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From "Eli Collins (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-3693) Job's shouldn't have to configure the location of compression libraries on the server in mapred-site.xml
Date Wed, 25 Jan 2012 22:36:41 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-3693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13193406#comment-13193406
] 

Eli Collins commented on MAPREDUCE-3693:
----------------------------------------

Oops, I forgot that mapred-default.xml isn't just docs, is actually used. In any case, we
typically make the default value in the code match the default.xml value (see HADOOP-7956
for removing this duplication) so good to be consistent.

(btw I assume you mean mapred-default.xml instead of yarn-default.xml)
                
> Job's shouldn't have to configure the location of compression libraries on the server
in mapred-site.xml
> --------------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-3693
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3693
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>    Affects Versions: 0.23.0
>            Reporter: Roman Shaposhnik
>            Assignee: Roman Shaposhnik
>         Attachments: MAPREDUCE-3693.patch.txt
>
>
> I have noticed that org.apache.hadoop.mapred.MapReduceChildJVM doesn't forward the value
of -Djava.library.path= from the parent JVM to the child JVM. Thus if one wants to use native
libraries for compression the only option seems to be to manually include relevant java.library.path
settings into the mapred-site.xml (as mapred.[map|reduce].child.java.opts).
> This seems to be a change in behavior compared to MR1 where TaskRunner.java used to do
that:
> {noformat}
> String libraryPath = System.getProperty("java.library.path");
>     if (libraryPath == null) {
>       libraryPath = workDir.getAbsolutePath();
>     } else {
>       libraryPath += SYSTEM_PATH_SEPARATOR + workDir;
>     }
>     boolean hasUserLDPath = false;
>     for(int i=0; i<javaOptsSplit.length ;i++) {
>       if(javaOptsSplit[i].startsWith("-Djava.library.path=")) {
>         javaOptsSplit[i] += SYSTEM_PATH_SEPARATOR + libraryPath;
>         hasUserLDPath = true;
>         break;
>       }
>     }
>     if(!hasUserLDPath) {
>       vargs.add("-Djava.library.path=" + libraryPath);
>     }
>     for (int i = 0; i < javaOptsSplit.length; i++) {
>       vargs.add(javaOptsSplit[i]);
>     }
> {noformat}
> Is this a regression or a deliberate choice?

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