The problem is what it says in the description. I have some code.
This is the reducer.
public class RTopLoc extends Reducer<CompositeKey, IntWritable, Text, Text> {
private static int number = 0;
private static CompositeKey lastCK = new CompositeKey();
private static Text lastLac = new Text();
@Override
public void reduce(CompositeKey key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
int sum = sumValues(values);
String str = Integer.toString(sum);
String str2 = Integer.toString(number);
String str3 = key.getSecond().toString();
context.write(key.getFirst(), new Text(str3 + " " + str2 + " " + str));
if(number == 0){
number = sum;
lastCK = key;
context.write(new Text("1"), new Text("1"));
}
else if(lastCK.getFirst().equals(key.getFirst()) && sum > number){
lastCK = key;
context.write(new Text("2"), new Text("2"));
}
else if(!lastCK.getFirst().equals(key.getFirst())){
// context.write(lastCK.getFirst(), lastCK.getSecond());
context.write(new Text("3"), new Text("3"));
number = sum;
lastCK = key;
}
}
it runs fine until the reducer. Then, when I run it in intelij idea (In windows), I get
0000000000 44137 0 2
1 1
902996760100000 44137 2 6
3 3
9029967602 44137 6 8
3 3
90299676030000 44137 8 1
3 3
9029967604 44137 1 5
3 3
905000 38704 5 1
3 3
9050000001 38702 1 24
3 3
9050000001 38704 24 14
9050000001 38705 24 12
9050000001 38706 24 13
9050000001 38714 24 24
9050000002 38704 24 12
3 3
9050000002 38706 12 12
9050000011 38704 12 6
3 3
9050000011 38706 6 12
2 2
9050000021 38702 6 12
3 3
9050000031 38704 12 6
3 3
9050000031 38705 6 6
9050000031 38714 6 12
2 2
After I package the code (I use maven) and run it on hadoop (Linux), I get
0000000000 44137 0 2
1 1
902996760100000 44137 2 6
2 2
9029967602 44137 2 8
2 2
90299676030000 44137 2 1
9029967604 44137 2 5
2 2
905000 38704 2 1
9050000001 38702 2 24
2 2
9050000001 38704 2 14
2 2
9050000001 38705 2 12
2 2
9050000001 38706 2 13
2 2
9050000001 38714 2 24
2 2
9050000002 38704 2 12
2 2
9050000002 38706 2 12
2 2
9050000011 38704 2 6
2 2
9050000011 38706 2 12
2 2
9050000021 38702 2 12
2 2
9050000031 38704 2 6
2 2
9050000031 38705 2 6
2 2
9050000031 38714 2 12
2 2
I use this to run the code.
hadoop jar Project.jar inputPath outputPath
It looks like the difference is caused by a problem comparing parts of your stored key (lastCK) and the current key.
I would change this line:
lastCK = key;
Keys and values are reused in Hadoop so when this is running on a real cluster, your keys will just be the same since lastCK
and key
will both be the same object.
You need to either properly copy key
into lastCK
, perhaps using a .set()
method (that you write and is a common pattern in hadoop) or create a new one using a constructor that accepts an CompositeKey
.