Guozhang Wang created KAFKA-14138:
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Summary: The Exception Throwing Behavior of Transactional Producer
is Inconsistent
Key: KAFKA-14138
URL: https://issues.apache.org/jira/browse/KAFKA-14138
Project: Kafka
Issue Type: Improvement
Components: producer
Reporter: Guozhang Wang
There's an issue for inconsistent error throwing inside Kafka Producer when
transactions are enabled. In short, there are two places where the received
error code from the brokers would be eventually thrown to the caller:
* Recorded on the batch's metadata, via "Sender#failBatch"
* Recorded on the txn manager, via "txnManager#handleFailedBatch".
The former would be thrown from 1) the `Future<RecordMetadata>` returned from
the `send`; or 2) the `callback` inside `send(record, callback)`. Whereas, the
latter would be thrown from `producer.send()` directly in which we call
`txnManager.maybeAddPartition -> maybeFailWithError`. However, when thrown from
the former, it's not wrapped hence the direct exception (e.g.
ClusterAuthorizationException), whereas in the latter it's wrapped as, e.g.
KafkaException(ClusterAuthorizationException). And which one would be thrown
depend on a race condition since we cannot control by the time the caller
thread calls `txnManager.maybeAddPartition`, if the previous produceRequest's
error has been sent back or not.
For example consider the following sequence:
1. caller thread: within future = producer.send(), call recordAccumulator.append
2. sender thread: drain the accumulator, send the produceRequest and get the
error back.
3. caller thread: within future = producer.send(), call
txnManager.maybeAddPartition
4. sender thread: get the addPartition token, send the txnRequest and get the
error back. NOTE the sender thread could send these two requests in any order.
5. caller thread: future.get()
In a sequence where then 3) happened before 2), we would only get the raw
exception at step 5; in a sequence where 2) happened before 3), then we would
throw the exception immediately at 3).
This inconsistent error throwing is pretty annoying for users since they'd need
to handle both cases, but many of them actually do not know this trickiness. We
should make the error throwing consistent, e.g. we should consider: 1) which
errors would be thrown from callback / future.get, and which would be thrown
from the `send` call directly, and these errors should better be
non-overlapping, 2) whether we should wrap the raw error or not, we should do
so consistently.
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