The upgrade to Debezium 2.5 brings a change to MongoDB’s default implementation. In previous builds, the default connection mode was replica_set; however with Debezium 2.5 this is now sharded. If you were connecting to a sharded cluster and not explicitly setting a connection mode; ergo, relying on the default behavior, you must review your connector configuration and make adjustments. (DBZ-7108)

Overall, this change is part of larger effort to remove the replica_set mode entirely. Please be sure to review your connector configurations for all MongoDB connectors when upgrading.

Part of the team’s focus in Debezium 2.5 was to improve the Debezium Embedded Engine’s experience. With that goal in mind, we took this preview release as an opportunity to clean-up the embedded engine’s API.

If your usage of the Debezium Embedded Engine utilized any of the previously deprecated APIs on EmbeddedEngine, you will find those methods have since been removed. (DBZ-7100) The recommended path forward is to make sure that you’re using the DebeziumEngine interface provided by the debezium-api artifact.

The MySQL community announced that MySQL 5.7 would enter its End of Life cycle at the end of October 2023, or just last month. This means that the MySQL community has no plans to continue offering security or bug fix patches for that edition of MySQL.

In accordance with this upstream community news, Debezium too is making adjustments, like other vendors, around this recent news. To that end, starting with Debezium 2.5, we will no longer be testing nor supporting MySQL 5.7 if full capacity, thus MySQL 5.7 enters what we call "best-effort" support. (DBZ-6874)

If you are presently using the CloudEvents converter to emit events that conform to the CloudEvents format, it’s important to note that the configuration option metadata.location was renamed to metadata.source. You will need to be sure to update your connector configurations to reflect this change with Debezium 2.5 and onward. (DBZ-7060)

Debezium first introduced the JDBC sink connector in March 2023 as a part of Debezium 2.2. Over the last several months, this connector has seen numerous iterations to improve its stability, feature set, and capabilities. Debezium 2.5 builds atop of those efforts, introducing batch-writes. (DBZ-6317)

In previous versions, the connector worked on each topic event separately; however, the new batch-write support mode will collect the events into buckets and write those changes to the target system using the fewest possible transaction boundaries as possible. This change increases the connector’s throughput capabilities and makes the interactions with the target database far more efficient.

Debezium has introduced several changes around large document processing in recent releases; however, those changes primarily focused on handling that use case with MongoDB 4 and 5. While these improvements certainly help for those older versions, the MongoDB community has introduced a way in MongoDB 6 to seamlessly deal with this at the database pipeline level.

Debezium 2.5’s MongoDB connector now uses the $changeStreamSplitLargeEvent aggregation feature, introduced as part of MongoDB 6.0.9. This avoids the BSONObjectTooLarge exception when working with documents that would exceed the 16MB document size limit of MongoDB. This new feature is controlled by the oversize.handling.mode option, which defaults to fail. Please adjust this configuration if you would like to take advantage of this new, opt-in feature. (DBZ-6726)

The MySQL community recently released a new innovation release, MySQL 8.2.0 at the end of October 2023. This new release has been tested with Debezium and we’re happy to announce that we officially support this new innovation release. (DBZ-6873)

Debezium for SQL Server works by reading the changes captured by the database in what are called capture instances. These instances can come and go based on a user’s needs, and it can be difficult to know if Debezium has concluded its own capture process for a given capture instance.

Debezium 2.5 remedies this problem by emitting a new notification aggregate called Capture Instance, allowing any observer to realize when a capture instance is no longer in use by Debezium. This new notification includes a variety of connector details including the connector’s name along with the start, stop, and commit LSN values. (DBZ-7043)

Debezium 2.5 introduces a new configuration option, schema.history.internal.redis.max.attempts designed to limit the number of retry attempts while connecting to a Redis database when it becomes unavailable, previously it simply retried forever. This new option defaults to 10 but is user configurable. (DBZ-7120)

SQL Serer 2019 introduced the ability to specify column-specific sensitivity classifications to provide better visibility and protections for sensitive data. Unfortunately, the current driver shipped with Debezium 2.4 and earlier does not support this feature. Debezium 2.5 introduces the latest 12.4.2 SQL Server driver so that users can now take advantage of this feature out of the box. (DBZ-7109)

Debezium Server Kinesis users will be happy to note that there has been some reliability improvements with the sink adapter with Debezium 2.5. The Kinesis Sink will now automatically retry the delivery of a failed record up to a maximum of 5 attempts before the adapter triggers a failure. This should improve the sink adapter’s delivery reliability and help situations where a batch of changes may overload the sink’s endpoint. (DBZ-7032)