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Introduction to Nutch Zhao Dongsheng 2008.9.29 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|JPE G|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&A thanks!