diff --git a/hadoop-yarn-project/CHANGES.txt b/hadoop-yarn-project/CHANGES.txt
index cd152156d06..0f4a4d7c44b 100644
--- a/hadoop-yarn-project/CHANGES.txt
+++ b/hadoop-yarn-project/CHANGES.txt
@@ -398,6 +398,9 @@ Release 2.8.0 - UNRELEASED
 
     YARN-3707. RM Web UI queue filter doesn't work. (Wangda Tan via jianhe)
 
+    YARN-3632. Ordering policy should be allowed to reorder an application when
+    demand changes. (Craig Welch via jianhe)
+
 Release 2.7.1 - 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/AppSchedulingInfo.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/AppSchedulingInfo.java
index 5604f0f3396..77ac5b3e640 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/AppSchedulingInfo.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/AppSchedulingInfo.java
@@ -128,11 +128,14 @@ public class AppSchedulingInfo {
    *
    * @param requests resources to be acquired
    * @param recoverPreemptedRequest recover Resource Request on preemption
+   * @return true if any resource was updated, false else
    */
-  synchronized public void updateResourceRequests(
+  synchronized public boolean updateResourceRequests(
       List<ResourceRequest> requests, boolean recoverPreemptedRequest) {
     QueueMetrics metrics = queue.getMetrics();
     
+    boolean anyResourcesUpdated = false;
+
     // Update resource requests
     for (ResourceRequest request : requests) {
       Priority priority = request.getPriority();
@@ -146,6 +149,7 @@ public class AppSchedulingInfo {
               + request);
         }
         updatePendingResources = true;
+        anyResourcesUpdated = true;
         
         // Premature optimization?
         // Assumes that we won't see more than one priority request updated
@@ -209,6 +213,7 @@ public class AppSchedulingInfo {
         }
       }
     }
+    return anyResourcesUpdated;
   }
 
   /**
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/SchedulerApplicationAttempt.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/SchedulerApplicationAttempt.java
index 0554c041380..dbc3cb57139 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/SchedulerApplicationAttempt.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/SchedulerApplicationAttempt.java
@@ -284,11 +284,12 @@ public class SchedulerApplicationAttempt implements SchedulableEntity {
     return queue;
   }
   
-  public synchronized void updateResourceRequests(
+  public synchronized boolean updateResourceRequests(
       List<ResourceRequest> requests) {
     if (!isStopped) {
-      appSchedulingInfo.updateResourceRequests(requests, false);
+      return appSchedulingInfo.updateResourceRequests(requests, false);
     }
+    return false;
   }
   
   public synchronized void recoverResourceRequests(
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/CapacityScheduler.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/CapacityScheduler.java
index 48c7f2fd4a3..06d282df148 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/CapacityScheduler.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/CapacityScheduler.java
@@ -895,6 +895,10 @@ public class CapacityScheduler extends
     // Release containers
     releaseContainers(release, application);
 
+    Allocation allocation;
+
+    LeafQueue updateDemandForQueue = null;
+
     synchronized (application) {
 
       // make sure we aren't stopping/removing the application
@@ -915,8 +919,10 @@ public class CapacityScheduler extends
         application.showRequests();
   
         // Update application requests
-        application.updateResourceRequests(ask);
-  
+        if (application.updateResourceRequests(ask)) {
+          updateDemandForQueue = (LeafQueue) application.getQueue();
+        }
+
         LOG.debug("allocate: post-update");
         application.showRequests();
       }
@@ -929,9 +935,16 @@ public class CapacityScheduler extends
 
       application.updateBlacklist(blacklistAdditions, blacklistRemovals);
 
-      return application.getAllocation(getResourceCalculator(),
+      allocation = application.getAllocation(getResourceCalculator(),
                    clusterResource, getMinimumResourceCapability());
     }
+
+    if (updateDemandForQueue != null) {
+      updateDemandForQueue.getOrderingPolicy().demandUpdated(application);
+    }
+
+    return allocation;
+
   }
 
