YARN-1128. FifoPolicy.computeShares throws NPE on empty list of Schedulables (Karthik Kambatla via Sandy Ryza)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1525315 13f79535-47bb-0310-9956-ffa450edef68

hadoop-yarn-project/CHANGES.txt

@@ -40,6 +40,9 @@ Release 2.2.0 - UNRELEASED
 
   BUG FIXES
 
+    YARN-1128. FifoPolicy.computeShares throws NPE on empty list of Schedulables
+    (Karthik Kambatla via Sandy Ryza)
+
 Release 2.1.1-beta - 2013-09-23
 
   INCOMPATIBLE CHANGES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/policies/FifoPolicy.java

@@ -20,6 +20,7 @@
 import java.io.Serializable;
 import java.util.Collection;
 import java.util.Comparator;
+import java.util.Iterator;
 
 import org.apache.hadoop.classification.InterfaceAudience.Private;
 import org.apache.hadoop.classification.InterfaceStability.Unstable;
@@ -73,6 +74,10 @@ public Comparator<Schedulable> getComparator() {
   @Override
   public void computeShares(Collection<? extends Schedulable> schedulables,
       Resource totalResources) {
+    if (schedulables.isEmpty()) {
+      return;
+    }
+
     Schedulable earliest = null;
     for (Schedulable schedulable : schedulables) {
       if (earliest == null ||

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/policies/TestEmptyQueues.java

@@ -0,0 +1,57 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.policies;
+
+import org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.Schedulable;
+import org.apache.hadoop.yarn.server.resourcemanager.scheduler.fair.SchedulingPolicy;
+import org.apache.hadoop.yarn.util.resource.Resources;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+public class TestEmptyQueues {
+  private Collection<? extends Schedulable> schedulables;
+
+  @Before
+  public void setup() {
+    schedulables = new ArrayList<Schedulable>();
+  }
+
+  private void testComputeShares(SchedulingPolicy policy) {
+    policy.computeShares(schedulables, Resources.none());
+  }
+
+  @Test (timeout = 1000)
+  public void testFifoPolicy() {
+    testComputeShares(SchedulingPolicy.getInstance(FifoPolicy.class));
+  }
+
+  @Test (timeout = 1000)
+  public void testFairSharePolicy() {
+    testComputeShares(SchedulingPolicy.getInstance(FairSharePolicy.class));
+  }
+
+  @Test (timeout = 1000)
+  public void testDRFPolicy() {
+    testComputeShares(
+        SchedulingPolicy.getInstance(DominantResourceFairnessPolicy.class));
+  }
+}