Status

Current state:  Voting Accepted

Discussion thread: https://lists.apache.org/thread/7y7svyp3f560fzv1bgcr893vn258cn06

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• Backward Compatibility: change is fully backward compatible. Existing custom StreamPartitioner implementations will continue to work as they will use the default implementation of the new method.
• Deprecation: Deprecate non-headers public methods to be able to remove them in Kafka 5.0
• Migration: Users wishing to leverage headers in their custom partitioning logic should migrate their StreamPartitioner implementations to override the new `partitions` method.
• Functional interface migration: StreamPartitioner is a functional interface that currently exposes headerless methods, which are going to be deprecated. Users will be notified about using the deprecated API, and they will need to implement the interface directly instead of using lambda syntax. However, they can return to using the functional style partitioner once the deprecated methods are completely removed, which is planned for Kafka 5.0

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