   @Override
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/policy/AbstractComparatorOrderingPolicy.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/AbstractComparatorOrderingPolicy.java
index e046fcf66bc..c4d2aae318b 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/AbstractComparatorOrderingPolicy.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/AbstractComparatorOrderingPolicy.java
@@ -37,6 +37,7 @@ public abstract class AbstractComparatorOrderingPolicy<S extends SchedulableEnti
                                             
   protected TreeSet<S> schedulableEntities;
   protected Comparator<SchedulableEntity> comparator;
+  protected Map<String, S> entitiesToReorder = new HashMap<String, S>();
   
   public AbstractComparatorOrderingPolicy() { }
   
@@ -47,11 +48,13 @@ public abstract class AbstractComparatorOrderingPolicy<S extends SchedulableEnti
   
   @Override
   public Iterator<S> getAssignmentIterator() {
+    reorderScheduleEntities();
     return schedulableEntities.iterator();
   }
   
   @Override
   public Iterator<S> getPreemptionIterator() {
+    reorderScheduleEntities();
     return schedulableEntities.descendingIterator();
   }
   
@@ -68,6 +71,22 @@ public abstract class AbstractComparatorOrderingPolicy<S extends SchedulableEnti
     schedulableEntities.add(schedulableEntity);
   }
   
+  protected void reorderScheduleEntities() {
+    synchronized (entitiesToReorder) {
+      for (Map.Entry<String, S> entry :
+          entitiesToReorder.entrySet()) {
+        reorderSchedulableEntity(entry.getValue());
+      }
+      entitiesToReorder.clear();
+    }
+  }
+
+  protected void entityRequiresReordering(S schedulableEntity) {
+    synchronized (entitiesToReorder) {
+      entitiesToReorder.put(schedulableEntity.getId(), schedulableEntity);
+    }
+  }
+
   @VisibleForTesting
   public Comparator<SchedulableEntity> getComparator() {
     return comparator; 
@@ -80,6 +99,9 @@ public abstract class AbstractComparatorOrderingPolicy<S extends SchedulableEnti
   
   @Override
   public boolean removeSchedulableEntity(S s) {
+    synchronized (entitiesToReorder) {
+      entitiesToReorder.remove(s.getId());
+    }
     return schedulableEntities.remove(s); 
   }
   
@@ -104,6 +126,9 @@ public abstract class AbstractComparatorOrderingPolicy<S extends SchedulableEnti
   public abstract void containerReleased(S schedulableEntity, 
     RMContainer r);
   
+  @Override
+  public abstract void demandUpdated(S schedulableEntity);
+
   @Override
   public abstract String getInfo();
   
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/policy/FairOrderingPolicy.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/FairOrderingPolicy.java
index 3ab74de1c03..ea14b426753 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/FairOrderingPolicy.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/FairOrderingPolicy.java
@@ -96,15 +96,22 @@ public class FairOrderingPolicy<S extends SchedulableEntity> extends AbstractCom
   @Override
   public void containerAllocated(S schedulableEntity,
     RMContainer r) {
-      reorderSchedulableEntity(schedulableEntity);
+      entityRequiresReordering(schedulableEntity);
     }
 
   @Override
   public void containerReleased(S schedulableEntity,
     RMContainer r) {
-      reorderSchedulableEntity(schedulableEntity);
+      entityRequiresReordering(schedulableEntity);
     }
 
+  @Override
+  public void demandUpdated(S schedulableEntity) {
+    if (sizeBasedWeight) {
+      entityRequiresReordering(schedulableEntity);
+    }
+  }
+
   @Override
   public String getInfo() {
     String sbw = sizeBasedWeight ? " with sizeBasedWeight" : "";
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/policy/FifoOrderingPolicy.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/FifoOrderingPolicy.java
index 932a5f9e19c..74a422cfbc6 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/FifoOrderingPolicy.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/FifoOrderingPolicy.java
@@ -46,7 +46,11 @@ public class FifoOrderingPolicy<S extends SchedulableEntity> extends AbstractCom
   public void containerReleased(S schedulableEntity, 
     RMContainer r) {
     }
-  
+
+  @Override
+  public void demandUpdated(S schedulableEntity) {
+  }
+
   @Override
   public String getInfo() {
     return "FifoOrderingPolicy";
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/policy/OrderingPolicy.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/OrderingPolicy.java
index aebdcdee990..e3f67ce5660 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/OrderingPolicy.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/OrderingPolicy.java
@@ -101,6 +101,11 @@ public interface OrderingPolicy<S extends SchedulableEntity> {
   public void containerReleased(S schedulableEntity, 
     RMContainer r);
   
