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From John <johnnyenglish...@gmail.com>
Subject Re: OutOfMemoryError in MapReduce Job
Date Sat, 02 Nov 2013 16:46:05 GMT
You mean I should use the BitSet, transform it into bytes and then compress
it by my own in the map-function? Hmmm ... I could try it. What is the best
way to compress it in java?

BTW. I'm not sure how exactly the hbase compression works. As I mentioned I
have allready enabled the LZO compression for the columnfamily. The
question is, where the bytes are compressed? Directly in the map-function
(If no, is it possible to compress it there with lzo?!) or in the region
server?

kind regards


2013/11/2 Asaf Mesika <asaf.mesika@gmail.com>

> If mean, if you take all those bytes if the bit set and zip them, wouldn't
> you reduce it significantly? Less traffic on the wire, memory in HBase,
> etc.
>
> On Saturday, November 2, 2013, John wrote:
>
> > I already use LZO compression in HBase. Or do you mean a compressed Java
> > object? Do you know an implementation?
> >
> > kind regards
> >
> >
> > 2013/11/2 Asaf Mesika <asaf.mesika@gmail.com <javascript:;>>
> >
> > > I would try to compress this bit set.
> > >
> > > On Nov 2, 2013, at 2:43 PM, John <johnnyenglish739@gmail.com
> <javascript:;>>
> > wrote:
> > >
> > > > Hi,
> > > >
> > > > thanks for your answer! I increase the "Map Task Maximum Heap Size"
> to
> > > 2gb
> > > > and it seems to work. The OutOfMemoryEroror is gone. But the HBase
> > Region
> > > > server are now crashing all the time :-/ I try to store the bitvector
> > > > (120mb in size) for some rows. This seems to be very memory
> intensive,
> > > the
> > > > usedHeapMB increase very fast (up to 2gb). I'm  not sure if it is the
> > > > reading or the writing task which causes this, but I thnk its the
> > writing
> > > > task. Any idea how to minimize the memory usage? My mapper looks like
> > > this:
> > > >
> > > > public class MyMapper extends TableMapper<ImmutableBytesWritable,
> Put>
> > {
> > > >
> > > > private void storeBitvectorToHBase(
> > > >        Put row = new Put(name);
> > > >        row.setWriteToWAL(false);
> > > >        row.add(cf,    Bytes.toBytes("columname"),
> > > toByteArray(bitvector));
> > > >        ImmutableBytesWritable key = new ImmutableBytesWritable(
> > > >                name);
> > > >        context.write(key, row);
> > > > }
> > > > }
> > > >
> > > >
> > > > kind regards
> > > >
> > > >
> > > > 2013/11/1 Jean-Marc Spaggiari <jean-marc@spaggiari.org<javascript:;>>
> > > >
> > > >> Ho John,
> > > >>
> > > >> You might be better to ask this on the CDH mailing list since it's
> > more
> > > >> related to Cloudera Manager than HBase.
> > > >>
> > > >> In the meantime, can you try to update the "Map Task Maximum Heap
> > Size"
> > > >> parameter too?
> > > >>
> > > >> JM
> > > >>
> > > >>
> > > >> 2013/11/1 John <johnnyenglish739@gmail.com <javascript:;>>
> > > >>
> > > >>> Hi,
> > > >>>
> > > >>> I have a problem with the memory. My use case is the following:
> I've
> > > >> crated
> > > >>> a MapReduce-job and iterate in this over every row. If the row
has
> > more
> > > >>> than for example 10k columns I will create a bloomfilter (a bitSet)
> > for
> > > >>> this row and store it in the hbase structure. This worked fine
so
> > far.
> > > >>>
> > > >>> BUT, now I try to store a BitSet with 1000000000 elements = ~120mb
> in
> > > >> size.
> > > >>> In every map()-function there exist 2 BitSet. If i try to execute
> the
> > > >>> MR-job I got this error: http://pastebin.com/DxFYNuBG
> > > >>>
> > > >>> Obviously, the tasktracker does not have enougth memory. I try
to
> > > adjust
> > > >>> the configuration for the memory, but I'm not sure which is the
> right
> > > >> one.
> > > >>> I try to change the "MapReduce Child Java Maximum Heap Size" value
> > from
> > > >> 1GB
> > > >>> to 2GB, but still got the same error.
> > > >>>
> > > >>> Which parameters do I have to adjust? BTW. I'm using CDH 4.4.0
with
> > the
> > > >>> Clouder Manager
> > > >>>
> > > >>> kind regards
> > > >>>
> > > >>
> > >
> > >
> >
>

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