Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
HBase, mail # user - [Error]Finding average using hbase hadoop


Copy link to this message
-
Re: [Error]Finding average using hbase hadoop
Jean-Marc Spaggiari 2013-08-16, 11:32
Hi Manish,

First, instead of "stocks".getBytes() you need to use
Bytes.toBytes("stocks"). Same for the other strings.
Second, on your map task, you creates 2 bytes arrays for those string at
each iteration. You don't want that on a production environment. You should
move that outside of the map method and make them final static.

JM

2013/8/16 manish dunani <[EMAIL PROTECTED]>

> hello,
>
> I am using apache hadoop 1.1.2 and hbase 0.94.9 on pseudo distibuted mode.
>
> I am trying to find Average open stocks values.
>
> *sample dataset in hbase::**(table name:nyse4)*
>
>
>  2010-02-04           column=stocks:open, timestamp=1376567559424,
> value=2.5
>  2010-02-04           column=stocks:symbol, timestamp=1376567559424,
> value=QXM
>  2010-02-05           column=stocks:open, timestamp=1376567559429,
> value=2.42
>  2010-02-05           column=stocks:symbol, timestamp=1376567559429,
> value=QXM
>  2010-02-08           column=stocks:open, timestamp=1376567559431,
> value=2.33
>  2010-02-08           column=stocks:symbol, timestamp=1376567559431,
> value=QXM
>
> *code:*(please ignores the lines that are commenting)
>
>
> > package com.maddy;
> >
> > import java.io.IOException;
> >
> > import org.apache.hadoop.conf.Configuration;
> > import org.apache.hadoop.fs.Path;
> > import org.apache.hadoop.hbase.HBaseConfiguration;
> > import org.apache.hadoop.hbase.client.Put;
> > import org.apache.hadoop.hbase.client.Result;
> > import org.apache.hadoop.hbase.client.Scan;
> > import org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter;
> > import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
> > import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
> > import org.apache.hadoop.hbase.mapreduce.TableMapper;
> > import org.apache.hadoop.hbase.mapreduce.TableReducer;
> > import org.apache.hadoop.hbase.util.Bytes;
> > //import org.apache.hadoop.io.DoubleWritable;
> > import org.apache.hadoop.io.FloatWritable;
> > import org.apache.hadoop.mapreduce.Job;
> > import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
> >
> >
> > public class openaveragestock
> > {
> >     public static class map extends
> > TableMapper<ImmutableBytesWritable,FloatWritable>
> >     {
> >         @Override
> >
> >         public void map(ImmutableBytesWritable row,Result value,Context
> > context) throws IOException
> >         {
> >
> >             byte[]
> > val=(value.getValue("stocks".getBytes(),"open".getBytes()));
> >             //byte[]
> > val1=(value.getValue("stocks".getBytes(),"symbol".getBytes()));
> >
> >
> >             ImmutableBytesWritable stock_symbol=new
> > ImmutableBytesWritable("symbol".getBytes());
> >
> >
> >             try
> >             {
> >                 context.write(stock_symbol,new
> > FloatWritable(Bytes.toFloat(val)));
> >             }
> >             catch(InterruptedException e)
> >
> >             {
> >                  throw new IOException(e);
> >             }
> >
> >
> >         }
> >
> >
> >     }
> >
> >
> >     public static class reduce extends
> > TableReducer<ImmutableBytesWritable,FloatWritable,ImmutableBytesWritable>
> >     {
> >
> >         @Override
> >         public void reduce(ImmutableBytesWritable
> > key,Iterable<FloatWritable>values,Context context) throws IOException,
> > InterruptedException
> >         {
> >             float sum=0;
> >             int count=0;
> >           //  float average=0;
> >             for(FloatWritable val:values)
> >             {
> >                 sum+=val.get();
> >                 count++;
> >             }
> >             //average=(sum/count);
> >             Put put=new Put(key.get());
> >
> >
> put.add(Bytes.toBytes("stocks_output"),Bytes.toBytes("average"),Bytes.toBytes(sum/count));
> >             System.out.println("For\t"+count+"\t average
> is:"+(sum/count));
> >             context.write(key,put);
> >
> >         }
> >
> >     }
> >
> >     public static void main(String args[]) throws IOException,
> > ClassNotFoundException, InterruptedException