diff --git a/hadoop-yarn-project/CHANGES.txt b/hadoop-yarn-project/CHANGES.txt
index 75416cbbcee..ccab2b7d031 100644
--- a/hadoop-yarn-project/CHANGES.txt
+++ b/hadoop-yarn-project/CHANGES.txt
@@ -88,6 +88,9 @@ Release 2.0.5-beta - UNRELEASED
     YARN-498. Unmanaged AM launcher does not set various constants in env for
     an AM, also does not handle failed AMs properly. (Hitesh Shah via bikas)
 
+    YARN-474. Fix CapacityScheduler to trigger application-activation when
+    am-resource-percent configuration is refreshed. (Zhijie Shen via vinodkv)
+
 Release 2.0.4-alpha - UNRELEASED
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/LeafQueue.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/LeafQueue.java
index 719cf1e578b..1785ec565a6 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/LeafQueue.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/LeafQueue.java
@@ -607,6 +607,10 @@ public class LeafQueue implements CSQueue {
         newlyParsedLeafQueue.getMaximumActiveApplications(), 
         newlyParsedLeafQueue.getMaximumActiveApplicationsPerUser(),
         newlyParsedLeafQueue.state, newlyParsedLeafQueue.acls);
+
+    // queue metrics are updated, more resource may be available
+    // activate the pending applications if possible
+    activateApplications();
   }
 
   @Override
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/TestLeafQueue.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/TestLeafQueue.java
index ccf2a47c128..0460b3f6ad3 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/TestLeafQueue.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/TestLeafQueue.java
@@ -138,6 +138,7 @@ public class TestLeafQueue {
   private static final String C = "c";
   private static final String C1 = "c1";
   private static final String D = "d";
+  private static final String E = "e";
   private void setupQueueConfiguration(
       CapacitySchedulerConfiguration conf, 
       final String newRoot) {
@@ -148,7 +149,7 @@ public class TestLeafQueue {
     conf.setAcl(CapacitySchedulerConfiguration.ROOT, QueueACL.SUBMIT_APPLICATIONS, " ");
     
     final String Q_newRoot = CapacitySchedulerConfiguration.ROOT + "." + newRoot;
-    conf.setQueues(Q_newRoot, new String[] {A, B, C, D});
+    conf.setQueues(Q_newRoot, new String[] {A, B, C, D, E});
     conf.setCapacity(Q_newRoot, 100);
     conf.setMaximumCapacity(Q_newRoot, 100);
     conf.setAcl(Q_newRoot, QueueACL.SUBMIT_APPLICATIONS, " ");
@@ -174,10 +175,14 @@ public class TestLeafQueue {
     conf.setCapacity(Q_C1, 100);
 
     final String Q_D = Q_newRoot + "." + D;
-    conf.setCapacity(Q_D, 10);
+    conf.setCapacity(Q_D, 9);
     conf.setMaximumCapacity(Q_D, 11);
     conf.setAcl(Q_D, QueueACL.SUBMIT_APPLICATIONS, "user_d");
     
+    final String Q_E = Q_newRoot + "." + E;
+    conf.setCapacity(Q_E, 1);
+    conf.setMaximumCapacity(Q_E, 1);
+    conf.setAcl(Q_E, QueueACL.SUBMIT_APPLICATIONS, "user_e");
   }
 
   static LeafQueue stubLeafQueue(LeafQueue queue) {
@@ -1567,6 +1572,59 @@ public class TestLeafQueue {
 
   }
 
+  @Test (timeout = 30000)
+  public void testActivateApplicationAfterQueueRefresh() throws Exception {
+
+    // Manipulate queue 'e'
+    LeafQueue e = stubLeafQueue((LeafQueue)queues.get(E));
+
+    // Users
+    final String user_e = "user_e";
+
+    // Submit applications
+    final ApplicationAttemptId appAttemptId_0 =
+        TestUtils.getMockApplicationAttemptId(0, 0);
+    FiCaSchedulerApp app_0 =
+        new FiCaSchedulerApp(appAttemptId_0, user_e, e,
+            mock(ActiveUsersManager.class), rmContext);
+    e.submitApplication(app_0, user_e, E);
+
+    final ApplicationAttemptId appAttemptId_1 =
+        TestUtils.getMockApplicationAttemptId(1, 0);
+    FiCaSchedulerApp app_1 =
+        new FiCaSchedulerApp(appAttemptId_1, user_e, e,
+            mock(ActiveUsersManager.class), rmContext);
+    e.submitApplication(app_1, user_e, E);  // same user
+
+    final ApplicationAttemptId appAttemptId_2 =
+        TestUtils.getMockApplicationAttemptId(2, 0);
+    FiCaSchedulerApp app_2 =
+        new FiCaSchedulerApp(appAttemptId_2, user_e, e,
+            mock(ActiveUsersManager.class), rmContext);
+    e.submitApplication(app_2, user_e, E);  // same user
+
+    // before reinitialization
+    assertEquals(2, e.activeApplications.size());
+    assertEquals(1, e.pendingApplications.size());
+
+    csConf.setDouble(CapacitySchedulerConfiguration
+        .MAXIMUM_APPLICATION_MASTERS_RESOURCE_PERCENT,
+        CapacitySchedulerConfiguration
+        .DEFAULT_MAXIMUM_APPLICATIONMASTERS_RESOURCE_PERCENT * 2);
+    Map<String, CSQueue> newQueues = new HashMap<String, CSQueue>();
+    CSQueue newRoot =
+        CapacityScheduler.parseQueue(csContext, csConf, null,
+            CapacitySchedulerConfiguration.ROOT,
+            newQueues, queues,
+            TestUtils.spyHook);
+    queues = newQueues;
+    root.reinitialize(newRoot, cs.getClusterResources());
+
+    // after reinitialization
+    assertEquals(3, e.activeApplications.size());
+    assertEquals(0, e.pendingApplications.size());
+  }
+
   public boolean hasQueueACL(List<QueueUserACLInfo> aclInfos, QueueACL acl) {
     for (QueueUserACLInfo aclInfo : aclInfos) {
       if (aclInfo.getUserAcls().contains(acl)) {