diff --git a/hadoop-yarn-project/CHANGES.txt b/hadoop-yarn-project/CHANGES.txt
index c88560b400..401fb102bf 100644
--- a/hadoop-yarn-project/CHANGES.txt
+++ b/hadoop-yarn-project/CHANGES.txt
@@ -227,6 +227,9 @@ Release 2.5.0 - UNRELEASED
     YARN-2128. FairScheduler: Incorrect calculation of amResource usage.
     (Wei Yan via kasha)
 
+    YARN-2124. Fixed NPE in ProportionalCapacityPreemptionPolicy. (Wangda Tan
+    via jianhe)
+
 Release 2.4.1 - 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/ResourceManager.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/ResourceManager.java
index 724dee14f3..77de2090a0 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/ResourceManager.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/ResourceManager.java
@@ -327,7 +327,7 @@ protected static void validateConfigs(Configuration conf) {
    * RMActiveServices handles all the Active services in the RM.
    */
   @Private
-  class RMActiveServices extends CompositeService {
+  public class RMActiveServices extends CompositeService {
 
     private DelegationTokenRenewer delegationTokenRenewer;
     private EventHandler<SchedulerEvent> schedulerDispatcher;
@@ -526,11 +526,9 @@ protected void createPolicyMonitors() {
                   (PreemptableResourceScheduler) scheduler));
           for (SchedulingEditPolicy policy : policies) {
             LOG.info("LOADING SchedulingEditPolicy:" + policy.getPolicyName());
-            policy.init(conf, rmContext.getDispatcher().getEventHandler(),
-                (PreemptableResourceScheduler) scheduler);
             // periodically check whether we need to take action to guarantee
             // constraints
-            SchedulingMonitor mon = new SchedulingMonitor(policy);
+            SchedulingMonitor mon = new SchedulingMonitor(rmContext, policy);
             addService(mon);
           }
         } else {
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/SchedulingMonitor.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/SchedulingMonitor.java
index 2e93a9e51c..1682f7d861 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/SchedulingMonitor.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/SchedulingMonitor.java
@@ -21,6 +21,8 @@
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.service.AbstractService;
+import org.apache.hadoop.yarn.server.resourcemanager.RMContext;
+import org.apache.hadoop.yarn.server.resourcemanager.scheduler.PreemptableResourceScheduler;
 
 import com.google.common.annotations.VisibleForTesting;
 
@@ -34,18 +36,29 @@ public class SchedulingMonitor extends AbstractService {
   private Thread checkerThread;
   private volatile boolean stopped;
   private long monitorInterval;
+  private RMContext rmContext;
 
-  public SchedulingMonitor(SchedulingEditPolicy scheduleEditPolicy) {
+  public SchedulingMonitor(RMContext rmContext,
+      SchedulingEditPolicy scheduleEditPolicy) {
     super("SchedulingMonitor (" + scheduleEditPolicy.getPolicyName() + ")");
     this.scheduleEditPolicy = scheduleEditPolicy;
-    this.monitorInterval = scheduleEditPolicy.getMonitoringInterval();
+    this.rmContext = rmContext;
   }
 
   public long getMonitorInterval() {
     return monitorInterval;
   }
+  
+  @VisibleForTesting
+  public synchronized SchedulingEditPolicy getSchedulingEditPolicy() {
+    return scheduleEditPolicy;
+  }
 
+  @SuppressWarnings("unchecked")
   public void serviceInit(Configuration conf) throws Exception {
+    scheduleEditPolicy.init(conf, rmContext.getDispatcher().getEventHandler(),
+        (PreemptableResourceScheduler) rmContext.getScheduler());
+    this.monitorInterval = scheduleEditPolicy.getMonitoringInterval();
     super.serviceInit(conf);
   }
 
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicy.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicy.java
index f94aedbf92..6d1516158b 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicy.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicy.java
@@ -165,6 +165,11 @@ public void init(Configuration config,
     observeOnly = config.getBoolean(OBSERVE_ONLY, false);
     rc = scheduler.getResourceCalculator();
   }
+  
+  @VisibleForTesting
+  public ResourceCalculator getResourceCalculator() {
+    return rc;
+  }
 
   @Override
   public void editSchedule(){
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 446bbae04a..67eac76e5f 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
@@ -571,4 +571,8 @@ public void clearQueueMetrics(RMApp app) {
       .getSchedulerApplications().get(app.getApplicationId()).getQueue()
       .getMetrics().clearQueueMetrics();
   }
+  
+  public RMActiveServices getRMActiveService() {
+    return activeServices;
+  }
 }
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/TestProportionalCapacityPreemptionPolicy.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/TestProportionalCapacityPreemptionPolicy.java
index 6a449f5c03..d0a80eb20b 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/TestProportionalCapacityPreemptionPolicy.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/TestProportionalCapacityPreemptionPolicy.java
@@ -17,6 +17,25 @@
  */
 package org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity;
 
