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From "Ferdy Galema (JIRA)" <>
Subject [jira] [Created] (NUTCH-1431) Introduce link 'distance' and add configurable max distance in the generator
Date Wed, 18 Jul 2012 10:19:35 GMT
Ferdy Galema created NUTCH-1431:

             Summary: Introduce link 'distance' and add configurable max distance in the generator
                 Key: NUTCH-1431
             Project: Nutch
          Issue Type: New Feature
            Reporter: Ferdy Galema
             Fix For: 2.1

Introducing a new feature that enables to crawl URLs within a specific distance (shortest
path) from the injected source urls. This is where the db-updater of Nutchgora really shines.
Because every url in the reducer has all of its inlinks present, it is really easy to determine
what the shortest path is to that url. (I would not know how to cleanly implement this feature
for trunk).

Injected urls have distance 0. Outlink urls on those pages have distance 1. Outlinks on those
pages have distance 2, etc. Outlinks that already had a smaller distance will keep that distance.
Of all inlinks to a page, it will always select the smallest distance in order to maintain
the shortest path garantuee.

Generator now has a property 'generate.max.distance' (default set to -1) that specifies the
maximum allowed distance of urls to select for fetch.

Note that this is fundamentally different from the concept crawl 'depth'. Depth is used for
crawl cycles. Distance allows to crawl for unlimited number of cycles AND always stay within
a certain number of 'hops' from injected urls.

I will attach a patch. Will commit in a few days. (It does not change crawl behaviour unless
otherwise configured). Let me know if you have comments.

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