MongoDB与Hadoop结合之使用MapReduce官方实例

MongoDB与Hadoop结合部署
下载mongo-hadoop-core-2.0.1.jar
http://central.maven.org/maven2/org/mongodb/mongo-hadoop/mongo-hadoop-core/2.0.1/mongo-hadoop-core-2.0.1.jar
下载mongo-java-driver-3.3.0.jar
http://central.maven.org/maven2/org/mongodb/mongo-java-driver/3.3.0/mongo-java-driver-3.3.0.jar
将mongo-hadoop-core-2.0.1.jar和mongo-java-driver-3.3.0.jar两个包发布到Hadoop集群节点上：

• 方案一：将文件复制到所有节点目录$HADOOP_PREFIX/share/hadoop/common
• 方案二：使用DistributedCache分发到集群节点上。
• 方案三：使用hadoop jar命令的-libjars选项。

$ hadoop jar -libjars mongo-hadoop-core.jar,mongo-java-driver.jar MyJob.jar com.mycompany.HadoopJob

编写MapReduce程序
MongoDB Hadoop Connector使用MongoDB集群或BSON文件处理input/output formats

Mapreduce 1.x对应的包：com.mongodb.hadoop.mapred
Mapreduce 2.x对应的包：com.mongodb.hadoop
Enron E-mails实例
Enron数据资料下载：http://mongodb-enron-email.s3-website-us-east-1.amazonaws.com/
解压下载的数据文件enron_mongo.tar.bz2

$ tar jxf enron_mongo.tar.bz2

将数据资料恢复到mongodb

$ bin/mongorestore -d testdb --drop /opt/datas/mongodb/backup/dump/enron_mail/ -h mongodb01 --port 27051

将恢复后的collection: messages创建index

mongos> db.messages.ensureIndex({filename:1});

将collection: messages设置为分片

mongos> sh.shardCollection(testdb.messages,{filename:1});

mongodb集群搭建参考我的博文【MongoDB实现分片复制集】http://blog.csdn.net/liuguangrong/article/details/52383953
需求分析
每封邮件对应messages中的一个document。headers中包含sender和recipients, 此需求是统计sender和recipients对在messages集合中出现的次数。
messages document样例

    {
        "_id" : ObjectId("4f2ad4c4d1e2d3f15a000000"),
        "body" : "Here is our forecast\n\n ",
        "subFolder" : "allen-p/_sent_mail",
        "mailbox" : "maildir",
        "filename" : "1.",
        "headers" : {
            "X-cc" : "",
            "From" : "[email protected]",
            "Subject" : "",
            "X-Folder" : "\\Phillip_Allen_Jan2002_1\\Allen, Phillip K.\\'Sent Mail",
            "Content-Transfer-Encoding" : "7bit",
            "X-bcc" : "",
            "To" : "[email protected]",
            "X-Origin" : "Allen-P",
            "X-FileName" : "pallen (Non-Privileged).pst",
            "X-From" : "Phillip K Allen",
            "Date" : "Mon, 14 May 2001 16:39:00 -0700 (PDT)",
            "X-To" : "Tim Belden ",
            "Message-ID" : "<18782981.1075855378110.JavaMail.evans@thyme>",
            "Content-Type" : "text/plain; charset=us-ascii",
            "Mime-Version" : "1.0"
        }
    }

编程实现
MailPair.java

package mongo.enron.emails;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import org.apache.hadoop.io.WritableComparable;

public class MailPair implements WritableComparable {
    private String from;
    private String to;

    public MailPair() {

    }

    public MailPair(final String from, final String to) {
        this.set(from, to);
    }

    public void set(final String from, final String to) {
        this.setFrom(from);
        this.setTo(to);
    }

    public String getFrom() {
        return from;
    }

    public void setFrom(String from) {
        this.from = from;
    }

    public String getTo() {
        return to;
    }

    public void setTo(String to) {
        this.to = to;
    }

    public void readFields(final DataInput in) throws IOException {
        this.setFrom(in.readUTF());
        this.setTo(in.readUTF());
    }

    @Override
    public void write(DataOutput out) throws IOException {
        out.writeUTF(this.from);
        out.writeUTF(this.to);
    }

    @Override
    public int compareTo(Object o) {
        if (!(o instanceof MailPair)) {
            return -1;
        }

