Status

Current state: Under DiscussionAdopted

Discussion thread: here 

JIRA:

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

Over time, certain exceptions and methods within the Kafka Streams exception handling interfaces have been deprecated are unused in favor of newer, more comprehensive alternatives. Retaining these deprecated elements can lead to confusion, and complicates future development and maintenance. This KIP proposes the deprecation and removal of these specific deprecated exceptions and methods to streamline the API BrokerNotFoundException and improve code clarity.

Public Interfaces

The removal will affect the public exceptions of Kafka Streams. Users who are still using the BrokerNotFoundException  class or implementing/calling these specific deprecated methods will encounter compilation errors.

Proposed Changes

This KIP proposes to remove the following deprecated Kafka Streams exception class and methods:

Deprecated Class for Removal:

• org.apache.kafka.streams.errors.BrokerNotFoundException

Deprecated Methods for Removal:

...

BrokerNotFoundException which is unused since Kafka Streams 2.8.

This change goes in two steps

Step1: mark unused BrokerNotFoundException as deprecated in 4.2 release

Step2: remove the deprecated exception in the next major release which can be 5.0

Unused Exception for Deprecation and Removal:

...

• org.apache.kafka.streams.errors.DeserializationExceptionHandler.handle(final ProcessorContext context, final ConsumerRecord<byte[], byte[]> record,final Exception exception)
• org.apache.kafka.streams.errors.LogAndContinueExceptionHandler.handle(final ProcessorContext context, final ConsumerRecord<byte[], byte[]> record,final Exception exception)
• org.apache.kafka.streams.errors.LogAndFailExceptionHandler.handle(final ProcessorContext context, final ConsumerRecord<byte[], byte[]> record, finalException exception)

...

• BrokerNotFoundException

...

The removal of these elements will simplify the interfaces and ensure users adopt the more robust exception handling mechanisms.

Compatibility, Deprecation, and Migration Plan

• Compatibility: This change is not backward compatible at the source code level for users who are still using the BrokerNotFoundException class or implementing/calling these specific deprecated methods.
• Deprecation: The BrokerNotFoundException was deprecated in unused since Kafka Streams version 2.8. The listed methods were deprecated in KafkaStreams version 3.9. 
  • Given that these elements were deprecated in earlier versions (2.8 and 3.9), a sufficient deprecation period has passed, making their removal appropriateBrokerNotFoundException is unused, we can mark it deprecated in 4.2, making their removal appropriate in 5.0 as sufficient deprecation period will be passed.
• Migration Plan:
  • For BrokerNotFoundException: Users should remove any handling of this exception as BrokerNotFoundException as it is no longer relevant.For deprecated methods: Users are advised to migrate their code to use the non-deprecated handle methods that accept ErrorHandlerContext. For example:Instead of DeserializationExceptionHandler.handle(ProcessorContext, ConsumerRecord, Exception), use DeserializationExceptionHandler.handle(ErrorHandlerContext, ConsumerRecord, Exception).
  • Instead of ProductionExceptionHandler.handle(ProducerRecord, Exception), use ProductionExceptionHandler.handle(ErrorHandlerContext,ProducerRecord, Exception).
  • Instead of ProductionExceptionHandler.handleSerializationException(ProducerRecord, Exception), use ProductionExceptionHandler.handleSerializationException(ErrorHandlerContext, ProducerRecord, Exception, SerializationExceptionOrigin).

Test Plan

This is a code cleanup. Existing test suite should catch any failures. Will add or update new unittests unit tests as needed.

Rejected Alternatives

Since BrokerNotFoundException is not used for a very long time, we can remove it directly. But, the protocol we follow is to deprecate them first and then remove them in the next major release.

We will have an unused class lying around for another release. Other than that, there is no damage if we follow the regular process. Hence, the two step process.N/A