svn merge -c 1309077 from trunk. FIXES MAPREDUCE-4072. User set java.library.path seems to overwrite default creating problems native lib loading (Anupam Seth via bobby)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1309079 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -103,6 +103,9 @@ Release 0.23.3 - UNRELEASED
 
   INCOMPATIBLE CHANGES
 
+    MAPREDUCE-4072. User set java.library.path seems to overwrite default
+    creating problems native lib loading (Anupam Seth via bobby)
+
   NEW FEATURES
 
   IMPROVEMENTS

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/resources/mapred-default.xml

@@ -412,7 +412,12 @@
         -Xmx1024m -verbose:gc -Xloggc:/tmp/@taskid@.gc
   
   The configuration variable mapred.child.ulimit can be used to control the
-  maximum virtual memory of the child processes. 
+  maximum virtual memory of the child processes.
+
+  Usage of -Djava.library.path can cause programs to no longer function if
+  hadoop native libraries are used. These values should instead be set as part 
+  of LD_LIBRARY_PATH in the map / reduce JVM env using the mapreduce.map.env and 
+  mapreduce.reduce.env config settings. 
   </description>
 </property>
 

hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-site/src/site/apt/WritingYarnApplications.apt.vm

@@ -779,6 +779,13 @@ Hadoop MapReduce Next Generation - Writing YARN Applications
   need to increase the value of the the cluster-wide configuration variable
   <<<yarn.nodemanager.vmem-pmem-ratio>>>.
 
+** How do I include native libraries?
+
+
+  Setting -Djava.library.path on the command line while launching a container 
+  can cause native libraries used by Hadoop to not be loaded correctly and can
+  result in errors. It is cleaner to use LD_LIBRARY_PATH instead.
+
 * Useful Links
 
   * {{{https://issues.apache.org/jira/secure/attachment/12486023/MapReduce_NextGen_Architecture.pdf}Map Reduce Next Generation Architecture}}