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• A new overloaded method partition(String topic, Object key, byte[] keyBytes, Object value, byte[] valueBytes, Cluster cluster, Headers headers) with default implementation to call the existing method.

• Details :

  Code Block

  /** * Compute the partition for the given record. * * @param topic The topic name * @param key The key to partition on (or null if no key) * @param keyBytes The serialized key to partition on( or null if no key) * @param value The value to partition on or null * @param valueBytes The serialized value to partition on or null * @param cluster The current cluster metadata * @param headers The headers to partition on or null */ default int partition(String topic, Object key, byte[] keyBytes, Object value, byte[] valueBytes, Cluster cluster, Headers headers) { return partition(topic, key, keyBytes, value, valueBytes, cluster); };

Proposed Changes

• Add a new overloaded method partition(String topic, Object key, byte[] keyBytes, Object value, byte[] valueBytes, Cluster cluster, Headers headers) with default implementation to call the existing method in the Partitioner interface in org/apache/kafka/clients/producer.
  • This lets the users to implement the partitioner with ability to choose partition based on header values.
  • If a partitioner implements both the methods, the override of new method (one which accepts headers) will be in effect.
• Make the call to partition method in KafkaProducer to use the new method.
  • Since it is defaulted to use the existing method, this should not cause any behaviour change.
  Mark headers as readonly before the first call for
  • Make sure the client cannot update the headers.
  • Ensure consistency as it get marked before the second call.

Total changes : https://github.com/apache/kafka/pull/13981

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• What impact (if any) will there be on existing users?
  • None
• If we are changing behavior how will we phase out the older behavior?
  • NA
• If we need special migration tools, describe them here.
  • NA
• When will we remove the existing behavior?
  • NA

This is a backward comparable change as mentioned in the proposed changes section. The new default method calls the existing method unless it is manually overridden by the user. 

Test Plan

Describe in few sentences how the KIP will be tested. We are mostly interested in system tests (since unit-tests are specific to implementation details). How will we know that the implementation works as expected? How will we know nothing broke?

<>This has an addition of a default method in the interface. The changes made in Kafka Producer should be covered in the existing tests and should not have any impact.

Rejected Alternatives

None