This document summarizes the history and development of the Nutch web search engine project. It discusses how Nutch evolved from its original version to incorporate Hadoop and become more modular by delegating functions like indexing and parsing to other Apache projects like Solr and Tika. The current version, Nutch 2.0, aims to have a slimmed down architecture where it acts as a delegator to these other frameworks rather than handling these functions itself. The document also reflects on lessons learned from earlier stages of the project around community engagement, maintenance, and configuration challenges.

1. Lessons Learned in the
Development of a Web-scale
Search Engine: Nutch2 and beyond
Chris A. Mattmann
Senior Computer Scientist, NASA Jet Propulsion Laboratory
Adjunct Assistant Professor, Univ. of Southern California
Member, Apache Software Foundation

2. Roadmap
• What is Nutch?
• What are the current versions of Nutch?
• What can it do?
• What did we do right?
• What did we do wrong?
• Where is Nutch going?

3. And you are?
• Apache Member involved in
– Tika (VP,PMC), Nutch (PMC), Incubator (PMC),
OODT (Mentor), SIS (Mentor), Lucy (Mentor) and
Gora (Champion)
• Architect/Developer at
NASA JPL in
Pasadena, CA
• Software
Architecture/Engineeri
ng Prof at USC

4. is…
• A project originally started by Doug
Cutting
• Nutch builds upon the lower level text
indexing library and API called Lucene
• Nutch provides crawling services,
protocol services, parsing services,
content management services on top of
the indexing capability provided by
Lucene
• Allows you to sand up a web-scale infra.

5. Community
• Mailing lists
– User: 972 peeps
– Dev: 520 peeps
• Committers/PMC
– 8 peeps
– All 8 active: SERIOUSLY
• Releases
– 11 releases so far
– Working on 2.0
Credit: svnsearch.org

6. What Currently Exists?
• Version 0.6.x
– First easily deployable version
• Version 0.7.x
– Added several new features including several new parsers (MS-WORD,
PowerPoint), URLFilter extension point, first Apache release after Incubation,
mime type system
• Version 0.8.x
– Completely new underlying architecture based on Hadoop
– Parse plugins framework, multi-valued metadata container
– Parser Factory enhancement
• Version 0.9.x
– Major bug fixes
– Hadoop, and Lucene library upgrades
• Version 1.0
– Flexible filter framework
– Flexible scoring
– Initial integration with Tika
– Full Search Engine functionality and capabilities, in production at large scale
(Internet Archive)

7. What are the recent
versions?
• Version 1.1, upgrade all Nutch
library deps (Hadoop, Tika, etc.) and
make Fetcher faster
• Version 1.2, fix some big time
bugs (NPE in distributed search),
lots of feature upgrades
– You should be using this version

8. Some active dev areas
• Plenty!
• Bug fixes (> 200 issues in JIRA right
now with no resolution)
• Nutch 2.0 architecture
– http://search-lucene.com/m/gbrBF1RMWk9
– Refactored Nutch architecture,
delegating to Solr, HBase, Tika, and
ORM

9. Why Nutch?
• Observation: Web Search is a
commodity
– Why can’t it be provided freely?
• Allows tweaking of typically “hidden” ranking
algorithms
• Allows developers to focus less on the
infrastructure (since Brin & Page’s paper, the
infrastructure is well-known), and more on
providing value-added capabilities

10. Why Nutch?
• Value-added capabilities
– Improving fetching speed
– Parsing and handling of the hundreds of
different content types available on the internet
– Handling different protocols for obtaining
content
– Better ranking algorithms (OPIC, PageRank)
• More or less, in Nutch, these capabilities all
map to extension points available via Nutch’s
plugin framework

11. Nutch’s Architecture
• Nutch Core facilities
– Parsing
– Indexing
– Crawling
– Content Acquisition
– Querying
– Plugin Framework
• Nutch’s extension points
– Scoring, Parsing, Indexing, Querying,
URLFiltering

12. Nutch’s Architecture
Maps to
Search engine
architecture
proposed by Brin
& Page

13. Real world application of
Nutch
• I work at NASA’s Jet Propulsion
Laboratory
• NASA’s Planetary Data System
– NASA’s archive for all planetary science
data collected by missions over the past
30 years
– Collected 20 TB over the past 30 years
• Increasing to over 200 TB in the next 3
years!
– Built up a catalog of all data collected
• Where does Nutch fit in?

