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HBase >> mail # user >> OutOfMemoryError in MapReduce Job


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Re: OutOfMemoryError in MapReduce Job
HBase will compress the entire KeyValue that's one thing.
Second thing: If you use TableOutputFormat I believe the Put will be
inserted into HBase in the reducer side.
3rd - the compression only takes place in the Flush - which means you data
is travelling uncompressed between teh mapper, reducer and HBase WAL /
Memstore.

Compressing in Java can be done through
http://commons.apache.org/proper/commons-compress/zip.html.
For speed - go for Snappy - but for POC zip should do the trick.

On Sat, Nov 2, 2013 at 6:46 PM, John <[EMAIL PROTECTED]> wrote:

> 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 <[EMAIL PROTECTED]>
>
> > 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 <[EMAIL PROTECTED] <javascript:;>>
> > >
> > > > I would try to compress this bit set.
> > > >
> > > > On Nov 2, 2013, at 2:43 PM, John <[EMAIL PROTECTED]
> > <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 <[EMAIL PROTECTED]
> <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 <[EMAIL PROTECTED] <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
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB