Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
Hadoop, mail # general - setNumReduceTasks(1)

Copy link to this message
Re: setNumReduceTasks(1)
Jeff Zhang 2010-01-26, 00:09
*See my comments below*

On Mon, Jan 25, 2010 at 3:22 PM, Something Something <

> If I set # of reduce tasks to 1 using setNumReduceTasks(1), would the class
> be instantiated only on one machine.. always?  I mean if I have a cluster
> of
> say 1 master, 10 workers & 3 zookeepers, is the Reducer class guaranteed to
> be instantiated only on 1 machine?
> *--Yes*
> If answer is yes, then I will use static variable as a counter to see how
> may rows have been added to my HBase table so far.  In my use case, I want
> to write only N number of rows to a table.  Is there a better way to do
> this?  Please let me know.  Thanks.

*--Maybe you can use Counter to track the number of rows you add to HBase,
then you do not need to limit the reduce task as 1*
Best Regards

Jeff Zhang