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From Ted Yu <yuzhih...@gmail.com>
Subject Re: Several questions about Hadoop
Date Sun, 06 Jun 2010 03:47:12 GMT
1. If you use org.apache.log4j.Logger, you would be able to observe log
messages through
    private final static Logger LOG =

2. After you submitted job to hadoop cluster, you need to use "hadoop job
-kill <job_id>"

On Sat, Jun 5, 2010 at 7:00 PM, Kevin Tse <kevintse.onjee@gmail.com> wrote:

> Hello,
> I have successfully run Hadoop on a cluster of 3 nodes on RedHat linux, I
> have several questions to ask.
> 1. When I submit an MR job using "hadoop jar mr-job.jar", it starts
> printing
> out log messages to the stdout, how do I make it run in the
> background?("hadoop jar mr-job.jar > log &" does not work). If it can be
> put
> in the background, where do I find those log messages that it used to print
> to the stdout?
> 2. While the MR job is being executed, will the MR job process be
> affected/killed if I press "Ctrl-c"? it seems not since I can see the
> tasktracker is still running, but I am not sure.
> 3. While the MR job is being executed, if I stop one of the
> tasktrackers/nodes in the cluster using hadoop-daemon.sh, will the result
> of
> the maps and reduces semi-completed by that tasktracker/node be submitted
> to
> the namenode to be merged with the results completed by other tasktrackers?
> Is it possible to restart a tasktracker at a point where it was stopped?
> Thank you in advance.
> - Kevin Tse

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