HDFS-8923. Add -source flag to balancer usage message. Contributed by Chris Trezzo

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -2817,6 +2817,9 @@ Release 2.7.3 - UNRELEASED
     HDFS-4946. Allow preferLocalNode in BlockPlacementPolicyDefault to be
     configurable (James Kinley and Nathan Roberts via kihwal)
 
+    HDFS-8923. Add -source flag to balancer usage message.  (Chris Trezzo
+    via szetszwo)
+
   OPTIMIZATIONS
 
   BUG FIXES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/balancer/Balancer.java

@@ -179,6 +179,8 @@ public class Balancer {
       + "\tExcludes the specified datanodes."
       + "\n\t[-include [-f <hosts-file> | <comma-separated list of hosts>]]"
       + "\tIncludes only the specified datanodes."
+      + "\n\t[-source [-f <hosts-file> | <comma-separated list of hosts>]]"
+      + "\tPick only the specified datanodes as source nodes."
       + "\n\t[-blockpools <comma-separated list of blockpool ids>]"
       + "\tThe balancer will only run on blockpools included in this list."
       + "\n\t[-idleiterations <idleiterations>]"

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSCommands.md

@@ -267,6 +267,7 @@ Usage:
               [-policy <policy>]
               [-exclude [-f <hosts-file> | <comma-separated list of hosts>]]
               [-include [-f <hosts-file> | <comma-separated list of hosts>]]
+              [-source [-f <hosts-file> | <comma-separated list of hosts>]]
               [-blockpools <comma-separated list of blockpool ids>]
               [-idleiterations <idleiterations>]
 
@@ -276,6 +277,7 @@ Usage:
 | `-threshold` \<threshold\> | Percentage of disk capacity. This overwrites the default threshold. |
 | `-exclude -f` \<hosts-file\> \| \<comma-separated list of hosts\> | Excludes the specified datanodes from being balanced by the balancer. |
 | `-include -f` \<hosts-file\> \| \<comma-separated list of hosts\> | Includes only the specified datanodes to be balanced by the balancer. |
+| `-source -f` \<hosts-file\> \| \<comma-separated list of hosts\> | Pick only the specified datanodes as source nodes. |
 | `-blockpools` \<comma-separated list of blockpool ids\> | The balancer will only run on blockpools included in this list. |
 | `-idleiterations` \<iterations\> | Maximum number of idle iterations before exit. This overwrites the default idleiterations(5). |