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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-8756) libsnappy loader issues
Date Wed, 05 Sep 2012 02:04:07 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-8756?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Colin Patrick McCabe updated HADOOP-8756:
-----------------------------------------

    Description: 
We use {{System.loadLibrary("snappy")}} from the Java side.  However in libhadoop, we use
{{dlopen}} to open libsnappy.so dynamically.  System.loadLibrary uses {{java.library.path}}
to resolve libraries, and {{dlopen}} uses {{LD_LIBRARY_PATH}} and the system paths to resolve
libraries.  Because of this, the two library loading functions can be at odds.

We should fix this so we only load the library once, preferably using the standard Java {{java.library.path}}.

We should also log the search path(s) we use for {{libsnappy.so}} when loading fails, so that
it's easier to diagnose configuration issues.

  was:
* We use {{System.loadLibrary("snappy")}} from the Java side.  However in libhadoop, we use
{{dlopen}} to open libsnappy.so dynamically.  It seems like the System.loadLibrary nonsense
is completely redundant-- we would only need this if we planned on accessing libsnappy methods
directly from Java (via the 'native' keyword)- - which we don't, and can't, since snappy is
not JNI.  At the end of the day, snappy is only accessible through libhadoop.so, so I think
snappy-related issues should be handled there.

* We should log the search path(s) we use for {{libsnappy.so}}, so that it's easier to diagnose
configuration issues.

    
> libsnappy loader issues
> -----------------------
>
>                 Key: HADOOP-8756
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8756
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: native
>    Affects Versions: 2.2.0-alpha
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>            Priority: Minor
>
> We use {{System.loadLibrary("snappy")}} from the Java side.  However in libhadoop, we
use {{dlopen}} to open libsnappy.so dynamically.  System.loadLibrary uses {{java.library.path}}
to resolve libraries, and {{dlopen}} uses {{LD_LIBRARY_PATH}} and the system paths to resolve
libraries.  Because of this, the two library loading functions can be at odds.
> We should fix this so we only load the library once, preferably using the standard Java
{{java.library.path}}.
> We should also log the search path(s) we use for {{libsnappy.so}} when loading fails,
so that it's easier to diagnose configuration issues.

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