14. Where does Nutch fit into
the PDS?
• PDS Management Council decide
they want “Google-like” search of the
PDS catalog
• Our plan: use Nutch to implement
capability for PDS

15. PDS Google-like Search
Architecture
Search Engine Architecture (e.g. Nutch, Google)
PDS
Catalog
P
D
S
-
D
Existing PDS
Query
Indexer Index
Lucene
Crawler
PDS
Extract
Parser
PDS
Parser
pds.war
Tomcat
Web
Server
Catalog
Metadata
Credit: D. Crichton, S. Hughes, P. Ramirez, R. Joyner, S.
Hardman, C. Mattmann

16. Approach
• Export PDS catalog datasets in RDF format (flat
files)
• Use nutch to crawl RDF files
– protocol-file plugin in Nutch
• Wrote our own parse-pds plugin
– Parse the RDF files, and then extract the metadata
• Wrote our own index-pds plugin
– Index the fields that we want from the parsed metadata
• Wrote our own query-pds plugin
– Search the index on the fields that we want

17. Search Interface

18. Results

19. Some Nutch History
• In the next few slides, we’ll go
through some of Nutch’s history,
including my involvement, the history
of Nutch dev, and how we came to
today

20. How I got involved
• In CS72: Seminar on Search Engines at USC
– Okay well it used to be called CS599, but you get the picture
• Started out by contributing RSS parsing plugin
– My final project in 599
• Moved on from there to
– NUTCH-88, redesign of the parsing framework
– NUTCH-139, Metadata container support
– NUTCH-210, Web Context application file
– And various other bug fixes, and contributions here and there
– Mailing list support
– Wiki support
• Became committer in October 2006
• Helped spin Nutch into Apache TLP, March 2010,
Nutch PMC member

21. The Big Yellow Elephant
• Before this guy was born
• Lots of folks interested in Nutch
Hadoop is born
(January 2008)
Credit: svnsearch.org

22. Post Hadoop Life
• Nutch project kind of withered
– Well more than “kind of” it did wither
– Went years in-between a release
• 0.8 to 1.0 took a while
• Dev Community went into
maintenance mode
– Many committers simply went inactive
• User Community deteriorated

23. Some Observations
• It was pretty difficult to attract new
committers
– Took too long to VOTE
them in
– They were only interested
in Hadoop type stuff
– Not many organizations were doing web-
scale search
• Existing active committers dwindled
• I was one of them!

24. Some Observations
• There wasn’t a plan for what to do
next
– What features to work on?
– What bugs to fix?
– Many considered Nutch to be
“production” worthy in its current form
and not a huge number of internet-scale
users so people just “put up” with its
existing issues, e.g., difficult to configure
?

25. Hadoop wasn’t the only
spinoff
• A lot of us interested in content
detection and analysis, another major
Nutch strength, went off to work on
that in some other Apache project
that I can’t remember the name of

26. How can Nutch reorganize?
• Strong feeling from Nutch community
that we should take whomever is left
and think about what the “next
generation” Nutch (Nutch2) would
look like
• (Several cycles of) Mailing threads
started by Andrzej Bialecki, Dennis
Kubes, Otis Gospondetic

27. Initial Nutch2 fizzles
• Ended up being a lot of talk, but there
wasn’t enough interest to pick up a
shovel and help dig the hole
• But…there were interesting
things going on
– Example: Nutchbase work
from Dogacan, and Enis

28. What was “Nutchbase”?
• Take the Apache implementation of
Google’s “BigTable”
– Col oriented storge, high scalability in columns
and rows
• Store Nutch Web page content
+

29. Lots of interest in Nutchbase
• But, sadly maintained as a patch for a year
or more
– NUTCH-650 Hbase integration
• Brought about some interesting thoughts
– If storage can be abstracted, what about?
• Messaging layer (JMS Nutch?)
• Parsing?
• Indexing (Solr, Lucene, you-name-it)

30. Post Nutch 1.0
• Nutch 1.0 release was a true “1.”-oh!
– Included production features
– Those using it were happy, b/c they had bought
into the model
– Useable, tuneable
• But, how do we get
to Nutch 2.0?

