-When and who move the reduce output file part-0000X to the final output directory
I am looking into the MR work flow, and want to know more details
about the reduce output data copy .
Here is my question.
For the DFSIO test or some other MR jobs. Each reduce task will run on a
TT, and generate files to some dirs named like this: "
XXX//_temporary/_attempt_201305101045_0005_r_000000_0/", there will also be
a result file named part-00000.
After the reducer done the task. the reducer output data part-00000
should be moved from the local disk to the HDFS.
My question is: Is that the time that when reducer finish the task that
part-00000 will be copied to the HDFS? Who make this file copy happen? The
Reducer child? The TaskTracker which run the reduce task? Or the JobTracker?
Harsh J 2013-05-10, 05:26
Ling Kun 2013-05-10, 05:40