+  /**
+   * Demand Updated for the passed schedulableEntity, reorder if needed.
+   */
+  void demandUpdated(S schedulableEntity);
+
   /**
    * Display information regarding configuration & status
    */
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/TestCapacityScheduler.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/TestCapacityScheduler.java
index d36058156bb..7b665e435f8 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/TestCapacityScheduler.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/TestCapacityScheduler.java
@@ -72,6 +72,8 @@ import org.apache.hadoop.yarn.conf.YarnConfiguration;
 import org.apache.hadoop.yarn.event.AsyncDispatcher;
 import org.apache.hadoop.yarn.exceptions.YarnException;
 import org.apache.hadoop.yarn.exceptions.YarnRuntimeException;
+import org.apache.hadoop.yarn.factories.RecordFactory;
+import org.apache.hadoop.yarn.factory.providers.RecordFactoryProvider;
 import org.apache.hadoop.yarn.ipc.YarnRPC;
 import org.apache.hadoop.yarn.nodelabels.RMNodeLabel;
 import org.apache.hadoop.yarn.server.api.protocolrecords.UpdateNodeResourceRequest;
@@ -126,6 +128,7 @@ import org.apache.hadoop.yarn.server.resourcemanager.webapp.dao.CapacitySchedule
 import org.apache.hadoop.yarn.server.resourcemanager.webapp.dao.CapacitySchedulerLeafQueueInfo;
 import org.apache.hadoop.yarn.server.resourcemanager.webapp.dao.CapacitySchedulerQueueInfo;
 import org.apache.hadoop.yarn.server.resourcemanager.webapp.dao.CapacitySchedulerQueueInfoList;
+import org.apache.hadoop.yarn.server.resourcemanager.scheduler.policy.FairOrderingPolicy;
 import org.apache.hadoop.yarn.server.utils.BuilderUtils;
 import org.apache.hadoop.yarn.util.resource.DominantResourceCalculator;
 import org.apache.hadoop.yarn.util.resource.Resources;
@@ -676,6 +679,118 @@ public class TestCapacityScheduler {
     rm.stop();
   }
   