        MailPair mp = (MailPair) o;
        int first = from.compareTo(mp.from);
        if (first != 0) {
            return first;
        }
        int second = to.compareTo(mp.to);
        if (second != 0) {
            return second;
        }
        return 0;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((from == null) ? 0 : from.hashCode());
        result = prime * result + ((to == null) ? 0 : to.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        MailPair other = (MailPair) obj;
        if (from == null) {
            if (other.from != null)
                return false;
        } else if (!from.equals(other.from))
            return false;
        if (to == null) {
            if (other.to != null)
                return false;
        } else if (!to.equals(other.to))
            return false;
        return true;
    }
}

EnronMailMapper.java

package mongo.enron.emails;

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.mapreduce.Mapper;
import org.bson.BSONObject;

public class EnronMailMapper extends
        Mapper {
    private final IntWritable outputValue;
    private final MailPair outputKey;

    public EnronMailMapper() {
        super();
        outputValue = new IntWritable(1);
        outputKey = new MailPair();
    }

    @Override
    protected void map(Object key, BSONObject value, Context context)
            throws IOException, InterruptedException {
        BSONObject headers = (BSONObject) value.get("headers");
        String to = (String) headers.get("To");
        if (null != to) {
            String[] recipients = to.split(",");
            for (final String recip : recipients) {
                String recipient = recip.trim();
                if (recip.length() > 0) {
                    outputKey.set((String) key, recipient);
                    context.write(outputKey, outputValue);
                }
            }
        }
    }
}

EnronMailReducer.java

package mongo.enron.emails;

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.mapreduce.Reducer;
import org.bson.BSONObject;

import com.mongodb.BasicDBObjectBuilder;
import com.mongodb.hadoop.io.BSONWritable;

public class EnronMailReducer extends
        Reducer {
    private BSONWritable outputKey;
    private IntWritable outputValue;

    public EnronMailReducer() {
        outputKey = new BSONWritable();
        outputValue = new IntWritable();
    }

    @Override
    protected void reduce(MailPair key, Iterable values,
            Context context) throws IOException, InterruptedException {
        int sum = 0;
        for (final IntWritable value : values) {
            sum += value.get();
        }
        BSONObject bson = BasicDBObjectBuilder.start().add("f", key.getFrom())
                .add("t", key.getTo()).get();
        outputKey.setDoc(bson);
        outputValue.set(sum);
        context.write(outputKey, outputValue);
    }
}

EnronMail.java

package mongo.enron.emails;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.util.ToolRunner;

import com.mongodb.hadoop.MongoConfig;
import com.mongodb.hadoop.MongoInputFormat;
import com.mongodb.hadoop.MongoOutputFormat;
import com.mongodb.hadoop.util.MongoConfigUtil;
import com.mongodb.hadoop.util.MongoTool;

public class EnronMail extends MongoTool {
    public EnronMail() {
        JobConf conf = new JobConf(new Configuration());
        if (MongoTool.isMapRedV1()) {

        } else {
            MongoConfigUtil.setInputFormat(conf, MongoInputFormat.class);
            MongoConfigUtil.setOutputFormat(conf, MongoOutputFormat.class);
        }
        //FileInputFormat.addInputPath(conf, new Path("/messages"));
        MongoConfig config = new MongoConfig(conf);
        config.setInputKey("headers.From");
        config.setMapper(EnronMailMapper.class);
        config.setReducer(EnronMailReducer.class);
        config.setMapperOutputKey(MailPair.class);
        config.setMapperOutputValue(IntWritable.class);
        config.setOutputKey(MailPair.class);
        config.setOutputValue(IntWritable.class);
        config.setInputURI("mongodb://mongodb01:27051,mongodb02:27051,mongodb03:27051/testdb.messages");
        config.setOutputURI("mongodb://mongodb01:27051,mongodb02:27051,mongodb03:27051/testdb.mailpairs");
        setConf(conf);
    }

    public static void main(String[] args) throws Exception {
        System.exit(ToolRunner.run(new EnronMail(), args));
    }
}

打jar包程序(略)，在Hadoop YARN环境运行这个mapreduce实例：

$ bin/yarn jar enronmail.jar

参考资料
https://github.com/mongodb/mongo-hadoop/wiki/MapReduce-Usage