From a35035db10b1173bb21428587a27af7022be3e18 Mon Sep 17 00:00:00 2001 From: Chris Egerton Date: Tue, 15 Feb 2022 23:49:06 -0500 Subject: [PATCH 1/6] KAFKA-10000: Add new public-facing APIs for preflight validation and connector-defined transaction boundaries --- .../ConnectorTransactionBoundaries.java | 31 ++++++++++ .../connect/source/ExactlyOnceSupport.java | 31 ++++++++++ .../kafka/connect/source/SourceConnector.java | 44 +++++++++++++ .../kafka/connect/source/SourceTask.java | 61 +++++++++++++++---- .../connect/source/SourceTaskContext.java | 25 ++++++++ .../connect/source/TransactionContext.java | 55 +++++++++++++++++ 6 files changed, 234 insertions(+), 13 deletions(-) create mode 100644 connect/api/src/main/java/org/apache/kafka/connect/source/ConnectorTransactionBoundaries.java create mode 100644 connect/api/src/main/java/org/apache/kafka/connect/source/ExactlyOnceSupport.java create mode 100644 connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/ConnectorTransactionBoundaries.java b/connect/api/src/main/java/org/apache/kafka/connect/source/ConnectorTransactionBoundaries.java new file mode 100644 index 0000000000000..73746ba0993f3 --- /dev/null +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/ConnectorTransactionBoundaries.java @@ -0,0 +1,31 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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.apache.kafka.connect.source; + +/** + * An enum to represent the level of support for connector-defined transaction boundaries. + */ +public enum ConnectorTransactionBoundaries { + /** + * Signals that a connector can define its own transaction boundaries. + */ + SUPPORTED, + /** + * Signals that a connector cannot define its own transaction boundaries. + */ + UNSUPPORTED +} diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/ExactlyOnceSupport.java b/connect/api/src/main/java/org/apache/kafka/connect/source/ExactlyOnceSupport.java new file mode 100644 index 0000000000000..3980410e4b538 --- /dev/null +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/ExactlyOnceSupport.java @@ -0,0 +1,31 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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.apache.kafka.connect.source; + +/** + * An enum to represent the level of support for exactly-once delivery from a source connector. + */ +public enum ExactlyOnceSupport { + /** + * Signals that a connector supports exactly-once delivery. + */ + SUPPORTED, + /** + * Signals that a connector does not support exactly-once delivery. + */ + UNSUPPORTED; +} diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java index 6e9694024d334..206abfad32034 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java @@ -18,6 +18,8 @@ import org.apache.kafka.connect.connector.Connector; +import java.util.Map; + /** * SourceConnectors implement the connector interface to pull data from another system and send * it to Kafka. @@ -28,4 +30,46 @@ public abstract class SourceConnector extends Connector { protected SourceConnectorContext context() { return (SourceConnectorContext) context; } + + /** + * Signals whether the connector supports exactly-once delivery guarantees with a proposed configuration. + * Developers can assume that worker-level exactly-once support is enabled when this method is invoked. + * + *

For backwards compatibility, the default implementation will return {@code null}, but connector developers are + * strongly encouraged to override this method to return a non-null value such as + * {@link ExactlyOnceSupport#SUPPORTED SUPPORTED} or {@link ExactlyOnceSupport#UNSUPPORTED UNSUPPORTED}. + * + *

Similar to {@link #validate(Map) validate}, this method may be called by the runtime before the + * {@link #start(Map) start} method is invoked when the connector will be run with exactly-once support. + * + * @param connectorConfig the configuration that will be used for the connector. + * @return {@link ExactlyOnceSupport#SUPPORTED} if the connector can provide exactly-once support with the given + * configuration, and {@link ExactlyOnceSupport#UNSUPPORTED} if it cannot. If this method is overridden by a + * connector, should not be {@code null}, but if {@code null}, it will be assumed that the connector cannot provide + * exactly-once guarantees. + * @since 3.2 + */ + public ExactlyOnceSupport exactlyOnceSupport(Map connectorConfig) { + return null; + } + + /** + * Signals whether the connector implementation is capable of defining the transaction boundaries for a + * connector with the given configuration. This method is called before {@link #start(Map)}, only when the + * runtime supports exactly-once and the connector configuration includes {@code transaction.boundary=connector}. + * + *

