nutch搜索引擎的搭建以及配置

最近公司需要搭建一个搜索引擎,于是就发现了apache旗下的这个nutch,也看了不少的文章,就在本地搭建了一个进行测试,发现局域网抓取还是比较好的,但是在互联网抓取还是有点问题,像百度、谷歌这些站点的页面基本就抓不到上信息.

nutch搜索引擎的搭建以及配置

实验环境:

   vmware 6.0

   redhat 5.1

软件环境

   apache-tomcat-6.0.29.tar.gz

   nutch-1.0.tar.gz

   jdk-6u21-linux-i586.bin

nutchg简介

Nutch的爬虫抓取网页有两种方式，一种方式是Intranet Crawling，针对的是企业内部网或少量网站，使用的是crawl命令；另一种方式是Whole-web crawling，针对的是整个互联网，使用inject、generate、fetch和updatedb等更底层的命令.本文档介绍Intranet Crawling的基本使用方法.

安装jdk

# cp jdk-6u21-linux-i586.bin  /usr/java

# cd  /usr/java

# chmod +x  jdk-6u21-linux-i586.bin

# ./ jdk-6u21-linux-i586

# vi /etc/profile      //添加如下的java环境变量

JAVA_HOME=/usr/java/jdk1.6.0_21

export JAVA_HOME

PATH=$JAVA_HOME/bin:$PATH

export PATH

CLASSPATH=$JAVA_HOME/lib/tools.jar:$JAVA_HOME/lib/dt.jar:$CLASSPATH

export CLASSPATH

# source /etc/profile     //让java环境变量立即生效

# java -version           //测试java环境是否正常,返回版本信息,就表示jdk安装没有问题

安装tomcat

#  tar zxvf apache-tomcat-6.0.29.tar.gz  -C /usr/local

#  cd /usr/local/

#  mv  apache-tomcat-6.0.29   tomcat

安装nutch

#  tar zxvf nutch-1.0.tar.gz  -C /usr/local

#  cd /usr/local

#  mv nutch-1.0 nutch

#  cd nutch

设置Nutch的环境变量

增加NUTCH_JAVA_HOME变量，并将其值设为JDK的安装目录

NUTCH_JAVA_HOME=/usr/java/jdk1.6.0_21

export NUTCH_JAVA_HOME

Nutch抓取网站页面前的准备工作

在Nutch的安装目录中建立一个名为url.txt的文本文件,文件中写入要抓取网站的顶级网址，即要抓取的起始页.

这里写入国内比较有名的站点

编辑conf/crawl-urlfilter.txt文件，修改MY.DOMAIN.NAME部分:

# accept hosts in MY.DOMAIN.NAME

+^http://([a-z0-9]*\.)*com/

    +^http://([a-z0-9]*\.)*cn/

    +^http://([a-z0-9]*\.)*net/

解决搜索动态内容的问题

  需要注意在conf下面的2个文件：regex-urlfilter.txt，crawl-urlfilter.txt

# skip URLs containing certain characters as probable queries, etc.

   -[?*!@=]

   这段意思是跳过在连接中存在? * ! @ = 的页面，因为默认是跳过所以,在动态页中存在?一般

按照默认的是不能抓取到的.可以在上面2个文件中都修改成：

# skip URLs containing certain characters as probable queries, etc.

    # -[?*!@=]    //前面加上注释.

另外增加允许的一行

    # accept URLs containing certain characters as probable queries, etc.

     +[?=&]

    意思是抓取时候允许抓取连接中带 ? = & 这三个符号的连接

   注意：两个文件都需要修改，因为NUTCH加载规则的顺序是crawl-urlfilter.txt->

     regex-urlfilter.txt

编辑conf/nutch-site.xml文件,在configuration中间加入一下内容

    <property>

        <name>http.agent.name</name>

        <value>sxit  nutch agent</value>

    </property>

    <property>

        <name>http.agent.version</name>

        <value>1.0</value>

    </property>

运行Crawl命令抓取网站内容

/usr/local/nutch/bin/nutch crawl /usr/local/nutch/url.txt  -dir /usr/local/nutch/sxit  -depth 3  -threads 4  >&  /usr/loca/nutch/crawl.log

等待大约一段时间后,程序运行结束.会发现在nutch目录下被创建了一个名为sxit的文件夹,同时还生成一个名为crawl.log的日志文件.利用这一日志文件,我们可以分析可能遇到的任何错误.另外,在上述命令的参数中,dir指定抓取内容所存放的目录,depth表示以要抓取网站顶级网址为起点的爬行深度,threads指定并发的线程数.

