YARN-483. Improve documentation on log aggregation in yarn-default.xml (Akira Ajisaka via Sandy Ryza)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1590150 13f79535-47bb-0310-9956-ffa450edef68

hadoop-yarn-project/CHANGES.txt

@@ -58,6 +58,9 @@ Release 2.5.0 - UNRELEASED
 
     YARN-1970. Prepare YARN codebase for JUnit 4.11. (cnauroth)
 
+    YARN-483. Improve documentation on log aggregation in yarn-default.xml
+    (Akira Ajisaka via Sandy Ryza)
+
   OPTIMIZATIONS
 
   BUG FIXES 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/resources/yarn-default.xml

@@ -733,7 +733,14 @@
   </property>
 
   <property>
-    <description>Whether to enable log aggregation</description>
+    <description>Whether to enable log aggregation. Log aggregation collects
+      each container's logs and moves these logs onto a file-system, for e.g.
+      HDFS, after the application completes. Users can configure the
+      "yarn.nodemanager.remote-app-log-dir" and
+      "yarn.nodemanager.remote-app-log-dir-suffix" properties to determine
+      where these logs are moved to. Users can access the logs via the
+      Application Timeline Server.
+    </description>
     <name>yarn.log-aggregation-enable</name>
     <value>false</value>
   </property>