+import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.MAX_IGNORED_OVER_CAPACITY;
+import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.MONITORING_INTERVAL;
+import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.NATURAL_TERMINATION_FACTOR;
+import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.OBSERVE_ONLY;
+import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.TOTAL_PREEMPTION_PER_ROUND;
+import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.WAIT_TIME_BEFORE_KILL;
+import static org.apache.hadoop.yarn.server.resourcemanager.scheduler.ContainerPreemptEventType.KILL_CONTAINER;
+import static org.apache.hadoop.yarn.server.resourcemanager.scheduler.ContainerPreemptEventType.PREEMPT_CONTAINER;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.fail;
+import static org.mockito.Matchers.argThat;
+import static org.mockito.Matchers.isA;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.Deque;
@@ -27,12 +46,16 @@
 import java.util.TreeSet;
 
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.service.Service;
 import org.apache.hadoop.yarn.api.records.ApplicationAttemptId;
 import org.apache.hadoop.yarn.api.records.ApplicationId;
 import org.apache.hadoop.yarn.api.records.Container;
 import org.apache.hadoop.yarn.api.records.ContainerId;
 import org.apache.hadoop.yarn.api.records.Resource;
+import org.apache.hadoop.yarn.conf.YarnConfiguration;
 import org.apache.hadoop.yarn.event.EventHandler;
+import org.apache.hadoop.yarn.server.resourcemanager.MockRM;
+import org.apache.hadoop.yarn.server.resourcemanager.monitor.SchedulingMonitor;
 import org.apache.hadoop.yarn.server.resourcemanager.resource.Priority;
 import org.apache.hadoop.yarn.server.resourcemanager.rmcontainer.RMContainer;
 import org.apache.hadoop.yarn.server.resourcemanager.scheduler.ContainerPreemptEvent;
@@ -52,17 +75,6 @@
 import org.mockito.ArgumentCaptor;
 import org.mockito.ArgumentMatcher;
 
-import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.MAX_IGNORED_OVER_CAPACITY;
-import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.MONITORING_INTERVAL;
-import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.NATURAL_TERMINATION_FACTOR;
-import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.OBSERVE_ONLY;
-import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.TOTAL_PREEMPTION_PER_ROUND;
-import static org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.ProportionalCapacityPreemptionPolicy.WAIT_TIME_BEFORE_KILL;
-import static org.apache.hadoop.yarn.server.resourcemanager.scheduler.ContainerPreemptEventType.KILL_CONTAINER;
-import static org.apache.hadoop.yarn.server.resourcemanager.scheduler.ContainerPreemptEventType.PREEMPT_CONTAINER;
-import static org.junit.Assert.*;
-import static org.mockito.Mockito.*;
-
 public class TestProportionalCapacityPreemptionPolicy {
 
   static final long TS = 3141592653L;
@@ -424,6 +436,36 @@ public void testContainerOrdering(){
     assert containers.get(4).equals(rm5);
 
   }
+  
+  @Test
+  public void testPolicyInitializeAfterSchedulerInitialized() {
+    Configuration conf = new Configuration();
+    conf.set(YarnConfiguration.RM_SCHEDULER_MONITOR_POLICIES,
+        ProportionalCapacityPreemptionPolicy.class.getCanonicalName());
+    conf.setBoolean(YarnConfiguration.RM_SCHEDULER_ENABLE_MONITORS, true);
+    
+    @SuppressWarnings("resource")
+    MockRM rm = new MockRM(conf);
+    rm.init(conf);
+    
+    // ProportionalCapacityPreemptionPolicy should be initialized after
+    // CapacityScheduler initialized. We will 
+    // 1) find SchedulingMonitor from RMActiveService's service list, 
+    // 2) check if ResourceCalculator in policy is null or not. 
+    // If it's not null, we can come to a conclusion that policy initialized
+    // after scheduler got initialized
+    for (Service service : rm.getRMActiveService().getServices()) {
+      if (service instanceof SchedulingMonitor) {
+        ProportionalCapacityPreemptionPolicy policy =
+            (ProportionalCapacityPreemptionPolicy) ((SchedulingMonitor) service)
+                .getSchedulingEditPolicy();
+        assertNotNull(policy.getResourceCalculator());
+        return;
+      }
+    }
+    
+    fail("Failed to find SchedulingMonitor service, please check what happened");
+  }
 
   static class IsPreemptionRequestFor
       extends ArgumentMatcher<ContainerPreemptEvent> {