WordCount MapReduce program using Pydoop (MapReduce framework for Python)

In WordCount MapReduce program using Hadoop streaming and python entry i used Hadoop Streaming for creating MapReduce program, but that program is quite verbose and it has limitations such as you cannot use counters,.. etc. So i decided to develop same program using Pydoop, which is framework that makes is easy to developing Hadoop Map Reduce program as well as working with HDFS easier. I followed these steps
  1. First i followed instructions on pydoop installation page to install pydoop on my machine. I ran into some issues during that process but eventually had pydoop installed
  2. Next i did create a HelloPydoop.py file which contains mapper function and reducer function like this. The mapper function gets linenumber and line at a time, in that function i am taking care of breaking the line into words and then writing them into output (writer.emit()). In the reducer method i am getting word and incount in the (key, [value,value1] format. Which is different that Hadoop streaming where i have to take care of change in key, so this code is much compact
  3. Once my HelloPydoop.py file is ready i could invoke it by passing to pydoop script in this aesop.txt is the name of the input file in HDFS and i want the output to get generated in output/pydoop directory in HDFS. pydoop script /home/user/PycharmProjects/HelloWorld/Pydoop/HelloPydoop.py aesop.txt output/pydoop
  4. After the map reducer is done executing i can look at its output by executing hdfs dfs -cat output/pydoop/part-00000 command

2 comments:

arun said...

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sowmiya gopal said...

Thanks for helping me to understand basic Hadoop Map reduce program on hadoop concepts. As a beginner in Hadoop your post help me a lot.
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