使用Tomcat进行搜索测试

将nutch目录的nutch-1.0.war复制到tomcat\webapps下,这里需要启动下tomcat,然后就在webapps下面生成一个nutch-1.0的文件夹,打开 nutch-1.0\WEB-INF\classes下的nutch-site.xml文件,

//由于这里是最新的版本,原来这个配置文件的内容都删掉,添加如下的内容

<?xml version="1.0"?>

<?xml-stylesheet type="text/xsl" href="nutch-conf.xsl"?>

<!-- Put site-specific property overrides in this file. -->

<nutch-conf>

<property>

<name>searcher.dir</name>

<value>/usr/local/nutch/sxit</value>   //这里为刚才抓取内容所存放的目录

</property>

</nutch-conf>

  启动Tomcat，打开浏览器在地址栏中输入：http://IP:8080,/nutch-1.0,就可以看到搜索页面了.、

在文本框中输入关键字,就可以进行搜索了.不过用户在使用时会发现，对于英文单词的搜索一切正常,而当要搜索中文词语时会出现乱码.其实这个问题是Tomcat设置的问题,解决办法是修改tomcat\conf下的server.xml文件，将其中的Connector部分改成如下形式即可：

<Connector port="8080" maxThreads="150" minSpareThreads="25" maxSpareThreads="75"

               enableLookups="false" redirectPort="8443" acceptCount="100"

               connectionTimeout="20000" disableUploadTimeout="true"

               URIEncoding="UTF-8" useBodyEncodingForURI="true" />

nutch的分页功能

# cd /usr/local/apache-tomcat-6.0.29/ webapps/nutch-1.0

# vi search.jsp

查找int hitsPerSite 把=后面的值改成0,

然后在这个jsp文件的末尾增加如下的代码:

<table align="center">

            <tr>

            <td>

                    <%

                        if (start >= hitsPerPage) // more hits to show

                        {

                    %>

                    <form name="pre" action="../search.jsp" method="get">

                        <input type="hidden" name="query" value="<%=htmlQueryString%>">

                        <input type="hidden" name="lang" value="<%=queryLang%>">

                        <input type="hidden" name="start" value="<%=start - hitsPerPage%>">

                        <input type="hidden" name="hitsPerPage" value="<%=hitsPerPage%>">

                        <input type="hidden" name="hitsPerSite" value="<%=hitsPerSite%>">

                        <input type="hidden" name="clustering" value="<%=clustering%>">

                        <input type="submit" value="上一页">

                        <%} %>

                    </form>

                    <%

                    int startnum=1;//页面中最前面的页码编号，我设定（满足）共10页，当页为第6页

                    if((int)(start/hitsPerPage)>=5)

                    startnum=(int)(start/hitsPerPage)-4;

                    for(int i=hitsPerPage*(startnum-1),j=0;i<=hits.getTotal()&&j<=10;)

                    {

                     %>

                     <td>

                     <form name="next" action="../search.jsp" method="get">

                        <input type="hidden" name="query" value="<%=htmlQueryString%>">

                        <input type="hidden" name="lang" value="<%=queryLang%>">

                        <input type="hidden" name="start" value="<%=i%>">

                        <input type="hidden" name="hitsPerPage" value="<%=hitsPerPage%>">

                        <input type="hidden" name="hitsPerSite" value="<%=hitsPerSite%>">

                        <input type="hidden" name="clustering" value="<%=clustering%>">

                        <input type="submit" value="<%=i/hitsPerPage+1 %>">

                    </form>

                    </td>

                    <%

                    i=i+10;  //这里的10是分页显示页面数

                    j++;

                    }

                     %>

                <td>

                    <%

         if ((hits.totalIsExact() && end < hits.getTotal()) // more hits to show

                                || (!hits.totalIsExact() && (hits.getLength() > start

                                + hitsPerPage))) {

                    %>

                    <form name="next" action="../search.jsp" method="get">

                        <input type="hidden" name="query" value="<%=htmlQueryString%>">

                        <input type="hidden" name="lang" value="<%=queryLang%>">

                        <input type="hidden" name="start" value="<%=end%>">

                        <input type="hidden" name="hitsPerPage" value="<%=hitsPerPage%>">

                        <input type="hidden" name="hitsPerSite" value="<%=hitsPerSite%>">

                        <input type="hidden" name="clustering" value="<%=clustering%>">

                        <input type="submit" value="<i18n:message key="next"/>">//下一页

                    </form>

                    <%} %>

     </td>

</tr>

</table>

由于每次都要进行增量抓取,就搞了一个增量抓取的脚本,代码如下:

#!/bin/sh    

depth=5   

threads=5    

RMARGS="-rf"   

