1. Nordic Perl Workshop 2013
Playing with Hadoop
Søren Lund (slu)
slu@369.dk

2. DISCLAIMER
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I have no experience with Hadoop in a realworld project
The installation notes I present are not
nescessarily suitable for production
The example scripts have not been used on
real (big) data
Hence the title Playing with Hadoop

3. About Hadoop (and Big Data)

4. The Problem (it's not new)
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We have (access to)
more and more data
Processing this data
takes longer and
longer
Not enough memory
Running out of disk
space
Our trusty old server
can't keep up
!!!!!

5. Scaling up
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Upgrade hardware:
bigger and faster
Redundancy: power
supply, RAID, hotswap
Expensive to keep
scaling up
Our software will run
without modifications

6. Scaling out
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Add more
(commodity) servers
Redundancy is
replaced by
replication
You can keep on
scaling out, it's cheap
How do we enable
our software to run
across multiple
servers?

7. Google solved this
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Google published two papers
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Google File System (GFS), 2003
http://research.google.com/archive/gfs.html
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MapReduce, 2004
http://research.google.com/archive/mapreduce.html
GFS and MapReduced provided a platform for
processing huge amounts of data in an efficient
way

8. Hadoop was born
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Doug Cutting read the Google papers
Based on those, he created Hadoop
(named after his sons toy elephant)
It is an implementation of GFS/MapReduce
(Open Source / Apache License)
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Written in Java and deployed on Linux
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First part of Lucene, now an Apache project
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https://hadoop.apache.org/

9. Hadoop Components
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Hadoop Common – utilities to control the rest
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HDFS – Hadoop Distributed File System
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YARN – Yet Another Resource Negotiator
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MapReduce – YARN-based parallel processing
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This enables us to write software that can
handle Big Data by scaling out

10. Big Data isn't just big
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Huge amounts of data (volume)
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Unstructured data (form)
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Highly dynamic data (burst/change rate)
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Big Data is actually hard-to-handle (with
traditional tools/methods) data

11. Examples of Big Data
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Log files, i.e.
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web server access logs
application logs
Internet feeds
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Twitter, Facebook, etc.
RSS
Images (face recognition, tagging)

12. Installing Hadoop

13. Needed to run Hadoop
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You need the following to run Hadoop
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Java JDK
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Linux server
Hadoop tarball
I'm using the following
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JDK 1.6.24 64 bit
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Ubuntu 12.04 LTS 64 bit
Hadoop 1.0.4
Could not get JDK7 + Hadoop 2.2 to work

14. Install Java

15. Setup Java home and path

16. Add hadoop user

17. Create SSH key for hadoop user

18. Accept SSH key

19. Install Hadoop and add to path

20. Disable IPv6

21. Reboot and check installation

22. Running an example job

23. Calculate Pi

24. Estimated value of Pi

25. Three modes of operation
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Pi was calculated in Local standalone mode
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it is the default mode (i.e. no configuration needed)
all components of Hadoop run in a single JVM
Pseudo-distributed mode
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components communicate using sockets
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a separate JVM is spawned for each component
it is a mini-cluster on a single host
Fully distributed mode
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components are spread across multiple machines

26. Create base directory for HDFS

27. Set JAVA_HOME

28. Edit core-site.xml

29. Edit hdfs-site.xml

30. Edit mapred-site.xml

31. Log out and log on as hadoop

32. Format HDFS

33. Start HDFS

34. Start Map Reduce

35. Create home directory & test data

36. Running Word Count

37. First let's try the example jar

38. Inspect the result

39. Compile and run our own jar
https://gist.github.com/soren/7213273

40. Inspect result

41. Run improved version
https://gist.github.com/soren/7213453

42. Inspect (improved) result

43. Hadoop MapReduce
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A reducer will get all values associated with a
given key
Precursor job can be used to normalize data
Combiners can be used to perform early sorting
of map output before it is send to the reducer

44. Perl MapReduce

45. Playing with MapReduce
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We don't need Hadoop to play with MapReduce
Instead we can emulate Hadoop using two
scripts
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wc_mapper.pl – a Word Count Mapper
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wc_reducer.pl – a Word Count Reducer
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We connect them using a pipe (|)
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Very Unix-like!

46. Run MapReduce without Hadoop
https://gist.github.com/soren/7596270 https://gist.github.com/soren/7596285

47. Hadoop's Streaming interface
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Enables you to write jobs in any programming
language, e.g. Perl
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Input from STDIN
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Output to STDOUT
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Key/Value pairs separated by TAB
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Reducers will get values one-by-one
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Not to be confused with Hadoop Pipes that
provides a native C++ interface to Hadoop

48. Run Perl Word Count
https://gist.github.com/soren/7596270
https://gist.github.com/soren/7596285

49. Inspect result

50. Hadoop::Streaming
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Perl interface to Hadoop's Streaming interface
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Implemented in Moose
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You'll can now implement you MapReduce as
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a class with a map() and reduce() method
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a mapper script
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a reducer script

51. Installing Hadoop::Streaming
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Btw, Perl was already installed on the server ;-)
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But we want to install Hadoop::Streaming
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I also had to install local::lib to make it work
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All you have to do is
sudo cpan local::lib Hadoop::Streaming
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Nice and easy

52. Run Hadoop::Streaming job
https://gist.github.com/soren/7596451
https://gist.github.com/soren/7600134 https://gist.github.com/soren/7600144

53. Inspect result

54. Some final notes and loose ends

55. The Web User Interface
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HDFS
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MapReduce
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http://localhost:8070/
File Browser
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http://localhost:8030/
http://localhost:8075/browseDirectory.jsp?namenodeInfo
Note: this is with port forwarding in VirtualBox
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50030 → 8030, 50070 → 8070, 50075 → 8075

56. Joins in Hadoop
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It's possible to implement joins in MapReduce
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Reduce-joins – simple
Map-joins – less data to transfer
Do you need joins?
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Maybe you're data has structure → SQL?
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Try Hive (HiveQL)
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Or Pig (Pig Latin)

57. Hadoop in the Cloud
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Elastic MapReduce (EMR)
http://aws.amazon.com/elasticmapreduce/
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Essentially Hadoop in the Cloud
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Build on EC2 and S3
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You can upload JARs or scripts

58. There's more
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Distributions
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Cloudera Distribution for Hadoop (CDH)
http://www.cloudera.com/
Hortonworks Data Platform (HDP)
http://hortonworks.com/
HBase, Hive, Pig and other related projects
https://hadoop.apache.org/
But, a basic Hadoop setup is a good start
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and a nice place to just play with Hadoop

59. I like big data and I can not lie
Oh, my God, Becky, look at the data, it's so big
It looks like one of those Hadoop guys setups
Who understands those Hadoop guys
They only map/reduce it because it is on a
distributed file system
I mean the data, it's just so big
I can't believe it's so huge
It's just out there, I mean, it's gross
Look, it's just so blah

60. The End
Questions?
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