Differences
This shows you the differences between two versions of the page.
Both sides previous revision Previous revision Next revision | Previous revision Next revision Both sides next revision | ||
courses:mapreduce-tutorial:step-5 [2012/01/24 22:37] straka |
courses:mapreduce-tutorial:step-5 [2012/01/28 12:07] majlis Scripts were removed. |
||
---|---|---|---|
Line 1: | Line 1: | ||
====== MapReduce Tutorial : Basic reducer ====== | ====== MapReduce Tutorial : Basic reducer ====== | ||
- | The interesting part of a MR job is the reducer -- after all mappers produce the (key, value) pairs, for every unique key and all its values a '' | + | The interesting part of a Hadoop |
- | The '' | + | The '' |
- | <file perl reducer.pl> | + | <file perl> |
package Mapper; | package Mapper; | ||
use Moose; | use Moose; | ||
Line 37: | Line 37: | ||
$runner-> | $runner-> | ||
</ | </ | ||
+ | |||
+ | As before, Hadoop silently handles failures. It can happen that even a successfully finished mapper needs to be executed again -- if the machine, where its output data were stored, gets disconnected from the network. | ||
===== Exercise 1 ===== | ===== Exercise 1 ===== | ||
- | Run a MR job on / | + | Run a Hadoop |
- | {{: | ||
===== Exercise 2 ===== | ===== Exercise 2 ===== | ||
- | Run a MR job on / | + | Run a Hadoop |
- | {{: |