diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/MockRM.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/MockRM.java
index d5b64c134c5..25c558f80e2 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/MockRM.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/MockRM.java
@@ -56,12 +56,12 @@
 import org.apache.hadoop.yarn.api.records.ContainerStatus;
 import org.apache.hadoop.yarn.api.records.FinalApplicationStatus;
 import org.apache.hadoop.yarn.api.records.LogAggregationContext;
-import org.apache.hadoop.yarn.api.records.ResourceRequest;
-import org.apache.hadoop.yarn.api.records.SignalContainerCommand;
 import org.apache.hadoop.yarn.api.records.NodeId;
 import org.apache.hadoop.yarn.api.records.NodeState;
 import org.apache.hadoop.yarn.api.records.Priority;
 import org.apache.hadoop.yarn.api.records.Resource;
+import org.apache.hadoop.yarn.api.records.ResourceRequest;
+import org.apache.hadoop.yarn.api.records.SignalContainerCommand;
 import org.apache.hadoop.yarn.conf.YarnConfiguration;
 import org.apache.hadoop.yarn.event.Dispatcher;
 import org.apache.hadoop.yarn.event.DrainDispatcher;
@@ -603,6 +603,7 @@ PrivilegedAction<SubmitApplicationResponse> setClientReq(
   public MockNM registerNode(String nodeIdStr, int memory) throws Exception {
     MockNM nm = new MockNM(nodeIdStr, memory, getResourceTrackerService());
     nm.registerNode();
+    drainEvents();
     return nm;
   }
 
@@ -611,6 +612,7 @@ public MockNM registerNode(String nodeIdStr, int memory, int vCores)
     MockNM nm =
         new MockNM(nodeIdStr, memory, vCores, getResourceTrackerService());
     nm.registerNode();
+    drainEvents();
     return nm;
   }
   
@@ -620,6 +622,7 @@ public MockNM registerNode(String nodeIdStr, int memory, int vCores,
         new MockNM(nodeIdStr, memory, vCores, getResourceTrackerService(),
             YarnVersionInfo.getVersion());
     nm.registerNode(runningApplications);
+    drainEvents();
     return nm;
   }
 
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestRMAdminService.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestRMAdminService.java
index 4513cbb337a..5c69411b981 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestRMAdminService.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestRMAdminService.java
@@ -27,9 +27,7 @@
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
 
 import org.apache.hadoop.conf.Configuration;
@@ -49,7 +47,6 @@
 import org.apache.hadoop.security.authorize.ServiceAuthorizationManager;
 import org.apache.hadoop.yarn.api.records.DecommissionType;
 import org.apache.hadoop.yarn.api.records.NodeId;
-import org.apache.hadoop.yarn.api.records.NodeId;
 import org.apache.hadoop.yarn.api.records.Resource;
 import org.apache.hadoop.yarn.conf.HAUtil;
 import org.apache.hadoop.yarn.conf.YarnConfiguration;
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestRMRestart.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestRMRestart.java
index 96066877236..3b9952b287f 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestRMRestart.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestRMRestart.java
@@ -81,8 +81,6 @@
 import org.apache.hadoop.yarn.api.records.ResourceRequest;
 import org.apache.hadoop.yarn.api.records.YarnApplicationState;
 import org.apache.hadoop.yarn.conf.YarnConfiguration;
-import org.apache.hadoop.yarn.event.Dispatcher;
-import org.apache.hadoop.yarn.event.DrainDispatcher;
 import org.apache.hadoop.yarn.exceptions.ApplicationAttemptNotFoundException;
 import org.apache.hadoop.yarn.security.AMRMTokenIdentifier;
 import org.apache.hadoop.yarn.security.client.RMDelegationTokenIdentifier;
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestResourceTrackerService.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestResourceTrackerService.java
index dd37b67fdfe..68ba7ecd424 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestResourceTrackerService.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestResourceTrackerService.java
@@ -176,7 +176,6 @@ public void testDecommissionWithExcludeHosts() throws Exception {
     MockNM nm2 = rm.registerNode("host2:5678", 10240);
     MockNM nm3 = rm.registerNode("localhost:4433", 1024);
 
