YARN-5825. ProportionalPreemptionalPolicy should use readLock over LeafQueue instead of synchronized block. Contributed by Sunil G

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/FifoCandidatesSelector.java

@@ -89,7 +89,8 @@ public class FifoCandidatesSelector
               .getResToObtainByPartitionForLeafQueue(preemptionContext,
                   queueName, clusterResource);
 
-      synchronized (leafQueue) {
+      try {
+        leafQueue.getReadLock().lock();
         // go through all ignore-partition-exclusivity containers first to make
         // sure such containers will be preemptionCandidates first
         Map<String, TreeSet<RMContainer>> ignorePartitionExclusivityContainers =
@@ -147,6 +148,8 @@ public class FifoCandidatesSelector
         preemptAMContainers(clusterResource, selectedCandidates, skippedAMContainerlist,
             resToObtainByPartition, skippedAMSize, maxAMCapacityForThisQueue,
             totalPreemptionAllowed);
+      } finally {
+        leafQueue.getReadLock().unlock();
       }
     }
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/IntraQueueCandidatesSelector.java

@@ -118,7 +118,8 @@ public class IntraQueueCandidatesSelector extends PreemptionCandidatesSelector {
 
         // 6. Based on the selected resource demand per partition, select
         // containers with known policy from inter-queue preemption.
-        synchronized (leafQueue) {
+        try {
+          leafQueue.getReadLock().lock();
           Iterator<FiCaSchedulerApp> desc = leafQueue.getOrderingPolicy()
               .getPreemptionIterator();
           while (desc.hasNext()) {
@@ -127,6 +128,8 @@ public class IntraQueueCandidatesSelector extends PreemptionCandidatesSelector {
                 totalPreemptedResourceAllowed, resToObtainByPartition,
                 leafQueue, app);
           }
+        } finally {
+          leafQueue.getReadLock().unlock();
         }
       }
     }

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

@@ -56,6 +56,7 @@ import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
 
 /**
  * This class implement a {@link SchedulingEditPolicy} that is designed to be
@@ -430,15 +431,19 @@ public class ProportionalCapacityPreemptionPolicy
   private TempQueuePerPartition cloneQueues(CSQueue curQueue,
       Resource partitionResource, String partitionToLookAt) {
     TempQueuePerPartition ret;
-    synchronized (curQueue) {
+    ReadLock readLock = curQueue.getReadLock();
+    try {
+      // Acquire a read lock from Parent/LeafQueue.
+      readLock.lock();
+
       String queueName = curQueue.getQueueName();
       QueueCapacities qc = curQueue.getQueueCapacities();
       float absCap = qc.getAbsoluteCapacity(partitionToLookAt);
       float absMaxCap = qc.getAbsoluteMaximumCapacity(partitionToLookAt);
       boolean preemptionDisabled = curQueue.getPreemptionDisabled();
 
-      Resource current = Resources.clone(
+      Resource current = Resources
-          curQueue.getQueueResourceUsage().getUsed(partitionToLookAt));
+          .clone(curQueue.getQueueResourceUsage().getUsed(partitionToLookAt));
       Resource killable = Resources.none();
 
       Resource reserved = Resources.clone(
@@ -472,7 +477,10 @@ public class ProportionalCapacityPreemptionPolicy
           ret.addChild(subq);
         }
       }
+    } finally {
+      readLock.unlock();
     }
+
     addTempQueuePartition(ret);
     return ret;
   }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/AbstractCSQueue.java

@@ -432,7 +432,6 @@ public abstract class AbstractCSQueue implements CSQueue {
     } finally {
       readLock.unlock();
     }
-
   }
 
   @Private
@@ -450,6 +449,11 @@ public abstract class AbstractCSQueue implements CSQueue {
     return queueUsage;
   }
 
+  @Override
+  public ReentrantReadWriteLock.ReadLock getReadLock() {
+    return readLock;
+  }
+
   /**
    * The specified queue is preemptable if system-wide preemption is turned on
    * unless any queue in the <em>qPath</em> hierarchy has explicitly turned

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/CSQueue.java

@@ -22,6 +22,7 @@ import java.io.IOException;
 import java.util.Collection;
 import java.util.List;
 import java.util.Set;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 import com.google.common.annotations.VisibleForTesting;
 import org.apache.hadoop.classification.InterfaceAudience.Private;
@@ -355,4 +356,10 @@ extends org.apache.hadoop.yarn.server.resourcemanager.scheduler.Queue {
 
   void apply(Resource cluster,
       ResourceCommitRequest<FiCaSchedulerApp, FiCaSchedulerNode> request);
+
+  /**
+   * Get readLock associated with the Queue.
+   * @return readLock of corresponding queue.
+   */
+  public ReentrantReadWriteLock.ReadLock getReadLock();
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicyMockFramework.java

@@ -70,6 +70,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeSet;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyString;
@@ -525,6 +526,8 @@ public class ProportionalCapacityPreemptionPolicyMockFramework {
         queue = leafQueue;
       }
 
+      ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+      when(queue.getReadLock()).thenReturn(lock.readLock());
       setupQueue(queue, q, queueExprArray, idx);
       if (queue.getQueueName().equals(ROOT)) {
         rootQueue = (ParentQueue) queue;

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

@@ -74,6 +74,7 @@ import java.util.NavigableSet;
 import java.util.Random;
 import java.util.StringTokenizer;
 import java.util.TreeSet;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 import static org.apache.hadoop.yarn.server.resourcemanager.scheduler.event.SchedulerEventType.MARK_CONTAINER_FOR_KILLABLE;
 import static org.apache.hadoop.yarn.server.resourcemanager.scheduler.event.SchedulerEventType.MARK_CONTAINER_FOR_PREEMPTION;
@@ -1203,6 +1204,8 @@ public class TestProportionalCapacityPreemptionPolicy {
     ParentQueue pq = mock(ParentQueue.class);
     List<CSQueue> cqs = new ArrayList<CSQueue>();
     when(pq.getChildQueues()).thenReturn(cqs);
+    ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+    when(pq.getReadLock()).thenReturn(lock.readLock());
     for (int i = 0; i < subqueues; ++i) {
       pqs.add(pq);
     }
@@ -1264,6 +1267,8 @@ public class TestProportionalCapacityPreemptionPolicy {
     if(setAMResourcePercent != 0.0f){
       when(lq.getMaxAMResourcePerQueuePercent()).thenReturn(setAMResourcePercent);
     }
+    ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+    when(lq.getReadLock()).thenReturn(lock.readLock());
     p.getChildQueues().add(lq);
     return lq;
   }