1、nutch抓取流程
当使用crawl命令进行抓取任务时，其基本流程步骤如下：
（1）InjectorJob
开始第一个迭代
（2）GeneratorJob
（3）FetcherJob
（4）ParserJob
（5）DbUpdaterJob
（6）SolrIndexerJob
开始第二个迭代
（2）GeneratorJob（3）FetcherJob（4）ParserJob（5）DbUpdaterJob（6）SolrIndexerJob
开始第三个迭代
……
使用crawl命令进行抓取时，console输出日志如下：
InjectorJob: starting at 2014-07-08 10:41:27
InjectorJob: Injecting urlDir: urls
InjectorJob: Using class org.apache.gora.hbase.store.HBaseStore as the Gora storage class.
InjectorJob: total number of urls rejected by filters: 0
InjectorJob: total number of urls injected after normalization and filtering: 2
Injector: finished at 2014-07-08 10:41:32, elapsed: 00:00:05
Tue Jul 8 10:41:33 CST 2014 : Iteration 1 of 5
Generating batchId
Generating a new fetchlist
GeneratorJob: starting at 2014-07-08 10:41:34
GeneratorJob: Selecting best-scoring urls due for fetch.
GeneratorJob: starting
GeneratorJob: filtering: false
GeneratorJob: normalizing: false
GeneratorJob: topN: 50000
GeneratorJob: finished at 2014-07-08 10:41:39, time elapsed: 00:00:05
GeneratorJob: generated batch id: 1404787293-26339
Fetching :
FetcherJob: starting
FetcherJob: batchId: 1404787293-26339
Fetcher: Your 'http.agent.name' value should be listed first in 'http.robots.agents' property.
FetcherJob: threads: 50
FetcherJob: parsing: false
FetcherJob: resuming: false
FetcherJob : timelimit set for : 1404798101129
Using queue mode : byHost
Fetcher: threads: 50
QueueFeeder finished: total 2 records. Hit by time limit :0
fetching http://www.csdn.net/ (queue crawl delay=5000ms)
Fetcher: throughput threshold: -1
Fetcher: throughput threshold sequence: 5
fetching http://www.itpub.net/ (queue crawl delay=5000ms)
-finishing thread FetcherThread47, activeThreads=48
-finishing thread FetcherThread46, activeThreads=47
-finishing thread FetcherThread45, activeThreads=46
-finishing thread FetcherThread44, activeThreads=45
-finishing thread FetcherThread43, activeThreads=44
-finishing thread FetcherThread42, activeThreads=43
-finishing thread FetcherThread41, activeThreads=42
-finishing thread FetcherThread40, activeThreads=41
-finishing thread FetcherThread39, activeThreads=40
-finishing thread FetcherThread38, activeThreads=39
-finishing thread FetcherThread37, activeThreads=38
-finishing thread FetcherThread36, activeThreads=37
-finishing thread FetcherThread35, activeThreads=36
-finishing thread FetcherThread34, activeThreads=35
-finishing thread FetcherThread33, activeThreads=34
-finishing thread FetcherThread32, activeThreads=33
-finishing thread FetcherThread31, activeThreads=32
-finishing thread FetcherThread30, activeThreads=31
-finishing thread FetcherThread29, activeThreads=30
-finishing thread FetcherThread48, activeThreads=29
-finishing thread FetcherThread27, activeThreads=29
-finishing thread FetcherThread26, activeThreads=28
-finishing thread FetcherThread25, activeThreads=27
-finishing thread FetcherThread24, activeThreads=26
-finishing thread FetcherThread23, activeThreads=25
-finishing thread FetcherThread22, activeThreads=24
-finishing thread FetcherThread21, activeThreads=23
-finishing thread FetcherThread20, activeThreads=22
-finishing thread FetcherThread19, activeThreads=21
-finishing thread FetcherThread18, activeThreads=20
-finishing thread FetcherThread17, activeThreads=19
-finishing thread FetcherThread16, activeThreads=18
-finishing thread FetcherThread15, activeThreads=17
-finishing thread FetcherThread14, activeThreads=16
-finishing thread FetcherThread13, activeThreads=15
-finishing thread FetcherThread12, activeThreads=14
-finishing thread FetcherThread11, activeThreads=13
-finishing thread FetcherThread10, activeThreads=12
