Apache Nutch（一）

Nutch 当前两个版本 ：

• 1.6 - Nutch1.6使用Hadoop Distributed File System (HDFS)来作为存储，稳定可靠。
• 2.1 - 通过gora对存储层进行了扩展，可以选择使用HBase、Accumulo、Cassandra 、MySQL 、DataFileAvroStore、AvroStore中任何一种来存储数据，但其中一些并不成熟。

在Linux（Centos）上搭建 Nutch 框架：

1. 安装 svn
   

   yum install subversion

2. 安装 ant
   

   yum install ant

3. check out nutch（进入 http://nutch.apache.org ，在 Version Control 板块可查看到svn地址。）
   

   svn co https://svn.apache.org/repos/asf/nutch/tags/release-1.6/

4. ant 构建 nutch
   

   cd release-1.6/
   
   ant

ant 构建完成之后，在 release-1.6 目录下生成两个目录 ：build、runtime，进入 runtime ，有两个子文件夹 ：deploy、local，分别代表了nutch两种运行方式 ：

• deploy - hadoop 运行
• local - 本地文件系统运行，只能有一个Map和Reduce。

local/bin/nutch ：分析nutch脚本是入门的重点，可以看到通过 nutch 脚本连接Hadoop与Nutch，把apache-nutch-1.6.job提交给Hadoop的JobTracker；同时也可以看到在命令中所指定的是哪个Java类。

Nutch 脚本

#!/bin/bash

#

# Licensed to the Apache Software Foundation (ASF) under one or more

# contributor license agreements.  See the NOTICE file distributed with

# this work for additional information regarding copyright ownership.

# The ASF licenses this file to You under the Apache License, Version 2.0

# (the "License"); you may not use this file except in compliance with

# the License.  You may obtain a copy of the License at

#

#     http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

# 

# The Nutch command script

#

# Environment Variables

#

#   NUTCH_JAVA_HOME The java implementation to use.  Overrides JAVA_HOME.

#

#   NUTCH_HEAPSIZE  The maximum amount of heap to use, in MB. 

#                   Default is 1000.

#

#   NUTCH_OPTS      Extra Java runtime options.

#

cygwin=false

case "`uname`" in

CYGWIN*) cygwin=true;;

esac



# resolve links - $0 may be a softlink

THIS="$0"

while [ -h "$THIS" ]; do

  ls=`ls -ld "$THIS"`

  link=`expr "$ls" : '.*-> \(.*\)$'`

  if expr "$link" : '.*/.*' > /dev/null; then

    THIS="$link"

  else

    THIS=`dirname "$THIS"`/"$link"

  fi

done



# if no args specified, show usage

if [ $# = 0 ]; then

  echo "Usage: nutch COMMAND"

  echo "where COMMAND is one of:"

  echo "  crawl             one-step crawler for intranets (DEPRECATED - USE CRAWL SCRIPT INSTEAD)"

  echo "  readdb            read / dump crawl db"

  echo "  mergedb           merge crawldb-s, with optional filtering"

  echo "  readlinkdb        read / dump link db"

  echo "  inject            inject new urls into the database"

  echo "  generate          generate new segments to fetch from crawl db"

  echo "  freegen           generate new segments to fetch from text files"

  echo "  fetch             fetch a segment's pages"

  echo "  parse             parse a segment's pages"

  echo "  readseg           read / dump segment data"

  echo "  mergesegs         merge several segments, with optional filtering and slicing"

  echo "  updatedb          update crawl db from segments after fetching"

  echo "  invertlinks       create a linkdb from parsed segments"

  echo "  mergelinkdb       merge linkdb-s, with optional filtering"

  echo "  solrindex         run the solr indexer on parsed segments and linkdb"

  echo "  solrdedup         remove duplicates from solr"

  echo "  solrclean         remove HTTP 301 and 404 documents from solr"

  echo "  parsechecker      check the parser for a given url"

  echo "  indexchecker      check the indexing filters for a given url"

  echo "  domainstats       calculate domain statistics from crawldb"

  echo "  webgraph          generate a web graph from existing segments"

  echo "  linkrank          run a link analysis program on the generated web graph"

  echo "  scoreupdater      updates the crawldb with linkrank scores"

  echo "  nodedumper        dumps the web graph's node scores"

  echo "  plugin            load a plugin and run one of its classes main()"

  echo "  junit             runs the given JUnit test"

  echo " or"

  echo "  CLASSNAME         run the class named CLASSNAME"

  echo "Most commands print help when invoked w/o parameters."

