hadoop安装与WordCount例子

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apache-hadoop

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1、JDK安装
下载网址：
http://www.oracle.com/technetwork/java/javase/downloads/jdk-6u29-download-513648.html
如果本地有安装包，则用SecureCRT连接Linux机器，然后用rz指令进行上传文件；

下载后获得jdk-6u29-linux-i586-rpm.bin文件，使用sh jdk-6u29-linux-i586-rpm.bin进行安装，
等待安装完成即可；java默认会安装在/usr/java下；

在命令行输入:vi /etc/profile在里面添加如下内容export JAVA_HOME=/usr/java/jdk1.6.0_29export JAVA_BIN=/usr/java/jdk1.6.0_29/binexport PATH=$PATH:$JAVA_HOME/binexport CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jarexport JAVA_HOME JAVA_BIN PATH CLASSPATH

进入 /usr/bin/目录cd /usr/binln -s -f /usr/java/jdk1.6.0_29/jre/bin/javaln -s -f /usr/java/jdk1.6.0_29/bin/javac
在命令行输入java -version屏幕输出:java version "jdk1.6.0_02"Java(TM) 2 Runtime Environment, Standard Edition (build jdk1.6.0_02)Java HotSpot(TM) Client VM (build jdk1.6.0_02, mixed mode)则表示安装JDK1.6完毕.

2、Hadoop安装
下载网址：http://www.apache.org/dyn/closer.cgi/hadoop/common/
如果本地有安装包，则用SecureCRT连接Linux机器，然后用rz指令进行上传文件；

下载后获得hadoop-0.21.0.tar.gz文件

解压 tar zxvf hadoop-0.21.0.tar.gz
压缩：tar zcvf hadoop-0.21.0.tar.gz 目录名

在命令行输入:vi /etc/profile在里面添加如下内容
export hadoop_home = /usr/george/dev/install/hadoop-0.21.0
export JAVA_HOME=/usr/java/jdk1.6.0_29export JAVA_BIN=/usr/java/jdk1.6.0_29/binexport PATH=$PATH:$JAVA_HOME/bin:$hadoop_home/binexport CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jarexport JAVA_HOME JAVA_BIN PATH CLASSPATH

需要注销用户或重启vm，就可以直接输入hadoop指令了；
WordCount例子代码
3.1 Java代码：
package demo;

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.setCombinerClass(Reduce.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);
}
}

3.2 编译：
javac -classpath /usr/george/dev/install/hadoop-0.21.0/hadoop-hdfs-0.21.0.jar:/usr/george/dev/install/hadoop-0.21.0/hadoop-mapred-0.21.0.jar:/usr/george/dev/install/hadoop-0.21.0/hadoop-common-0.21.0.jar WordCount.java -d /usr/george/dev/wkspace/hadoop/wordcount/classes
在windows中，多个classpath参数值用;分割；在linux中用:分割；

编译后，会在/usr/george/dev/wkspace/hadoop/wordcount/classes目录下生成三个class文件：
WordCount.class WordCount$Map.class WordCount$Reduce.class

3.3将class文件打成jar包
到/usr/george/dev/wkspace/hadoop/wordcount/classes目录，运行jar cvf WordCount.jar *.class就会生成：
WordCount.class WordCount.jar WordCount$Map.class WordCount$Reduce.class

3.4 创建输入数据：
创建/usr/george/dev/wkspace/hadoop/wordcount/datas目录，在其下创建input1.txt和input2.txt文件：
Touch input1.txt
Vi input1.txt

文件内容如下：
i love chinaare you ok?

按照同样的方法创建input2.txt，内容如下：
hello, i love word
You are ok

创建成功后可以通过cat input1.txt 和 cat input2.txt查看内容；

3.5 创建hadoop输入与输出目录：
hadoop fs -mkdir wordcount/inputhadoop fs -mkdir wordcount/outputhadoop fs -put input1.txt wordcount/input/hadoop fs -put input2.txt wordcount/input/

Ps : 可以不创建out目录，要不运行WordCount程序时会报output文件已经存在，所以下面的命令行中使用了output1为输出目录；
3.6运行
到/usr/george/dev/wkspace/hadoop/wordcount/classes目录，运行
[root@localhost classes]# hadoop jar WordCount.jar WordCount wordcount/input wordcount/output1
11/12/02 05:53:59 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/12/02 05:53:59 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
11/12/02 05:53:59 WARN mapreduce.JobSubmitter: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
11/12/02 05:53:59 INFO mapred.FileInputFormat: Total input paths to process : 2
11/12/02 05:54:00 WARN conf.Configuration: mapred.map.tasks is deprecated. Instead, use mapreduce.job.maps
11/12/02 05:54:00 INFO mapreduce.JobSubmitter: number of splits:2
11/12/02 05:54:00 INFO mapreduce.JobSubmitter: adding the following namenodes' delegation tokens:null
11/12/02 05:54:00 INFO mapreduce.Job: Running job: job_201112020429_0003
11/12/02 05:54:01 INFO mapreduce.Job: map 0% reduce 0%
11/12/02 05:54:20 INFO mapreduce.Job: map 50% reduce 0%
11/12/02 05:54:23 INFO mapreduce.Job: map 100% reduce 0%
11/12/02 05:54:29 INFO mapreduce.Job: map 100% reduce 100%
11/12/02 05:54:32 INFO mapreduce.Job: Job complete: job_201112020429_0003
11/12/02 05:54:32 INFO mapreduce.Job: Counters: 33
        FileInputFormatCounters
                BYTES_READ=54
        FileSystemCounters
                FILE_BYTES_READ=132
                FILE_BYTES_WRITTEN=334
                HDFS_BYTES_READ=274
                HDFS_BYTES_WRITTEN=65
        Shuffle Errors
                BAD_ID=0
                CONNECTION=0
                IO_ERROR=0
                WRONG_LENGTH=0
                WRONG_MAP=0
                WRONG_REDUCE=0
        Job Counters
                Data-local map tasks=2
                Total time spent by all maps waiting after reserving slots (ms)=0
                Total time spent by all reduces waiting after reserving slots (ms)=0
                SLOTS_MILLIS_MAPS=24824
                SLOTS_MILLIS_REDUCES=6870
                Launched map tasks=2
                Launched reduce tasks=1
        Map-Reduce Framework
                Combine input records=12
                Combine output records=12
                Failed Shuffles=0
                GC time elapsed (ms)=291
                Map input records=4
                Map output bytes=102
                Map output records=12
                Merged Map outputs=2
                Reduce input groups=10
                Reduce input records=12
                Reduce output records=10
                Reduce shuffle bytes=138
                Shuffled Maps =2
                Spilled Records=24
                SPLIT_RAW_BYTES=220

3.7 查看输出目录
[root@localhost classes]# hadoop fs -ls wordcount/output1
11/12/02 05:54:59 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/12/02 05:55:00 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
Found 2 items
-rw-r--r--   1 root supergroup          0 2011-12-02 05:54 /user/root/wordcount/output1/_SUCCESS
-rw-r--r--   1 root supergroup         65 2011-12-02 05:54 /user/root/wordcount/output1/part-00000

[root@localhost classes]# hadoop fs -cat /user/root/wordcount/output1/part-00000
11/12/02 05:56:05 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/12/02 05:56:05 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
You     1
are     2
china   1
hello,i 1
i       1
love    2
ok      1
ok?     1
word    1
you     1

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