-finishing thread FetcherThread9, activeThreads=11
-finishing thread FetcherThread8, activeThreads=10
-finishing thread FetcherThread7, activeThreads=9
-finishing thread FetcherThread5, activeThreads=8
-finishing thread FetcherThread4, activeThreads=7
-finishing thread FetcherThread3, activeThreads=6
-finishing thread FetcherThread2, activeThreads=5
-finishing thread FetcherThread49, activeThreads=4
-finishing thread FetcherThread6, activeThreads=3
-finishing thread FetcherThread28, activeThreads=2
-finishing thread FetcherThread0, activeThreads=1
fetch of http://www.itpub.net/ failed with: java.io.IOException: unzipBestEffort returned null
-finishing thread FetcherThread1, activeThreads=0
0/0 spinwaiting/active, 2 pages, 1 errors, 0.4 0 pages/s, 93 93 kb/s, 0 URLs in 0 queues
-activeThreads=0
FetcherJob: done
Parsing :
ParserJob: starting
ParserJob: resuming: false
ParserJob: forced reparse: false
ParserJob: batchId: 1404787293-26339
Parsing http://www.csdn.net/
http://www.csdn.net/ skipped. Content of size 92777 was truncated to 59561
Parsing http://www.itpub.net/
ParserJob: success
CrawlDB update for csdnitpub
DbUpdaterJob: starting
DbUpdaterJob: done
Indexing csdnitpub on SOLR index -> http://ip:8983/solr/
SolrIndexerJob: starting
SolrIndexerJob: done.
SOLR dedup -> http://ip:8983/solr/
Tue Jul 8 10:42:18 CST 2014 : Iteration 2 of 5
Generating batchId
Generating a new fetchlist
GeneratorJob: starting at 2014-07-08 10:42:19
GeneratorJob: Selecting best-scoring urls due for fetch.
GeneratorJob: starting
GeneratorJob: filtering: false
GeneratorJob: normalizing: false
GeneratorJob: topN: 50000
GeneratorJob: finished at 2014-07-08 10:42:25, time elapsed: 00:00:05
GeneratorJob: generated batch id: 1404787338-30453
Fetching :
FetcherJob: starting
FetcherJob: batchId: 1404787338-30453
Fetcher: Your 'http.agent.name' value should be listed first in 'http.robots.agents' property.
FetcherJob: threads: 50
FetcherJob: parsing: false
FetcherJob: resuming: false
FetcherJob : timelimit set for : 1404798146676
Using queue mode : byHost
Fetcher: threads: 50
QueueFeeder finished: total 0 records. Hit by time limit :0
二、使用命令进行逐步抓取
1、InjectorJob
此步骤将seed.txt中的url注入抓取队列中进行初始化。
（1）基本命令$ bin/nutch inject
Usage: InjectorJob <url_dir> [-crawlId <id>]
$ bin/nutch inject urls
InjectorJob: starting at 2014-12-20 22:32:01
InjectorJob: Injecting urlDir: urls
InjectorJob: Using class org.apache.gora.hbase.store.HBaseStore as the Gora storage class.
InjectorJob: total number of urls rejected by filters: 0
InjectorJob: total number of urls injected after normalization and filtering: 1
Injector: finished at 2014-12-20 22:32:15, elapsed: 00:00:14
其中urls/seed.txt的内容如下：
http://*.com/
（2）查看注入的url
上述步骤会在hbase中新建一个表，表名为test_1_webpage，url的相应内容会写入这张表
hbase(main):002:0> scan '334_webpage'
ROW COLUMN+CELL
com.*:http/ column=f:fi, timestamp=1408953100271, value=\x00'\x8D\x00
com.*:http/ column=f:ts, timestamp=1408953100271, value=\x00\x00\x01H\x0C&\x11\x8D
com.*:http/ column=mk:_injmrk_, timestamp=1408953100271, value=y
com.*:http/ column=mk:dist, timestamp=1408953100271, value=0
com.*:http/ column=mtdt:_csh_, timestamp=1408953100271, value=?\x80\x00\x00
com.*:http/ column=s:s, timestamp=1408953100271, value=?\x80\x00\x00
1 row(s) in 0.3020 seconds
(3)关于**_webpage表
对于每一个任务，均会生成一个crawlId_webpage的表，所有已抓取及未抓取的url相关信息均会存入此表。
若url未抓取，则该url相应的行信息较少。若url已经抓取，则抓取到的内容也会放入该行，如网页内容等。
2、GeneratorJob
（1）基本命令
[jediael@jediael local]$ bin/nutch generate -crawlId 334
GeneratorJob: starting at 2014-08-25 15:57:12
GeneratorJob: Selecting best-scoring urls due for fetch.
