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Public Interfaces

This new mode (name is enable.parallel.rebalance) will by default not be used by KafkaConsumer (e.g. will be by default equal to false). If the user chooses, he or she can activate this mode by setting the config's value to true.

Proposed Changes

When rebalancing, instead of allowing the current consumer (consumer1) to restart from the last committed offset (70), we should allow it to start processing from the latest offset (120) that could be polled at the time of the consumer's recovery (assuming that the log has grown within the time that the process was down). Meanwhile, a new KafkaConsumer (consumer2) will be created to start processing from the last committed offset (70) and run in concurrency with consumer1. Consumer2 will terminate when it has reached offset 120. By default, this setup will support at-least-once semantics.

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