+  @Test
+  public void testAllocateReorder() throws Exception {
+
+    //Confirm that allocation (resource request) alone will trigger a change in
+    //application ordering where appropriate
+
+    Configuration conf = new Configuration();
+    conf.setClass(YarnConfiguration.RM_SCHEDULER, CapacityScheduler.class,
+        ResourceScheduler.class);
+    MockRM rm = new MockRM(conf);
+    rm.start();
+    CapacityScheduler cs = (CapacityScheduler) rm.getResourceScheduler();
+
+    LeafQueue q = (LeafQueue) cs.getQueue("default");
+    Assert.assertNotNull(q);
+
+    FairOrderingPolicy fop = new FairOrderingPolicy();
+    fop.setSizeBasedWeight(true);
+    q.setOrderingPolicy(fop);
+
+    String host = "127.0.0.1";
+    RMNode node =
+        MockNodes.newNodeInfo(0, MockNodes.newResource(4 * GB), 1, host);
+    cs.handle(new NodeAddedSchedulerEvent(node));
+
+    //add app begin
+    ApplicationId appId1 = BuilderUtils.newApplicationId(100, 1);
+    ApplicationAttemptId appAttemptId1 = BuilderUtils.newApplicationAttemptId(
+        appId1, 1);
+
+    RMAppAttemptMetrics attemptMetric1 =
+        new RMAppAttemptMetrics(appAttemptId1, rm.getRMContext());
+    RMAppImpl app1 = mock(RMAppImpl.class);
+    when(app1.getApplicationId()).thenReturn(appId1);
+    RMAppAttemptImpl attempt1 = mock(RMAppAttemptImpl.class);
+    when(attempt1.getAppAttemptId()).thenReturn(appAttemptId1);
+    when(attempt1.getRMAppAttemptMetrics()).thenReturn(attemptMetric1);
+    when(app1.getCurrentAppAttempt()).thenReturn(attempt1);
+
+    rm.getRMContext().getRMApps().put(appId1, app1);
+
+    SchedulerEvent addAppEvent1 =
+        new AppAddedSchedulerEvent(appId1, "default", "user");
+    cs.handle(addAppEvent1);
+    SchedulerEvent addAttemptEvent1 =
+        new AppAttemptAddedSchedulerEvent(appAttemptId1, false);
+    cs.handle(addAttemptEvent1);
+    //add app end
+
+    //add app begin
+    ApplicationId appId2 = BuilderUtils.newApplicationId(100, 2);
+    ApplicationAttemptId appAttemptId2 = BuilderUtils.newApplicationAttemptId(
+        appId2, 1);
+
+    RMAppAttemptMetrics attemptMetric2 =
+        new RMAppAttemptMetrics(appAttemptId2, rm.getRMContext());
+    RMAppImpl app2 = mock(RMAppImpl.class);
+    when(app2.getApplicationId()).thenReturn(appId2);
+    RMAppAttemptImpl attempt2 = mock(RMAppAttemptImpl.class);
+    when(attempt2.getAppAttemptId()).thenReturn(appAttemptId2);
+    when(attempt2.getRMAppAttemptMetrics()).thenReturn(attemptMetric2);
+    when(app2.getCurrentAppAttempt()).thenReturn(attempt2);
+
+    rm.getRMContext().getRMApps().put(appId2, app2);
+
+    SchedulerEvent addAppEvent2 =
+        new AppAddedSchedulerEvent(appId2, "default", "user");
+    cs.handle(addAppEvent2);
+    SchedulerEvent addAttemptEvent2 =
+        new AppAttemptAddedSchedulerEvent(appAttemptId2, false);
+    cs.handle(addAttemptEvent2);
+    //add app end
+
+    RecordFactory recordFactory =
+      RecordFactoryProvider.getRecordFactory(null);
+
+    Priority priority = TestUtils.createMockPriority(1);
+    ResourceRequest r1 = TestUtils.createResourceRequest(ResourceRequest.ANY, 1*GB, 1, true, priority, recordFactory);
+
+    //This will allocate for app1
+    cs.allocate(appAttemptId1,
+        Collections.<ResourceRequest>singletonList(r1),
+        Collections.<ContainerId>emptyList(),
+        null, null);
+
+    //And this will result in container assignment for app1
+    CapacityScheduler.schedule(cs);
+
+    //Verify that app1 is still first in assignment order
+    //This happens because app2 has no demand/a magnitude of NaN, which
+    //results in app1 and app2 being equal in the fairness comparison and
+    //failling back to fifo (start) ordering
+    assertEquals(q.getOrderingPolicy().getAssignmentIterator().next().getId(),
+      appId1.toString());
+
+    //Now, allocate for app2 (this would be the first/AM allocation)
+    ResourceRequest r2 = TestUtils.createResourceRequest(ResourceRequest.ANY, 1*GB, 1, true, priority, recordFactory);
+    cs.allocate(appAttemptId2,
+        Collections.<ResourceRequest>singletonList(r2),
+        Collections.<ContainerId>emptyList(),
+        null, null);
+
+    //In this case we do not perform container assignment because we want to
+    //verify re-ordering based on the allocation alone
+
+    //Now, the first app for assignment is app2
+    assertEquals(q.getOrderingPolicy().getAssignmentIterator().next().getId(),
+      appId2.toString());
+
+    rm.stop();
+  }
+
   @Test
   public void testResourceOverCommit() throws Exception {
     Configuration conf = new Configuration();