Spostamento dei dati HDFS in MongoDB

Questa ricetta utilizzerà la classe MongoOutputFormat per caricare i dati da un'istanza HDFS in una raccolta MongoDB.

Getting ready

Il modo più semplice per iniziare con Mongo Hadoop Adapter è clonare Mongo-Hadoopproject da GitHub e creare il progetto configurato per una versione specifica di Hadoop. È necessario installare un Gitclient per clonare questo progetto. Questa ricetta presuppone che tu stia utilizzando la distribuzione CDH3 di Hadoop. Il client Git ufficiale può essere trovato su http://git-scm.com/downloads .

L'adattatore Mongo Hadoop può essere trovato su GitHub all'indirizzo https://github.com/mongodb/ mongo-hadoop. Questo progetto deve essere creato per una versione specifica di Hadoop. Il file JAR risultante deve essere installato su ogni nodo nella cartella $HADOOP_HOME/lib. Il driver Mongo Java deve essere installato su ogni nodo nella cartella $HADOOP_HOME/lib. Può essere trovato su https://github.com/mongodb/mongo-java-driver / download.

Come farlo...

 Complete the following steps to copy data form HDFS into MongoDB:
    1.   Clone the mongo-hadoop repository with the following command line:
    git clone https://github.com/mongodb/mongo-hadoop.git


    2.   Switch to the stable release 1.0 branch:
    git checkout release-1.0


    3.   Set the Hadoop version which mongo-hadoop should target. In the folder
    that mongo-hadoop was cloned to, open the build.sbt file with a text editor.
    Change the following line:
    hadoopRelease in ThisBuild := "default"
    to
    hadoopRelease in ThisBuild := "cdh3"


    4.   Build mongo-hadoop :
    ./sbt package
    This will create a file named mongo-hadoop-core_cdh3u3-1.0.0.jar in the
    core/target folder.


    5.   Download the MongoDB Java Driver Version 2.8.0 from https://github.com/
    mongodb/mongo-java-driver/downloads .


    6.   Copy mongo-hadoop and the MongoDB Java Driver to $HADOOP_HOME/lib on
    each node:


    cp mongo-hadoop-core_cdh3u3-1.0.0.jar mongo-2.8.0.jar $HADOOP_
    HOME/lib


    7.   Create a Java MapReduce program that will read the weblog_entries.txt file
    from HDFS and write them to MongoDB using the MongoOutputFormat class:


import java.io.*;
import org.apache.commons.logging.*;
import org.apache.hadoop.conf.*;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.*;
import org.bson.*;
import org.bson.types.ObjectId;
import com.mongodb.hadoop.*;
import com.mongodb.hadoop.util.*;
public class ExportToMongoDBFromHDFS {
private static final Log log = LogFactory.getLog(ExportToMongoDBFromHDFS.class);
public static class ReadWeblogs extends Mapper<LongWritable, Text, ObjectId, BSONObject>{
public void map(Text key, Text value, Context context)
throws IOException, InterruptedException{
           System.out.println("Key: " + key);
           System.out.println("Value: " + value);
           String[] fields = value.toString().split("\t");
           String md5 = fields[0];
           String url = fields[1];
           String date = fields[2];
           String time = fields[3];
           String ip = fields[4];
           BSONObject b = new BasicBSONObject();
            b.put("md5", md5);
            b.put("url", url);
            b.put("date", date);
            b.put("time", time);
              b.put("ip", ip);
          context.write( new ObjectId(), b);
       }
}
public static void main(String[] args) throws Exception{
       final Configuration conf = new Configuration();
          MongoConfigUtil.setOutputURI(conf,"mongodb://<HOST>:<PORT>/test.        weblogs");
System.out.println("Configuration: " + conf);
        final Job job = new Job(conf, "Export to Mongo");
         Path in = new Path("/data/weblogs/weblog_entries.txt");
            FileInputFormat.setInputPaths(job, in);
            job.setJarByClass(ExportToMongoDBFromHDFS.class);
            job.setMapperClass(ReadWeblogs.class);
            job.setOutputKeyClass(ObjectId.class);
            job.setOutputValueClass(BSONObject.class);
            job.setInputFormatClass(TextInputFormat.class);
            job.setOutputFormatClass(MongoOutputFormat.class);
            job.setNumReduceTasks(0);
           System.exit(job.waitForCompletion(true) ? 0 : 1 );
       }
}

8.   Export as a runnable JAR file and run the job:
hadoop jar ExportToMongoDBFromHDFS.jar
9.   Verify that the weblogs MongoDB collection was populated from the Mongo shell:
db.weblogs.find();