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From "Subramaniam Krishnan (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-3298) Add support for transitive native library dependencies in DistributedCache
Date Tue, 22 Apr 2008 13:04:41 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-3298?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Subramaniam Krishnan updated HADOOP-3298:
-----------------------------------------

      Description: 

[Hadoop 1660] add the tasks's working directory to it's JAVA_LIBRARY_PATH, this allows to
distribute JNI based native libs with the DistributedCache by symbolically linking them to
the tasks's working directory.

There are many instances when the JNI components have transitive dependencies to other native
libraries. Even if we have symlinks for these in  tasks's working directory, they'll not resolved
as transitive dependencies of native libraries are looked up in the shell's LD_LIBRARY_PATH
and not in the JAVA_LIBRARY_PATH. This can be tackled by adding CWD to JAVA_LIBRARY_PATH in
the *hadoop-env.sh*.
A better way to do this would be to add the CWD only in environment of the Task Tracker as
only it needs it.


  was:
Currently if a M/R job depends on JNI based component the dynamic library must be available
in all the task nodes. This is not possible specially when you have not control on the cluster
machines, just using it as a service.

It should be possible to specify using the DistributedCache what are the native libraries
a job needs.

For example via a new method 'public void addLibrary(Path libraryPath, JobConf conf)'.

The added libraries would make it to the local FS of the task nodes (same way as cached resources)
but instead been part of the classpath they would be copied to a lib directory and that lib
directory would be added t the LD_LIBRARY_PATH of the task JVM.

An alternative would be to set the '-Djava.library.path=' task JVM parameter to the lib directory
above. However, this would break for libraries that depend on other libraries as the dependent
one would not be in the LD_LIBRARY_PATH and the OS would fail to find it as it is not the
JVM the one doing the load of the dependent one.

For uncached usage of native libraries, a special directory in the JAR could be used for native
libraries. But I'd argue that the DistributedCache enhancement would be enough, and if somebody
wants to use a native library s/he should use the DistributedCached. Or a JobConf addLibrary
method that uses the DistributedCached under the hood at submission time.



    Fix Version/s:     (was: 0.16.0)
                   0.18.0
         Assignee:     (was: Arun C Murthy)
          Summary: Add support for transitive native library dependencies in DistributedCache
  (was: Add support for transitive native libraries to DistributedCache )

> Add support for transitive native library dependencies in DistributedCache 
> ---------------------------------------------------------------------------
>
>                 Key: HADOOP-3298
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3298
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>         Environment: unix (different handling would be required for windows)
>            Reporter: Subramaniam Krishnan
>             Fix For: 0.18.0
>
>
> [Hadoop 1660] add the tasks's working directory to it's JAVA_LIBRARY_PATH, this allows
to distribute JNI based native libs with the DistributedCache by symbolically linking them
to the tasks's working directory.
> There are many instances when the JNI components have transitive dependencies to other
native libraries. Even if we have symlinks for these in  tasks's working directory, they'll
not resolved as transitive dependencies of native libraries are looked up in the shell's LD_LIBRARY_PATH
and not in the JAVA_LIBRARY_PATH. This can be tackled by adding CWD to JAVA_LIBRARY_PATH in
the *hadoop-env.sh*.
> A better way to do this would be to add the CWD only in environment of the Task Tracker
as only it needs it.

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