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MapReduce >> mail # user >> Re: EOF when Combiner works


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Harsh J 2013-01-23, 14:43
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Re: Re: EOF when Combiner works
Hi, Harsh. Sorry, I failed to write to [EMAIL PROTECTED] (http://mail-archives.apache.org/mod_mbox/hadoop-user/201301.mbox/%3CCAOcnVr2A%2BmDQ%2BVY3iovxuP13VTXk2Wog7ui_o6x%3DW0et5igUSg%40mail.gmail.com%3E)
The logic of combiner is the same as reducer's one - summation of some statistical parameters:

        @Override
  protected void reduce(Text hostname, Iterable hostsCounters, Context context) throws IOException, InterruptedException {
    HostCounters totals = new HostCounters();
    totals.calculate(hostsCounters);    context.write(hostname, totals);}

where HostCounters - Writable with public fields of types int, long and MapWritable; and function clculate() is:

public void calculate(Iterable hostsCounters) {    for (HostCounters hostCounters : hostsCounters) {        a += hostCounters.a;        b += hostCounters.b;        //...    }}

Thank you! Sergey.