Add transaction interruption support for internal use (#1242)

* Add transaction interruption support for internal use

This update is for Neo4j internal use only.

* Add additional warning to documentation

Author: injectives

driver/src/main/java/org/neo4j/driver/internal/async/UnmanagedTransaction.java

@@ -91,6 +91,7 @@ private enum State {
     private CompletableFuture<Void> commitFuture;
     private CompletableFuture<Void> rollbackFuture;
     private Throwable causeOfTermination;
+    private CompletionStage<Void> interruptStage;
 
     public UnmanagedTransaction(Connection connection, BookmarksHolder bookmarksHolder, long fetchSize) {
         this(connection, bookmarksHolder, fetchSize, new ResultCursorsHolder());
@@ -303,4 +304,21 @@ private CompletionStage<Void> closeAsync(boolean commit, boolean completeWithNul
 
         return stage;
     }
+
+    /**
+     * Marks transaction as terminated and sends {@code RESET} message over allocated connection.
+     * <p>
+     * <b>THIS METHOD IS NOT PART OF PUBLIC API. This method may be changed or removed at any moment in time.</b>
+     *
+     * @return {@code RESET} response stage
+     */
+    public CompletionStage<Void> interruptAsync() {
+        return executeWithLock(lock, () -> {
+            if (interruptStage == null) {
+                markTerminated(null);
+                interruptStage = connection.reset();
+            }
+            return interruptStage;
+        });
+    }
 }

driver/src/main/java/org/neo4j/driver/internal/reactive/InternalReactiveTransaction.java

@@ -57,4 +57,15 @@ public Publisher<ReactiveResult> run(Query query) {
                 })
                 .map(InternalReactiveResult::new);
     }
+
+    /**
+     * Marks transaction as terminated and sends {@code RESET} message over allocated connection.
+     * <p>
+     * <b>THIS METHOD IS NOT PART OF PUBLIC API. This method may be changed or removed at any moment in time.</b>
+     *
+     * @return {@code RESET} response publisher
+     */
+    public Publisher<Void> interrupt() {
+        return Mono.fromCompletionStage(tx.interruptAsync());
+    }
 }

driver/src/test/java/org/neo4j/driver/internal/async/UnmanagedTransactionTest.java

@@ -440,6 +440,33 @@ void shouldReturnCompletedWithNullStageOnClosingInactiveTransactionExceptCommitt
         assertNull(closeStage.toCompletableFuture().join());
     }
 
+    @Test
+    void shouldInterruptOnInterruptAsync() {
+        // Given
+        Connection connection = connectionMock(BoltProtocolV4.INSTANCE);
+        UnmanagedTransaction tx = beginTx(connection);
+
+        // When
+        await(tx.interruptAsync());
+
+        // Then
+        then(connection).should().reset();
+    }
+
+    @Test
+    void shouldServeTheSameStageOnInterruptAsync() {
+        // Given
+        Connection connection = connectionMock(BoltProtocolV4.INSTANCE);
+        UnmanagedTransaction tx = beginTx(connection);
+
+        // When
+        CompletionStage<Void> stage0 = tx.interruptAsync();
+        CompletionStage<Void> stage1 = tx.interruptAsync();
+
+        // Then
+        assertEquals(stage0, stage1);
+    }
+
     private static UnmanagedTransaction beginTx(Connection connection) {
         return beginTx(connection, Collections.emptySet());
     }

driver/src/test/java/org/neo4j/driver/internal/reactive/InternalReactiveTransactionTest.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.neo4j.driver.internal.reactive;
+
+import static java.util.concurrent.CompletableFuture.completedFuture;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.BDDMockito.then;
+import static org.mockito.Mockito.mock;
+import static org.neo4j.driver.internal.util.Futures.failedFuture;
+
+import org.junit.jupiter.api.Test;
+import org.neo4j.driver.internal.async.UnmanagedTransaction;
+import reactor.test.StepVerifier;
+
+public class InternalReactiveTransactionTest {
+    private InternalReactiveTransaction tx;
+
+    @Test
+    void shouldDelegateInterrupt() {
+        // Given
+        UnmanagedTransaction utx = mock(UnmanagedTransaction.class);
+        given(utx.interruptAsync()).willReturn(completedFuture(null));
+        tx = new InternalReactiveTransaction(utx);
+
+        // When
+        StepVerifier.create(tx.interrupt()).expectComplete().verify();
+
+        // Then
+        then(utx).should().interruptAsync();
+    }
+
+    @Test
+    void shouldDelegateInterruptAndReportError() {
+        // Given
+        UnmanagedTransaction utx = mock(UnmanagedTransaction.class);
+        RuntimeException e = mock(RuntimeException.class);
+        given(utx.interruptAsync()).willReturn(failedFuture(e));
+        tx = new InternalReactiveTransaction(utx);
+
+        // When
+        StepVerifier.create(tx.interrupt()).expectErrorMatches(ar -> ar == e).verify();
+
+        // Then
+        then(utx).should().interruptAsync();
+    }
+}