實作四: MapReduce 程式編譯
Lab4: Compiling Hadoop MapReduce Java Program

Practice 1 : Word Count (Basic)

• 上傳內容到 HDFS 內
  upload data to HDFS

$ cd /opt/hadoop
$ mkdir lab4_input
$ echo "I like NCHC Cloud Course." > lab4_input/input1
$ echo "I like nchc Cloud Course, and we enjoy this course." > lab4_input/input2
$ bin/hadoop fs -put lab4_input lab4_input
$ bin/hadoop fs -ls lab4_input

• 下載 ​WordCount.java 並存到/opt/hadoop;
  Download WordCount.java and save to /opt/hadoop

  ~$ cd /opt/hadoop
  /opt/hadoop$ wget http://trac.nchc.org.tw/cloud/raw-attachment/wiki/WordCount/WordCount.java
  

• 運作程式
  Compile WordCount.java and run it by hadoop jar command

$ mkdir MyJava
$ javac -classpath hadoop-*-core.jar -d MyJava WordCount.java
$ jar -cvf wordcount.jar -C MyJava .
$ bin/hadoop jar wordcount.jar WordCount lab4_input/ lab4_out1/
$ bin/hadoop fs -cat lab4_out1/part-00000

• lab4_out1 執行結果
  You should see results like this :

  Cloud 2
  Course, 1
  Course. 1
  I 2
  NCHC  1
  and 1
  course. 1
  enjoy 1
  like  2
  nchc  1
  this  1
  we  1
  

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Practice 2 : Word Count (Advanced)

$ echo "\." >pattern.txt && echo "\," >>pattern.txt
$ bin/hadoop fs -put pattern.txt ./
$ mkdir MyJava2

• 下載 WordCount2.java 並存到/opt/hadoop;
  Download WordCount2.java to /opt/hadoop

  ~$ cd /opt/hadoop
  /opt/hadoop$ wget http://trac.nchc.org.tw/cloud/raw-attachment/wiki/Hadoop_Lab4/WordCount2.java
  

$ javac -classpath hadoop-*-core.jar -d MyJava2 WordCount2.java
$ jar -cvf wordcount2.jar -C MyJava2 .
$ bin/hadoop jar wordcount2.jar WordCount2 lab4_input lab4_out2 -skip pattern.txt
$ bin/hadoop fs -cat lab4_out2/part-00000

• lab4_out2 執行結果
  You should see results like this:

  Cloud 2
  Course  2
  I 2
  NCHC  1
  and 1
  course  1
  enjoy 1
  like  2
  nchc  1
  this  1
  we  1
  

• Let's given case insensitive and ignore pattern for this example

  /opt/hadoop$ bin/hadoop jar wordcount2.jar WordCount2 -Dwordcount.case.sensitive=false lab4_input lab4_out3 -skip pattern.txt
  /opt/hadoop$ bin/hadoop fs -cat lab4_out3/part-00000
  

• lab4_out3 執行結果
  You should see results like this:

  and 1
  cloud 2
  course  3
  enjoy 1
  i 2
  like  2
  nchc  2
  this  1
  we  1