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Lessons Learned in the Development of a Web-scale Search Engine: Nutch2 and beyond

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My ApacheconNA 2010 presentation on Nutch: its history, and l

My ApacheconNA 2010 presentation on Nutch: its history, and l

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Lessons Learned in the Development of a Web-scale Search Engine: Nutch2 and beyond Lessons Learned in the Development of a Web-scale Search Engine: Nutch2 and beyond Presentation Transcript

  • 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
  • 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?
  • 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/Engineering Prof at USC
  • 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.
  • 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
  • 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)
  • 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
  • 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
  • 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
  • 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
  • Nutch’s Architecture
    • Nutch Core facilities
      • Parsing
      • Indexing
      • Crawling
      • Content Acquisition
      • Querying
      • Plugin Framework
    • Nutch’s extension points
      • Scoring, Parsing, Indexing, Querying, URLFiltering
  • Nutch’s Architecture Maps to Search engine architecture proposed by Brin & Page
  • 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?
  • 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
  • PDS Google-like Search Architecture Credit: D. Crichton, S. Hughes, P. Ramirez, R. Joyner, S. Hardman, C. Mattmann 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
  • 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
  • Search Interface
  • Results
  • 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
  • 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
  • The Big Yellow Elephant
    • Before this guy was born
    • Lots of folks interested in Nutch
    Hadoop is born (January 2008) Credit: svnsearch.org
  • 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
  • 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!
  • 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
    ?
  • 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
  • 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
  • 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
  • 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
    +
  • 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)
  • 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?
  • 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
  • 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…
  • 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
  • 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.
  • 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.
  • 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
  • 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
  • Nutch2 Architecture
  • 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
  • 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
  • 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
  • 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
  • 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
  • Alright, I’ll shut up now
    • Any questions?
    • THANK YOU!
      • [email_address]
      • @chrismattmann on Twitter
  • Acknowledgements
    • Nutch team
    • Some material inspired from Andrzej Bialecki’s talks here
    • OODT team at JPL