I encountered some weird problem when trying to migrate to HaDoop 0.20.1.
I have some old Map/Reduce jobs (with old APIs) that do compile and run on the new cluster. But they return no result.
On a closer look, the configuration() and close() functions of the Mapper class are called during the map phase. But the map() function is not. That's why it outputs 0 record.
Any idea what's going on?