Nutch 1.3 学习笔记1
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1. Nutch是什么?
Nutch是一个开源的网页抓取工具，主要用于收集网页数据，然后对其进行分析，建立索引，以提供相应的接口来对其网页数据进行查询的一套工具。其底层使用了Hadoop来做分布式计算与存储，索引使用了Solr分布式索引框架来做，Solr是一个开源的全文索引框架，从Nutch 1.3开始，其集成了这个索引架构2. 在哪里要可以下载到最新的Nutch?
在下面地址中可以下载到最新的Nutch 1.3二进制包和源代码http://mirror.bjtu.edu.cn/apache//nutch/
3. 如何配置Nutch?
3.1 对下载后的压缩包进行解压，然后cd $HOME/nutch-1.3/runtime/local
3.2 配置bin/nutch这个文件的权限，使用chmod +x bin/nutch
3.3 配置JAVA_HOME，使用export JAVA_HOME=$PATH
4. 抓取前要做什么准备工作?
4.1 配置http.agent.name这个属性，如下<property> <name>http.agent.name</name> <value>My Nutch Spider</value> </property>
4.2 建立一个地址目录,mkdir -p urls
在这个目录中建立一个url文件，写上一些url，如http://nutch.apache.org/
4.3 然后运行如下命令
bin/nutch crawl urls -dir crawl -depth 3 -topN 5
注意，这里是不带索引的，如果要对抓取的数据建立索引，运行如下命令
bin/nutch crawl urls -solr http://localhost:8983/solr/ -depth 3 -topN 5
5. Nutch的抓取流程是什么样子的？
5.1 初始化crawlDb，注入初始url
bin/nutch inject Usage: Injector <crawldb> <url_dir>
在我本地运行这个命令后的输出结果如下：
lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ bin/nutch inject db/crawldb urls/
Injector: starting at 2011-08-22 10:50:01
Injector: crawlDb: db/crawldb
Injector: urlDir: urls
Injector: Converting injected urls to crawl db entries.
Injector: Merging injected urls into crawl db.
Injector: finished at 2011-08-22 10:50:05, elapsed: 00:00:035.2 产生新的抓取urls
bin/nutch generate
Usage: Generator <crawldb> <segments_dir> [-force] [-topN N] [-numFetchers numFetchers] [-adddays numDays] [-noFilter] [-noNorm][-maxNumSegments num]本机输出结果如下：
lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ bin/nutch generate db/crawldb/ db/segments
Generator: starting at 2011-08-22 10:52:41
Generator: Selecting best-scoring urls due for fetch.
Generator: filtering: true
Generator: normalizing: true
Generator: jobtracker is 'local', generating exactly one partition.
Generator: Partitioning selected urls for politeness.
Generator: segment: db/segments/20110822105243 // 这里会产生一个新的segment
Generator: finished at 2011-08-22 10:52:44, elapsed: 00:00:035.3 对上面产生的url进行抓取
bin/nutch fetch
Usage: Fetcher <segment> [-threads n] [-noParsing]
这里是本地的输出结果：
lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ bin/nutch fetch db/segments/20110822105243/
Fetcher: Your 'http.agent.name' value should be listed first in 'http.robots.agents' property.