GeneratorJob: starting
GeneratorJob: filtering: true
GeneratorJob: normalizing: true
GeneratorJob: finished at 2014-08-25 15:57:18, time elapsed: 00:00:06
GeneratorJob: generated batch id: 1408953432-1171377744
（2）命令选项
[root@jediael local]# bin/nutch generate
Usage: GeneratorJob [-topN N] [-crawlId id] [-noFilter] [-noNorm] [-adddays numDays]
-topN <N> - number of top URLs to be selected, default is Long.MAX_VALUE
-crawlId <id> - the id to prefix the schemas to operate on, default: storage.crawl.id)");
-noFilter - do not activate the filter plugin to filter the url, default is true
-noNorm - do not activate the normalizer plugin to normalize the url, default is true
-adddays - Adds numDays to the current time to facilitate crawling urls already fetched sooner then db.fetch.interval.default. Default value is 0.
-batchId - the batch id
----------------------
Please set the params.
（3）查看数据库
hbase(main):003:0> scan '334_webpage'
ROW COLUMN+CELL
com.*:http/ column=f:bid, timestamp=1408953437910, value=1408953432-1171377744
com.*:http/ column=f:fi, timestamp=1408953100271, value=\x00'\x8D\x00
com.*:http/ column=f:ts, timestamp=1408953100271, value=\x00\x00\x01H\x0C&\x11\x8D
com.*:http/ column=mk:_gnmrk_, timestamp=1408953437910, value=1408953432-1171377744
com.*:http/ column=mk:_injmrk_, timestamp=1408953100271, value=y
com.*:http/ column=mk:dist, timestamp=1408953100271, value=0
com.*:http/ column=mtdt:_csh_, timestamp=1408953100271, value=?\x80\x00\x00
com.*:http/ column=s:s, timestamp=1408953100271, value=?\x80\x00\x00
1 row(s) in 0.0490 seconds
此步骤新增了f:bid，mk:_gnmrk_ 两列。
3、FetcherJob
（1）基本命令
[jediael@jediael local]$ bin/nutch generate -crawlId 334
GeneratorJob: starting at 2014-08-25 15:57:12
GeneratorJob: Selecting best-scoring urls due for fetch.
GeneratorJob: starting
GeneratorJob: filtering: true
GeneratorJob: normalizing: true
GeneratorJob: finished at 2014-08-25 15:57:18, time elapsed: 00:00:06
GeneratorJob: generated batch id: 1408953432-1171377744
[jediael@jediael local]$ bin/nutch fetch -all -crawlId 334
FetcherJob: starting
FetcherJob: fetching all
Fetcher: Your 'http.agent.name' value should be listed first in 'http.robots.agents' property.
