Lucene

1
Lucene Nutch

• Lucene
• Project name
• Started as text index engine
• Nutch
• A complete web search engine, including
• Crawling, indexing, searching
• Index 100M pages, crawl gt10M/day
• Provide distributed architecture
• Written in JAVA
• Other language ports are work-in-progress

2
Lucene

• Open source search project
• http//lucene.apache.org
• Index search local files
• Download lucene-2.2.0.tar.gz from
  http//www.apache.org/dyn/closer.cgi/lucene/java/
• Extract files
• Build an index for a directory
• java org.apache.lucene.demo.IndexFiles dir_path
• Try search at command line
• java org.apache.lucene.demo.SearchFiles

3
Deploy Lucene

• Copy luceneweb.war to your tomcat-home/webapps
• Browse to http//localhost8080/luceneweb
• Tomcat will deploy the web app.
• Edit webapps/luceneweb/configuration.jsp
• Point indexLocationto your indexes
• Search at http//localhost8080/luceneweb

4
Nutch

• A complete search engine http//lucene.apache.org/
  nutch/release/
• Mode
• Intranet/local search
• Internet search
• Usage
• Crawl
• Index
• Search

5
Intranet Search

• Configuration
• Input URLs create a directory and seed file
• mkdir urls
• echo http//www.cs.ucsb.edu gt urls/ucsb
• Edit conf/crawl-urlfilter.txt and replace
  MY.DOMAIN.NAME with cs.ucsb.edu
• Edit conf/nutch-site.xml

6
Intranet Running the Crawl

• Crawl options include
• -dir dir names the directory to put the crawl
  in.
• -threads threads determines the number of
  threads that will fetch in parallel.
• -depth depth indicates the link depth from the
  root page that should be crawled.
• -topN N determines the maximum number of pages
  that will be retrieved at each level up to the
  depth.
• E.g.
• bin/nutch crawl urls -dir crawl -depth 3
  -topN 50

7
Intranet Search

• Deploy nutch war file
• rm -rf TOMCAT_DIR/webapps/ROOT
• cp nutch-0.9.war TOMCAT_DIR/webapps/ROOT.war
• The webapp finds indexes in ./crawl, relative to
  where you start Tomcat
• TOMCAT_DIR/bin/catalina.sh start
• Search at http//localhost8080/
• CS.UCSB domain demo http//hactar.cs.ucsb.edu808
  0

8
Internet Crawling

• Concept
• crawldb all URL info
• linkdb list of known links to each url
• segments each is a set of urls that are fetched
  as a unit
• indexes Lucene-format indexes

9
Internet Crawling Process

1. Get seed URLs
2. Fetch
3. Update crawl DB
4. Compute top URLs, goto 2
5. Create Index
6. Deploy

10
Seed URL

• URLs from the DMOZ Open Directory
• wget http//rdf.dmoz.org/rdf/content.rdf.u8.gz
• gunzip content.rdf.u8.gz
• mkdir dmoz
• bin/nutch org.apache.nutch.tools.DmozParser
  content.rdf.u8 -subset 5000 gt dmoz/urls
• Kids search URL from ask.com
• Inject URLs
• bin/nutch inject kids/crawldb 67k-url/
• Edit conf/nutch-site.xml

11
Fetch

• Generate a fetchlist from the database
• bin/nutch generate kids/crawldb kids/segments
• Save the name of fetchlist in variable s1
• s1ls -d kids/segments/2 tail -1
• Run the fetcher on this segment
• bin/nutch fetch s1

12
Update Crawl DB and Re-fetch

• Update craw db with the results of the fetch
• bin/nutch updatedb kids/crawldb s1
• Generate top-scoring 50K pages
• bin/nutch generate kids/crawldb kids/segments
  -topN 50000
• Refetch
• s1ls -d kids/segments/2 tail -1
• bin/nutch fetch s1

13
Index, Deploy, and Search

• Create inverted index
• bin/nutch invertlinks kids/linkdb kids/segments/
• Index the segments
• bin/nutch index kids/indexes kids/crawldb
  kids/linkdb kids/segments/
• Deploy Search
• Same as in Intranet search
• Demo of 1M pages (570K 500K)?

14
Issues

• Default crawling cycle is 30 days for all URLs
• Duplicates are those have same URL or md5 of page
  content
• JavaScript parser uses regular expression to
  extract URL literals from code.