KAFKA-19367: Fix InitProducerId with TV2 double-increments epoch if ongoing transaction is aborted #19910
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core/src/main/scala/kafka/coordinator/transaction/TransactionCoordinator.scala
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jolshan
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Jun 6, 2025
core/src/main/scala/kafka/coordinator/transaction/TransactionCoordinator.scala
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| if (!clientTransactionVersion.supportsEpochBump()) { | ||
| // For TV1, manually bump // the epoch in the transaction metadata we are about to append. | ||
| txnMetadata.producerEpoch = producerEpoch | ||
| txnMetadata.lastProducerEpoch = RecordBatch.NO_PRODUCER_EPOCH |
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Could you check whether we need to reset lastProducerEpoch even for TV2?
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For TV2, it looks like the last producer epoch is immediately set in prepareAbortOrCommit, so we don't need to set it here
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When InitProducerId is handled on the transaction coordinator, the producer epoch is incremented (so that we fence stale requests), then if a transaction was ongoing during this time, it's aborted. With transaction version 2 (a.k.a. KIP-890 part 2), abort increments the producer epoch again (it's the part of the new abort / commit protocol), so the epoch ends up incremented twice.
In most cases, this is benign, but in the case where the epoch of the ongoing transaction is 32766, it's incremented to 32767, which is the maximum value for short. Then, when it's incremented for the second time, it goes negative, causing an illegal argument exception.
To fix this we just avoid bumping the epoch a second time.