HADOOP-13189. FairCallQueue makes callQueue larger than the configured capacity. Contributed by Vinitha Gankidi.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/CallQueueManager.java

@@ -72,8 +72,8 @@ public class CallQueueManager<E> {
     this.clientBackOffEnabled = clientBackOffEnabled;
     this.putRef = new AtomicReference<BlockingQueue<E>>(bq);
     this.takeRef = new AtomicReference<BlockingQueue<E>>(bq);
-    LOG.info("Using callQueue: " + backingClass + " scheduler: " +
-        schedulerClass);
+    LOG.info("Using callQueue: " + backingClass + " queueCapacity: " +
+        maxQueueSize + " scheduler: " + schedulerClass);
   }
 
   private static <T extends RpcScheduler> T createScheduler(

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/FairCallQueue.java

@@ -75,11 +75,12 @@ public class FairCallQueue<E extends Schedulable> extends AbstractQueue<E>
 
   /**
    * Create a FairCallQueue.
-   * @param capacity the maximum size of each sub-queue
+   * @param capacity the total size of all sub-queues
    * @param ns the prefix to use for configuration
    * @param conf the configuration to read from
-   * Notes: the FairCallQueue has no fixed capacity. Rather, it has a minimum
-   * capacity of `capacity` and a maximum capacity of `capacity * number_queues`
+   * Notes: Each sub-queue has a capacity of `capacity / numSubqueues`.
+   * The first or the highest priority sub-queue has an excess capacity
+   * of `capacity % numSubqueues`
    */
   public FairCallQueue(int priorityLevels, int capacity, String ns,
       Configuration conf) {
@@ -88,13 +89,19 @@ public class FairCallQueue<E extends Schedulable> extends AbstractQueue<E>
           "at least 1");
     }
     int numQueues = priorityLevels;
-    LOG.info("FairCallQueue is in use with " + numQueues + " queues.");
+    LOG.info("FairCallQueue is in use with " + numQueues +
+        " queues with total capacity of " + capacity);
 
     this.queues = new ArrayList<BlockingQueue<E>>(numQueues);
     this.overflowedCalls = new ArrayList<AtomicLong>(numQueues);
-
+    int queueCapacity = capacity / numQueues;
+    int capacityForFirstQueue = queueCapacity + (capacity % numQueues);
     for(int i=0; i < numQueues; i++) {
-      this.queues.add(new LinkedBlockingQueue<E>(capacity));
+      if (i == 0) {
+        this.queues.add(new LinkedBlockingQueue<E>(capacityForFirstQueue));
+      } else {
+        this.queues.add(new LinkedBlockingQueue<E>(queueCapacity));
+      }
       this.overflowedCalls.add(new AtomicLong(0));
     }
 

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/ipc/TestCallQueueManager.java

@@ -214,9 +214,9 @@ public class TestCallQueueManager {
     assertTrue(queue.getCanonicalName().equals(queueClassName));
 
     manager = new CallQueueManager<FakeCall>(queue, scheduler, false,
-        2, "", conf);
+        8, "", conf);
 
-    // Default FCQ has 4 levels and the max capacity is 2 x 4
+    // Default FCQ has 4 levels and the max capacity is 8
     assertCanPut(manager, 3, 3);
   }
 

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/ipc/TestFairCallQueue.java

@@ -18,12 +18,6 @@
 
 package org.apache.hadoop.ipc;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertTrue;
-
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
@@ -68,7 +62,26 @@ public class TestFairCallQueue extends TestCase {
     Configuration conf = new Configuration();
     conf.setInt("ns." + FairCallQueue.IPC_CALLQUEUE_PRIORITY_LEVELS_KEY, 2);
 
-    fcq = new FairCallQueue<Schedulable>(2, 5, "ns", conf);
+    fcq = new FairCallQueue<Schedulable>(2, 10, "ns", conf);
+  }
+
+  // Validate that the total capacity of all subqueues equals
+  // the maxQueueSize for different values of maxQueueSize
+  public void testTotalCapacityOfSubQueues() {
+    Configuration conf = new Configuration();
+    FairCallQueue<Schedulable> fairCallQueue;
+    fairCallQueue = new FairCallQueue<Schedulable>(1, 1000, "ns", conf);
+    assertEquals(fairCallQueue.remainingCapacity(), 1000);
+    fairCallQueue = new FairCallQueue<Schedulable>(4, 1000, "ns", conf);
+    assertEquals(fairCallQueue.remainingCapacity(), 1000);
+    fairCallQueue = new FairCallQueue<Schedulable>(7, 1000, "ns", conf);
+    assertEquals(fairCallQueue.remainingCapacity(), 1000);
+    fairCallQueue = new FairCallQueue<Schedulable>(1, 1025, "ns", conf);
+    assertEquals(fairCallQueue.remainingCapacity(), 1025);
+    fairCallQueue = new FairCallQueue<Schedulable>(4, 1025, "ns", conf);
+    assertEquals(fairCallQueue.remainingCapacity(), 1025);
+    fairCallQueue = new FairCallQueue<Schedulable>(7, 1025, "ns", conf);
+    assertEquals(fairCallQueue.remainingCapacity(), 1025);
   }
 
   //