As we’ve hit the mid-mark of the quarter, the team is pleased to announce the second installment of the Debezium 2.6 release stream, Debezium 2.6.0.Alpha2. This release is filled to the brim with new features, improvements, and bug fixes, so let’s dive into these…​

Breaking changes

The team aims to avoid any potential breaking changes between minor releases; however, such changes are sometimes inevitable.

  • The task configuration format used by previous versions of the connector could de-stabilize the Kafka Connect cluster. To resolve the problem, Debezium 2.6 introduces a new configuration format that is incompatible with the previous format (DBZ-7250). When upgrading, you may experience a NullPointerException and the error indicating that the connector was unable to instantiate a task because it contains an invalid task configuration.

    If you experience this problem, delete and re-create the connector, using the same name and configuration as before. The connector(s) will start and re-use the offsets last stored by using the same name, but will not re-use the old task configurations, avoiding the start-up failure.

Improvements and changes

Java 17 now compile-time requirement

Debezium 3.0 which will debut later this fall will once again shift the Java baseline requirement from Java 11 to 17 to use Debezium. In preparation for Debezium 3 later this year, we are making the shift to a compile-time baseline for Debezium 2.6 and 2.7 to require Java 17 (DBZ-7387).

If you are a Debezium user, and you consume Debezium connectors, this will require no action on your part. You can continue to use Java 11 for now without issue, understanding that Debezium 3 will require Java 17 later this year.

If you are developing Debezium connectors, Java 17 is now baseline to compile the Debezium source. If you have been using Java 17, there should be no action taken on your part. If you previously were using Java 11, you will need to move to Java 17 in order to compile from source.

If you are using the Debezium Quarkus Outbox Extension (not the Outbox SMT), as Quarkus 3.7+ is making the move to Java 17 as their baseline, the Debezium Quarkus Outbox Extension will now require Java 17 as a baseline for both runtime and compile time.

We expect this transition to be mostly seamless for most users as this should have absolutely no impact on the runtime of Debezium’s connectors nor Debezium Server at this time.

Asynchronous Embedded Engine

If you’re hearing about the Embedded Engine for the first time, Debezium ships with three ways to run Debezium connectors. The most common is to deploy Debezium on Kafka Connect while the second most common is to use Debezium Server, a read-made runtime for Debezium connectors. However, there is a third option called the Embedded Engine, and it is what Debezium uses internally for its test suite, it’s the foundation for Debezium Server, and it’s meant to provide a way to embed Debezium connectors inside your own application. The embedded engine is used by a variety of external contributors and frameworks, most notably Apache Flink heavily relies on the embedded engine for their Debezium based CDC connectors.

One of the biggest and major new features of Debezium 2.6 is the work on the asynchronous embedded engine that we are debuting in this alpha release. This new asynchronous version the foundation for which Debezium Server and the future of embedding Debezium is based. This change focuses on several key goals and initiatives:

  • Run multiple source tasks for a given connector, if the connector supports multiple tasks

  • Run time-consuming code (transformations or serialization) in dedicated threads

  • Allow additional performance by disabling event dispatch order

  • Provide future technology benefits of things such as virtual threads and delegating to external workers

  • Better integration with Debezium Operator for Kubernetes and Debezium UI

  • Seamlessly integrate with Quarkus for Debezium Server

What this new asynchronous model does not include or focus on are the following:

  • Implement parallelization inside a connector’s main capture loop.

  • Remove any dependency from Kafka Connect

  • Add support for multiple source connectors per Engine deployment

  • Add support for sink connectors

Even if a connector is single-threaded and does not support multiple tasks, a connector deployment using the Embedded Engine or Debezium Server can take advantage of the new asynchronous model. A large portion of time during even dispatch is spent on transformation and serialization phases, so utilizing the new dedicated worker threads for such stages improves throughput.

For developers who want to get started with the new asynchronous embedded engine, a new package is now included in the debezium-embedded artifact called io.debezium.embedded.async and this package contains all the pertinent components to utilizing this new implementation. The asynchronous model can be constructed in a similar way to the serial version using the builder pattern, shown below.

final DebeziumEngine engine = new AsyncEngine.AsyncEngineBuilder()

We encourage everyone to take a look at the new Asynchronous Embedded Engine model, let us know your thoughts and if you spot any bugs or problems. We will be updating the documentation in coming releases to highlight all the benefits and changes, including examples. Until then, you can find all the details in the design document, DDD-7.

Timestamp converter improvements

Debezium released the new TimezoneConverter in Debezium 2.4, allowing users to target a specific time zone and to convert the outgoing payload time values to that targeted time zone. The original implementation was specifically restricted to allow conversion of values within the before or after parts of the payload; however, thanks to an improvement as a part of DBZ-7022, the converter can now be used to convert other time-based fields in the metadata, such as ts_ms in the source information block.

