How can Kafka prevent consumers from consuming multiple times?

Kafka provides mechanisms to prevent consumers from consuming messages multiple times.

1. Utilizing message offsets: Consumers can track the offset of consumed messages and continue consuming from the previous offset after restarting, ensuring that messages are not duplicated.
2. Utilize Consumer Groups: Kafka enables multiple consumers to subscribe to the same consumer group. In this scenario, Kafka automatically distributes messages to different consumers to ensure each message is only consumed by one consumer. This helps prevent consumers from consuming the same message multiple times.
3. Consumers can opt to manually submit offsets instead of relying on automatic submission, ensuring that offsets are only committed after processing messages to prevent duplicate consumption in case of failures during message handling.
4. Utilizing idempotent processing: Consumers can achieve idempotent processing, meaning that the same message being processed multiple times will result in the same outcome. Therefore, even if a message is consumed multiple times, it will not affect the final result.

Please note that the above methods can be combined to provide a more reliable message consumption guarantee.