Close open transaction when session is closed

driver/src/main/java/org/neo4j/driver/internal/ExplicitTransaction.java

@@ -20,6 +20,7 @@
 
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
 import java.util.concurrent.CompletionStage;
 import java.util.function.BiFunction;
 
@@ -361,28 +362,12 @@ private BiFunction<Void,Throwable,Void> handleCommitOrRollback( Throwable cursor
     {
         return ( ignore, commitOrRollbackError ) ->
         {
-            if ( cursorFailure != null && commitOrRollbackError != null )
+            CompletionException combinedError = Futures.combineErrors( cursorFailure, commitOrRollbackError );
+            if ( combinedError != null )
             {
-                Throwable cause1 = Futures.completionExceptionCause( cursorFailure );
-                Throwable cause2 = Futures.completionExceptionCause( commitOrRollbackError );
-                if ( cause1 != cause2 )
-                {
-                    cause1.addSuppressed( cause2 );
-                }
-                throw Futures.asCompletionException( cause1 );
-            }
-            else if ( cursorFailure != null )
-            {
-                throw Futures.asCompletionException( cursorFailure );
-            }
-            else if ( commitOrRollbackError != null )
-            {
-                throw Futures.asCompletionException( commitOrRollbackError );
-            }
-            else
-            {
-                return null;
+                throw combinedError;
             }
+            return null;
         };
     }
 

driver/src/main/java/org/neo4j/driver/internal/NetworkSession.java

@@ -167,24 +167,23 @@ public CompletionStage<Void> closeAsync()
         {
             return resultCursorStage.thenCompose( cursor ->
             {
-                if ( cursor == null )
+                if ( cursor != null )
                 {
-                    return completedWithNull();
+                    // there exists a cursor with potentially unconsumed error, try to extract and propagate it
+                    return cursor.failureAsync();
                 }
-                return cursor.failureAsync();
-            } ).thenCompose( error -> releaseResources().thenApply( ignore ->
+                // no result cursor exists so no error exists
+                return completedWithNull();
+            } ).thenCompose( cursorError -> closeTransactionAndReleaseConnection().thenApply( txCloseError ->
             {
-                if ( error != null )
-                {
-                    // connection has been acquired and there is an unconsumed error in result cursor
-                    throw Futures.asCompletionException( error );
-                }
-                else
+                // now we have cursor error, active transaction has been closed and connection has been released
+                // back to the pool; try to propagate cursor and transaction close errors, if any
+                CompletionException combinedError = Futures.combineErrors( cursorError, txCloseError );
+                if ( combinedError != null )
                 {
-                    // either connection acquisition failed or
-                    // there are no unconsumed errors in the result cursor
-                    return null;
+                    throw combinedError;
                 }
+                return null;
             } ) );
         }
         return completedWithNull();
@@ -520,26 +519,22 @@ private CompletionStage<Connection> acquireConnection( AccessMode mode )
         return newConnectionStage;
     }
 
-    private CompletionStage<Void> releaseResources()
-    {
-        return rollbackTransaction().thenCompose( ignore -> releaseConnection() );
-    }
-
-    private CompletionStage<Void> rollbackTransaction()
+    private CompletionStage<Throwable> closeTransactionAndReleaseConnection()
     {
         return existingTransactionOrNull().thenCompose( tx ->
         {
             if ( tx != null )
             {
-                return tx.rollbackAsync();
+                // there exists an open transaction, let's close it and propagate the error, if any
+                return tx.closeAsync()
+                        .thenApply( ignore -> (Throwable) null )
+                        .exceptionally( error -> error );
             }
+            // no open transaction so nothing to close
             return completedWithNull();
-        } ).exceptionally( error ->
-        {
-            Throwable cause = Futures.completionExceptionCause( error );
-            logger.warn( "Active transaction rolled back with an error", cause );
-            return null;
-        } );
+        } ).thenCompose( txCloseError ->
+                // then release the connection and propagate transaction close error, if any
+                releaseConnection().thenApply( ignore -> txCloseError ) );
     }
 
     private CompletionStage<Void> releaseConnection()
@@ -548,8 +543,10 @@ private CompletionStage<Void> releaseConnection()
         {
             if ( connection != null )
             {
+                // there exists connection, try to release it back to the pool
                 return connection.release();
             }
+            // no connection so return null
             return completedWithNull();
         } );
     }

driver/src/main/java/org/neo4j/driver/internal/util/Futures.java

@@ -172,6 +172,40 @@ public static CompletionException asCompletionException( Throwable error )
         return new CompletionException( error );
     }
 
