Nutch 1.0配置与运行

有一段时间没有关注Nutch了，借最近假期，尝试一下，以后可能会慢慢深入了解Nutch及其相关的内容（像Hadoop），话不多说，先把最简单配置的Nutch运行起来。 

这次下载了Nutch 1.0，貌似和之前版本在配置上有轻微的变化。

由于Nutch基于Hadoop项目，肯定需要满足Hadoop运行的一些配置，为了更能详细地说明实际的配置和运行过程，还是采用按步骤进行解释的方式来表达。我直接使用root帐户了，Linux为RHEL 5。

 

1、Linux系统无密码验证配置

 

启动命令行窗口，执行命令行： 

$ ssh-keygen -t dsa -P '' -f ~/.ssh/id_dsa 
$ cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys 

然后执行如下命令： 

$ ssh localhost 

如果不需要使用密码登录，表示无密码验证配置成功。

 

2、配置Hadoop

 

（1）修改conf/hadoop-env.sh中JAVA_HOME

（2）修改conf/hadoop-site.xml的内容，如下所示：

<?xml version="1.0"?> <?xml-stylesheet type="text/xsl" href="configuration.xsl"?> <!-- Put site-specific property overrides in this file. --> <configuration> <property> <name>fs.default.name</name> <value>hdfs://localhost:9000</value> </property> <property> <name>mapred.job.tracker</name> <value>localhost:9001</value> </property> <property> <name>dfs.replication</name> <value>1</value> </property> </configuration>

 

 

3、配置Nutch

 

（1）配置conf/nutch-site.xml，内容如下所示： 

<?xml version="1.0"?> <?xml-stylesheet type="text/xsl" href="configuration.xsl"?> <!-- Put site-specific property overrides in this file. --> <configuration> <property> <name>http.agent.name</name> <value>z-hacker</value> </property> <property> <name>http.agent.description</name> <value>I'm z-hacker.</value> </property> <property> <name>http.agent.url</name> <value>www.z-hacker.com</value> </property> <property> <name>http.agent.email</name> <value>[email protected]</value> </property> </configuration>

其中，http.agent.name是必须配置的，其它为可选。

（2）配置conf/crawl-urlfilter.txt，修改如下一行即可： 

# accept hosts in MY.DOMAIN.NAME
+^http://([a-z0-9]*/.)*sina.com.cn/ 

上述配置，表示抓取新浪的网页。

 

4、准备Nutch爬虫入口url文件

 

在当前目录下创建一个目录，例如urls，在url下面可以创建文本文件，文本文件中每行一个合法的url即可。

 

5、格式化HDFS文件系统

 

[root@localhost nutch-1.0]# bin/hadoop namenode -format 

如果第一次在本机Linux上运行，则不出错就应该没问题；如果第一次执行格式化，可能提示你是否重新格式化： 

Re-format filesystem in /tmp/hadoop-root/dfs/name ? (Y or N) Y 

输入Y即可，重新格式化。

 

6、启动Hadoop相关的5个后台进程

 

[root@localhost nutch-1.0]# bin/start-all.sh 

如果没有出错，表示成功，此时启动了5个后台进程，可以通过jps命令查看一下，是否是下面5个进程： 

[root@localhost nutch-1.0]# jps
15559 Jps
15407 JobTracker
15243 DataNode
15150 NameNode
15512 TaskTracker
15349 SecondaryNameNode 

如果缺少某个，说明你的配置还是存在问题，需要查看日志。

例如，我的日志目录为logs，假如通过jps查看发现NameNode进程不存在，说明NameNode服务进程启动失败，查看/logs/hadoop-root-namenode-localhost.log日志文件，即可查明原因。

 

7、上传Nutch爬虫入口url目录

 

需要将本地准备好的爬虫入口目录（例如urls）及文件（目录urls下面存在url文件）上传到HDFS上，执行如下命令： 

[root@localhost nutch-1.0]# bin/hadoop fs -put urls/ urls 

如果没有发生异常，则上传成功。

 

8、简单模式启动Nutch

 

执行如下命令启动Nutch： 

[root@localhost nutch-1.0]# bin/nutch crawl urls -dir storeDir -depth 10 -threads 5 -topN 50 >&./logs/nutch.log 