  exit 1

fi



# get arguments

COMMAND=$1

shift



# some directories

THIS_DIR=`dirname "$THIS"`

NUTCH_HOME=`cd "$THIS_DIR/.." ; pwd`



# some Java parameters

if [ "$NUTCH_JAVA_HOME" != "" ]; then

  #echo "run java in $NUTCH_JAVA_HOME"

  JAVA_HOME=$NUTCH_JAVA_HOME

fi

  

if [ "$JAVA_HOME" = "" ]; then

  echo "Error: JAVA_HOME is not set."

  exit 1

fi



local=true



# NUTCH_JOB 

if [ -f ${NUTCH_HOME}/*nutch*.job ]; then

    local=false

  for f in $NUTCH_HOME/*nutch*.job; do

    NUTCH_JOB=$f;

  done

fi



# cygwin path translation

if $cygwin; then

  NUTCH_JOB=`cygpath -p -w "$NUTCH_JOB"`

fi



JAVA=$JAVA_HOME/bin/java

JAVA_HEAP_MAX=-Xmx1000m 



# check envvars which might override default args

if [ "$NUTCH_HEAPSIZE" != "" ]; then

  #echo "run with heapsize $NUTCH_HEAPSIZE"

  JAVA_HEAP_MAX="-Xmx""$NUTCH_HEAPSIZE""m"

  #echo $JAVA_HEAP_MAX

fi



# CLASSPATH initially contains $NUTCH_CONF_DIR, or defaults to $NUTCH_HOME/conf

CLASSPATH=${NUTCH_CONF_DIR:=$NUTCH_HOME/conf}

CLASSPATH=${CLASSPATH}:$JAVA_HOME/lib/tools.jar



# so that filenames w/ spaces are handled correctly in loops below

IFS=



# add libs to CLASSPATH

if $local; then

  for f in $NUTCH_HOME/lib/*.jar; do

   CLASSPATH=${CLASSPATH}:$f;

  done

  # local runtime

  # add plugins to classpath

  if [ -d "$NUTCH_HOME/plugins" ]; then

     CLASSPATH=${NUTCH_HOME}:${CLASSPATH}

  fi

fi



# cygwin path translation

if $cygwin; then

  CLASSPATH=`cygpath -p -w "$CLASSPATH"`

fi



# setup 'java.library.path' for native-hadoop code if necessary

# used only in local mode 

JAVA_LIBRARY_PATH=''

if [ -d "${NUTCH_HOME}/lib/native" ]; then

  JAVA_PLATFORM=`CLASSPATH=${CLASSPATH} ${JAVA} org.apache.hadoop.util.PlatformName | sed -e 's/ /_/g'`

  

  if [ -d "${NUTCH_HOME}/lib/native" ]; then

    if [ "x$JAVA_LIBRARY_PATH" != "x" ]; then

      JAVA_LIBRARY_PATH=${JAVA_LIBRARY_PATH}:${NUTCH_HOME}/lib/native/${JAVA_PLATFORM}

    else

      JAVA_LIBRARY_PATH=${NUTCH_HOME}/lib/native/${JAVA_PLATFORM}

    fi

  fi

fi



if [ $cygwin = true -a "X${JAVA_LIBRARY_PATH}" != "X" ]; then

  JAVA_LIBRARY_PATH=`cygpath -p -w "$JAVA_LIBRARY_PATH"`

fi



# restore ordinary behaviour

unset IFS



# default log directory & file

if [ "$NUTCH_LOG_DIR" = "" ]; then

  NUTCH_LOG_DIR="$NUTCH_HOME/logs"

fi

if [ "$NUTCH_LOGFILE" = "" ]; then

  NUTCH_LOGFILE='hadoop.log'

fi



#Fix log path under cygwin

if $cygwin; then

  NUTCH_LOG_DIR=`cygpath -p -w "$NUTCH_LOG_DIR"`

fi



NUTCH_OPTS="$NUTCH_OPTS -Dhadoop.log.dir=$NUTCH_LOG_DIR"

