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-4 [2012/01/24 21:03] straka |
courses:mapreduce-tutorial:step-4 [2012/01/28 11:49] majlis Odstranen odkaz |
||
---|---|---|---|
Line 1: | Line 1: | ||
====== MapReduce Tutorial : Counters ====== | ====== MapReduce Tutorial : Counters ====== | ||
- | Sometimes it is useful to | + | Sometimes it is useful to count events differently than outputting them as (key, value) pairs. For that reason Hadoop offers simple counter framework. |
- | {{a.png}} | + | Hadoop maintains |
+ | |||
+ | <code perl> | ||
+ | sub map { | ||
+ | my ($self, $key, $value, $context) = @_; | ||
+ | |||
+ | $context-> | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | At the end of computation, | ||
+ | |||
+ | ===== Exercise ===== | ||
+ | |||
+ | Run a Hadoop job on ''/ | ||
- | {{filelist>: |