[jira] [Commented] (HADOOP-8642) Document that io.native.lib.available only controls native bz2 and zlib compression codecs.

["Colin Patrick McCabe (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-8642?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14325181#comment-14325181 ] 

Colin Patrick McCabe commented on HADOOP-8642:
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Thanks, guys.  I agree with the patch as it's written here.  It is a good solution for 2.x.

I wonder if we can get rid of this property completely in 3.x?  I don't see a lot of use for it, to be honest.  Don't we (semi) silently omit the native support for bz2 and zlib during the build if those libraries are not installed?

Stepping back even further than that, we have too many options for doing partial or weirdo builds that nobody actually wants.  Would that many tears be shed if we just made zlib and bz2 mandatory for {{\-Pnative}}?  I bet that probably fewer tears would be shed because fewer people would accidentally get incomplete builds (nobody in the world actually wants a {{\-Pnative}} build without bz2 and zlib.... it's a square wheel)

> Document that io.native.lib.available only controls native bz2 and zlib compression codecs.
> -------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-8642
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8642
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: documentation, native
>    Affects Versions: 2.0.0-alpha
>            Reporter: Eli Collins
>            Assignee: Akira AJISAKA
>         Attachments: HADOOP-8642.2.patch, HADOOP-8642.3.patch, HADOOP-8642.4.patch, HADOOP-8642.5.patch, HADOOP-8642.patch
>
>
> Per core-default.xml {{io.native.lib.available}} indicates "Should native hadoop libraries, if present, be used" however it looks like it only affects zlib. Since we always load the native library this means we may use native libraries even if io.native.lib.available is set to false.
> Let's make the flag to work as advertised - rather than always load the native hadoop library we only attempt to load the library (and report that native is available) if this flag is set. Since io.native.lib.available defaults to true the default behavior should remain unchanged (except that now we wont actually try to load the library if this flag is disabled).



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