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Currently if a transactional producer hits a fatal exception, the caller usually catches the exception and handle it by aborting invoking abortTransaction to abort the transaction by invoking abortTransaction, and then closing the the producer, which makes sense and sounds clean. The tricky scenario is that abortTransaction is not a safe call when the producer is already in an error state, which means user has to do another try-catch with the first layer catch block, making the error handling pretty annoying. It is more appropriate and user-friendly to ensure that the producer client does not throw the same exception again while aborting transaction.

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Our proposal is quite straightforward and simple. To avoid throwing the same exception twice, we would remember whether a fatal exception has already been thrown to the application level, so that in abortTransaction we will not throw it again, thus making the function safe to be called in an error state.

...

/**
* Aborts the ongoing transaction. Any unflushed produce messages will be aborted when this call is made.
* This call will be a no-op if previous transactional call has thrown an exception and made the producer in an error state.
*
* Note that this method will raise {@link TimeoutException} if the transaction cannot be aborted before expiration
* of {@code max.block.ms}. Additionally, it will raise {@link InterruptException} if interrupted.
* It is safe to retry in either case, but it is not possible to attempt a different operation (such as commitTransaction)
* since the abort may already be in the progress of completing. If not retrying, the only option is to close the producer.
*
* @throws TimeoutException if the time taken for aborting the transaction has surpassed <code>max.block.ms</code>.
* @throws InterruptException if the thread is interrupted while blocked
*/
public void abortTransaction();

Suggested Coding Pattern

With this proposed change, users may use transactional APIs as follows.

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("transactional.id", "my-transactional-id");
Producer<String, String> producer = new KafkaProducer<>(props, new StringSerializer(), new StringSerializer());

producer.initTransactions();

try {
    producer.beginTransaction();
    for (int i = 0; i < 100; i++)
        producer.send(new ProducerRecord<>("my-topic", Integer.toString(i), Integer.toString(i)));
    producer.commitTransaction();
} catch (Exception e) {
    producer.abortTransaction();
    if(e instanceof IllegalStateException || 
        e instanceof ProducerFencedException ||
	    e instanceof UnsupportedVersionException || 
        e instanceof AuthorizationException) {
        producer.close();
    }
}

Compatibility, Deprecation, and Migration Plan

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The alternatives are rejected because they all require a bigger changechanges.