nutch搜索引擎的搭建以及配置

最近公司須要搭建一個搜索引擎,因而就發現了apache旗下的這個nutch,也看了很多的文章,就在本地搭建了一個進行測試,發現局域網抓取仍是比較好的,可是在互聯網抓取仍是有點問題,像百度、谷歌這些站點的頁面基本就抓不到上信息.

nutch搜索引擎的搭建以及配置

實驗環境:

   vmware 6.0

   redhat 5.1

軟件環境

   apache-tomcat-6.0.29.tar.gz

   nutch-1.0.tar.gz

   jdk-6u21-linux-i586.bin

nutchg簡介

Nutch的爬蟲抓取網頁有兩種方式，一種方式是Intranet Crawling，針對的是企業內部網或少許網站，使用的是crawl命令；另外一種方式是Whole-web crawling，針對的是整個互聯網，使用inject、generate、fetch和updatedb等更底層的命令.本文檔介紹Intranet Crawling的基本使用方法.

安裝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      //添加以下的java環境變量

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     //讓java環境變量當即生效

# java -version           //測試java環境是否正常,返回版本信息,就表示jdk安裝沒有問題

安裝tomcat

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

#  cd /usr/local/

#  mv  apache-tomcat-6.0.29   tomcat

安裝nutch

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

#  cd /usr/local

#  mv nutch-1.0 nutch

#  cd nutch

設置Nutch的環境變量

增長NUTCH_JAVA_HOME變量，並將其值設爲JDK的安裝目錄

NUTCH_JAVA_HOME=/usr/java/jdk1.6.0_21

export NUTCH_JAVA_HOME

Nutch抓取網站頁面前的準備工做

在Nutch的安裝目錄中創建一個名爲url.txt的文本文件,文件中寫入要抓取網站的頂級網址，即要抓取的起始頁.

這裏寫入國內比較有名的站點

編輯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/

解決搜索動態內容的問題

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

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

   -[?*!@=]

   這段意思是跳過在鏈接中存在? * ! @ = 的頁面，由於默認是跳過因此,在動態頁中存在?通常

按照默認的是不能抓取到的.能夠在上面2個文件中都修改爲：

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

    # -[?*!@=]    //前面加上註釋.

另外增長容許的一行

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

     +[?=&]

    意思是抓取時候容許抓取鏈接中帶 ? = & 這三個符號的鏈接

   注意：兩個文件都須要修改，由於NUTCH加載規則的順序是crawl-urlfilter.txt->

     regex-urlfilter.txt

編輯conf/nutch-site.xml文件,在configuration中間加入一下內容

    <property>

        <name>http.agent.name</name>

        <value>sxit  nutch agent</value>

    </property>

    <property>

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

        <value>1.0</value>

    </property>

運行Crawl命令抓取網站內容

/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

等待大約一段時間後,程序運行結束.會發如今nutch目錄下被建立了一個名爲sxit的文件夾,同時還生成一個名爲crawl.log的日誌文件.利用這一日誌文件,咱們能夠分析可能遇到的任何錯誤.另外,在上述命令的參數中,dir指定抓取內容所存放的目錄,depth表示以要抓取網站頂級網址爲起點的爬行深度,threads指定併發的線程數.

使用Tomcat進行搜索測試

將nutch目錄的nutch-1.0.war複製到tomcat\webapps下,這裏須要啓動下tomcat,而後就在webapps下面生成一個nutch-1.0的文件夾,打開 nutch-1.0\WEB-INF\classes下的nutch-site.xml文件,

//因爲這裏是最新的版本,原來這個配置文件的內容都刪掉,添加以下的內容

<?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>   //這裏爲剛纔抓取內容所存放的目錄

</property>

</nutch-conf>

  啓動Tomcat，打開瀏覽器在地址欄中輸入：http://IP:8080,/nutch-1.0,就能夠看到搜索頁面了.、

在文本框中輸入關鍵字,就能夠進行搜索了.不過用戶在使用時會發現，對於英文單詞的搜索一切正常,而當要搜索中文詞語時會出現亂碼.其實這個問題是Tomcat設置的問題,解決辦法是修改tomcat\conf下的server.xml文件，將其中的Connector部分改爲以下形式便可：

<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的分頁功能

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

# vi search.jsp

查找int hitsPerSite 把=後面的值改爲0,

而後在這個jsp文件的末尾增長以下的代碼:

<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="上一頁">

                        <%} %>

                    </form>

                    <%

                    int startnum=1;//頁面中最前面的頁碼編號，我設定（知足）共10頁，當頁爲第6頁

                    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;  //這裏的10是分頁顯示頁面數

                    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"/>">//下一頁

                    </form>

                    <%} %>

     </td>

</tr>

</table>

因爲每次都要進行增量抓取,就搞了一個增量抓取的腳本,代碼以下:

#!/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 ""