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https://issues.apache.org/jira/browse/NUTCH-2378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16128727#comment-16128727
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ASF GitHub Bot commented on NUTCH-2378:
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sebastian-nagel closed pull request #213: NUTCH-2378 ChildFirst plugin
classloader
URL: https://github.com/apache/nutch/pull/213
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> ChildFirst plugin classloader
> -----------------------------
>
> Key: NUTCH-2378
> URL: https://issues.apache.org/jira/browse/NUTCH-2378
> Project: Nutch
> Issue Type: Improvement
> Components: plugin
> Affects Versions: 1.13
> Reporter: Jurian Broertjes
> Fix For: 1.14
>
> Attachments: NUTCH-2378-childfirst-plugin-classloader.patch
>
>
> While working on upgrading the indexer-elastic plugin from 2.x to 5.x, I ran
> into several nasty runtime dependency issues (both local and on Hadoop).
> After seeking help on the mailing list, I still was unable to resolve these
> issues and after digging further, decided to try a different plugin
> classloader strategy.
> The normal classloader delegates class loading requests to it's parent
> classloader. This can cause all sorts of nasty runtime dependency version
> conflicts (jar hell, version conflicts), since the plugin's own classloader
> gets queried last. The child-first classloader approach tries to load a class
> from the plugin's dependencies first and when unavailable, delegates to it's
> parent classloader. This fixed the issues I had.
> The new approach can give runtime LinkageErrors, but these are easily
> resolvable (see the patch for a few examples)
> I've tested the new loader a bit and am curious about others' findings.
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