-    rm.drainEvents();
 
     int metricCount = ClusterMetrics.getMetrics().getNumDecommisionedNMs();
     NodeHeartbeatResponse nodeHeartbeat = nm1.nodeHeartbeat(true);
@@ -208,7 +207,6 @@ public void testDecommissionWithExcludeHosts() throws Exception {
     rm.getNodesListManager().refreshNodes(conf);
 
     nm3 = rm.registerNode("localhost:4433", 1024);
-    rm.drainEvents();
     nodeHeartbeat = nm3.nodeHeartbeat(true);
     rm.drainEvents();
     Assert.assertTrue(NodeAction.NORMAL.equals(nodeHeartbeat.getNodeAction()));
@@ -1027,7 +1025,6 @@ public void handle(SchedulerEvent event) {
     
     // unhealthy node changed back to healthy
     nm2 = rm.registerNode("host2:5678", 5120);
-    rm.drainEvents();
     response = nm2.nodeHeartbeat(true);
     response = nm2.nodeHeartbeat(true);
     rm.drainEvents();
@@ -1035,7 +1032,6 @@ public void handle(SchedulerEvent event) {
 
     // reconnect of node with changed capability
     nm1 = rm.registerNode("host2:5678", 10240);
-    rm.drainEvents();
     response = nm1.nodeHeartbeat(true);
     rm.drainEvents();
     Assert.assertTrue(NodeAction.NORMAL.equals(response.getNodeAction()));
@@ -1045,7 +1041,6 @@ public void handle(SchedulerEvent event) {
     List<ApplicationId> runningApps = new ArrayList<ApplicationId>();
     runningApps.add(ApplicationId.newInstance(1, 0));
     nm1 = rm.registerNode("host2:5678", 15360, 2, runningApps);
-    rm.drainEvents();
     response = nm1.nodeHeartbeat(true);
     rm.drainEvents();
     Assert.assertTrue(NodeAction.NORMAL.equals(response.getNodeAction()));
@@ -1055,7 +1050,6 @@ public void handle(SchedulerEvent event) {
     nm1 = new MockNM("host1:1234", 5120, rm.getResourceTrackerService());
     nm1.setHttpPort(3);
     nm1.registerNode();
-    rm.drainEvents();
     response = nm1.nodeHeartbeat(true);
     response = nm1.nodeHeartbeat(true);
     rm.drainEvents();
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/TestNodesListManager.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/TestNodesListManager.java
index e747df40753..507165d3676 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/TestNodesListManager.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/TestNodesListManager.java
@@ -29,8 +29,8 @@
 import org.apache.hadoop.yarn.api.records.Resource;
 import org.apache.hadoop.yarn.conf.YarnConfiguration;
 import org.apache.hadoop.yarn.event.AbstractEvent;
-import org.apache.hadoop.yarn.event.AsyncDispatcher;
 import org.apache.hadoop.yarn.event.Dispatcher;
+import org.apache.hadoop.yarn.event.DrainDispatcher;
 import org.apache.hadoop.yarn.event.EventHandler;
 import org.apache.hadoop.yarn.server.resourcemanager.MockAM;
 import org.apache.hadoop.yarn.server.resourcemanager.MockNM;
@@ -43,7 +43,6 @@
 import org.apache.hadoop.yarn.server.resourcemanager.rmapp.attempt.RMAppAttemptState;
 import org.apache.hadoop.yarn.server.resourcemanager.rmnode.RMNode;
 import org.apache.hadoop.yarn.util.ControlledClock;
-import org.apache.hadoop.yarn.util.SystemClock;
 import org.apache.log4j.Level;
 import org.apache.log4j.LogManager;
 import org.apache.log4j.Logger;
@@ -236,7 +235,7 @@ public void testCachedResolverWithEvent() throws Exception {
    * Create dispatcher object
    */
   private Dispatcher getDispatcher() {
-    Dispatcher dispatcher = new AsyncDispatcher() {
+    Dispatcher dispatcher = new DrainDispatcher() {
       @SuppressWarnings({ "rawtypes", "unchecked" })
       @Override
       public EventHandler getEventHandler() {