NUTCH_OPTS="$NUTCH_OPTS -Dhadoop.log.file=$NUTCH_LOGFILE"



if [ "x$JAVA_LIBRARY_PATH" != "x" ]; then

  NUTCH_OPTS="$NUTCH_OPTS -Djava.library.path=$JAVA_LIBRARY_PATH"

fi



# figure out which class to run

if [ "$COMMAND" = "crawl" ] ; then

  CLASS=org.apache.nutch.crawl.Crawl

elif [ "$COMMAND" = "inject" ] ; then

  CLASS=org.apache.nutch.crawl.Injector

elif [ "$COMMAND" = "generate" ] ; then

  CLASS=org.apache.nutch.crawl.Generator

elif [ "$COMMAND" = "freegen" ] ; then

  CLASS=org.apache.nutch.tools.FreeGenerator

elif [ "$COMMAND" = "fetch" ] ; then

  CLASS=org.apache.nutch.fetcher.Fetcher

elif [ "$COMMAND" = "parse" ] ; then

  CLASS=org.apache.nutch.parse.ParseSegment

elif [ "$COMMAND" = "readdb" ] ; then

  CLASS=org.apache.nutch.crawl.CrawlDbReader

elif [ "$COMMAND" = "mergedb" ] ; then

  CLASS=org.apache.nutch.crawl.CrawlDbMerger

elif [ "$COMMAND" = "readlinkdb" ] ; then

  CLASS=org.apache.nutch.crawl.LinkDbReader

elif [ "$COMMAND" = "readseg" ] ; then

  CLASS=org.apache.nutch.segment.SegmentReader

elif [ "$COMMAND" = "mergesegs" ] ; then

  CLASS=org.apache.nutch.segment.SegmentMerger

elif [ "$COMMAND" = "updatedb" ] ; then

  CLASS=org.apache.nutch.crawl.CrawlDb

elif [ "$COMMAND" = "invertlinks" ] ; then

  CLASS=org.apache.nutch.crawl.LinkDb

elif [ "$COMMAND" = "mergelinkdb" ] ; then

  CLASS=org.apache.nutch.crawl.LinkDbMerger

elif [ "$COMMAND" = "solrindex" ] ; then

  CLASS=org.apache.nutch.indexer.solr.SolrIndexer

elif [ "$COMMAND" = "solrdedup" ] ; then

  CLASS=org.apache.nutch.indexer.solr.SolrDeleteDuplicates

elif [ "$COMMAND" = "solrclean" ] ; then

  CLASS=org.apache.nutch.indexer.solr.SolrClean

elif [ "$COMMAND" = "parsechecker" ] ; then

  CLASS=org.apache.nutch.parse.ParserChecker

elif [ "$COMMAND" = "indexchecker" ] ; then

  CLASS=org.apache.nutch.indexer.IndexingFiltersChecker

elif [ "$COMMAND" = "domainstats" ] ; then 

  CLASS=org.apache.nutch.util.domain.DomainStatistics

elif [ "$COMMAND" = "webgraph" ] ; then

  CLASS=org.apache.nutch.scoring.webgraph.WebGraph

elif [ "$COMMAND" = "linkrank" ] ; then

  CLASS=org.apache.nutch.scoring.webgraph.LinkRank

elif [ "$COMMAND" = "scoreupdater" ] ; then

  CLASS=org.apache.nutch.scoring.webgraph.ScoreUpdater

elif [ "$COMMAND" = "nodedumper" ] ; then

  CLASS=org.apache.nutch.scoring.webgraph.NodeDumper

elif [ "$COMMAND" = "plugin" ] ; then

  CLASS=org.apache.nutch.plugin.PluginRepository

elif [ "$COMMAND" = "junit" ] ; then

  CLASSPATH=$CLASSPATH:$NUTCH_HOME/test/classes/

  CLASS=junit.textui.TestRunner

else

  CLASS=$COMMAND

fi



# distributed mode

EXEC_CALL="hadoop jar $NUTCH_JOB"



if $local; then

 EXEC_CALL="$JAVA $JAVA_HEAP_MAX $NUTCH_OPTS -classpath $CLASSPATH"

else

 # check that hadoop can be found on the path

 if [ $(which hadoop | wc -l ) -eq 0 ]; then

    echo "Can't find Hadoop executable. Add HADOOP_HOME/bin to the path or run in local mode."