This change helps to improve lag metric calculations in situations where the JVM running the connector is using a time zone that differs from the database and the calculation of the envelope ts_ms - source ts_ms results in a variance caused by the time zone. By using the TimezoneConverter to convert metadata fields, you can easily calculate the lag between those two fields without the time zone interfering.

SQL Server query improvements

The Debezium SQL Server utilizes a common SQL Server stored procedure called fn_cdc_get_all_changes…​ to fetch all the relevant captured changes for a given table. This query performs several unions and only ever returns data from one of the union sub-queries, which can be inefficient.

Debezium 2.6 for SQL Server introduces a new configuration property data.query.mode that can be used to influence which specific method the connector will use to gather the details about table changes (DBZ-7273). The default remains unchanged from older releases, using the value function to delegate to the above aforementioned stored procedure. A new option, called direct, can be used instead to build the query directly within the connector to gather the changes more efficiently.

Scoped Key/Trust - store support with MongoDB

Debezium supports secure connections; however, MongoDB requires that the key/trust -store configurations be supplied as JVM process arguments, which is less than ideal for environments like the cloud. As a first step toward aligning how secure connection configuration is specified across our connectors, Debezium 2.6 for MongoDB now supports specifying scoped key/trust -store configurations in the connector configuration (DBZ-7379).

The MongoDB connector now includes the following new configuration properties:


Specifies the path to the SSL keystore file.


Specifies the credentials to open and access the SSL keystore provided by mongodb.ssl.keystore.


Specifies the SSL keystore file type, defaults to PKC512.


Specifies the path to the SSL truststore file.


Specifies the credentials to open and access the SSL truststore provided by mongodb.ssl.truststore.


Specifies the SSL truststore file type, defaults to PKC512.

Source transaction id changes

All Debezium change events contain a special metadata block called the source information block. This part of the event payload is responsible for providing metadata about the change event, including the unique identifier of the change, the time the change happened, the database and table the change is in reference to, as well as transaction metadata about the transaction that the change participated in.

In Debezium 2.6, the transaction_id field in the source information block will no longer be provided unless the field is populated with a value. This should present no issue for users as this field was only populated when the connector was configured with provide.transaction.metadata set to true (DBZ-7380).

If you have tooling that expects the existence of the source information block’s transaction_id field although its optional, you will need to adjust that behavior as the field will no longer be present unless populated.

Google PubSub Ordering Key Support

The Debezium Server Google PubSub sink adapter has received a small update in Debezium 2.6. If you are streaming changes that have foreign key relationships, you may have wondered whether it was possible to specify an ordering key so that foreign key constraints could be maintained.

Debezium 2.6 introduces a new configurable property for the Google PubSub sink adapter, ordering.key, which allows the sink adapter to use an externally provided ordering key from the connector configuration for the events rather than using the default behavior based on the event’s key (DBZ-7435).

MongoDB UUID key support for Incremental snapshots

As a small improvement to the Incremental Snapshot process for the Debezium for MongoDB connector, Debezium 2.6 adds support for the UUID data type, allowing this data type to be used within the Incremental Snapshot process like other data types (DBZ-7451).

MongoDB post-image changes

The MongoDB connector’s event payload can be configured to include the full document that was changed in an update. The connector previously made an opinionated choice about how the full document would be fetched as part of the change stream; however, this behavior was not consistent with our expectations in all use cases.

Debezium 2.6 introduces a new configuration option, capture.mode.full.update.type, allowing the connector to explicitly control how the change stream’s full document lookup should be handled (DBZ-7299). The default value for this option is lookup, meaning that the database will make a separate look-up to fetch the full document. If you are working with MongoDB 6+, you can also elect to use post_image to rely on MongoDB change stream’s post-image support.

Other changes

Altogether, 66 issues were fixed in this release:

  • Add Number of records captured and processed as metrics for Debezium MongoDB Connector DBZ-6432

  • Connector is getting stopped while processing bulk update(50k) records in debezium server 2.0.1.Final DBZ-6955

  • Error when fail converting value with internal schema DBZ-7143

  • Remove obsolete MySQL version from TF DBZ-7173

  • Correctly handle METADATA records DBZ-7176

  • Move Snapshotter interface to core module as SPI DBZ-7300

  • Implement Snapshotter SPI MySQL/MariaDB DBZ-7301

  • Update the Debezium UI repo with local development infra and readme file. DBZ-7353

  • Debezium fails after table split operation DBZ-7360

  • Update QOSDK to the latest version DBZ-7361

  • Support DECFLOAT in Db2 connector DBZ-7362

  • Create PubSub example for DS deployed via operator DBZ-7370

  • Upstream artefact server image preparation job failing DBZ-7371

  • Informix-Connector breaks on table with numerical default value DBZ-7372

  • Tests in RHEL system testsuite fail to initialize Kafka containers DBZ-7373

  • MSSQL wrong default values in db schema for varchar, nvarchar, char columns DBZ-7374

