I have two reducers running on two different machines. I ran the example word count program with some of my own System.out.println() statements to see what is going on.
There were 2 slaves each running datanode as well as tasktracker. There was one namenode and one jobtracker. I know there is a very elaborate setup for such a small cluster but I did it only to learn. I gave two input files, a.txt and b.txt with a few lines of english text. Now, here are my questions. (1) I found that three mapper tasks ran, all in the first slave. The first task processed the first file. The second task processed the second file. The third task didn't process anything. Why is it that the third task did not process anything? Why was this task created in the first place? (2) I found only one reducer task, on the second slave. It processed all the values for keys. keys were words in this case of Text type. I tried printing out the key.hashCode() for each key and some of them were even and some of them were odd. I was expecting the keys with even hashcodes to go to one slave and the others to go to another slave. Why didn't this happen?