    exit -1;

 fi

fi



# run it

exec $EXEC_CALL $CLASS "$@"

nutch 的所有参数

[root@localhost local]# bin/nutch 

Usage: nutch COMMAND

where COMMAND is one of:

  crawl             one-step crawler for intranets (DEPRECATED - USE CRAWL SCRIPT INSTEAD)

  readdb            read / dump crawl db

  mergedb           merge crawldb-s, with optional filtering

  readlinkdb        read / dump link db

  inject            inject new urls into the database

  generate          generate new segments to fetch from crawl db

  freegen           generate new segments to fetch from text files

  fetch             fetch a segment's pages

  parse             parse a segment's pages

  readseg           read / dump segment data

  mergesegs         merge several segments, with optional filtering and slicing

  updatedb          update crawl db from segments after fetching

  invertlinks       create a linkdb from parsed segments

  mergelinkdb       merge linkdb-s, with optional filtering

  solrindex         run the solr indexer on parsed segments and linkdb

  solrdedup         remove duplicates from solr

  solrclean         remove HTTP 301 and 404 documents from solr

  parsechecker      check the parser for a given url

  indexchecker      check the indexing filters for a given url

  domainstats       calculate domain statistics from crawldb

  webgraph          generate a web graph from existing segments

  linkrank          run a link analysis program on the generated web graph

  scoreupdater      updates the crawldb with linkrank scores

  nodedumper        dumps the web graph's node scores

  plugin            load a plugin and run one of its classes main()

  junit             runs the given JUnit test

 or

  CLASSNAME         run the class named CLASSNAME

Most commands print help when invoked w/o parameters.

[root@localhost local]# bin/nutch crawl

Usage: Crawl <urlDir> -solr <solrURL> [-dir d] [-threads n] [-depth i] [-topN N]

参数的意义：

• urlDir - 种子url的目录地址
• -solr - <solrUrl>为solr的地址（如果没有则为空）
• -dir - 保存爬取文件的目录
• -threads - 爬取线程数量（默认10）
• -depth - 爬取深度 (默认5）
• -topN - 访问的广度 （默认是Long.max)

配置 local/conf/nutch-site.xml

Nutch 的提高在于研读nutch-default.xml中每一个配置的实际含义，需要结合源代码理解。打开 local/conf/nutch-default.xml，找到 ：

<property>

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

  <value></value>

  <description>HTTP 'User-Agent' request header. MUST NOT be empty - 

  please set this to a single word uniquely related to your organization.



  NOTE: You should also check other related properties:



    http.robots.agents

    http.agent.description

    http.agent.url

    http.agent.email

    http.agent.version



  and set their values appropriately.



  </description>

</property>

将以上配置复制到 nutch-site.xml 的 <configuration></configuration> 中，http.agent.name 的value值（<value></value>）是基于浏览器的User-Agent（ 用户代理 ），它是一个特殊字符串头，使得服务器能够识别客户使用的操作系统及版本、CPU 类型、浏览器及版本、浏览器渲染引擎、浏览器语言、浏览器插件等，如：Opera/9.80 (Windows NT 5.1; Edition IBIS) Presto/2.12.388 Version/12.15。这个是Nutch服从Robot协议，所以要改。

添加种子url

在local目录下建文件夹如urls，在urls里面建文件如url，里面加入你要爬取的网站的入口url，如 ：http://www.163.com/

配置local/conf/regex-urlfilter.txt

打开local/conf/regex-urlfilter.txt，注释掉最后一行，并添上你要抓取的网站的域名 ：

# skip URLs with slash-delimited segment that repeats 3+ times, to break loops

-.*(/[^/]+)/[^/]+\1/[^/]+\1/



# accept anything else

# +.

+^http://([a-z0-9]*\.)*163\.com/

现在就可以爬取163所有的网页了， 在local目录下新建文件夹data，保存爬取内容，选择合适的参数：

nohup bin/nutch crawl urls -dir data &

nohup 命令将把输出的信息附加到的 nohup.out 文件中；在执行 nutch 会把爬虫的记录生成到 local/logs/hadoop.log

在爬取完成后，在 data 的文件夹下会有三个文件夹crawldb、linkdb、segments ：

• crawldb - 是所有需要爬取的超链接
• Linkdb - 存放的是所有超连接及其每个连接的链入地址和锚文本
• segments - 存放的是抓取的页面，以爬取的时间命名，个数不多于爬取的深度，Nutch的爬取策略是广度优先，每一层url生成一个文件夹，直到没有新的url。

