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Date: Tue, 15 Mar 2011 04:42:29 +0000 (UTC)
From: "Denny Ye (JIRA)" <jira@apache.org>
To: mapreduce-dev@hadoop.apache.org
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Subject: [jira] Created: (MAPREDUCE-2384) Can MR make error response
 Immediately?
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Can MR make error response Immediately?
---------------------------------------

                 Key: MAPREDUCE-2384
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2384
             Project: Hadoop Map/Reduce
          Issue Type: Improvement
          Components: job submission
    Affects Versions: 0.21.0
            Reporter: Denny Ye


When I read the source code of MapReduce in Hadoop 0.21.0, sometimes it made me confused about error response. For example:
        1. JobSubmitter checking output for each job. MapReduce makes rule to limit that each job output must be not exist to avoid fault overwrite. In my opinion, MR should verify output at the point of client submitting. Actually, it copies related files to specified target and then, doing the verifying. 
        2. JobTracker.   Job has been submitted to JobTracker. In first step, JT create JIT object that is very "huge" . Next step, JT start to verify job queue authority and memory requirements.
 
        In normal case, verifying client input then response immediately if any cases in fault. Regular logic can be performed if all the inputs have passed.  
        It seems like that those code does not make sense for understanding. Is only my personal opinion? Wish someone help me to explain the details. Thanks!

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