[GitHub] [kafka] guozhangwang edited a comment on pull request #9569: KAFKA-10687: make ProduceRespone only returns INVALID_PRODUCER_EPOCH

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guozhangwang edited a comment on pull request #9569:
URL: https://github.com/apache/kafka/pull/9569#issuecomment-725014616


   Okay I think I need to rephrase my thoughts above in another way: right now when abort txns due to timeout, the txn coordinator would 1) first bump up the epoch, and 2) append the prepare-abort log with the newly bumped epoch, and then 3) send the txn-markers to the partition leaders with the newly bumped epoch. As a result, the partition leaders will bump their local epoch of the pid as well.
   
   This makes sense for disallowing the old producer to append more records with the old epoch, but like KIP-588 mentioned it does not help differentiating the timeout scenario from the new initPID scenario where only the latter indeed gets a new producer. And although txn coordinators may be able to tell the difference based on its old cache values, the partition leader would not know at all and hence forcing its fenced-producer to always be translated to invalid producer error seems sub-optimal.
   
   IF, we do want to let the partition leader to never return fenced-producer, then at least we should change that in `ProducerStateManager#checkProducerEpoch` and not in `KafkaApis`, and changing `InvalidProducerEpochException` to `ApiException` **but we'd need to document that very clearly what users should do upon getting InvalidProducerEpochException**; IF, we'd like to let the partition leader be able to distinguish txn timeout from new initPID as well, we should let the txn markers to piggyback that information. **The benefits are that we do not need to expose a new exception and users still only get ProducerFencedException.**
   


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