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https://issues.apache.org/jira/browse/NUTCH-766?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12805661#action_12805661
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Sami Siren commented on NUTCH-766:
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{quote}
Sure, it's more of a configuration backwards-compat issue. For those folks who
have gone to the trouble of customizing their nutch configuration
(nuch-site.xml, or nutch-default.xml, or even parse-plugins), to remove out the
parsing plugins (e.g., basically say they don't exist anymore and update your
deployed configuration to use the tika-plugin), this patch would require a
configuration update in their deployed environments. Because of that, why don't
we ease them into that upgrade with at least one released version before the
plugins go away. It would make it easier from a configuration backwards-compat
perspective.
{quote}
Ok, so you mean that we need to have duplicate parser plugins because we don't
want to ask people already using nutch to reconfigure the bits this involves
now even though we have to do it later? How is postponing going to ease the
task they need to do anyway at some point? I still don't understand the (longer
term) benefit.
I am not strongly against the idea of keeping duplicate plugins, I mean it's
just another ~20M in the .job, what I am worried about is that the history will
repeat itself and we will end up having one more case of duplicate components
(in this case many of them) doing the same work and no interest in cleaning up
afterwards. Doing it the way I suggested would guarantee that this will not
happen.
> Tika parser
> -----------
>
> Key: NUTCH-766
> URL: https://issues.apache.org/jira/browse/NUTCH-766
> Project: Nutch
> Issue Type: New Feature
> Reporter: Julien Nioche
> Assignee: Chris A. Mattmann
> Fix For: 1.1
>
> Attachments: Nutch-766.ParserFactory.patch, NUTCH-766.tika.patch
>
>
> Tika handles a lot of different formats under the bonnet and exposes them
> nicely via SAX events. What is described here is a tika-parser plugin which
> delegates the pasring mechanism of Tika but can still coexist with the
> existing parsing plugins which is useful for formats partially handled by
> Tika (or not at all). Some of the elements below have already been discussed
> on the mailing lists. Note that this is work in progress, your feedback is
> welcome.
> Tika is already used by Nutch for its MimeType implementations. Tika comes as
> different jar files (core and parsers), in the work described here we decided
> to put the libs in 2 different places
> NUTCH_HOME/lib : tika-core.jar
> NUTCH_HOME/tika-plugin/lib : tika-parsers.jar
> Tika being used by the core only for its Mimetype functionalities we only
> need to put tika-core at the main lib level whereas the tika plugin obviously
> needs the tika-parsers.jar + all the jars used internally by Tika
> Due to limitations in the way Tika loads its classes, we had to duplicate the
> TikaConfig class in the tika-plugin. This might be fixed in the future in
> Tika itself or avoided by refactoring the mimetype part of Nutch using
> extension points.
> Unlike most other parsers, Tika handles more than one Mime-type which is why
> we are using "*" as its mimetype value in the plugin descriptor and have
> modified ParserFactory.java so that it considers the tika parser as
> potentially suitable for all mime-types. In practice this means that the
> associations between a mime type and a parser plugin as defined in
> parse-plugins.xml are useful only for the cases where we want to handle a
> mime type with a different parser than Tika.
> The general approach I chose was to convert the SAX events returned by the
> Tika parsers into DOM objects and reuse the utilities that come with the
> current HTML parser i.e. link detection, metatag handling but also means
> that we can use the HTMLParseFilters in exactly the same way. The main
> difference though is that HTMLParseFilters are not limited to HTML documents
> anymore as the XHTML tags returned by Tika can correspond to a different
> format for the original document. There is a duplication of code with the
> html-plugin which will be resolved by either a) getting rid of the
> html-plugin altogether or b) exporting its jar and make the tika parser
> depend on it.
> The following libraries are required in the lib/ directory of the tika-parser
> :
> <library name="asm-3.1.jar"/>
> <library name="bcmail-jdk15-144.jar"/>
> <library name="commons-compress-1.0.jar"/>
> <library name="commons-logging-1.1.1.jar"/>
> <library name="dom4j-1.6.1.jar"/>
> <library name="fontbox-0.8.0-incubator.jar"/>
> <library name="geronimo-stax-api_1.0_spec-1.0.1.jar"/>
> <library name="hamcrest-core-1.1.jar"/>
> <library name="jce-jdk13-144.jar"/>
> <library name="jempbox-0.8.0-incubator.jar"/>
> <library name="metadata-extractor-2.4.0-beta-1.jar"/>
> <library name="mockito-core-1.7.jar"/>
> <library name="objenesis-1.0.jar"/>
> <library name="ooxml-schemas-1.0.jar"/>
> <library name="pdfbox-0.8.0-incubating.jar"/>
> <library name="poi-3.5-FINAL.jar"/>
> <library name="poi-ooxml-3.5-FINAL.jar"/>
> <library name="poi-scratchpad-3.5-FINAL.jar"/>
> <library name="tagsoup-1.2.jar"/>
> <library name="tika-parsers-0.5-SNAPSHOT.jar"/>
> <library name="xml-apis-1.0.b2.jar"/>
> <library name="xmlbeans-2.3.0.jar"/>
> There is a small test suite which needs to be improved. We will need to have
> a look at each individual format and check that it is covered by Tika and if
> so to the same extent; the Wiki is probably the right place for this. The
> language identifier (which is a HTMLParseFilter) seemed to work fine.
>
> Again, your comments are welcome. Please bear in mind that this is just a
> first step.
> Julien
> http://www.digitalpebble.com
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