Hi Mathijs,
We use this in the fetcher (parse=true) and when updating the CrawlDB
and with the free generator. We use it in the fetcher because we follow
outlinks and make sure we follow the desired host and in the CrawlDB
because there we update records for recently added host normalizer
rules.
It is just an URL normalizer like the others but only changes the host
part. This is not covered in other standard normalizers. The
BasicURLNormalizer cannot do this and the RegexURLNormalizer is far too
heavy to take 20MB of expressions and harder to auto-generate. A simple
map lookup is very fast.
Cheers,
On Wed, 21 Mar 2012 22:22:54 +0100, Mathijs Homminga
<mathijs.hommi...@kalooga.com> wrote:
Hi Markus,
How (where in the process) do you like to use this normalizer. Isn't
this functionality already covered by the URL normalizer(s)?
Mathijs Homminga
On Mar 21, 2012, at 22:06, "Markus Jelsma (Created) (JIRA)"
<j...@apache.org> wrote:
HostNormalizer
--------------
Key: NUTCH-1319
URL:
https://issues.apache.org/jira/browse/NUTCH-1319
Project: Nutch
Issue Type: New Feature
Reporter: Markus Jelsma
Assignee: Markus Jelsma
Fix For: 1.5
Nutch would benefit from having a host normalizer. A host normalizer
maps a given host to the desired host. A basic example is to map
www.apache.org to apache.org. The Apache website is one of many on the
internet that has a duplicate website on the same domain just because
it allows both www and non-www to return HTTP 200 and proper content.
It is also able to handle wildcards such as *.example.org to
example.org if there are multiple sub domains that actually point to
the same website.
Large internet crawls tend to get polluted very quickly due to these
problems. It also leads to skewed scores in the webgraph as different
websites link to different versions of the same duplicate website.
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