Throw PostgresqlRollbackException on silent rollback

We now throw PostgresqlRollbackException if Postgres silently rolls back a transaction when calling commitTransaction().

https://www.postgresql.org/message-id/b9fb50dc-0f6e-15fb-6555-8ddb86f4aa71%40postgresfriends.org

[resolves pgjdbc#274]

Author: mp911de

pom.xml

@@ -33,6 +33,7 @@
 
     <properties>
         <assertj.version>3.16.1</assertj.version>
+        <awaitility.version>4.0.3</awaitility.version>
         <blockhound.version>1.0.3.RELEASE</blockhound.version>
         <hikari-cp.version>3.4.5</hikari-cp.version>
         <java.version>1.8</java.version>
@@ -186,6 +187,12 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <version>${awaitility.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter-api</artifactId>

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

@@ -16,6 +16,7 @@
 
 package io.r2dbc.postgresql;
 
+import io.r2dbc.postgresql.api.ErrorDetails;
 import io.r2dbc.postgresql.api.Notification;
 import io.r2dbc.postgresql.api.PostgresqlResult;
 import io.r2dbc.postgresql.api.PostgresqlStatement;
@@ -24,6 +25,8 @@
 import io.r2dbc.postgresql.client.SimpleQueryMessageFlow;
 import io.r2dbc.postgresql.client.TransactionStatus;
 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.NotificationResponse;
 import io.r2dbc.postgresql.util.Assert;
 import io.r2dbc.postgresql.util.Operators;
@@ -112,8 +115,26 @@ public Mono<Void> cancelRequest() {
     @Override
     public Mono<Void> commitTransaction() {
         return useTransactionStatus(transactionStatus -> {
-            if (OPEN == transactionStatus) {
-                return exchange("COMMIT");
+            if (IDLE != transactionStatus) {
+                return Flux.from(exchange("COMMIT"))
+                    .filter(CommandComplete.class::isInstance)
+                    .cast(CommandComplete.class)
+                    .<BackendMessage>handle((message, sink) -> {
+
+                        // Certain backend versions (e.g. 12.2, 11.7, 10.12, 9.6.17, 9.5.21, etc)
+                        // silently rollback the transaction in the response to COMMIT statement
+                        // in case the transaction has failed.
+                        // 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?)")));
+                            return;
+                        }
+
+                        sink.next(message);
+                    });
             } else {
                 this.logger.debug("Skipping commit transaction because status is {}", transactionStatus);
                 return Mono.empty();
@@ -341,9 +362,10 @@ private <T> Mono<T> withTransactionStatus(Function<TransactionStatus, T> f) {
         return Mono.defer(() -> Mono.just(f.apply(this.client.getTransactionStatus())));
     }
 
-    private Publisher<?> exchange(String sql) {
+    @SuppressWarnings("unchecked")
+    private <T> Publisher<T> exchange(String sql) {
         ExceptionFactory exceptionFactory = ExceptionFactory.withSql(sql);
-        return SimpleQueryMessageFlow.exchange(this.client, sql)
+        return (Publisher<T>) SimpleQueryMessageFlow.exchange(this.client, sql)
             .handle(exceptionFactory::handleErrorResponse)
             .as(Operators::discardOnCancel);
     }

src/main/java/io/r2dbc/postgresql/api/ErrorDetails.java

@@ -21,6 +21,7 @@
 import io.r2dbc.postgresql.message.backend.Field.FieldType;
 import io.r2dbc.postgresql.util.Assert;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -89,7 +90,7 @@ public final class ErrorDetails {
 
 
     /**
-     * Creates a new exception.
+     * Create new {@link ErrorDetails} from {@link List} of {@link Field fields}.
      *
      * @param fields the fields to be used to populate the exception
      * @throws IllegalArgumentException if {@code fields} is {@code null}
@@ -120,6 +121,16 @@ private ErrorDetails(Map<FieldType, String> fields) {
         this.where = fields.get(WHERE);
     }
 
+    /**
+     * Create a new {@link ErrorDetails}
+     *
+     * @param message the error message
+     * @return the {@link ErrorDetails} object
+     */
+    public static ErrorDetails fromMessage(String message) {
+        return new ErrorDetails(Collections.singletonMap(MESSAGE, message));
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) {

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

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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 io.r2dbc.postgresql;
+
+import io.r2dbc.postgresql.api.PostgresqlConnection;
+import io.r2dbc.postgresql.api.PostgresqlResult;
+import io.r2dbc.spi.R2dbcBadGrammarException;
+import io.r2dbc.spi.R2dbcRollbackException;
+import org.awaitility.Awaitility;
+import org.junit.jupiter.api.Test;
+import reactor.test.StepVerifier;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for various error cases using {@link PostgresqlConnection}.
+ */
+final class PostgresqlConnectionErrorsIntegrationTests extends AbstractIntegrationTests {
+
+    @Test
+    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);
+
+        Awaitility.await().until(() -> this.connection.isAutoCommit());
+        assertThat(this.connection.isAutoCommit()).isTrue();
+    }
+
+    @Test
+    void rollbackShouldRecoverFromFailedTransaction() {
+
+        this.connection.beginTransaction().as(StepVerifier::create).verifyComplete();
+        this.connection.createStatement("error").execute().flatMap(PostgresqlResult::getRowsUpdated).as(StepVerifier::create).verifyError(R2dbcBadGrammarException.class);
+
+        this.connection.rollbackTransaction().as(StepVerifier::create).verifyComplete();
+
+        assertThat(this.connection.isAutoCommit()).isTrue();
+    }
+
+}