Data lost on MapReduce? - mapreduce

Question

My code executes 10000 rows.
Mapper pseudo-code:
int rows=0;
map()
{rows++}
cleanup(Context c)
{print(rows)}
This code prints:
2669
3354
3353
621
(sum=9997)
Why the sum is 9997?
Reducer pseudo-code:
int rows=0;
reduce()
{rows++}
cleanup(Context c)
{print(rows)}
The reducer prints:
3354
Where is all the other data?
Edit 1
I have found the main problem.
My fault is that the key that is sent is the number of the row. When the mapper calls the cleanup() function, it resets the counter of rows (held in the driver of the application). Therefore the key isn't unique. Can I resolve that by sending the key from the parameters of the map function? I don't think the cleanup() resets this parameter.
If instead I use a global variable in the driver of the application, is there a synchronization problem?
Edit 2
My code executes 10000 rows (and 1 header line)
Driver pseudo-code:
public static enum COUNTER {ROW};
Mapper pseudo-code:
map()
{row=context.getCounter(RWDriver.COUNTER.ROW).increment(1);
context.write(row,new Text(...))
}
cleanup(Context c)
{print(c.getCounter(RWDriver.COUNTER.ROW).getValue());}
This code prints:
2670
3355
3354
622
(sum=10001 correct)
After 2670,3355, the buffer is full and MapReduce automatically resets the counter ROW to 0. I need the actual number of rows, but this method don't work.

Answer 1

The interpretation of the Data might be wrong .
You should either use Map-Reduce Framework Counters or user defined counters :
Map-Reduce Framework Counters
Map input records
Map output records
Map output bytes
Reduce input groups
Reduce input records
Reduce output records
User Defined Counter
class mapper()
{
static enum Counters { INPUT_LINES }
map()
{
context.getCounter(Counters.INPUT_LINES).increment(1);
}
similarly in Reducer too .
Get your value of counters
Configuration conf = new Configuration();
Cluster cluster = new Cluster(conf);
Job job = Job.getInstance(cluster,conf);
result = job.waitForCompletion(true);
...
Counters counters = job.getCounters();
for (CounterGroup group : counters) {
System.out.println("* Counter Group: " + group.getDisplayName() + " (" + group.getName() + ")");
System.out.println(" number of counters in this group: " + group.size());
for (Counter counter : group) {
System.out.println(" - " + counter.getDisplayName() + ": " + counter.getName() + ": "+counter.getValue());
}
}