在segments有6个文件夹 ：

• crawl_generate - names a set of urls to be fetched（待爬取的url）
• crawl_fetch - contains the status of fetching each url（爬取的url的状态）
• content - contains the content of each url（页面内容）
• parse_text - contains the parsed text of each url（网页的文本信息）
• parse_data - contains outlinks and metadata parsed from each url（url解析出来的外链和元数据）
• crawl_parse - contains the outlink urls, used to update the crawldb（更新crawldb的外链）

这些文件夹都是不可读的，以方便存取并在高一层进行检索用。如果想看到具体内容，要使用Nutch定义的读取命令 ：

1、查看CrawlDB（readdb）

[root@localhost local]# bin/nutch readdb

Usage: CrawlDbReader <crawldb> (-stats | -dump <out_dir> | -topN <nnnn> <out_dir> [<min>] | -url <url>)

    <crawldb>    directory name where crawldb is located

    -stats [-sort]     print overall statistics to System.out

        [-sort]    list status sorted by host

    -dump <out_dir> [-format normal|csv|crawldb]    dump the whole db to a text file in <out_dir>

        [-format csv]    dump in Csv format

        [-format normal]    dump in standard format (default option)

        [-format crawldb]    dump as CrawlDB

        [-regex <expr>]    filter records with expression

        [-status <status>]    filter records by CrawlDatum status

    -url <url>    print information on <url> to System.out

    -topN <nnnn> <out_dir> [<min>]    dump top <nnnn> urls sorted by score to <out_dir>

        [<min>]    skip records with scores below this value.

            This can significantly improve performance.

查看URL地址总数和它的状态及评分 ：

[root@localhost local]# bin/nutch readdb data/crawldb/ -stats

CrawlDb statistics start: data/crawldb/

Statistics for CrawlDb: data/crawldb/

TOTAL urls:    10635

retry 0:    10615

retry 1:    20

min score:    0.0

avg score:    2.6920545E-4

max score:    1.123

status 1 (db_unfetched):    9614

status 2 (db_fetched):    934

status 3 (db_gone):    2

status 4 (db_redir_temp):    81

status 5 (db_redir_perm):    4

CrawlDb statistics: done

 导出每个url地址的详细内容：bin/nutch readdb data/crawldb/ -dump crawldb(导出的地址)

2、查看linkdb

查看链接情况：bin/nutch readlinkdb data/linkdb/ -url http://www.163.com/
导出linkdb数据库文件：bin/nutch readlinkdb 163/linkdb/ -dump linkdb(导出的地址)

3、查看segments

bin/nutch readseg -list -dir data/segments/  -  可以看到每一个segments的名称，产生的页面数，抓取的开始时间和结束时间，抓取数和解析数。

[root@localhost local]# bin/nutch readseg -list -dir data/segments/

NAME              GENERATED    FETCHER START          FETCHER END            FETCHED    PARSED

20130427150144    53           2013-04-27T15:01:52    2013-04-27T15:05:15    53         51

20130427150553    1036         2013-04-27T15:06:01    2013-04-27T15:58:09    1094       921

20130427150102    1            2013-04-27T15:01:10    2013-04-27T15:01:10    1          1

导出segments ：bin/nutch readseg -dump data/segments/20130427150144 segdb
其中data/segments/20130427150144 为一个segments文件夹，segdb为存放转换后的内容的文件夹。

最后一个命令可能是最有用的，用于获得页面内容，一般会加上几个选项
bin/nutch readseg -dump  data/segments/20130427150144/ data_oscar /segments -nofetch -nogenerate -noparse -noparsedata -nocontent
这样得到的 dump文件只包含网页的正文信息，没有标记。

 

 

感谢：http://yangshangchuan.iteye.com