FetcherJob: threads: 10
FetcherJob: parsing: false
FetcherJob: resuming: false
FetcherJob : timelimit set for : -1
Using queue mode : byHost
Fetcher: threads: 10
QueueFeeder finished: total 1 records. Hit by time limit :0
Fetcher: throughput threshold: -1
Fetcher: throughput threshold sequence: 5
fetching http://*.com/ (queue crawl delay=5000ms)
-finishing thread FetcherThread1, activeThreads=8
-finishing thread FetcherThread7, activeThreads=7
-finishing thread FetcherThread6, activeThreads=6
-finishing thread FetcherThread5, activeThreads=5
-finishing thread FetcherThread4, activeThreads=4
-finishing thread FetcherThread3, activeThreads=3
-finishing thread FetcherThread2, activeThreads=2
-finishing thread FetcherThread8, activeThreads=1
-finishing thread FetcherThread9, activeThreads=1
-finishing thread FetcherThread0, activeThreads=0
0/0 spinwaiting/active, 1 pages, 0 errors, 0.2 0 pages/s, 102 102 kb/s, 0 URLs in 0 queues
-activeThreads=0
FetcherJob: done
（2）查看数据库
见db1.txt
新增f:bas，column=f:cnt，column=f:prot，f:pts，f:st，f:ts，f:typ，h:Cache-Control，h:Connection，h:Content-Encoding，h:Content-Length, h:Content-Type,h:Date,h:Expires, h:Last-Modified,h:Set-Cookie,h:Vary,h:X-Frame-Options, mk:_ftcmrk_等字段
4、ParserJob
（1）基本命令
[jediael@jediael local]$ bin/nutch parse -all -crawlId 334
ParserJob: starting
ParserJob: resuming: false
ParserJob: forced reparse: false
ParserJob: parsing all
Parsing http://*.com/
ParserJob: success
（2）命令参数
[root@jediael local]# bin/nutch parse
Usage: ParserJob (<batchId> | -all) [-crawlId <id>] [-resume] [-force]
<batchId> - symbolic batch ID created by Generator
-crawlId <id> - the id to prefix the schemas to operate on,
(default: storage.crawl.id)
-all - consider pages from all crawl jobs
-resume - resume a previous incomplete job
-force - force re-parsing even if a page is already parsed
（3）查看数据库
见db_parse.txt
新增了很多类似column=ol:http://*.com/help的列，在此例*有115个。
5、DbUpdaterJob
（1）基本命令
[jediael@jediael local]$ bin/nutch updatedb -crawlId 334
DbUpdaterJob: starting
DbUpdaterJob: done
（2）查看数据库
见db_updatedb.txt
解释了上述的115个column=ol:http，并生成了115行新数据，举其中一个例子如下：
com.*:http/users/39 column=f:fi, timestamp=1408954979355, value=\x00'\x8D\x00
44974/silviu-oncioiu
com.*:http/users/39 column=f:st, timestamp=1408954979355, value=\x00\x00\x00\x01
44974/silviu-oncioiu
com.*:http/users/39 column=f:ts, timestamp=1408954979355, value=\x00\x00\x01H\x0CB\xD4\x09
44974/silviu-oncioiu
com.*:http/users/39 column=mk:dist, timestamp=1408954979355, value=1
44974/silviu-oncioiu
com.*:http/users/39 column=mtdt:_csh_, timestamp=1408954979355, value=<\x0Ex5
44974/silviu-oncioiu
com.*:http/users/39 column=s:s, timestamp=1408954979355, value=<\x0Ex5
44974/silviu-oncioiu
com.*:http/users/39 column=f:fi, timestamp=1408954979355, value=\x00'\x8D\x00
74525/laosi
com.*:http/users/39 column=f:st, timestamp=1408954979355, value=\x00\x00\x00\x01
74525/laosi
com.*:http/users/39 column=f:ts, timestamp=1408954979355, value=\x00\x00\x01H\x0CB\xD4\x09
74525/laosi
com.*:http/users/39 column=mk:dist, timestamp=1408954979355, value=1
74525/laosi
com.*:http/users/39 column=mtdt:_csh_, timestamp=1408954979355, value=<\x0Ex5
74525/laosi
com.*:http/users/39 column=s:s, timestamp=1408954979355, value=<\x0Ex5
74525/laosi
此时数据已准备好，等待下一轮的抓取。
6、SolrIndexerJob
（1）基本命令
[jediael@jediael local]$ bin/nutch solrindex http://****/solr/ -all -crawlId 334
SolrIndexerJob: starting
Adding 1 documents
SolrIndexerJob: done.
（2）命令参数
[root@jediael local]# bin/nutch solrindex
Usage: SolrIndexerJob <solr url> (<batchId> | -all | -reindex) [-crawlId <id>]
（3）查看数据库
无变化