Simplified state in connection queue

Commit replaces two state variables with a single one and adds couple
unit tests for state transitions.

Author: lutovich

driver/src/main/java/org/neo4j/driver/internal/net/pooling/BlockingPooledConnectionQueue.java

@@ -23,7 +23,7 @@
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.LinkedBlockingQueue;
-import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.neo4j.driver.internal.logging.DelegatingLogger;
 import org.neo4j.driver.internal.net.BoltServerAddress;
@@ -40,12 +40,15 @@ public class BlockingPooledConnectionQueue
 {
     public static final String LOG_NAME = "ConnectionQueue";
 
+    private static final int ACTIVE = 1;
+    private static final int INACTIVE = 2;
+    private static final int TERMINATED = 3;
+
     /** The backing queue, keeps track of connections currently in queue */
     private final BlockingQueue<PooledConnection> queue;
     private final Logger logger;
 
-    private final AtomicBoolean isDeactivated = new AtomicBoolean( false );
-    private final AtomicBoolean isTerminating = new AtomicBoolean( false );
+    private final AtomicInteger state = new AtomicInteger( ACTIVE );
 
     /** Keeps track of acquired connections */
     private final Set<PooledConnection> acquiredConnections =
@@ -72,7 +75,7 @@ public boolean offer( PooledConnection pooledConnection )
         {
             disposeSafely( pooledConnection );
         }
-        if ( isDeactivated.get() || isTerminating.get() )
+        if ( state.get() != ACTIVE )
         {
             terminateIdleConnections();
         }
@@ -93,12 +96,13 @@ public PooledConnection acquire( Supplier<PooledConnection> supplier )
         }
         acquiredConnections.add( connection );
 
-        if ( isDeactivated.get() || isTerminating.get() )
+        int poolState = state.get();
+        if ( poolState != ACTIVE )
         {
             acquiredConnections.remove( connection );
             disposeSafely( connection );
-            throw new IllegalStateException( "Pool is " + (isDeactivated.get() ? "deactivated" : "terminated") + ", " +
-                                             "new connections can't be acquired" );
+            throw new IllegalStateException( "Pool is " + (poolState == INACTIVE ? "deactivated" : "terminated") +
+                                             ", new connections can't be acquired" );
         }
         else
         {
@@ -129,20 +133,20 @@ public boolean contains( PooledConnection pooledConnection )
 
     public void activate()
     {
-        isDeactivated.compareAndSet( true, false );
+        state.compareAndSet( INACTIVE, ACTIVE );
     }
 
     public void deactivate()
     {
-        if ( isDeactivated.compareAndSet( false, true ) )
+        if ( state.compareAndSet( ACTIVE, INACTIVE ) )
         {
             terminateIdleConnections();
         }
     }
 
     public boolean isActive()
     {
-        return !isDeactivated.get();
+        return state.get() == ACTIVE;
     }
 
     /**
@@ -153,7 +157,7 @@ public boolean isActive()
      */
     public void terminate()
     {
-        if ( isTerminating.compareAndSet( false, true ) )
+        if ( state.getAndSet( TERMINATED ) != TERMINATED )
         {
             terminateIdleConnections();
             terminateAcquiredConnections();

driver/src/test/java/org/neo4j/driver/internal/net/pooling/BlockingPooledConnectionQueueTest.java

@@ -32,6 +32,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -333,11 +334,104 @@ public void shouldTerminateOfferedConnectionWhenDeactivated()
     }
 
     @Test
-    public void shouldReportWhenActive()
+    public void shouldBeActiveWhenNotDeactivatedAndNotTerminated()
     {
         BlockingPooledConnectionQueue queue = newConnectionQueue( 1 );
         assertTrue( queue.isActive() );
+    }
+
+    @Test
+    public void shouldNotBeActiveWhenDeactivated()
+    {
+        BlockingPooledConnectionQueue queue = newConnectionQueue( 1 );
+        assertTrue( queue.isActive() );
+        queue.deactivate();
+        assertFalse( queue.isActive() );
+    }
+
+    @Test
+    public void shouldNotBeActiveWhenTerminated()
+    {
+        BlockingPooledConnectionQueue queue = newConnectionQueue( 1 );
+        assertTrue( queue.isActive() );
+        queue.terminate();
+        assertFalse( queue.isActive() );
+    }
+
+    @Test
+    public void shouldBeActiveAfterDeactivationAndActivation()
+    {
+        BlockingPooledConnectionQueue queue = newConnectionQueue( 1 );
+        assertTrue( queue.isActive() );
+        queue.deactivate();
+        assertFalse( queue.isActive() );
+        queue.activate();
+        assertTrue( queue.isActive() );
+    }
+
+    @Test
+    public void shouldNotBeActiveAfterTerminationAndActivation()
+    {
+        BlockingPooledConnectionQueue queue = newConnectionQueue( 1 );
+        assertTrue( queue.isActive() );
+        queue.terminate();
+        assertFalse( queue.isActive() );
+        queue.activate();
+        assertFalse( queue.isActive() );
+    }
+
+    @Test
+    public void shouldBePossibleToAcquireFromActivatedQueue()
+    {
+        Supplier<PooledConnection> connectionSupplier = connectionSupplierMock();
+        when( connectionSupplier.get() ).thenReturn( mock( PooledConnection.class ) );
+        BlockingPooledConnectionQueue queue = newConnectionQueue( 3 );
         queue.deactivate();
+
+        try
+        {
+            queue.acquire( connectionSupplier );
+            fail( "Exception expected" );
+        }
+        catch ( IllegalStateException e )
+        {
+            assertThat( e.getMessage(), startsWith( "Pool is deactivated" ) );
+        }
+
+        queue.activate();
+
+        assertNotNull( queue.acquire( connectionSupplier ) );
+    }
+
+    @Test
+    public void shouldNotBePossibleToActivateTerminatedQueue()
+    {
+        Supplier<PooledConnection> connectionSupplier = connectionSupplierMock();
+        when( connectionSupplier.get() ).thenReturn( mock( PooledConnection.class ) );
+        BlockingPooledConnectionQueue queue = newConnectionQueue( 3 );
+        queue.terminate();
+
+        try
+        {
+            queue.acquire( connectionSupplier );
+            fail( "Exception expected" );
+        }
+        catch ( IllegalStateException e )
+        {
+            assertThat( e.getMessage(), startsWith( "Pool is terminated" ) );
+        }
+
+        queue.activate();
+
+        try
+        {
+            queue.acquire( connectionSupplier );
+            fail( "Exception expected" );
+        }
+        catch ( IllegalStateException e )
+        {
+            assertThat( e.getMessage(), startsWith( "Pool is terminated" ) );
+        }
         assertFalse( queue.isActive() );
     }