将HDFS数据移至MongoDB

Question

我正在尝试将HDFS数据移动到MongoDB中。 我知道如何使用sqoop将数据导出到mysql中。 我认为我不能为MongoDb使用sqoop。 我需要帮助来了解如何执行此操作。

Answer 1

此配方将使用MongoOutputFormat类将数据从HDFS实例加载到MongoDB集合中。

Getting ready

开始使用Mongo Hadoop适配器的最简单方法是从GitHub克隆Mongo-Hadoop项目，并构建为特定Hadoop版本配置的项目。 必须安装Git客户端才能克隆此项目。 本食谱假设您正在使用Hadoop的CDH3发行版。 可以在http://git-scm.com/downloads上找到Git官方客户端。

可以在GitHub上的https://github.com/mongodb/mongo-hadoop上找到Mongo Hadoop适配器。 需要为特定版本的Hadoop构建该项目。 必须将生成的JAR文件安装在$ HADOOP_HOME / lib文件夹中的每个节点上。 Mongo Java驱动程序需要安装在$ HADOOP_HOME / lib文件夹中的每个节点上。 可以在https://github.com/mongodb/mongo-java-driver/downloads中找到。

怎么做...

 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();

Answer 2

基本问题是mongo以BSON格式（二进制JSON）存储其数据，而hdfs数据可能具有不同的格式（txt，sequence和avro）。 最简单的方法是使用Pig使用此驱动程序加载结果：

https://github.com/mongodb/mongo-hadoop/tree/master/pig

进入mongo db。 您必须将值映射到您的集合-git枢纽页面上有一个很好的例子。