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From "Stefan Bodewig (JIRA)" <>
Subject [jira] [Commented] (COMPRESS-285) checking of availability of XZ compression is expensive - result should be reused
Date Thu, 14 Aug 2014 09:50:12 GMT


Stefan Bodewig commented on COMPRESS-285:

svn revision 1617904 

docs are missing and I'm not sure how to test this properly.

I've merged the two AtomicBooleans from Wojciech's idea into a single AtomicInteger and immediately
check for XZ's presence if caching is enabled to avoid race conditions.

> checking of availability of XZ compression is expensive - result should be reused
> ---------------------------------------------------------------------------------
>                 Key: COMPRESS-285
>                 URL:
>             Project: Commons Compress
>          Issue Type: Improvement
>          Components: Compressors
>    Affects Versions: 1.5, 1.6, 1.7, 1.8
>         Environment: linux 64-bit, java 7, glassfish, solr, tika
>            Reporter: Wojciech Ɓozowicki
>            Priority: Minor
>              Labels: XZ, performance
>             Fix For: 1.9
> I use solr with apache tika for indexing documents. Tika uses commons-compress to handle
compressed files. Using sampler (jvisualvm) I have seen that quite a lot of time (5-7%) during
my tests is spent in XZUtils.isXZCompressionAvailable because of unavailable XZ compression
(I guess for each time classloaders spend some time looking for unavailable classes, then
> I think the result of the first check should be stored and reused.
> Here is the stacktrace (just to show the way tika is using commons-compress):
> org.apache.commons.compress.compressors.xz.XZUtils.isXZCompressionAvailable(
> 	at org.apache.commons.compress.compressors.CompressorStreamFactory.createCompressorInputStream(
> 	at org.apache.tika.parser.pkg.ZipContainerDetector.detectCompressorFormat(
> 	at org.apache.tika.parser.pkg.ZipContainerDetector.detect(
> 	at org.apache.tika.detect.CompositeDetector.detect(

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