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From Chhaya Vishwakarma <Chhaya.Vishwaka...@lntinfotech.com>
Subject RE: XML parsing in Hadoop
Date Thu, 28 Nov 2013 08:47:55 GMT
Hi,

Yes I have run it without MR it takes few seconds to run. So I think its MR issue only
I have a single node cluster its launching 4 map tasks. Trying with only one file.


Regards,
Chhaya Vishwakarma



From: Mirko Kämpf [mailto:mirko.kaempf@gmail.com]
Sent: Thursday, November 28, 2013 12:53 PM
To: user@hadoop.apache.org
Subject: Re: XML parsing in Hadoop

Chhaya,

did you run the same code in stand alone mode without MapReduce framework?
How long takes the code in you map() function standalone?
Compare those two different times (t_0 MR mode, t_1 standalone mode) to find out
if it is a MR issue or something which comes from the xml-parser logic or the data ...

Usually it should be not that slow. But what cluster do you have and how many mappers / reducers
and how many of such 2NB files do you have?

Best wishes
Mirko


2013/11/28 Chhaya Vishwakarma <Chhaya.Vishwakarma@lntinfotech.com<mailto:Chhaya.Vishwakarma@lntinfotech.com>>
Hi,


The below code parses XML file, Here the output of the code is correct but the job takes long
time for completion.
It took 20 hours to parse 2MB file.
Kindly suggest what changes could be done to increase the performance.



package xml;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.*;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

import org.apache.hadoop.conf.*;
import org.apache.hadoop.io.*;

import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapreduce.*;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;


import org.apache.log4j.Logger;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;


public class ReadXmlMR
{
                static Logger log = Logger.getLogger(ReadXmlMR.class.getName());
                 public static String fileName = new String();
                 public static Document dom;
                 public void configure(JobConf job) {
         fileName = job.get("map.input.file");
}


                public static class Map extends Mapper<LongWritable,Text,Text,Text>
               {

                                public void map(LongWritable key, Text value,Context context
) throws IOException, InterruptedException
                                {
                                                try {
                                                                FileSplit fileSplit = (FileSplit)context.getInputSplit();
                                                                Configuration conf = context.getConfiguration();

                                                                DocumentBuilderFactory dbf
= DocumentBuilderFactory.newInstance();

                                                                FSDataInputStream fstream1;
                                                                Path file = fileSplit.getPath();
                                                FileSystem fs = file.getFileSystem(conf);
                                                fstream1 = fs.open(fileSplit.getPath());
                                                                DocumentBuilder db = dbf.newDocumentBuilder();
                                                                dom = db.parse(fstream1);
                                                                Element docEle = null;
                                                                docEle = dom.getDocumentElement();

                                                                XPath xpath = XPathFactory.newInstance().newXPath();

                                                                Object result =  xpath.compile("//*").evaluate(dom,
XPathConstants.NODESET);

                                                                NodeList nodes = (NodeList)
result;


                                                                for (int n = 2; n < nodes.getLength();
n++)

                                                                {
                                                                                Text colvalue=new
Text("");
                                                                                Text nodename=
new Text("");

                                                                                nodename =
new Text(nodes.item(n).getNodeName());
                                                                                try{colvalue
= new Text(nodes.item(n).getFirstChild().getNodeValue());}catch(Exception e){}
                                                                                if(colvalue.toString().equalsIgnoreCase(null)){colvalue=new
Text("");}
                                                                                context.write(nodename,
colvalue);
                                                                }


                                                                } catch (ParserConfigurationException
e) {
                                                                // TODO Auto-generated catch
block
                                                                e.printStackTrace();
                                                                } catch (SAXException e) {
                                                                // TODO Auto-generated catch
block
                                                                e.printStackTrace();

                                                                } catch (XPathExpressionException
e) {
                                                                // TODO Auto-generated catch
block
                                                                e.printStackTrace();
                                                                }

                                                                }

                                }



                public static void main(String[] args) throws Exception

                {

                Configuration conf = new Configuration();

        Job job = new Job(conf, "XmlParsing");
        job.setJarByClass(ReadXmlMR.class);
                job.setOutputKeyClass(Text.class);
                job.setOutputValueClass(Text.class);


                job.setMapperClass(Map.class);


                job.setInputFormatClass(TextInputFormat.class);
                job.setOutputFormatClass(TextOutputFormat.class);

                FileInputFormat.addInputPath(job, new Path(args[0]));
                FileOutputFormat.setOutputPath(job, new Path(args[1]));


                job.submit();

                job.waitForCompletion(true);


                }

}



Regards,
Chhaya Vishwakarma


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