Apache Kafka® 3.5 is here with the capability of previewing migrations between ZooKeeper clusters to KRaft mode. Follow along as Danica Fine highlights key release updates.

Kafka Core:

• KIP-833 provides an updated timeline for KRaft.
• KIP-866 now is preview and allows migration from an existing ZooKeeper cluster to KRaft mode.
• KIP-900 introduces a way to bootstrap the KRaft controllers with SCRAM credentials.
• KIP-903 prevents a data loss scenario by preventing replicas with stale broker epochs from joining the ISR list. 
• KIP-915 streamlines the process of downgrading Kafka's transaction and group coordinators by introducing tagged fields.

Kafka Connect:

• KIP-710 provides the option to use a REST API for internal server communication that can be enabled by setting `dedicated.mode.enable.internal.rest` equal to true. 
• KIP-875 offers support for native offset management in Kafka Connect. Connect cluster administrators can now read offsets for both source and sink connectors. This KIP adds a new STOPPED state for connectors, enabling users to shut down connectors and maintain connector configurations without utilizing resources.
• KIP-894 makes `IncrementalAlterConfigs` API available for use in MirrorMaker 2 (MM2), adding a new use.incremental.alter.config configuration which takes values “requested,” “never,” and “required.”
• KIP-911 adds a new source tag for metrics generated by the `MirrorSourceConnector` to help monitor mirroring deployments.

Kafka Streams:

• KIP-339 improves Kafka Streams' error-handling capabilities by addressing serialization errors that occur before message production and extending the interface for custom error handling. 
• KIP-889 introduces versioned state stores in Kafka Streams for temporal join semantics in stream-to-table joins. 
• KIP-904 simplifies table aggregation in Kafka by proposing a change in serialization format to enable one-step aggregation and reduce noise from events with old and new keys/values. 
• KIP-914 modifies how versioned state stores are used in Kafka Streams. Versioned state stores may impact different DSL processors in varying ways, see the documentation for details.

Kafka Client:

• KIP-881 is now complete and introduces new client-side assignor logic for rack-aware consumer balancing for Kafka Consumers. 
• KIP-887 adds the `EnvVarConfigProvider` implementation to Kafka so custom configurations stored in environment variables can be injected into the system by providing the map returned by `System.getEnv()`.
• KIP 641 introduces the `RecordReader` interface to Kafka's clients module, replacing the deprecated MessageReader Scala trait. 

EPISODE LINKS

• See release notes for Apache Kafka 3.5
• Read the blog to learn more
• Download and get started with Apache Kafka 3.5
• Watch the video version of this podcast