31. A few things happen in parallel
• 1.1 Release?
– I had some free
time and was
willing to RM a
Nutch 1.1 release
to get things going
• Dogacan, Enis,
Julien and Andrzej
got interested in
moving Nutchbase
forward
– But took it to the
next level…we’ll get
back to this
• We elected a new
committer
• Julien Nioche
• Patches that had sat for years now
got committed

32. Oh, and Nutch became TLP
• Grabbed folks that were active in Nutch
community
• Decided to move forward with
Nutch/HBase as the de-facto platform
– No need to maintain home-grown storage
formats
– And, take it to the next level, to ORM-ness
• Decided to make Nutch a “delegator”
rather than a workhorse
– In other words…

33. Nutch2: “Delegator”
• Indexing/Querying?
– Solr has a lot of interest and
does tons of work in this area:
let’s use it instead of vanilla Lucene
• Parsing?
– Tika: ditto
• Storage
– Let’s use the ORM layer that some of the
Nutch committers were working on

34. Enter Gora:
“that ORM technology”
• Initially baked up at Github
• Decided to move
to the Incubator in Sept 2010
– I was contacted and asked to
champion the effort
• What is Gora?
– Uses Apache Avro to specify objects and
their schema
– ORM middleware takes Avro specs,
generates Java code – plugs for HBase,
Cassandra, in-memory SQL store, etc.

35. Nutch and Gora
• Throw out all code in Nutch that had to do
with Writeable interface
– Generated now by “Web Page” schema in
Gora
– Web Page is canonical Nutch object for
storage
• Parse text, parse data, etc.
• No more web-db, crawl-db, etc.

36. Out with the old…
• Throw out Nutch
webapp
– Solr provides
REST-ful services
to get at
metadata/index
– We’ll add the REST
(pun) for
storage/etc.
• Throw out Lucene
code • Slowly trash existing Nutch parsers

37. In with the new
• Get rid of webapp
– Nutch 2.x has seen contributions of REST
web services for full crawl cycle, storage I/F
• Delegate indexing to Solr
– Nutch 1.x first appearance of SolrIndexer and
Nutch Solr schema
• Delegate parsing to Tika
– Nutch 1.1 first appearance of parse-tika
– Have been decommissioning existing parsers
• Suggested improvements to Tika during this
process

38. Nutch2 Architecture

39. Learning from our mistakes
• Maintenance
– Checking in jars made the Nutch checkout
huge (even of just the “source”)
• Now using Ivy to manage dependencies
– Patches sitting?
• Not on my watch! Encouragement to find and commit
patches that have been sitting for a while, or simply
disposition them
– People want to use Nutch code as “dep”
• Build now includes ability for RM to push to Maven
Central
NOTE: CHRIS’S OPINION SLIDE

40. Learning from our mistakes
• Community
– Folks contributing patches?
• Make em’ a committer
– Folks providing good testing results?
• Make em’ a committer
– Folks making good documentation?
• Make em’ a committer
– It’s the sign of a healthy Apache project if new
committers (and members) are being elected
NOTE: CHRIS’S OPINION SLIDE

41. Learning from our mistakes
• Configuration of Nutch is hard
– It still is 
– Getting easier though
– Anyone have any great ideas or patches to
integrate with a DI framework?
– Things like GORA, Solr, etc, are making this
easier
• Providing flexible service interfaces beyond
Java APIs
– Existing work on NUTCH-932, NUTCH-931 and
NUTCH-880 is just the beginning

42. Interesting work going on
• I taught a class on Search Engines this
past summer
• Some neat projects that I’m working with
my students to contribute back to Apache
– Implementation of Authority/Hub scoring
– Deduplication improvements
– Clustering plugin improvements
– Work to improve Nutch-Solr-Drupal integration

43. Wrapup
• Nutch has seen tremendous highs and
lows over years
– We’re still kicking
• The newest version of Nutch (2.0) will have
a vastly slimmed down footprint, and will
use existing successful frameworks for
heavy lifting
– Solr, Tika, Gora, Hadoop
• If you’re interested in our dev, check us out
at http://nutch.apache.org

44. Alright, I’ll shut up now
• Any questions?
• THANK YOU!
– mattmann@apache.org
– @chrismattmann on Twitter

45. Acknowledgements
• Nutch team
• Some material inspired from Andrzej
Bialecki’s talks here
• OODT team at JPL