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https://issues.apache.org/jira/browse/TIKA-1149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13715180#comment-13715180
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Jukka Zitting commented on TIKA-1149:
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Note that for example {{DefaultParser.getParsers(ParseContext)}} can return a
different set of parsers on each invocation, thanks to the dynamic service
lookup mechanism in {{ServiceLoader}}. Thus caching the return value can lead
to incorrect behavior.
An alternative optimization would be to refactor the
{{CompositeParser.getParser(Metadata, ParseContext)}} method so that it doesn't
need to always instantiate the full type->parser map. Instead it could for
example restrict the search to only the specified type and its supertypes.
> 12% performance improvement by caching in CompositeParser
> ---------------------------------------------------------
>
> Key: TIKA-1149
> URL: https://issues.apache.org/jira/browse/TIKA-1149
> Project: Tika
> Issue Type: Improvement
> Components: parser
> Affects Versions: 1.3, 1.4
> Reporter: Luca Della Toffola
> Priority: Minor
> Labels: performance
> Attachments: CompositeParser.patch, ParseContext.patch
>
>
> We found an easy way to improve Tika's performance. The idea is to avoid
> recomputing parsers map over and over
> in CompositeParser.getParsers(...) if the context is empty and to cache the
> returned value instead.
> This can be done safely even under the assumption that the media-registry and
> the list of component parsers do change while Tika is executing, by
> invalidating the cache in the case.
> Our attached patch computes the parsers map once per instance of
> CompositeParser.
> The patch checks for the case where the context is empty and invalidates the
> cache if both media-registry and the list of component parsers change in the
> corresponding setters.
> For example, when running Tika 1.3 on a set of large (~50k classes) JAR files
> (i.e., Java class library + Tika app + other apps), the patch reduces the
> running time
> from 32 seconds to 29 seconds -- i.e., a speedup of ~12%. Speedups of the
> same order of magnitude are found also for smaller workloads.
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