On 10/04/2012 05:00, Xiaolong Yang wrote:
Hiļ¼all
I'm reading source code of nutch and I have some puzzled about the
ObjectCache.java in package org.apache.nutch.util.I just find it may be
little benefit to use it in urlnormalizers and urlfiters.I also have
read some discuss about cache in Nutch-169 and Nutch-501.But I can't
understand it.
Can anyone tell me where ObjectCache be used and get a good benefit in
nutch ?
ObjectCache is designed to cache ready-to-use instances of Nutch
plugins. The process of finding, instantiating and initializing plugins
is inefficient, because it involves parsing plugin descriptors,
initializing plugins, collecting the ones that implement correct
extension points, etc.
It would kill performance if this process were invoked each time you
want to run all plugins of a given type (e.g. URLNormalizer-s). The
facade URLNormalizers/URLFilters and others make sure that plugin
instances of a given type are initialized once per lifetime of a JVM,
and then they are cached in ObjectCache, so that next time you want to
use them they can be retrieved from a cache, instead of going again
through the process of parsing/instantiating/initializing.
--
Best regards,
Andrzej Bialecki <><
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