In the connection pool, moved wait queue size increment into its own try block so that wait queue start and end events are only delivered if the wait queue is actually entered.

 JAVA-1873

Author: jyemin

driver-core/src/main/com/mongodb/connection/DefaultConnectionPool.java

@@ -83,28 +83,31 @@ public InternalConnection get() {
     @Override
     public InternalConnection get(final long timeout, final TimeUnit timeUnit) {
         try {
-            connectionPoolListener.waitQueueEntered(new ConnectionPoolWaitQueueEvent(serverId, currentThread().getId()));
             if (waitQueueSize.incrementAndGet() > settings.getMaxWaitQueueSize()) {
                 throw createWaitQueueFullException();
             }
-            PooledConnection pooledConnection = getPooledConnection(timeout, timeUnit);
-            if (!pooledConnection.opened()) {
-                try {
-                    pooledConnection.open();
-                } catch (Throwable t) {
-                    pool.release(pooledConnection.wrapped, true);
-                    if (t instanceof MongoException) {
-                        throw (MongoException) t;
-                    } else {
-                        throw new MongoInternalException(t.toString(), t);
+            try {
+                connectionPoolListener.waitQueueEntered(new ConnectionPoolWaitQueueEvent(serverId, currentThread().getId()));
+                PooledConnection pooledConnection = getPooledConnection(timeout, timeUnit);
+                if (!pooledConnection.opened()) {
+                    try {
+                        pooledConnection.open();
+                    } catch (Throwable t) {
+                        pool.release(pooledConnection.wrapped, true);
+                        if (t instanceof MongoException) {
+                            throw (MongoException) t;
+                        } else {
+                            throw new MongoInternalException(t.toString(), t);
+                        }
                     }
                 }
-            }
 
-            return pooledConnection;
+                return pooledConnection;
+            } finally {
+                connectionPoolListener.waitQueueExited(new ConnectionPoolWaitQueueEvent(serverId, currentThread().getId()));
+            }
         } finally {
             waitQueueSize.decrementAndGet();
-            connectionPoolListener.waitQueueExited(new ConnectionPoolWaitQueueEvent(serverId, currentThread().getId()));
         }
     }
 

driver-core/src/test/functional/com/mongodb/connection/DefaultConnectionPoolTest.java

@@ -24,6 +24,7 @@
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.MINUTES;
+import static java.util.concurrent.TimeUnit.SECONDS;
 import static junit.framework.TestCase.assertNotNull;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -237,14 +238,15 @@ public void shouldNotCallWaitQueueExitedIfWaitQueueEnteredWasNotCalled() throws
                                              ConnectionPoolSettings.builder()
                                                                    .maxSize(1)
                                                                    .maxWaitQueueSize(1)
-                                                                   .maxWaitTime(500, MILLISECONDS)
+                                                                   .maxWaitTime(5, SECONDS)
                                                                    .build(),
                                              listener);
 
         // when
-        provider.get();
+        InternalConnection connection = provider.get();
 
-        new Thread(new TimeoutTrackingConnectionGetter(provider)).start();
+        TimeoutTrackingConnectionGetter timeoutTrackingConnectionGetter = new TimeoutTrackingConnectionGetter(provider);
+        new Thread(timeoutTrackingConnectionGetter).start();
         Thread.sleep(100);
 
         try {
@@ -254,7 +256,15 @@ public void shouldNotCallWaitQueueExitedIfWaitQueueEnteredWasNotCalled() throws
             // all good
         }
 
+        // when
+        connection.close();
+
+        timeoutTrackingConnectionGetter.getLatch().await();
+
         // then
-        assertEquals(1, listener.getWaitQueueSize());
+        connection = provider.get();
+
+        // cleanup
+        connection.close();
     }
 }

driver-core/src/test/functional/com/mongodb/connection/QueueEventsConnectionPoolListener.java

@@ -25,12 +25,12 @@ class QueueEventsConnectionPoolListener extends ConnectionPoolListenerAdapter {
     private final AtomicInteger waitQueueSize = new AtomicInteger();
 
     @Override
-    public void waitQueueExited(ConnectionPoolWaitQueueEvent event) {
+    public void waitQueueExited(final ConnectionPoolWaitQueueEvent event) {
         waitQueueSize.decrementAndGet();
     }
 
     @Override
-    public void waitQueueEntered(ConnectionPoolWaitQueueEvent event) {
+    public void waitQueueEntered(final ConnectionPoolWaitQueueEvent event) {
         waitQueueSize.incrementAndGet();
     }
 

driver-core/src/test/unit/com/mongodb/connection/TimeoutTrackingConnectionGetter.java

@@ -37,7 +37,8 @@ boolean isGotTimeout() {
     @Override
     public void run() {
         try {
-            connectionPool.get();
+            InternalConnection connection = connectionPool.get();
+            connection.close();
         } catch (MongoTimeoutException e) {
             gotTimeout = true;
         } finally {