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courses:mapreduce-tutorial:step-24 [2012/01/31 11:29]
straka
courses:mapreduce-tutorial:step-24 [2012/01/31 11:39]
straka
Line 105: Line 105:
 ===== Counters ===== ===== Counters =====
  
-As in the Perl API, a mapper or a reducer can increment various counters by using ''context.getCounter("Group", "Name").increment(value)'':+As in the Perl API, a mapper (or a reducercan increment various counters by using ''context.getCounter("Group", "Name").increment(value)'':
 <code java> <code java>
 public void map(Text key, Text value, Context context) throws IOException, InterruptedException { public void map(Text key, Text value, Context context) throws IOException, InterruptedException {
Line 115: Line 115:
 The ''getCounter'' method returns a [[http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/mapreduce/Counter.html|Counter]] object, so if a counter is incremented frequently, the ''getCounter'' method can be called only once: The ''getCounter'' method returns a [[http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/mapreduce/Counter.html|Counter]] object, so if a counter is incremented frequently, the ''getCounter'' method can be called only once:
 <code java> <code java>
-public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {+public void map(Text key, Text value, Context context) throws IOException, InterruptedException {
   ...   ...
-  Counter values = context.getCounter("Reducer", "Number of values"); +  Counter words = context.getCounter("Mapper", "Number of words"); 
-  for (IntWritable value values) {+  for (String word value.toString().split("\\W+")) {
     ...     ...
-    values.increment(1);+    words.increment(1);
   }   }
 } }

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