上面，urls是上传的入口url的目录，storeDir是抓取下来的数据存储目录。

如果执行上述命令，查看日志，能够按照正确的流程执行，就表示配置运行成功了，可以通过如下命令查看日志： 

[root@localhost nutch-1.0]# tail -100f logs/nutch.log
crawl started in: storeDir
rootUrlDir = urls
threads = 5
depth = 10
topN = 50
Injector: starting
Injector: crawlDb: storeDir/crawldb
Injector: urlDir: urls
Injector: Converting injected urls to crawl db entries.
Injector: Merging injected urls into crawl db.
Injector: done
Generator: Selecting best-scoring urls due for fetch.
Generator: starting
Generator: segment: storeDir/segments/20101004091724
Generator: filtering: true
Generator: topN: 50
Generator: Partitioning selected urls by host, for politeness.
Generator: done.
Fetcher: Your 'http.agent.name' value should be listed first in 'http.robots.agents' property.
Fetcher: starting
Fetcher: segment: storeDir/segments/20101004091724
Fetcher: done
CrawlDb update: starting
CrawlDb update: db: storeDir/crawldb
CrawlDb update: segments: [storeDir/segments/20101004091724]
CrawlDb update: additions allowed: true
CrawlDb update: URL normalizing: true
CrawlDb update: URL filtering: true
CrawlDb update: Merging segment data into db.
CrawlDb update: done
Generator: Selecting best-scoring urls due for fetch.
Generator: starting
Generator: segment: storeDir/segments/20101004091902
Generator: filtering: true
Generator: topN: 50
Generator: Partitioning selected urls by host, for politeness.
Generator: done.
Fetcher: Your 'http.agent.name' value should be listed first in 'http.robots.agents' property.
Fetcher: starting
Fetcher: segment: storeDir/segments/20101004091902
Fetcher: done
CrawlDb update: starting
CrawlDb update: db: storeDir/crawldb
CrawlDb update: segments: [storeDir/segments/20101004091902]
CrawlDb update: additions allowed: true
CrawlDb update: URL normalizing: true
CrawlDb update: URL filtering: true
CrawlDb update: Merging segment data into db.
CrawlDb update: done
Generator: Selecting best-scoring urls due for fetch.
Generator: starting
Generator: segment: storeDir/segments/20101004092053
Generator: filtering: true
Generator: topN: 50
Generator: Partitioning selected urls by host, for politeness.
Generator: done.
Fetcher: Your 'http.agent.name' value should be listed first in 'http.robots.agents' property.
Fetcher: starting
Fetcher: segment: storeDir/segments/20101004092053
Fetcher: done
CrawlDb update: starting
CrawlDb update: db: storeDir/crawldb
CrawlDb update: segments: [storeDir/segments/20101004092053]
CrawlDb update: additions allowed: true
CrawlDb update: URL normalizing: true
CrawlDb update: URL filtering: true
CrawlDb update: Merging segment data into db.
CrawlDb update: done
Generator: Selecting best-scoring urls due for fetch.
Generator: starting
Generator: segment: storeDir/segments/20101004092711
Generator: filtering: true
Generator: topN: 50
Generator: Partitioning selected urls by host, for politeness.
Generator: done.
Fetcher: Your 'http.agent.name' value should be listed first in 'http.robots.agents' property.
Fetcher: starting
Fetcher: segment: storeDir/segments/20101004092711
Fetcher: done
CrawlDb update: starting
CrawlDb update: db: storeDir/crawldb
CrawlDb update: segments: [storeDir/segments/20101004092711]
CrawlDb update: additions allowed: true
CrawlDb update: URL normalizing: true
CrawlDb update: URL filtering: true
CrawlDb update: Merging segment data into db.
CrawlDb update: done
Generator: Selecting best-scoring urls due for fetch.
Generator: starting
Generator: segment: storeDir/segments/20101004092833
Generator: filtering: true
Generator: topN: 50
Generator: 0 records selected for fetching, exiting ...
Stopping at depth=4 - no more URLs to fetch.
LinkDb: starting
LinkDb: linkdb: storeDir/linkdb
LinkDb: URL normalize: true
LinkDb: URL filter: true
LinkDb: adding segment: hdfs://localhost:9000/user/root/storeDir/segments/20101004091724
LinkDb: adding segment: hdfs://localhost:9000/user/root/storeDir/segments/20101004091902
LinkDb: adding segment: hdfs://localhost:9000/user/root/storeDir/segments/20101004092053
LinkDb: adding segment: hdfs://localhost:9000/user/root/storeDir/segments/20101004092711
LinkDb: done
Indexer: starting
Indexer: done
Dedup: starting
Dedup: adding indexes in: storeDir/indexes
Dedup: done
merging indexes to: storeDir/index
Adding hdfs://localhost:9000/user/root/storeDir/indexes/part-00000
done merging
crawl finished: storeDir

 

9、查看Nutch执行结果

 

可以根据上面我们指定的数据存储目录来查看HDFS上存储情况，执行如下命令： 

[root@localhost nutch-1.0]# bin/hadoop fs -ls /user/root/storeDir
Found 5 items
drwxr-xr-x   - root supergroup          0 2010-10-04 09:28 /user/root/storeDir/crawldb
drwxr-xr-x   - root supergroup          0 2010-10-04 09:31 /user/root/storeDir/index
drwxr-xr-x   - root supergroup          0 2010-10-04 09:30 /user/root/storeDir/indexes
drwxr-xr-x   - root supergroup          0 2010-10-04 09:29 /user/root/storeDir/linkdb
drwxr-xr-x   - root supergroup          0 2010-10-04 09:27 /user/root/storeDir/segments