Dmitriy,
I just double-checked, and the caveat I stated earlier is incorrect.
So, "-Djava.library.path" set in the client's {mapred.child.java.opts}
should just append to to the "-Djava.library.path" that each TaskTracker
has when creating the library path for each child (M/R) task. So that's
even better I guess.
George
On 2012/03/28 11:06, George Datskos wrote:
Dmitriy,
To deal with different servers having various shared libraries in
different locations, you can simply make sure the _TaskTracker_'s
-Djava.library.path is set correctly on each server. That library
path should be passed along to each child (M/R) task. (in *addition*
to the {mapred.child.java.opts} that you specify on the client-side
configuration options)
One caveat: on the client-side, don't include "-Djava.library.path" or
that path will be passed along to all of the child tasks, overriding
site-specific one you set on the TaskTracker.
George
On 2012/03/28 10:43, Dmitriy Lyubimov wrote:
Hello,
I have a couple of questions regarding mapreduce configurations.
We install various platforms on data nodes that require mixed set of
native libraries.
Part of the problem is that in general case, this software platforms
may be installed into different locations in the backend. (we try to
unify it, but still). What it means, it may require site-specific
-Djava.library.path setting.
I configured individual jvm options (mapred.child.java.opts) on each
node to include specific set of paths. However, i encountered 2
problems:
#1: my setting doesn't go into effect unless I also declare it final
in the data node. It's just being overriden by default -Xmx200 value
from the driver EVEN when i don't set it on the driver at all (and
there seems to be no way to unset it).
However, using "final" spec at the backend creates a problem if some
of numerous jobs we run wishes to override the setting still. The
ideal behavior is if i don't set it in the driver, then backend value
kicks in, otherwise it's driver's value. But i did not find a way to
do that for this particular setting for some reason.Could somebody
clarify the best workaround? thank you.
#2. Ideal behavior would actually be to merge driver-specific and
backend-specific settings. E.g. backend may need to configure specific
software package locations while client may wish sometimes to set heap
etc. Is there a best practice to achieve this effect?
Thank you very much in advance.
-Dmitriy
