Await ReadyForQuery before emitting errors from transactional control methods.

commitTransaction, rollbackTransaction and other methods now await completion of the exchange before emitting error signals to properly synchronize completion.

Previously, error signals were emitted before updating the transaction state which could lead to invalid cleanup states if e.g. the commit failed.

[resolves #541]

Signed-off-by: Mark Paluch <[email protected]>

Author: mp911de

src/main/java/io/r2dbc/postgresql/ExceptionFactory.java

@@ -61,7 +61,7 @@ static ExceptionFactory withSql(String sql) {
      * @return the {@link R2dbcException}.
      * @see ErrorResponse
      */
-    private static R2dbcException createException(ErrorResponse response, String sql) {
+    static R2dbcException createException(ErrorResponse response, String sql) {
         return createException(new ErrorDetails(response.getFields()), sql);
     }
 

src/main/java/io/r2dbc/postgresql/PostgresqlConnection.java

@@ -30,12 +30,14 @@
 import io.r2dbc.postgresql.codec.Codecs;
 import io.r2dbc.postgresql.message.backend.BackendMessage;
 import io.r2dbc.postgresql.message.backend.CommandComplete;
+import io.r2dbc.postgresql.message.backend.ErrorResponse;
 import io.r2dbc.postgresql.message.backend.NotificationResponse;
 import io.r2dbc.postgresql.util.Assert;
 import io.r2dbc.postgresql.util.Operators;
 import io.r2dbc.spi.Connection;
 import io.r2dbc.spi.IsolationLevel;
 import io.r2dbc.spi.Option;
+import io.r2dbc.spi.R2dbcException;
 import io.r2dbc.spi.TransactionDefinition;
 import io.r2dbc.spi.ValidationDepth;
 import org.reactivestreams.Publisher;
@@ -189,6 +191,8 @@ public Mono<Void> cancelRequest() {
 
     @Override
     public Mono<Void> commitTransaction() {
+
+        AtomicReference<R2dbcException> ref = new AtomicReference<>();
         return useTransactionStatus(transactionStatus -> {
             if (IDLE != transactionStatus) {
                 return Flux.from(exchange("COMMIT"))
@@ -203,13 +207,17 @@ public Mono<Void> commitTransaction() {
                         // See discussion in pgsql-hackers: https://www.postgresql.org/message-id/b9fb50dc-0f6e-15fb-6555-8ddb86f4aa71%40postgresfriends.org
 
                         if ("ROLLBACK".equalsIgnoreCase(message.getCommand())) {
-                            sink.error(new ExceptionFactory.PostgresqlRollbackException(ErrorDetails.fromMessage("The database returned ROLLBACK, so the transaction cannot be committed. Transaction" +
-                                " " +
-                                "failure is not known (check server logs?)"), "COMMIT"));
+                            ErrorDetails details = ErrorDetails.fromMessage("The database returned ROLLBACK, so the transaction cannot be committed. Transaction " +
+                                "failure is not known (check server logs?)");
+                            ref.set(new ExceptionFactory.PostgresqlRollbackException(details, "COMMIT"));
                             return;
                         }
 
                         sink.next(message);
+                    }).doOnComplete(() -> {
+                        if (ref.get() != null) {
+                            throw ref.get();
+                        }
                     });
             } else {
                 this.logger.debug(this.connectionContext.getMessage("Skipping commit transaction because status is {}"), transactionStatus);
@@ -452,9 +460,21 @@ private <T> Mono<T> withTransactionStatus(Function<TransactionStatus, T> f) {
 
     @SuppressWarnings("unchecked")
     private <T> Flux<T> exchange(String sql) {
-        ExceptionFactory exceptionFactory = ExceptionFactory.withSql(sql);
+        AtomicReference<R2dbcException> ref = new AtomicReference<>();
         return (Flux<T>) SimpleQueryMessageFlow.exchange(this.client, sql)
-            .handle(exceptionFactory::handleErrorResponse);
+            .handle((backendMessage, synchronousSink) -> {
+
+                if (backendMessage instanceof ErrorResponse) {
+                    ref.set(ExceptionFactory.createException((ErrorResponse) backendMessage, sql));
+                } else {
+                    synchronousSink.next(backendMessage);
+                }
+            })
+            .doOnComplete(() -> {
+                if (ref.get() != null) {
+                    throw ref.get();
+                }
+            });
     }
 
     private void cleanupIsolationLevel() {

src/test/java/io/r2dbc/postgresql/PostgresqlConnectionErrorsIntegrationTests.java

@@ -18,12 +18,15 @@
 
 import io.r2dbc.postgresql.api.PostgresqlConnection;
 import io.r2dbc.postgresql.api.PostgresqlResult;
+import io.r2dbc.postgresql.client.Client;
+import io.r2dbc.postgresql.client.TransactionStatus;
 import io.r2dbc.spi.R2dbcBadGrammarException;
-import io.r2dbc.spi.R2dbcRollbackException;
-import org.awaitility.Awaitility;
+import io.r2dbc.spi.R2dbcException;
 import org.junit.jupiter.api.Test;
 import reactor.test.StepVerifier;
 
+import java.lang.reflect.Field;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
@@ -37,12 +40,26 @@ void commitShouldRecoverFromFailedTransaction() {
         this.connection.beginTransaction().as(StepVerifier::create).verifyComplete();
         this.connection.createStatement("error").execute().flatMap(PostgresqlResult::getRowsUpdated).as(StepVerifier::create).verifyError(R2dbcBadGrammarException.class);
 
-        this.connection.commitTransaction().as(StepVerifier::create).verifyError(R2dbcRollbackException.class);
+        this.connection.commitTransaction().as(StepVerifier::create).verifyErrorSatisfies(throwable -> {
+            assertThat(throwable).isInstanceOf(R2dbcException.class);
+
+            Client client = extractClient();
+            assertThat(client.getTransactionStatus()).isEqualTo(TransactionStatus.IDLE);
+        });
 
-        Awaitility.await().until(() -> this.connection.isAutoCommit());
         assertThat(this.connection.isAutoCommit()).isTrue();
     }
 
+    private Client extractClient() {
+        try {
+            Field field = io.r2dbc.postgresql.PostgresqlConnection.class.getDeclaredField("client");
+            field.setAccessible(true);
+            return (Client) field.get(this.connection);
+        } catch (ReflectiveOperationException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     @Test
     void rollbackShouldRecoverFromFailedTransaction() {