+    /**
+     * Combine given errors into a single {@link CompletionException} to be rethrown from inside a
+     * {@link CompletionStage} chain.
+     *
+     * @param error1 the first error or {@code null}.
+     * @param error2 the second error or {@code null}.
+     * @return {@code null} if both errors are null, {@link CompletionException} otherwise.
+     */
+    public static CompletionException combineErrors( Throwable error1, Throwable error2 )
+    {
+        if ( error1 != null && error2 != null )
+        {
+            Throwable cause1 = completionExceptionCause( error1 );
+            Throwable cause2 = completionExceptionCause( error2 );
+            if ( cause1 != cause2 )
+            {
+                cause1.addSuppressed( cause2 );
+            }
+            return asCompletionException( cause1 );
+        }
+        else if ( error1 != null )
+        {
+            return asCompletionException( error1 );
+        }
+        else if ( error2 != null )
+        {
+            return asCompletionException( error2 );
+        }
+        else
+        {
+            return null;
+        }
+    }
+
     private static void safeRun( Runnable runnable )
     {
         try

driver/src/test/java/org/neo4j/driver/internal/util/FuturesTest.java

@@ -37,6 +37,7 @@
 import org.neo4j.driver.internal.async.EventLoopGroupFactory;
 
 import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
@@ -360,4 +361,43 @@ public void shouldKeepCompletionExceptionAsIs()
         CompletionException error = new CompletionException( new RuntimeException( "Hello" ) );
         assertEquals( error, Futures.asCompletionException( error ) );
     }
+
+    @Test
+    public void shouldCombineTwoErrors()
+    {
+        RuntimeException error1 = new RuntimeException( "Error1" );
+        RuntimeException error2Cause = new RuntimeException( "Error2" );
+        CompletionException error2 = new CompletionException( error2Cause );
+
+        CompletionException combined = Futures.combineErrors( error1, error2 );
+
+        assertEquals( error1, combined.getCause() );
+        assertArrayEquals( new Throwable[]{error2Cause}, combined.getCause().getSuppressed() );
+    }
+
+    @Test
+    public void shouldCombineErrorAndNull()
+    {
+        RuntimeException error1 = new RuntimeException( "Error1" );
+
+        CompletionException combined = Futures.combineErrors( error1, null );
+
+        assertEquals( error1, combined.getCause() );
+    }
+
+    @Test
+    public void shouldCombineNullAndError()
+    {
+        RuntimeException error2 = new RuntimeException( "Error2" );
+
+        CompletionException combined = Futures.combineErrors( null, error2 );
+
+        assertEquals( error2, combined.getCause() );
+    }
+
+    @Test
+    public void shouldCombineNullAndNullErrors()
+    {
+        assertNull( Futures.combineErrors( null, null ) );
+    }
 }

driver/src/test/java/org/neo4j/driver/v1/integration/SessionIT.java

@@ -37,16 +37,19 @@
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.logging.Level;
 
