Introduction to Nutch

Zhao Dongsheng2008.9.29

Summary

What's Nutch Nutch's architecture How to use Nutch About the first homework

What's Nutch

Written in java Open-source project An Application that can build SE Behind a lot of web sites

What's Nutch Lucene and Nutch Nutch grow out of Lucene Both open-source project Both written in java But Lucene is a Java library for

text indexing and search Nutch is an Application Nutch uses lucene for indexing

Nutch's architecture

Nutch's core components Fecher

Requests web pages Parses and extracts links

Web DB Page DB

Used for fetch sheduling Link DB

Store link gragh Store anchor text with each link Link-analysis and Anchor text indexing

Nutch's core components (cont.)

Indexer Creates inverted index Uses Lucene

Searcher Finds relelant docs quickly Ranks the docs Summarizing

Functions Nutch supports Politeness when crawling Duplicates removing PageRank analysis Distributed searching Summarizing ......

Nutch's Technical Goals Fetch several billion pages per month Maintain an index of these pages Search that index up to 1000 times per

second Provide very high quality search results Operate at minimal cost

Source code & API Source Dirs

analysis crawl html plugin scoring segment tools fetcher indexer net parse protocol searcher ...

crawl/Crawl.java fetcher/Fetcher.java

How to use Nutch Download & unpack

Nutch required JVM Set environment variables

Configure Specify root URLs Specify URLs filters Optionally specify

Number of threads Levels to crawl Fetch delay

How to use Nutch (cont.) Root URLs Example

http://www.pku.edu.cn URL Filter Example

crawl-urlfilter.txt -^(file|ftp|mailto): -\.(gif|GIF|jpg|JPG|png|PNG|ico|ICO|css|sit|eps|

wmf|zip|ppt|mpg|xls|gz|rpm|tgz|mov|MOV|exe|jpeg|JPEG|bmp|BMP)$

-[?*!@=] +^http://([a-z0-9]*\.)*pku.edu.cn/

How to use Nutch (cont.) Run Nutch

Just a command line bin/nutch crawl myurl.txt -dir mycrawl -

depth 4 >& crawl.log Use Tomcat to experience!

Home page

Search result

Score Explanation

Anchor texts with a link

About the first Homework About web crawling Familiar with Nutch & java Fetch blog/bbs etc ? Need your advice!

Q & Athanks!