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Hadoop, mail # dev - definition of slots in Hadoop scheduling


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Re: definition of slots in Hadoop scheduling
Allen Wittenauer 2011-03-12, 16:34

(Removing common-dev, because this isn't really a dev question)

On Feb 25, 2011, at 5:52 AM, bikash sharma wrote:

> Hi,
> How is task slot in Hadoop defined with respect to scheduling a map/reduce
> task on such slots available on TaskTrackers?
On a TaskTracker, one sets how many maps and reduces one wants to run on that node.  The JobTracker is informed of this value.  When a job is getting scheduled, it compares the various tasks's input to see if a DataNode is providing a matching block.  If a block exists or is nearby, the task is scheduled on that node.