This method need not be implemented if the connector implementation does not support defining + * transaction boundaries. + * + * @param connectorConfig the configuration that will be used for the connector + * @return {@link ConnectorTransactionBoundaries#SUPPORTED} if the connector will define its own transaction boundaries, + * or {@link ConnectorTransactionBoundaries#UNSUPPORTED} otherwise. If this method is overridden by a + * connector, should not be {@code null}, but if {@code null}, it will be assumed that the connector cannot define its own + * transaction boundaries. + * @since 3.2 + * @see TransactionContext + */ + public ConnectorTransactionBoundaries canDefineTransactionBoundaries(Map connectorConfig) { + return ConnectorTransactionBoundaries.UNSUPPORTED; + } } diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTask.java b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTask.java index f5209e1ccab64..2159e68e8a88a 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTask.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTask.java @@ -16,10 +16,11 @@ */ package org.apache.kafka.connect.source; -import org.apache.kafka.connect.connector.Task; import org.apache.kafka.clients.producer.RecordMetadata; +import org.apache.kafka.connect.connector.Task; import java.util.List; +import java.util.Locale; import java.util.Map; /** @@ -27,6 +28,51 @@ */ public abstract class SourceTask implements Task { + /** + * The configuration key that determines how source tasks will define transaction boundaries + * when exactly-once support is enabled. + */ + public static final String TRANSACTION_BOUNDARY_CONFIG = "transaction.boundary"; + + /** + * Represents the permitted values for the {@link #TRANSACTION_BOUNDARY_CONFIG} property. + */ + public enum TransactionBoundary { + /** + * A new transaction will be started and committed for every batch of records returned by {@link #poll()}. + */ + POLL, + /** + * Transactions will be started and committed on a user-defined time interval. + */ + INTERVAL, + /** + * Transactions will be defined by the connector itself, via a {@link TransactionContext}. + */ + CONNECTOR; + + /** + * The default transaction boundary style that will be used for source connectors when no style is explicitly + * configured. + */ + public static final TransactionBoundary DEFAULT = POLL; + + /** + * Parse a {@link TransactionBoundary} from the given string. + * @param property the string to parse; should not be null + * @return the {@link TransactionBoundary} whose name matches the given string + * @throws IllegalArgumentException if there is no transaction boundary type with the given name + */ + public static TransactionBoundary fromProperty(String property) { + return TransactionBoundary.valueOf(property.toUpperCase(Locale.ROOT).trim()); + } + + @Override + public String toString() { + return name().toLowerCase(Locale.ROOT); + } + } + protected SourceTaskContext context; /** @@ -44,16 +90,13 @@ public void initialize(SourceTaskContext context) { public abstract void start(Map props); /** - *

* Poll this source task for new records. If no data is currently available, this method * should block but return control to the caller regularly (by returning {@code null}) in * order for the task to transition to the {@code PAUSED} state if requested to do so. - *

*

* The task will be {@link #stop() stopped} on a separate thread, and when that happens * this method is expected to unblock, quickly finish up any remaining processing, and * return. - *

* * @return a list of source records */ @@ -63,12 +106,10 @@ public void initialize(SourceTaskContext context) { *

* Commit the offsets, up to the offsets that have been returned by {@link #poll()}. This * method should block until the commit is complete. - *

*

* SourceTasks are not required to implement this functionality; Kafka Connect will record offsets * automatically. This hook is provided for systems that also need to store offsets internally * in their own system. - *

*/ public void commit() throws InterruptedException { // This space intentionally left blank. @@ -91,17 +132,14 @@ public void commit() throws InterruptedException { *

* Commit an individual {@link SourceRecord} when the callback from the producer client is received. This method is * also called when a record is filtered by a transformation, and thus will never be ACK'd by a broker. - *

*

* This is an alias for {@link #commitRecord(SourceRecord, RecordMetadata)} for backwards compatibility. The default * implementation of {@link #commitRecord(SourceRecord, RecordMetadata)} just calls this method. It is not necessary * to override both methods. - *

*

* SourceTasks are not required to implement this functionality; Kafka Connect will record offsets * automatically. This hook is provided for systems that also need to store offsets internally * in their own system. - *

* * @param record {@link SourceRecord} that was successfully sent via the producer or filtered by a transformation * @throws InterruptedException @@ -115,19 +153,16 @@ public void commitRecord(SourceRecord record) throws InterruptedException { /** *

* Commit an individual {@link SourceRecord} when the callback from the producer client is received. This method is - * also called when a record is filtered by a transformation or when {@link ConnectorConfig} "errors.tolerance" is set to "all" + * also called when a record is filtered by a transformation or when "errors.tolerance" is set to "all" * and thus will never be ACK'd by a broker. * In both cases {@code metadata} will be null. - *

*

* SourceTasks are not required to implement this functionality; Kafka Connect will record offsets * automatically. This hook is provided for systems that also need to store offsets internally * in their own system. - *

*

* The default implementation just calls {@link #commitRecord(SourceRecord)}, which is a nop by default. It is * not necessary to implement both methods. - *

