Kafka hard
When implementing 'Exactly-Once Semantics' (EOS) in a Kafka stream, what is the role of the `isolation.level=read_committed` setting on the Consumer?
- A It prevents the consumer from reading any messages that have not yet been backed up to an external database.
- B It ensures that the consumer ONLY sees messages from transactions that have been successfully committed, automatically filtering out records from 'aborted' or 'active' transactions.
- C It disables the `poll()` timeout to ensure that the consumer waits forever for a perfect record.
- D It forces the consumer to perform an MD5 checksum on every single payload.
Answer: B. It ensures that the consumer ONLY sees messages from transactions that have been successfully committed, automatically filtering out records from 'aborted' or 'active' transactions.
Without this setting, a consumer would see all messages, including those from a 'failed' producer transaction (e.g., if a producer sent 100 records and then crashed before committing). `read_committed` preserves the integrity of the transactional boundary.
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