for testing.

> Exposing MiniDFS and MiniMR clusters as a single process command-line
> ---------------------------------------------------------------------
>
>                 Key: MAPREDUCE-987
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-987
>             Project: Hadoop Map/Reduce
>          Issue Type: New Feature
>          Components: build, test
>            Reporter: Philip Zeyliger
>            Assignee: Philip Zeyliger
>            Priority: Minor
>         Attachments: HDFS-621-0.20-patch, HDFS-621.patch, MAPREDUCE-987.patch
>
>
> It's hard to test non-Java programs that rely on significant mapreduce functionality.
 The patch I'm proposing shortly will let you just type "bin/hadoop jar hadoop-hdfs-hdfswithmr-test.jar
minicluster" to start a cluster (internally, it's using Mini{MR,HDFS}Cluster) with a specified
number of daemons, etc.  A test that checks how some external process interacts with Hadoop
might start minicluster as a subprocess, run through its thing, and then simply kill the java
subprocess.
> I've been using just such a system for a couple of weeks, and I like it.  It's significantly
easier than developing a lot of scripts to start a pseudo-distributed cluster, and then clean
up after it.  I figure others might find it useful as well.
> I'm at a bit of a loss as to where to put it in 0.21.  hdfs-with-mr tests have all the
required libraries, so I've put it there.  I could conceivably split this into "minimr" and
"minihdfs", but it's specifically the fact that they're configured to talk to each other that
I like about having them together.  And one JVM is better than two for my test programs.

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