Added unit test

Author: Ashutosh Gupta

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/sink/ganglia/AbstractGangliaSink.java

@@ -27,6 +27,7 @@
 import java.util.Map;
 
 import org.apache.commons.configuration2.SubsetConfiguration;
+import org.apache.hadoop.classification.VisibleForTesting;
 import org.apache.hadoop.metrics2.MetricsSink;
 import org.apache.hadoop.metrics2.util.Servers;
 import org.apache.hadoop.net.DNS;
@@ -79,6 +80,11 @@ public abstract class AbstractGangliaSink implements MetricsSink {
   private int offset;
   private boolean supportSparseMetrics = SUPPORT_SPARSE_METRICS_DEFAULT;
 
+  @VisibleForTesting
+  public List<? extends SocketAddress> getMetricsServers() {
+    return metricsServers;
+  }
+
   /**
    * Used for visiting Metrics
    */

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/sink/ganglia/TestGangliaSink.java

@@ -78,4 +78,14 @@ public void testShouldSetMulticastSocketTtl() throws Exception {
         int ttl = ((MulticastSocket) socket).getTimeToLive();
         assertEquals("Did not set TTL", 3, ttl);
     }
+
+    @Test
+    public void testMultipleMetricsServers() {
+        SubsetConfiguration conf =
+            new ConfigBuilder().add("test.sink.ganglia.servers", "server1,server2")
+                .subset("test.sink.ganglia");
+        GangliaSink30 gangliaSink = new GangliaSink30();
+        gangliaSink.init(conf);
+        assertEquals(2, gangliaSink.getMetricsServers().size());
+    }
 }