I have successfully run Hadoop on a cluster of 3 nodes on RedHat linux, I
have several questions to ask.
1. When I submit an MR job using "hadoop jar mr-job.jar", it starts printing
out log messages to the stdout, how do I make it run in the
background?("hadoop jar mr-job.jar > log &" does not work). If it can be put
in the background, where do I find those log messages that it used to print
to the stdout?
2. While the MR job is being executed, will the MR job process be
affected/killed if I press "Ctrl-c"? it seems not since I can see the
tasktracker is still running, but I am not sure.
3. While the MR job is being executed, if I stop one of the
tasktrackers/nodes in the cluster using hadoop-daemon.sh, will the result of
the maps and reduces semi-completed by that tasktracker/node be submitted to
the namenode to be merged with the results completed by other tasktrackers?
Is it possible to restart a tasktracker at a point where it was stopped?
Thank you in advance.
- Kevin Tse