跟我一起hadoop（1）-hadoop2.6安裝與使用

偽分散式

hadoop的三種安裝方式：

• Local (Standalone) Mode
• Pseudo-Distributed Mode
• Fully-Distributed Mode

安裝之前需要

$ sudo apt-get install ssh
     $ sudo apt-get install rsync

詳見：http://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-common/SingleCluster.html

偽分散式配置

Configuration

修改下邊:

etc/hadoop/core-site.xml:

<configuration>
    <property>
        <name>fs.defaultFS</name>
        <value>hdfs://localhost:9000</value>
    </property>
</configuration>

etc/hadoop/hdfs-site.xml:

<configuration>
    <property>
        <name>dfs.replication</name>
        <value>1</value>
    </property>
</configuration>

配置ssh

  $ ssh-keygen -t dsa -P '' -f ~/.ssh/id_dsa
  $ cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys

如果想執行在yarn上

需要執行下邊的步驟：

1. Configure parameters as follows:

   etc/hadoop/mapred-site.xml:

   <configuration>
       <property>
           <name>mapreduce.framework.name</name>
           <value>yarn</value>
       </property>
   </configuration>

   etc/hadoop/yarn-site.xml:

   <configuration>
       <property>
           <name>yarn.nodemanager.aux-services</name>
           <value>mapreduce_shuffle</value>
       </property>
   </configuration>

2. Start ResourceManager daemon and NodeManager daemon:

     $ sbin/start-yarn.sh

3. Browse the web interface for the ResourceManager; by default it is available at:
   • ResourceManager - http://localhost:8088/
4. Run a MapReduce job.
5. When you're done, stop the daemons with:

     $ sbin/stop-yarn.sh

輸入：

http://localhost:8088/

可以看到

啟動yarn後

1. Format the filesystem:

     $ bin/hdfs namenode -format

2. Start NameNode daemon and DataNode daemon:

     $ sbin/start-dfs.sh

   The hadoop daemon log output is written to the $HADOOP_LOG_DIR directory (defaults to $HADOOP_HOME/logs).

3. Browse the web interface for the NameNode; by default it is available at:
   • NameNode - http://localhost:50070/

輸入後得到：

然後執行測試

1. Make the HDFS directories required to execute MapReduce jobs:

     $ bin/hdfs dfs -mkdir /user
     $ bin/hdfs dfs -mkdir /user/<username>

2. Copy the input files into the distributed filesystem:

     $ bin/hdfs dfs -put etc/hadoop input

3. Run some of the examples provided:

     $ bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.6.0.jar grep input output 'dfs[a-z.]+'

4. Examine the output files:

   Copy the output files from the distributed filesystem to the local filesystem and examine them:

     $ bin/hdfs dfs -get output output
     $ cat output/*

   or

   View the output files on the distributed filesystem:

     $ bin/hdfs dfs -cat output/*

看執行的情況：

檢視結果

測試執行成功，可以編寫原生程式碼了。

eclipse hadoop2.6外掛使用

下載原始碼：

git clone https://github.com/winghc/hadoop2x-eclipse-plugin.git

下載過程：

編譯外掛：

cd src/contrib/eclipse-plugin
ant jar -Dversion=2.6.0 -Declipse.home=/usr/local/eclipse -Dhadoop.home=/usr/local/hadoop-2.6.0  //路徑根據自己的配置

• 複製編譯好的jar到eclipse外掛目錄，重啟eclipse

• 配置 hadoop 安裝目錄

window ->preference -> hadoop Map/Reduce -> Hadoop installation directory

• 配置Map/Reduce 檢視

window ->Open Perspective -> other->Map/Reduce -> 點選“OK”

windows → show view → other->Map/Reduce Locations-> 點選“OK”

• 控制檯會多出一個“Map/Reduce Locations”的Tab頁

在“Map/Reduce Locations” Tab頁 點選圖示<大象+>或者在空白的地方右鍵，選擇“New Hadoop location…”，彈出對話方塊“New hadoop location…”，配置如下內容：將ha1改為自己的hadoop使用者

注意：MR Master和DFS Master配置必須和mapred-site.xml和core-site.xml等配置檔案一致。

開啟Project Explorer,檢視HDFS檔案系統。

• 新建Map/Reduce任務

File->New->project->Map/Reduce Project->Next

編寫WordCount類：記得先把服務都起來

/**
 * 
 */
package com.zongtui;

/**
 * ClassName: WordCount <br/>
 * Function: TODO ADD FUNCTION. <br/>
 * date: Jun 28, 2015 5:34:18 AM <br/>
 *
 * @author zhangfeng
 * @version 
 * @since JDK 1.7
 */

import java.io.IOException;
import java.util.Iterator;
import java.util.StringTokenizer;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;

public class WordCount {
    public static class Map extends MapReduceBase implements
            Mapper<LongWritable, Text, Text, IntWritable> {
        private final static IntWritable one = new IntWritable(1);
        private Text word = new Text();

        public void map(LongWritable key, Text value,
                OutputCollector<Text, IntWritable> output, Reporter reporter)
                throws IOException {
            String line = value.toString();
            StringTokenizer tokenizer = new StringTokenizer(line);
            while (tokenizer.hasMoreTokens()) {
                word.set(tokenizer.nextToken());
                output.collect(word, one);
            }
        }
    }

    public static class Reduce extends MapReduceBase implements
            Reducer<Text, IntWritable, Text, IntWritable> {
        public void reduce(Text key, Iterator<IntWritable> values,
                OutputCollector<Text, IntWritable> output, Reporter reporter)
                throws IOException {
            int sum = 0;
            while (values.hasNext()) {
                sum += values.next().get();
            }
            output.collect(key, new IntWritable(sum));
        }
    }

    public static void main(String[] args) throws Exception {
        JobConf conf = new JobConf(WordCount.class);
        conf.setJobName("wordcount");

        conf.setOutputKeyClass(Text.class);
        conf.setOutputValueClass(IntWritable.class);

        conf.setMapperClass(Map.class);
        conf.setReducerClass(Reduce.class);

        conf.setInputFormat(TextInputFormat.class);
        conf.setOutputFormat(TextOutputFormat.class);

        FileInputFormat.setInputPaths(conf, new Path(args[0]));
        FileOutputFormat.setOutputPath(conf, new Path(args[1]));

        JobClient.runJob(conf);
    }
}

user/admin123/input/hadoop是你上傳在hdfs的資料夾（自己建立），裡面放要處理的檔案。ouput1放輸出結果

將程式放在hadoop叢集上執行：右鍵-->Runas -->Run on Hadoop,最終的輸出結果會在HDFS相應的資料夾下顯示。至此，ubuntu下hadoop-2.6.0 eclipse外掛配置完成。

遇到異常

Exception in thread "main" org.apache.hadoop.mapred.FileAlreadyExistsException: Output directory hdfs://localhost:9000/output already exists
    at org.apache.hadoop.mapred.FileOutputFormat.checkOutputSpecs(FileOutputFormat.java:132)
    at org.apache.hadoop.mapreduce.JobSubmitter.checkSpecs(JobSubmitter.java:564)
    at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:432)
    at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1296)
    at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1293)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:415)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)
    at org.apache.hadoop.mapreduce.Job.submit(Job.java:1293)
    at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:562)
    at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:557)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:415)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)
    at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:557)
    at org.apache.hadoop.mapred.JobClient.submitJob(JobClient.java:548)
    at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:833)
    at com.zongtui.WordCount.main(WordCount.java:83)

1、改變輸出路徑。

2、刪除重新建。

執行完成後看結果：