MVARGS="--verbose"      

safe=yes    

NUTCH_HOME=/usr/local/nutch           

CATALINA_HOME=/usr/local/apache-tomcat-6.0.29 

if [ -z "$NUTCH_HOME" ]    

then    

  echo runbot: $0 could not find environment variable NUTCH_HOME    

  echo runbot: NUTCH_HOME=$NUTCH_HOME has been set by the script     

else   

  echo runbot: $0 found environment variable NUTCH_HOME=$NUTCH_HOME     

fi    

if [ -z "$CATALINA_HOME" ]    

then    

  echo runbot: $0 could not find environment variable NUTCH_HOME    

  echo runbot: CATALINA_HOME=$CATALINA_HOME has been set by the script     

else   

  echo runbot: $0 found environment variable CATALINA_HOME=$CATALINA_HOME     

fi    

if [ -n "$topN" ]    

then    

  topN="-topN $topN"   

else   

  topN=""   

fi   

steps=8 

echo "----- Inject (Step 1 of $steps) -----"   

$NUTCH_HOME/bin/nutch inject $NUTCH_HOME/sxit/crawldb $NUTCH_HOME/url.txt    

echo "----- Generate, Fetch, Parse, Update (Step 2 o $steps) -----"   

for((i=0; i <= $depth; i++))    

do   

  echo "--- Beginning crawl at depth `expr $i + 1` of $depth ---"   

  $NUTCH_HOME/bin/nutch generate $NUTCH_HOME/sxit/crawldb  $NUTCH_HOME/sxit/segments  

  if [ $? -ne 0 ]    

  then    

    echo "runbot: Stopping at depth $depth. No more URLs to fetcfh."   

    break   

  fi    

  segment=`ls -d $NUTCH_HOME/sxit/segments/* | tail -1`   

  $NUTCH_HOME/bin/nutch fetch $segment -threads $threads    

  if [ $? -ne 0 ]    

  then    

    echo "runbot: fetch $segment at depth `expr $i + 1` failed."   

    echo "runbot: Deleting segment $segment."   

    rm $RMARGS $segment    

    continue   

  fi    

  $NUTCH_HOME/bin/nutch updatedb $NUTCH_HOME/sxit/crawldb  $segment    

done    

echo "----- Merge Segments (Step 3 of $steps) -----"      

$NUTCH_HOME/bin/nutch mergesegs $NUTCH_HOME/sxit/MERGEDsegments $NUTCH_HOME/sxit/segments/*    

mv $MVARGS $NUTCH_HOME/sxit/segments $NUTCH_HOME/sxit/BACKUPsegments    

mkdir $NUTCH_HOME/sxit/segments    

mv $MVARGS $NUTCH_HOME/sxit/MERGEDsegments/* $NUTCH_HOME/sxit/segments    

rm $RMARGS $NUTCH_HOME/sxit/MERGEDsegments    

echo "----- Invert Links (Step 4 of $steps) -----"   

$NUTCH_HOME/bin/nutch invertlinks $NUTCH_HOME/sxit/linkdb $NUTCH_HOME/sxit/segments/*    

echo "----- Index (Step 5 of $steps) -----"   

$NUTCH_HOME/bin/nutch index $NUTCH_HOME/sxit/NEWindexes $NUTCH_HOME/sxit/crawldb $NUTCH_HOME/sxit/linkdb $NUTCH_HOME/sxit/segments/*     

echo "----- Dedup (Step 6 of $steps) -----"   

$NUTCH_HOME/bin/nutch dedup $NUTCH_HOME/sxit/NEWindexes    

echo "----- Merge Indexes (Step 7 of $steps) -----"   

$NUTCH_HOME/bin/nutch merge $NUTCH_HOME/sxit/NEWindex $NUTCH_HOME/sxit/NEWindexes    

echo "----- Loading New Index (Step 8 of $steps) -----"   

tom_pid=`ps aux |awk '/usr\/local\/apache-tomcat-6.0.29/ {print $2}'` 

`kill -9 $tom_pid` 

if [ "$safe" != "yes" ]    

then    

  rm $RMARGS $NUTCH_HOME/sxit/NEWindexes    

  rm $RMARGS $NUTCH_HOME/sxit/index

else   

  mv $MVARGS $NUTCH_HOME/sxit/NEWindexes $NUTCH_HOME/sxit/indexes 

  mv $MVARGS $NUTCH_HOME/sxit/NEWindex   $NUTCH_HOME/sxit/index    

fi  

${CATALINA_HOME}/bin/startup.sh    

echo "runbot: FINISHED: Crawl completed!"   

echo ""