HDFS-7001. Tests in TestTracing should not depend on the order of execution. (iwasakims via cmccabe)

(cherry picked from commit 7b8df93ce1b7204a247e64b394d57eef748e73aa)

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

@@ -450,6 +450,9 @@ Release 2.6.0 - UNRELEASED
     HDFS-7106. Reconfiguring DataNode volumes does not release the lock files
     in removed volumes. (cnauroth via cmccabe)
 
+    HDFS-7001. Tests in TestTracing depends on the order of execution
+    (iwasakims via cmccabe)
+
     BREAKDOWN OF HDFS-6134 AND HADOOP-10150 SUBTASKS AND RELATED JIRAS
   
       HDFS-6387. HDFS CLI admin tool for creating & deleting an

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/tracing/TestTracing.java

@@ -53,13 +53,15 @@ public class TestTracing {
   private static Configuration conf;
   private static MiniDFSCluster cluster;
   private static DistributedFileSystem dfs;
+  private static SpanReceiverHost spanReceiverHost;
 
   @Test
-  public void testSpanReceiverHost() throws Exception {
-    Configuration conf = new Configuration();
-    conf.set(SpanReceiverHost.SPAN_RECEIVERS_CONF_KEY,
-        SetSpanReceiver.class.getName());
-    SpanReceiverHost spanReceiverHost = SpanReceiverHost.getInstance(conf);
+  public void testGetSpanReceiverHost() throws Exception {
+    Configuration c = new Configuration();
+    // getting instance already loaded.
+    c.set(SpanReceiverHost.SPAN_RECEIVERS_CONF_KEY, "");
+    SpanReceiverHost s = SpanReceiverHost.getInstance(c);
+    Assert.assertEquals(spanReceiverHost, s);
   }
 
   @Test
@@ -228,8 +230,10 @@ public class TestTracing {
     cluster = new MiniDFSCluster.Builder(conf)
         .numDataNodes(3)
         .build();
+    cluster.waitActive();
 
     dfs = cluster.getFileSystem();
+    spanReceiverHost = SpanReceiverHost.getInstance(conf);
   }
 
   @AfterClass