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From Vinod Kumar Vavilapalli <vino...@apache.org>
Subject Re: Resource limits with Hadoop and JVM
Date Mon, 16 Sep 2013 21:04:17 GMT
I assume you are on Linux. Also assuming that your tasks are so resource intensive that they
are taking down nodes. You should enable limits per task, see http://hadoop.apache.org/docs/stable/cluster_setup.html#Memory+monitoring

What it does is that jobs are now forced to up front provide their resource requirements,
and TTs enforce those limits.

+Vinod Kumar Vavilapalli
Hortonworks Inc.

On Sep 16, 2013, at 1:35 PM, Forrest Aldrich wrote:

> We recently experienced a couple of situations that brought one or more Hadoop nodes
down (unresponsive).   One was related to a bug in a utility we use (ffmpeg) that was resolved
by compiling a new version. The next, today, occurred after attempting to join a new node
to the cluster.   
> A basic start of the (local) tasktracker and datanode did not work -- so based on reference,
I issued:  hadoop mradmin -refreshNodes, which was to be followed by hadoop dfsadmin -refreshNodes.
   The load average literally jumped to 60 and the master (which also runs a slave) became
> Seems to me that this should never happen.   But, looking around, I saw an article from
Spotify which mentioned the need to set certain resource limits on the JVM as well as in the
system itself (limits.conf, we run RHEL).    I (and we) are fairly new to Hadoop, so some
of these issues are very new.
> I wonder if some of the experts here might be able to comment on this issue - perhaps
point out settings and other measures we can take to prevent this sort of incident in the
> Our setup is not complicated.   Have 3 hadoop nodes, the first is also a master and a
slave (has more resources, too).   The underlying system we do is split up tasks to ffmpeg
 (which is another issue as it tends to eat resources, but so far with a recompile, we are
good).   We have two more hardware nodes to add shortly.
> Thanks!

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