* * @param record {@link SourceRecord} that was successfully sent via the producer, filtered by a transformation, or dropped on producer exception * @param metadata {@link RecordMetadata} record metadata returned from the broker, or null if the record was filtered or if producer exceptions are ignored diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTaskContext.java b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTaskContext.java index ddb0a78718351..5bd7889cb2aa5 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTaskContext.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTaskContext.java @@ -38,4 +38,29 @@ public interface SourceTaskContext { * Get the OffsetStorageReader for this SourceTask. */ OffsetStorageReader offsetStorageReader(); + + /** + * Get a {@link TransactionContext} that can be used to define producer transaction boundaries + * when exactly-once support is enabled for the connector. + * + *

This method was added in Apache Kafka 3.2. Source tasks that use this method but want to + * maintain backward compatibility so they can also be deployed to older Connect runtimes + * should guard the call to this method with a try-catch block, since calling this method will result in a + * {@link NoSuchMethodException} or {@link NoClassDefFoundError} when the source connector is deployed to + * Connect runtimes older than Kafka 3.2. For example: + * 

+     *     TransactionContext transactionContext;
+     *     try {
+     *         transactionContext = context.transactionContext();
+     *     } catch (NoSuchMethodError | NoClassDefFoundError e) {
+     *         transactionContext = null;
+     *     }
+     *
+ * + * @return the transaction context, or null if the connector was not configured to specify transaction boundaries + * @since 3.2 + */ + default TransactionContext transactionContext() { + return null; + } } diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java b/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java new file mode 100644 index 0000000000000..d8aac108be180 --- /dev/null +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java @@ -0,0 +1,55 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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.apache.kafka.connect.source; + +/** + * Provided to source tasks to allow them to define their own producer transaction boundaries when + * exactly-once support is enabled. + */ +public interface TransactionContext { + + /** + * Request a transaction commit after the next batch of records from {@link SourceTask#poll()} + * is processed. + */ + void commitTransaction(); + + /** + * Request a transaction commit after a source record is processed. The source record will be the + * last record in the committed transaction. + * @param record the record to commit the transaction after; may not be null. + */ + void commitTransaction(SourceRecord record); + + /** + * Requests a transaction abort the next batch of records from {@link SourceTask#poll()}. All of + * the records in that transaction will be discarded and will not appear in a committed transaction. + * However, offsets for that transaction will still be committed. If the data should be reprocessed, + * the task should not invoke this method and should instead throw an exception. + */ + void abortTransaction(); + + /** + * Requests a transaction abort after a source record is processed. The source record will be the + * last record in the aborted transaction. All of the records in that transaction will be discarded + * and will not appear in a committed transaction. However, offsets for that transaction will still + * be committed. If the data should be reprocessed, the task should not invoke this method and + * should instead throw an exception. + * @param record the record to abort the transaction after; may not be null. + */ + void abortTransaction(SourceRecord record); +} From c2a192bc2e8ecf3528d7a6bee9996d862605c902 Mon Sep 17 00:00:00 2001 From: Chris Egerton Date: Tue, 1 Mar 2022 21:17:51 -0500 Subject: [PATCH 2/6] Update connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java Co-authored-by: Tom Bentley --- .../org/apache/kafka/connect/source/TransactionContext.java | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java b/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java index d8aac108be180..a844c8906a9de 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java @@ -38,7 +38,7 @@ public interface TransactionContext { /** * Requests a transaction abort the next batch of records from {@link SourceTask#poll()}. All of * the records in that transaction will be discarded and will not appear in a committed transaction. - * However, offsets for that transaction will still be committed. If the data should be reprocessed, + * However, offsets for that transaction will still be committed so than the records in that transaction are not reprocessed. If the data should instead be reprocessed, * the task should not invoke this method and should instead throw an exception. */ void abortTransaction(); From fd77d2dd3e3c96308e31620e285ef632614f3a1a Mon Sep 17 00:00:00 2001 From: Chris Egerton Date: Tue, 1 Mar 2022 21:22:58 -0500 Subject: [PATCH 3/6] Add detail to some Javadocs --- .../org/apache/kafka/connect/source/SourceConnector.java | 2 +- .../apache/kafka/connect/source/TransactionContext.java | 9 +++++---- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java index 206abfad32034..e1511c6c20e6d 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java @@ -33,7 +33,7 @@ protected SourceConnectorContext context() { /** * Signals whether the connector supports exactly-once delivery guarantees with a proposed configuration. - * Developers can assume that worker-level exactly-once support is enabled when this method is invoked. + * Connector authors can assume that worker-level exactly-once support is enabled when this method is invoked. * *

