Hi all, I'm running a mapreduce job that has custom counters incremented in the combiner's reduce function. Looking at the mapreduce web UI I see that, like all counters, its has three columns: Map, Reduce and Total. >From what I know, the combiner is executed on the map output, hence runs in Mapper (?). The strange thing is that I see the counter incrementing in both the Map and Reduce columns...
If the combiner runs on the Mapper output, locally on the Mapper, why do I see reduce counts as well ? Thanks, Amit.
