问题
If I have a Kafka stream application that fails to post to a topic (because the topic does not exist) does it commit the consumer offset and continue, or will it loop on the same message until it can resolve the output topic? The application merely prints an error and runs fine otherwise from what I can observe.
An example of the error when trying to post to topic:
Error while fetching metadata with correlation id 80 : {super.cool.test.topic=UNKNOWN_TOPIC_OR_PARTITION}
In my mind it would just spin on the same message until the issue is resolved in order to not lose data? I could not find a clear answer on what the default behavior is. We haven't set autocommit to off or anything like that, most of the settings are set to the default.
I am asking as we don't want to end up in a situation where the health check is fine (application is running while printing errors to log) and we are just throwing away tons of Kafka messages.
回答1:
Kafka Streams will not commit the offsets for this case, as it provides at-least-once processing guarantees (in fact, it's not even possible to reconfigure Kafka Streams differently -- only stronger exactly-once guarantees are possible). Also, Kafka Streams disables auto-commit on the consumer always (and does not allow you to enable it), as Kafka Streams manages committing offset itself.
If you run with default setting, the producer should actually throw an exception and the corresponding thread should die -- you can get a callback if a thread dies, by registering KafkaStreams#uncaughtExceptionHandler().
You can also observe KafkaStreams#state() (or register a callback KafkaStreams#setStateListener()). The state will go to DEAD if all threads are dead (note, there was a bug in older version for which the state was still RUNNING for this case: https://issues.apache.org/jira/browse/KAFKA-5372)
Hence, the application should not be in a healthy state and Kafka Streams will not retry the input message but stop processing and you would need to restart the client. On restart, it would re-read the failed input message an re-try to write to the output topic.
If you want Kafka Streams to retry, you need to increase the producer config reties to avoid that the producer throws an exception and retries writing internally. This may "block" further processing eventually if producer write buffer becomes full.
来源：https://stackoverflow.com/questions/56390128/is-consumer-offset-commited-even-when-failing-to-post-to-output-topic-in-kafka-s