For backwards compatibility, the default implementation will return {@code null}, but connector developers are * strongly encouraged to override this method to return a non-null value such as diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java b/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java index a844c8906a9de..fe433352031be 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java @@ -38,8 +38,9 @@ public interface TransactionContext { /** * Requests a transaction abort the next batch of records from {@link SourceTask#poll()}. All of * the records in that transaction will be discarded and will not appear in a committed transaction. - * However, offsets for that transaction will still be committed so than the records in that transaction are not reprocessed. If the data should instead be reprocessed, - * the task should not invoke this method and should instead throw an exception. + * However, offsets for that transaction will still be committed so than the records in that transaction + * are not reprocessed. If the data should instead be reprocessed, the task should not invoke this method + * and should instead throw an exception. */ void abortTransaction(); @@ -47,8 +48,8 @@ public interface TransactionContext { * Requests a transaction abort after a source record is processed. The source record will be the * last record in the aborted transaction. All of the records in that transaction will be discarded * and will not appear in a committed transaction. However, offsets for that transaction will still - * be committed. If the data should be reprocessed, the task should not invoke this method and - * should instead throw an exception. + * be committed so that the records in that transaction are not reprocessed. If the data should be + * reprocessed, the task should not invoke this method and should instead throw an exception. * @param record the record to abort the transaction after; may not be null. */ void abortTransaction(SourceRecord record); From 759051bed8743dc836e58254ea755f185b5f409f Mon Sep 17 00:00:00 2001 From: Chris Egerton Date: Thu, 3 Mar 2022 11:26:53 -0500 Subject: [PATCH 4/6] Replace 'connector developers' with 'connector authors' --- .../java/org/apache/kafka/connect/source/SourceConnector.java | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java index e1511c6c20e6d..b0dfd8baf11c9 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java @@ -35,7 +35,7 @@ protected SourceConnectorContext context() { * Signals whether the connector supports exactly-once delivery guarantees with a proposed configuration. * Connector authors can assume that worker-level exactly-once support is enabled when this method is invoked. * - *

For backwards compatibility, the default implementation will return {@code null}, but connector developers are + *

For backwards compatibility, the default implementation will return {@code null}, but connector authors are * strongly encouraged to override this method to return a non-null value such as * {@link ExactlyOnceSupport#SUPPORTED SUPPORTED} or {@link ExactlyOnceSupport#UNSUPPORTED UNSUPPORTED}. * From ea9ae469c06d85e4e9baf46a54e5e0338dd9a430 Mon Sep 17 00:00:00 2001 From: Chris Egerton Date: Mon, 7 Mar 2022 12:12:47 -0500 Subject: [PATCH 5/6] Fix Jacadoc on TransactionContext::abortTransaction --- .../org/apache/kafka/connect/source/TransactionContext.java | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java b/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java index fe433352031be..f90d75baf4748 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/TransactionContext.java @@ -36,7 +36,7 @@ public interface TransactionContext { void commitTransaction(SourceRecord record); /** - * Requests a transaction abort the next batch of records from {@link SourceTask#poll()}. All of + * Requests a transaction abort after the next batch of records from {@link SourceTask#poll()}. All of * the records in that transaction will be discarded and will not appear in a committed transaction. * However, offsets for that transaction will still be committed so than the records in that transaction * are not reprocessed. If the data should instead be reprocessed, the task should not invoke this method From 955ee492fccc3de8f863cb03d9e68f17acf8e769 Mon Sep 17 00:00:00 2001 From: Chris Egerton Date: Tue, 12 Apr 2022 22:46:42 -0400 Subject: [PATCH 6/6] Update @since to 3.3 --- .../java/org/apache/kafka/connect/source/SourceConnector.java | 4 ++-- .../org/apache/kafka/connect/source/SourceTaskContext.java | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java index b0dfd8baf11c9..7fc2a5d11cfea 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceConnector.java @@ -47,7 +47,7 @@ protected SourceConnectorContext context() { * configuration, and {@link ExactlyOnceSupport#UNSUPPORTED} if it cannot. If this method is overridden by a * connector, should not be {@code null}, but if {@code null}, it will be assumed that the connector cannot provide * exactly-once guarantees. - * @since 3.2 + * @since 3.3 */ public ExactlyOnceSupport exactlyOnceSupport(Map connectorConfig) { return null; @@ -66,7 +66,7 @@ public ExactlyOnceSupport exactlyOnceSupport(Map connectorConfig * or {@link ConnectorTransactionBoundaries#UNSUPPORTED} otherwise. If this method is overridden by a * connector, should not be {@code null}, but if {@code null}, it will be assumed that the connector cannot define its own * transaction boundaries. - * @since 3.2 + * @since 3.3 * @see TransactionContext */ public ConnectorTransactionBoundaries canDefineTransactionBoundaries(Map connectorConfig) { diff --git a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTaskContext.java b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTaskContext.java index 5bd7889cb2aa5..7745b197c2d4c 100644 --- a/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTaskContext.java +++ b/connect/api/src/main/java/org/apache/kafka/connect/source/SourceTaskContext.java @@ -58,7 +58,7 @@ public interface SourceTaskContext { * * * @return the transaction context, or null if the connector was not configured to specify transaction boundaries - * @since 3.2 + * @since 3.3 */ default TransactionContext transactionContext() { return null;