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Date: Wed, 3 Oct 2012 10:41:08 +1100 (NCT)
From: "Eli Collins (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HADOOP-8756) Fix SEGV when libsnappy is in
 java.library.path but not LD_LIBRARY_PATH
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    [ https://issues.apache.org/jira/browse/HADOOP-8756?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13468192#comment-13468192 ] 

Eli Collins commented on HADOOP-8756:
-------------------------------------

+1 looks good to me as well

For those who haven't been following along, we're segfaulting because the compressor/decompressor ignore failures in initIDS, we now detect this failure and check for it in SnappyCodec so we don't run with snappy when we failed to load it. We still require that libsnappy is present in LD_LIBRARY_PATH (HADOOP-8806 improves how it is located).
                
> Fix SEGV when libsnappy is in java.library.path but not LD_LIBRARY_PATH
> -----------------------------------------------------------------------
>
>                 Key: HADOOP-8756
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8756
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: native
>    Affects Versions: 2.0.2-alpha
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>            Priority: Minor
>         Attachments: HADOOP-8756.002.patch, HADOOP-8756.003.patch, HADOOP-8756.004.patch
>
>
> 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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