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From Andrzej Bialecki ...@getopt.org>
Subject Re: various questions
Date Tue, 24 Oct 2006 13:59:21 GMT
Grant Ingersoll wrote:
> Hi,
> I want to put Hadoop into my webapp and have it start up when the 
> servlet starts up.  Based on the shell scripts, I think I would need 
> to do the following:
> 1.  Package the appropriate libraries and config files (hadoop-site, 
> slaves, etc.) into the webapp
> 2. (based on start-all.sh)
>      a. Start the namenode: org.apache.hadoop.dfs.NameNode (need to 
> look into what is in the main() method to make sure I construct/invoke 
> this correctly)
>      b. Start the datanode:  org.apache.hadoop.dfs.DataNode
>      c. Start the Jobtracker:  org.apache.hadoop.mapred.JobTracker
>      d. Start the TaskTracker: org.apache.hadoop.mapred.TaskTracker
> I am new to Hadoop, so is this reasonable?  What am I missing?

You need to make sure that you run only single instance of namenode and 
jobtracker per cluster. Then, you can run one datanode and one 
tasktracker per cluster node.

> Also, is it possible to dynamically register slave nodes?  I have been 
> looking a little bit at zeroconf/bonjour network stuff and was 
> wondering if it could be used to bring resources online automatically 
> (would limit the nodes to a subnet, but that is fine for my needs).

Yes, just point them at the same namenode (for datanodes) and jobtracker 
(for tasktrackers), they will join the cluster automatically. The 
conf/slaves file is just for the initial startup of the cluster.

Best regards,
Andrzej Bialecki     <><
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