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Hadoop, mail # user - Reduce java.lang.OutOfMemoryError


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Re: Reduce java.lang.OutOfMemoryError
Rahul Jain 2011-02-16, 19:58
If you google for such memory failures, you'll find the mapreduce tunable
that'll help you:

mapred.job.shuffle.input.buffer.percent ; it is well known that the default
values in hadoop config

don't work well for large data systems

-Rahul
On Wed, Feb 16, 2011 at 10:36 AM, James Seigel <[EMAIL PROTECTED]> wrote:

> Good luck.
>
> Let me know how it goes.
>
> James
>
> Sent from my mobile. Please excuse the typos.
>
> On 2011-02-16, at 11:11 AM, Kelly Burkhart <[EMAIL PROTECTED]>
> wrote:
>
> > OK, the job was preferring the config file on my local machine which
> > is not part of the cluster over the cluster config files.  That seems
> > completely broken to me; my config was basically empty other than
> > containing the location of the cluster and my job apparently used
> > defaults rather than the cluster config.  It doesn't make sense to me
> > to keep configuration files synchronized on every machine that may
> > access the cluster.
> >
> > I'm running again; we'll see if it completes this time.
> >
> > -K
> >
> > On Wed, Feb 16, 2011 at 10:30 AM, James Seigel <[EMAIL PROTECTED]> wrote:
> >> Hrmmm. Well as you've pointed out. 200m is quite small and is probably
> >> the cause.
> >>
> >> Now thEre might be some overriding settings in something you are using
> >> to launch or something.
> >>
> >> You could set those values in the config to not be overridden in the
> >> main conf then see what tries to override it in the logs
> >>
> >> Cheers
> >> James
> >>
> >> Sent from my mobile. Please excuse the typos.
> >>
> >> On 2011-02-16, at 9:21 AM, Kelly Burkhart <[EMAIL PROTECTED]>
> wrote:
> >>
> >>> I should have mentioned this in my last email: I thought of that so I
> >>> logged into every machine in the cluster; each machine's
> >>> mapred-site.xml has the same md5sum.
> >>>
> >>> On Wed, Feb 16, 2011 at 10:15 AM, James Seigel <[EMAIL PROTECTED]> wrote:
> >>>> He might not have that conf distributed out to each machine
> >>>>
> >>>>
> >>>> Sent from my mobile. Please excuse the typos.
> >>>>
> >>>> On 2011-02-16, at 9:10 AM, Kelly Burkhart <[EMAIL PROTECTED]>
> wrote:
> >>>>
> >>>>> Our clust admin (who's out of town today) has mapred.child.java.opts
> >>>>> set to -Xmx1280 in mapred-site.xml.  However, if I go to the job
> >>>>> configuration page for a job I'm running right now, it claims this
> >>>>> option is set to -Xmx200m.  There are other settings in
> >>>>> mapred-site.xml that are different too.  Why would map/reduce jobs
> not
> >>>>> respect the mapred-site.xml file?
> >>>>>
> >>>>> -K
> >>>>>
> >>>>> On Wed, Feb 16, 2011 at 9:43 AM, Jim Falgout <
> [EMAIL PROTECTED]> wrote:
> >>>>>> You can set the amount of memory used by the reducer using the
> mapreduce.reduce.java.opts property. Set it in mapred-site.xml or override
> it in your job. You can set it to something like: -Xm512M to increase the
> amount of memory used by the JVM spawned for the reducer task.
> >>>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: Kelly Burkhart [mailto:[EMAIL PROTECTED]]
> >>>>>> Sent: Wednesday, February 16, 2011 9:12 AM
> >>>>>> To: [EMAIL PROTECTED]
> >>>>>> Subject: Re: Reduce java.lang.OutOfMemoryError
> >>>>>>
> >>>>>> I have had it fail with a single reducer and with 100 reducers.
> >>>>>> Ultimately it needs to be funneled to a single reducer though.
> >>>>>>
> >>>>>> -K
> >>>>>>
> >>>>>> On Wed, Feb 16, 2011 at 9:02 AM, real great..
> >>>>>> <[EMAIL PROTECTED]> wrote:
> >>>>>>> Hi,
> >>>>>>> How many reducers are you using currently?
> >>>>>>> Try increasing the number or reducers.
> >>>>>>> Let me know if it helps.
> >>>>>>>
> >>>>>>> On Wed, Feb 16, 2011 at 8:30 PM, Kelly Burkhart <
> [EMAIL PROTECTED]>wrote:
> >>>>>>>
> >>>>>>>> Hello, I'm seeing frequent fails in reduce jobs with errors
> similar
> >>>>>>>> to
> >>>>>>>> this:
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> 2011-02-15 15:21:10,163 INFO org.apache.hadoop.mapred.ReduceTask:
> >>>>>>>> header: attempt_201102081823_0175_m_002153_0, compressed len: