Fixed a bug found on idle and inUse counters

Before we always decrement idle counters when a channel is closed. However, this is wrong when a channel is closed before it is returen to the pool.
So change the code to make sure that no matter the channel is closed inside or outside the pool, the idle and inUse counters should be correct.

Author: Zhen

driver/src/main/java/org/neo4j/driver/internal/async/pool/NettyChannelPool.java

@@ -69,7 +69,6 @@ protected ChannelFuture connectChannel( Bootstrap bootstrap )
                 // notify pool handler about a successful connection
                 Channel channel = channelFuture.channel();
                 handler.channelCreated( channel, creatingEvent );
-                channel.closeFuture().addListener( closeFuture -> handler.channelClosed( channel ) );
             }
             else
             {

driver/src/main/java/org/neo4j/driver/internal/async/pool/NettyChannelTracker.java

@@ -19,6 +19,7 @@
 package org.neo4j.driver.internal.async.pool;
 
 import io.netty.channel.Channel;
+import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.pool.ChannelPoolHandler;
 
 import java.util.Map;
@@ -39,6 +40,7 @@ public class NettyChannelTracker implements ChannelPoolHandler
     private final Map<BoltServerAddress,AtomicInteger> addressToIdleChannelCount = new ConcurrentHashMap<>();
     private final Logger log;
     private final MetricsListener metricsListener;
+    private final ChannelFutureListener closeListener = future -> channelClosed( future.channel() );
 
     public NettyChannelTracker( MetricsListener metricsListener, Logging logging )
     {
@@ -52,6 +54,7 @@ public void channelReleased( Channel channel )
         log.debug( "Channel %s released back to the pool", channel );
         decrementInUse( channel );
         incrementIdle( channel );
+        channel.closeFuture().addListener( closeListener );
     }
 
     @Override
@@ -60,6 +63,7 @@ public void channelAcquired( Channel channel )
         log.debug( "Channel %s acquired from the pool", channel );
         incrementInUse( channel );
         decrementIdle( channel );
+        channel.closeFuture().removeListener( closeListener );
     }
 
     @Override

driver/src/test/java/org/neo4j/driver/internal/async/pool/NettyChannelTrackerTest.java

@@ -110,6 +110,48 @@ public void shouldDecrementCountForAddress()
         assertEquals( 3, tracker.idleChannelCount( address ) );
     }
 
+    @Test
+    public void shouldDecreaseIdleWhenClosedOutsidePool() throws Throwable
+    {
+        // Given
+        Channel channel = newChannel();
+        tracker.channelCreated( channel, null );
+        assertEquals( 1, tracker.inUseChannelCount( address ) );
+        assertEquals( 0, tracker.idleChannelCount( address ) );
+
+        // When closed before session.close
+        channel.close();
+
+        // Then
+        assertEquals( 1, tracker.inUseChannelCount( address ) );
+        assertEquals( 0, tracker.idleChannelCount( address ) );
+
+        tracker.channelReleased( channel );
+        assertEquals( 0, tracker.inUseChannelCount( address ) );
+        assertEquals( 0, tracker.idleChannelCount( address ) );
+    }
+
+    @Test
+    public void shouldDecreaseIdleWhenClosedInsidePool() throws Throwable
+    {
+        // Given
+        Channel channel = newChannel();
+        tracker.channelCreated( channel, null );
+        assertEquals( 1, tracker.inUseChannelCount( address ) );
+        assertEquals( 0, tracker.idleChannelCount( address ) );
+
+        tracker.channelReleased( channel );
+        assertEquals( 0, tracker.inUseChannelCount( address ) );
+        assertEquals( 1, tracker.idleChannelCount( address ) );
+
+        // When closed before acquire
+        channel.close();
+        // Then
+        assertEquals( 0, tracker.inUseChannelCount( address ) );
+        assertEquals( 0, tracker.idleChannelCount( address ) );
+
+    }
+
     @Test
     public void shouldThrowWhenDecrementingForUnknownAddress()
     {