Fetcher: starting at 2011-08-22 10:56:07
Fetcher: segment: db/segments/20110822105243
Fetcher: threads: 10
QueueFeeder finished: total 1 records + hit by time limit :0
fetching http://www.baidu.com/
-finishing thread FetcherThread, activeThreads=1
-finishing thread FetcherThread, activeThreads=
-finishing thread FetcherThread, activeThreads=1
-finishing thread FetcherThread, activeThreads=1
-finishing thread FetcherThread, activeThreads=0
-activeThreads=0, spinWaiting=0, fetchQueues.totalSize=0
-activeThreads=0
Fetcher: finished at 2011-08-22 10:56:09, elapsed: 00:00:02我们来看一下这里的segment目录结构
lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ ls db/segments/20110822105243/
content crawl_fetch crawl_generate5.4 对上面的结果进行解析
bin/nutch parse Usage: ParseSegment segment
本机输出结果：
lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ bin/nutch parse db/segments/20110822105243/ ParseSegment: starting at 2011-08-22 10:58:19 ParseSegment: segment: db/segments/20110822105243 ParseSegment: finished at 2011-08-22 10:58:22, elapsed: 00:00:02
我们再来看一下解析后的目录结构
lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ ls db/segments/20110822105243/ content crawl_fetch crawl_generate crawl_parse parse_data parse_text
这里多了三个解析后的目录。
5.5 更新外链接数据库
bin/nutch updatedb
Usage: CrawlDb <crawldb> (-dir <segments> | <seg1> <seg2> ...) [-force] [-normalize] [-filter] [-noAdditions]本机输出结果：
lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ bin/nutch updatedb db/crawldb/ -dir db/segments/ CrawlDb update: starting at 2011-08-22 11:00:09 CrawlDb update: db: db/crawldb CrawlDb update: segments: [file:/home/lemo/Workspace/java/Apache/Nutch/nutch-1.3/db/segments/20110822105243] CrawlDb update: additions allowed: true CrawlDb update: URL normalizing: false CrawlDb update: URL filtering: false CrawlDb update: Merging segment data into db. CrawlDb update: finished at 2011-08-22 11:00:10, elapsed: 00:00:01
这时它会更新crawldb链接库，这里是放在文件系统中的，像taobao抓取程序的链接库是用redis来做的，一种key-value形式的NoSql数据库。
5.6 计算反向链接
bin/nutch invertlinks Usage: LinkDb <linkdb> (-dir <segmentsDir> | <seg1> <seg2> ...) [-force] [-noNormalize] [-noFilter]
本地输出结果：
lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ bin/nutch invertlinks db/linkdb -dir db/segments/ LinkDb: starting at 2011-08-22 11:02:49 LinkDb: linkdb: db/linkdb LinkDb: URL normalize: true LinkDb: URL filter: true LinkDb: adding segment: file:/home/lemo/Workspace/java/Apache/Nutch/nutch-1.3/db/segments/20110822105243 LinkDb: finished at 2011-08-22 11:02:50, elapsed: 00:00:01
5.7 使用Solr为抓取的内容建立索引
bin/nutch solrindex
Usage: SolrIndexer <solr url> <crawldb> <linkdb> (<segment> ... | -dir <segments>
Nutch端的输出如下：
lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ bin/nutch solrindex http://127.0.0.1:8983/solr/ db/crawldb/ db/linkdb/ db/segments/*SolrIndexer: starting at 2011-08-22 11:05:33SolrIndexer: finished at 2011-08-22 11:05:35, elapsed: 00:00:02
Solr端的部分输出如下：
INFO: SolrDeletionPolicy.onInit: commits:num=1
commit{dir=/home/lemo/Workspace/java/Apache/Solr/apache-solr-3.3.0/example/solr/data/index,segFN=segments_1,version=1314024228223,generation=1,filenames=[segments_1]
Aug 22, 2011 11:05:35 AM org.apache.solr.core.SolrDeletionPolicy updateCommits
INFO: newest commit = 1314024228223
Aug 22, 2011 11:05:35 AM org.apache.solr.update.processor.LogUpdateProcessor finish
INFO: {add=[http://www.baidu.com/]} 0 183
Aug 22, 2011 11:05:35 AM org.apache.solr.core.SolrCore execute
INFO: [] webapp=/solr path=/update params={wt=javabin&version=2} status=0 QTime=183
Aug 22, 2011 11:05:35 AM org.apache.solr.update.DirectUpdateHandler2 commit
INFO: start commit(optimize=false,waitFlush=true,waitSearcher=true,expungeDeletes=false)5.8 在Solr的客户端查询
在浏览器中输入
http://localhost:8983/solr/admin/
查询条件为baidu
输出的XML结构为
如果你要以HTML结构显示把Solr的配置文件solrconfig.xml中的content改为如下就可以
<field name="content" type="text" stored="true" indexed="true"/>
<response>
<lst name="responseHeader">
<int name="status">0</int>
<int name="QTime">0</int>
<lst name="params">
<str name="indent">on</str>
<str name="start">0</str>
<str name="q">baidu</str>
<str name="version">2.2</str>
<str name="rows">10</str>
</lst>
</lst>
<result name="response" numFound="1" start="0">
<doc>
<float name="boost">1.0660036</float>
<str name="digest">7be5cfd6da4a058001300b21d7d96b0f</str>
<str name="id">http://www.baidu.com/</str>
<str name="segment">20110822105243</str>
<str name="title">百度一下，你就知道</str>
<date name="tstamp">2011-08-22T14:56:09.194Z</date>
<str name="url">http://www.baidu.com/</str>
</doc>
</result>
</response>
6 参考
http://wiki.apache.org/nutch/RunningNutchAndSolr
最后
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