  • Fix logging for schema only recovery mode in mysql connector DBZ-7376

  • Replace additional rolebinding definition in kubernetes.yml with @RBACRule DBZ-7381

  • Records from snapshot delivered out of order DBZ-7382

  • Upgrade json-path to 2.9.0 DBZ-7383

  • Fix mysql version in mysql-replication container images DBZ-7384

  • Reduce size of docker image for Debezium 2.6 and up DBZ-7385

  • Remove the use of Lombok in Debezium testsuite DBZ-7386

  • Upgrade Outbox Extension to Quarkus 3.7.0 DBZ-7388

  • Add dependancy update bot to the UI Repo DBZ-7392

  • Duplicate Debezium SMT transform DBZ-7416

  • Kinesis Sink Exception on PutRecord DBZ-7417

  • ParsingException (MariaDB Only): alterSpec drop foreign key with 'tablename.' prefix DBZ-7420

  • Poor performance with incremental snapshot with long list of tables DBZ-7421

  • Fix the unit test cases DBZ-7423

  • Oracle Snapshot mistakenly uses LogMiner Offset Loader by default DBZ-7425

  • Reselect columns should source key values from after Struct when not using event-key sources DBZ-7429

  • Allow the C3P0ConnectionProvider to be customized via configuration DBZ-7431

  • Stopwatch throw NPE when toString is called without having statistics DBZ-7436

  • ReselectColumnsPostProcessor filter not use exclude predicate DBZ-7437

  • Adopt Oracle 23 to Testing Farm DBZ-7439

  • Adhoc snapshots are not triggered via File channel signal when submitted before the start of the application DBZ-7441

  • Upgrade protobuf to 3.25.2 DBZ-7442

  • Correct debezium.sink.pubsub.flowcontrol.* variable names in Debezium Server docs site DBZ-7443

  • LogMiner batch size does not increase automatically DBZ-7445

  • Reduce string creation during SQL_REDO column read DBZ-7446

  • Evaluate container image size for Debezium UI served by nginx DBZ-7447

  • Upgrade Quarkus for Debezium Server to 3.2.9.Final DBZ-7449

  • Fix TimescaleDbDatabaseTest to run into test container DBZ-7452

  • Consolidate version management DBZ-7455

  • Oracle connector does not ignore reselection for excluded clob/blob columns DBZ-7456

  • Upgrade example-mongo image version to 6.0 DBZ-7457

  • The expected value pattern for table.include.list does not align with the documentation DBZ-7460

  • SQL Server queries with special characters fail after applying DBZ-7273 DBZ-7463

  • Signals actions are not loaded for SQLServer DBZ-7467

  • MySQL connector cannot parse table with WITH SYSTEM VERSIONING PARTITION BY SYSTEM_TIME DBZ-7468

  • Test Db2ReselectColumnsProcessorIT randomly fails DBZ-7471

  • Postgres images require clang-11 DBZ-7475

  • Make readiness and liveness proble timouts configurable DBZ-7476

  • Snapshotter SPI wrongly loaded on Debezium Server DBZ-7481

Outlook & What’s next?

We’ve reached the mid-way point for the quarter’s development cycle for 2.6 and the team is beginning our transition to the latter half where our focus is more on stability, regressions, and bug fixes. There are still a number of new features and improvements on the horizon, so you can expect those in the coming two weeks when our first beta preview release will be published for Debezium 2.6.

As always, if you have any questions or interested in what the roadmap holds for not only 2.6 but also the road to the new Debezium 3.0 later this fall, we encourage you to take a look at our road map. If you have any suggestions or ideas, please feel free to get in touch with us on our mailing list or in our Zulip chat.

Until next time…​

Chris Cranford

Chris is a software engineer at Red Hat. He previously was a member of the Hibernate ORM team and now works on Debezium. He lives in North Carolina just a few hours from Red Hat towers.


About Debezium

Debezium is an open source distributed platform that turns your existing databases into event streams, so applications can see and respond almost instantly to each committed row-level change in the databases. Debezium is built on top of Kafka and provides Kafka Connect compatible connectors that monitor specific database management systems. Debezium records the history of data changes in Kafka logs, so your application can be stopped and restarted at any time and can easily consume all of the events it missed while it was not running, ensuring that all events are processed correctly and completely. Debezium is open source under the Apache License, Version 2.0.

Get involved

We hope you find Debezium interesting and useful, and want to give it a try. Follow us on Twitter @debezium, chat with us on Zulip, or join our mailing list to talk with the community. All of the code is open source on GitHub, so build the code locally and help us improve ours existing connectors and add even more connectors. If you find problems or have ideas how we can improve Debezium, please let us know or log an issue.