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= 實作九 Lab 9 =
[[PageOutline]]
{{{
#!html
<div style="text-align: center;"><big style="font-weight: bold;"><big>Hadoop Streaming 搭配不同程式語言練習<br/>Hadoop Streaming in different Language</big></big></div>
}}}

{{{
#!text
以下練習，請連線至 hadoop.nchc.org.tw 操作。底下的 hXXXX 等於您的用戶名稱。
}}}

== 搭配現存二進位執行檔 ==
== Existing Binary ==

{{{
~$ hadoop fs -put /etc/hadoop/conf lab9_input
~$ hadoop jar hadoop-streaming.jar -input lab9_input -output lab9_out1 -mapper /bin/cat -reducer /usr/bin/wc
~$ hadoop fs -cat lab9_out1/part-00000
}}}

== 搭配 Bash Shell Script ==

{{{
~$ echo "sed -e \"s/ /\n/g\" | grep ." > streamingMapper.sh
~$ echo "uniq -c | awk '{print \$2 \"\t\" \$1}'" > streamingReducer.sh
~$ chmod a+x streamingMapper.sh
~$ chmod a+x streamingReducer.sh
~$ hadoop jar hadoop-streaming.jar -input lab9_input -output lab9_out2 -mapper streamingMapper.sh -reducer streamingReducer.sh -file streamingMapper.sh -file streamingReducer.sh
~$ hadoop fs -cat lab9_out2/part-00000
}}}

== 搭配 PHP Script ==

 * 編輯 mapper 的 php 程式 
{{{
~$ cat > mapper.php << EOF
#!/usr/bin/php
<?php

\$word2count = array();

// 標準輸入為 STDIN (standard input)
while ((\$line = fgets(STDIN)) !== false) {
   // 移除小寫與空白
   \$line = strtolower(trim(\$line));
   // 將行拆解成各個字於 words 陣列中
   \$words = preg_split('/\W/', \$line, 0, PREG_SPLIT_NO_EMPTY);
   // 將字 +1
   foreach (\$words as \$word) {
       \$word2count[\$word] += 1;
   }
}

// 將結果寫到 STDOUT (standard output)
foreach (\$word2count as \$word => \$count) {
   // 印出 [字 , "tab符號" ,  "數字" , "結束字元"]
   echo \$word, chr(9), \$count, PHP_EOL;
}
?>
EOF
}}}
 * 編輯 reduce 的 php 程式 
{{{
~$ cat > reducer.php << EOF
#!/usr/bin/php
<?php

\$word2count = array();

// 輸入為 STDIN
while ((\$line = fgets(STDIN)) !== false) {
    // 移除多餘的空白
    \$line = trim(\$line);
    // 每一行的格式為 (單字 "tab" 數字) ，紀錄到(\$word, \$count)
    list(\$word, \$count) = explode(chr(9), \$line);
    // 轉換格式string -> int
    \$count = intval(\$count);
    // 加總
    if (\$count > 0) \$word2count[\$word] += \$count;
}

// 此行不必要，但可讓output排列更完整
ksort(\$word2count);

// 將結果寫到 STDOUT (standard output)
foreach (\$word2count as \$word => \$count) {
    echo \$word, chr(9), \$count, PHP_EOL;
}
?>
EOF
}}}
 * 修改執行權限
{{{
~$ chmod a+x *.php
}}}
 * 測試是否能運作
{{{
~$ echo "i love hadoop, hadoop love u" | ./mapper.php | ./reducer.php
}}}
 * 開始執行
{{{
~$ hadoop jar hadoop-streaming.jar -mapper mapper.php -reducer reducer.php -input lab9_input -output lab9_out3 -file mapper.php -file reducer.php
}}}
 * 檢查結果 
{{{
~$ hadoop fs -cat lab9_out3/part-00000
}}}