A brief, hands-on introduction to Hadoop & Pig
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A brief, hands-on introduction to Hadoop & Pig

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Intention: ...

Intention:
approach hadoop from a tool-user's perspective, specifically, a web dev's perspective

Intended audience:
anyone with a desire to begin using Hadoop
Requirements
VMWare
Hadoop will be demonstrated using a VMWare virtual machine
I’ve found the use of a virtual machine to be the easiest way to get started with Hadoop

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    A brief, hands-on introduction to Hadoop & Pig A brief, hands-on introduction to Hadoop & Pig Presentation Transcript

    • A brief, hands-on introduction to Hadoop & Pig Erik Eldridge Yahoo! Developer Network OSCAMP 2009 Photo credit: http://www.flickr.com/photos/mckaysavage/1059144105/sizes/l/
    • Preamble
      • Intention: approach hadoop from a tool-user's perspective, specifically, a web dev's perspective
      • Intended audience: anyone with a desire to begin using Hadoop
    • Requirements
      • VMWare
        • Hadoop will be demonstrated using a VMWare virtual machine
        • I’ve found the use of a virtual machine to be the easiest way to get started with Hadoop
    • Setup VM
      • Get hadoop vm from: http://developer.yahoo.com/hadoop/tutorial/module3.html#vm-setup
      • Note:
        • user name: hadoop-user
        • password: hadoop
      • Launch vm
      • Log in
      • Note ip of machine
    • Start Hadoop
      • Run the util to launch hadoop: $ ~/start-hadoop
      • If it's already running, we'll get an error like "172.16.83.132: datanode running as process 6752. Stop it first. 172.16.83.132: secondarynamenode running as process 6845. Stop it first. ..."
    • Saying “hi” to Hadoop
      • Call hadoop command line util: $ hadoop
      • Hadoop command line options are listed here: http://hadoop.apache.org/common/docs/r0.17.0/hdfs_shell.html
      • Hadoop should have been launched on boot. verify this is the case: $ hadoop dfs -ls /
    • Saying “hi” to Hadoop
      • If hadoop has not been started, you'll see something like: "09/07/22 10:01:24 INFO ipc.Client: Retrying connect to server: /172.16.83.132:9000. Already tried 0 time(s). 09/07/22 10:01:24 INFO ipc.Client: Retrying connect to server: /172.16.83.132:9000. Already tried 1 time(s)...”
      • If hadoop has been launched, the dfs -ls command should show the contents of hdfs
      • Before continuing, view all the hadoop utilities and sample files: $ ls
    • Install Apache
      • Why? In the interest of creating a relevant example, I'm going to work on Apache access logs
      • Update apt-get so it can find apache2: $ sudo apt-get update
      • Install apache2 so we can generate access log data: $ sudo apt-get install apache2
    • Generate data
      • Jump into the directory containing the apache logs: $ cd /var/log/apache2
      • Show the top n lines of the access log: $ tail -f -n 10 access.log
    • Generate data
      • Put this script, or something similar, in an executable file on your local machine:
        • #!/bin/bash
        • url='http://{VM IP address}:’
        • for i in {1..1000}
        • do
        • curl $url
        • done
      • Edit the IP address to that of your VM
    • Generate data
      • Set executable permissions on the file: $ chmod +x generate.sh
      • Run the file: $ ./generate.sh
      • Note log data in tail output in VM
    • Exploring HDFS
      • Ref: http://hadoop.apache.org/common/docs/r0.18.3/hdfs_shell.html
      • Show home dir structure:
        • $ hadoop dfs -ls /user
        • $ hadoop dfs -ls /user/hadoop-user
      • Create a directory: $ hadoop dfs -mkdir /user/hadoop-user/foo
      • Show new dir: $ hadoop dfs -ls /user/hadoop-user/
    • Exploring HDFS
      • Attempt to re-create new dir and note error: $ hadoop dfs -mkdir /user/hadoop-user/foo
      • Create a destination directory using implicit path: $ hadoop dfs -mkdir bar
      • Auto-create nested destination directories: $ hadoop dfs -mkdir dir1/dir2/dir3
      • Remove dir: $ hadoop dfs -rmr /user/hadoop-user/foo
      • Remove dir: $ hadoop dfs -rmr bar dir1
      • Try to re-remove dir and note error: $ hadoop dfs -rmr bar
    • Browse HDFS using web UI
      • Open http://{VM IP address}:500750 in browser
      • More info: http://hadoop.apache.org/common/docs/r0.18.3/hdfs_user_guide.html#Web+Interface
    • Import access log data
      • Load access log into hdfs: $ hadoop dfs -put /var/log/apache2/access.log input/access.log
      • Verify it's in there: $ hadoop dfs -ls input/access.log
      • View the contents: $ hadoop dfs -cat input/access.log
    • Do something w/ the data
      • Ref: http://www.michael-noll.com/wiki/Running_Hadoop_On_Ubuntu_Linux_%28Single-Node_Cluster%29
      • Credit: http://www.michael-noll.com/wiki/Writing_An_Hadoop_MapReduce_Program_In_Python
      • Save the mapper and reducer code in two separate files, e.g., mapper.py and reducer.py
    • Do something w/ the data
      • Stream data through these two files, saving the output back to HDFS: #!/bin/bash $HADOOP_HOME/bin/hadoop jar $HADOOP_HOME/contrib/streaming/hadoop-0.18.0-streaming.jar -mapper /home/hadoop-user/wordcount/mapper.py -reducer /home/hadoop-user/wordcount/reducer.py -input /user/hadoop-user/input/access.log -output /user/hadoop-user/output/mapReduceOut
    • Do something w/ the data
      • View output files: $ hadoop dfs -ls output/mapReduceOut
      • Note multiple output files ("part-00000", "part-00001", etc)
      • View output file contents: $ hadoop dfs -cat output/mapReduceOut/part-00000
    • Pig
      • Pig is a higher-level interface for hadoop
        • Interactive shell Grunt
        • Declarative, SQL-like language, Pig Latin
        • Pig engine compiles Pig Latin into MapReduce
        • Extensible via Java files
      • "writing mapreduce routines, is like coding in assembly”
      • Pig, Hive, etc.
    • Exploring Pig
      • Ref: http://wiki.apache.org/pig/PigTutorial
      • Pig is already on the VM
      • Launch pig w/ connection to cluster: $ java -cp pig/pig.jar:$HADOOPSITEPATH org.apache.pig.Main
      • View contents of HDFS from grunt: > ls
    • Perform word count w/ Pig
      • Save this script in a file, e.g, wordcount.pig: myinput = LOAD 'input/access.log' USING TextLoader(); words = FOREACH myinput GENERATE FLATTEN(TOKENIZE($0)); grouped = GROUP words BY $0; counts = FOREACH grouped GENERATE group, COUNT(words); ordered = ORDER counts BY $0; STORE ordered INTO 'output/pigOut' USING PigStorage();
    • Perform word count w/ Pig
      • Run this script: $ java -cp pig/pig.jar:$HADOOPSITEPATH org.apache.pig.Main -f wordcount.pig
      • View output $ hadoop dfs -cat output/pigOut/part-00000
    • Resources
      • Apache Hadoop Site
      • Apache Pig Site
      • YDN Hadoop Tutorial
        • Virtual Machine
    • Thank you
      • Follow me on Twitter: http://twitter.com/erikeldridge
      • Find these slides on Slideshare: http://slideshare.net/erikeldridge
      • Rate this talk on SpeakerRate: http://speakerrate.com/erikeldridge