 import org.neo4j.driver.internal.DriverFactory;
 import org.neo4j.driver.internal.cluster.RoutingContext;
 import org.neo4j.driver.internal.cluster.RoutingSettings;
+import org.neo4j.driver.internal.logging.ConsoleLogging;
 import org.neo4j.driver.internal.retry.RetrySettings;
 import org.neo4j.driver.internal.util.DriverFactoryWithFixedRetryLogic;
 import org.neo4j.driver.internal.util.DriverFactoryWithOneEventLoopThread;
 import org.neo4j.driver.internal.util.ServerVersion;
 import org.neo4j.driver.v1.AccessMode;
 import org.neo4j.driver.v1.AuthToken;
+import org.neo4j.driver.v1.AuthTokens;
 import org.neo4j.driver.v1.Config;
 import org.neo4j.driver.v1.Driver;
 import org.neo4j.driver.v1.GraphDatabase;
@@ -62,6 +65,7 @@
 import org.neo4j.driver.v1.exceptions.TransientException;
 import org.neo4j.driver.v1.summary.ResultSummary;
 import org.neo4j.driver.v1.summary.StatementType;
+import org.neo4j.driver.v1.util.StubServer;
 import org.neo4j.driver.v1.util.TestNeo4j;
 import org.neo4j.driver.v1.util.TestUtil;
 
@@ -1296,6 +1300,50 @@ public void shouldNotAllowStartingMultipleTransactions()
         }
     }
 
+    @Test
+    public void shouldCloseOpenTransactionWhenClosed()
+    {
+        try ( Session session = neo4j.driver().session() )
+        {
+            Transaction tx = session.beginTransaction();
+            tx.run( "CREATE (:Node {id: 123})" );
+            tx.run( "CREATE (:Node {id: 456})" );
+
+            tx.success();
+        }
+
+        assertEquals( 1, countNodesWithId( 123 ) );
+        assertEquals( 1, countNodesWithId( 456 ) );
+    }
+
+    @Test
+    public void shouldRollbackOpenTransactionWhenClosed()
+    {
+        try ( Session session = neo4j.driver().session() )
+        {
+            Transaction tx = session.beginTransaction();
+            tx.run( "CREATE (:Node {id: 123})" );
+            tx.run( "CREATE (:Node {id: 456})" );
+
+            tx.failure();
+        }
+
+        assertEquals( 0, countNodesWithId( 123 ) );
+        assertEquals( 0, countNodesWithId( 456 ) );
+    }
+
+    @Test
+    public void shouldPropagateTransactionCommitErrorWhenClosed() throws Exception
+    {
+        testTransactionCloseErrorPropagationWhenSessionClosed( "commit_error.script", true, "Unable to commit" );
+    }
+
+    @Test
+    public void shouldPropagateTransactionRollbackErrorWhenClosed() throws Exception
+    {
+        testTransactionCloseErrorPropagationWhenSessionClosed( "rollback_error.script", false, "Unable to rollback" );
+    }
+
     private void testExecuteReadTx( AccessMode sessionMode )
     {
         Driver driver = neo4j.driver();
@@ -1501,6 +1549,52 @@ private static void await( CountDownLatch latch )
         }
     }
 
+    private static void testTransactionCloseErrorPropagationWhenSessionClosed( String script, boolean commit,
+            String expectedErrorMessage ) throws Exception
+    {
+        StubServer server = StubServer.start( script, 9001 );
+        try
+        {
+            Config config = Config.build()
+                    .withLogging( DEV_NULL_LOGGING )
+                    .withLogging( new ConsoleLogging( Level.INFO ) )
+                    .withoutEncryption()
+                    .toConfig();
+            try ( Driver driver = GraphDatabase.driver( "bolt://localhost:9001", AuthTokens.none(), config ) )
+            {
+                Session session = driver.session();
+
+                Transaction tx = session.beginTransaction();
+                StatementResult result = tx.run( "CREATE (n {name:'Alice'}) RETURN n.name AS name" );
+                assertEquals( "Alice", result.single().get( "name" ).asString() );
+
+                if ( commit )
+                {
+                    tx.success();
+                }
+                else
+                {
+                    tx.failure();
+                }
+
+                try
+                {
+                    session.close();
+                    fail( "Exception expected" );
+                }
+                catch ( TransientException e )
+                {
+                    assertEquals( "Neo.TransientError.General.DatabaseUnavailable", e.code() );
+                    assertEquals( expectedErrorMessage, e.getMessage() );
+                }
+            }
+        }
+        finally
+        {
+            assertEquals( 0, server.exitStatus() );
+        }
+    }
+
     private static class ThrowingWork implements TransactionWork<Record>
     {
         final String query;